PS

ESP Ardiuno program to controll a Motor through Firebase on Internet.

2024-11-08T05:33:00.000-08:00

Here sharing a ESP8266 (Using Nodemcu) ariuno program to controller a motor over internet using firebase.

In below example as i am controller a motor that have a capacitor so as i ON Motor (RelayStart =13) program should ON a capacitor (RelayCapaciter=14) for 3 second then Off it.

Below code have i wifi configuration page where you can enter your wifi router SSID and password. Follow below steps:

1- First paste your firebase Host and Auth key in code.

2- Connect Nodemcu GPIO pin 13 to Relay (Motor) ON.

3- Connect Nodemcu GPIO pin 14 to RelayCapaciter (for capacitor).

4- Now burn the code in node mcu 8266.

5- To configure your router ssid password. Press Flash button of nodemcu for 3 to 5 seconds. It will enable esp to AP mode and you can get a wifi network with name of ESP-TEST.

6- Connect to this Access Point.

7- Now open borwser and type 192.168.4.1 and you will get a page to enter SSID and Password of your router.

8- Finally click on Submit. Now it has been successfullly connected to your router.

9- Now open your firebase account and you will get two veriable in firebase database. MotorCommand and MotorStatus. Enter ON in MotorCommand it will on the ESP (Motor) as motor on ESP will write back the ON status to MotorStatus variable at firebase.

10- Done.

#include <ESP8266WiFi.h>

#include <ESP8266HTTPClient.h>

#include <ESP8266WebServer.h>

#include "FirebaseESP8266.h"

#include <ESP8266mDNS.h>

#include <ArduinoJson.h>

#include <EEPROM.h>

//------------------ Variables--------------------------

int statusCode;

String ssid = "";

String passphrase = "";

String st;

String content;

const int triggerPin = 0;

bool IN_ST_MODE_FLAGE = true;

bool IN_AP_MODE_FLAGE = false;

int c = 0;

int Current_Gate_Status;

int Last_Gate_Status;

const int RelayStart = 13; //On-off

const int RelayCapaciter = 14; // for capacitor

String Last_Status = "OFF";

unsigned long triggerStartTime = 0; // Variable to store the start time of trigger pin low state

//======================= ON NET =========================================

#define FIREBASE_HOST "Paste you firebase host"

#define FIREBASE_AUTH "Paster your firebase Auth key"

FirebaseData fbdo;

unsigned long sendDataPrevMillis = 0;

String commandpath = "/MotorCommand";

String currentStatusPath = "/MotorStatus";

uint16_t count = 0;

void printResult(FirebaseData &data);

ESP8266WebServer server(80);

void setup()

{

Serial.begin(115200);

pinMode(triggerPin, INPUT);

pinMode(RelayCapaciter,OUTPUT);

pinMode(RelayStart,OUTPUT);

digitalWrite(RelayStart, HIGH);

digitalWrite(RelayCapaciter, HIGH);

//Serial.println();

//Serial.println("Disconnecting previously connected WiFi");

WiFi.disconnect();

EEPROM.begin(512);

//Serial.println();

//Serial.println("Startup");

//Serial.println("Reading EEPROM ssid");

String esid;

for (int i = 0; i < 32; ++i) {

esid += char(EEPROM.read(i));

}

//Serial.println();

Serial.print("SSID: ");

Serial.println(esid);

//Serial.println("Reading EEPROM pass");

String epass = "";

for (int i = 32; i < 96; ++i) {

epass += char(EEPROM.read(i));

}

//Serial.print("PASS: ");

//Serial.println(epass);

WiFi.mode(WIFI_STA);

// WiFi.forceSleepWake(); // Ensure it's awake set it before wifi.begin()

// WiFi.setSleepMode(WIFI_NONE_SLEEP); // Disable sleep mode

if(ssid!="")

WiFi.begin(ssid, passphrase);

else

WiFi.begin(esid, epass);

if (waitForWiFiConnection())

{

Serial.println("Connected to WiFi");

Serial.println(WiFi.localIP());

}

else

Serial.println("Failed to connect to WiFi");

ESP.wdtEnable(10000); //set watchdog timer for 10 second

firebaseConnect(); //connecting to firebase

}

void firebaseConnect()

{

Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);

Firebase.reconnectWiFi(true);

fbdo.setBSSLBufferSize(1024, 1024);

fbdo.setResponseSize(1024);

if (!Firebase.beginStream(fbdo, commandpath))

{

Serial.println("------------------------------------");

Serial.println("Can't begin stream connection...");

Serial.println("REASON: " + fbdo.errorReason());

Serial.println("------------------------------------");

Serial.println();

}

Firebase.setString(fbdo, commandpath , String("OFF"));

Firebase.setString(fbdo, currentStatusPath , String("OFF"));

}

void loop()

{

ESP.wdtFeed();

//Serial.println(ESP.getFreeHeap());

//===============================================================================

if (IN_ST_MODE_FLAGE == true) //Current ST MODE

{

if (digitalRead(triggerPin) == LOW)

{

if (triggerStartTime == 0)

{ // If trigger pin just went low, start the timer

triggerStartTime = millis();

Serial.println("Trigger Pin Low");

}

else

if (millis() - triggerStartTime >= 3000)

{ // If trigger/flash button pressed more than 3 seconds than move to AP mode

WiFi.disconnect();

WiFi.softAP("GateController", ""); // Fixed AP name

IN_ST_MODE_FLAGE = false;

IN_AP_MODE_FLAGE = true;

Serial.println("Switched to AP mode");

}

else

triggerStartTime = 0; // Reset the timer if trigger pin goes high

if (WiFi.status() != WL_CONNECTED && IN_ST_MODE_FLAGE == true)

Serial.println("Not connected to WiFi");

if (!fbdo.httpConnected() && IN_ST_MODE_FLAGE == true)

{

Serial.println("Unable to connect firebase"); // if firebase connection failed then reconnect

firebaseConnect(); //reconnect to firebase;

}

/* if (!checkInternetConnection()) //check Internet working or not

Serial.println("No Internet.");

else

Serial.println("Internet Connected."); */

if (WiFi.status() == WL_CONNECTED && IN_ST_MODE_FLAGE == true)

{

String State = (fbdo.stringData());

if( State == "ON" && Last_Status=="OFF")

{

// Serial.print("--State ");

// Serial.println(State);

digitalWrite(RelayStart, LOW);

digitalWrite(RelayCapaciter, LOW);

delay(3000);

digitalWrite(RelayCapaciter, HIGH);

Last_Status="ON";

Firebase.setString(fbdo, currentStatusPath , String("ON"));

}

else

{

if( State == "OFF" && Last_Status=="ON")

{

//Serial.print("--State ");

// Serial.println(State);

digitalWrite(RelayStart, HIGH);

Last_Status="OFF";

Firebase.setString(fbdo, currentStatusPath , String("OFF"));

}

if (!Firebase.readStream(fbdo)){}

if (fbdo.streamAvailable()){}

}

//------------------------------------------------------------------------------

if (IN_ST_MODE_FLAGE == false) // Current AP MODE

{

//waitForWiFiConnection();

if (IN_AP_MODE_FLAGE == true)

{

Serial.println("IN AP Mode ");

launchWeb();

setupAP();

IN_AP_MODE_FLAGE = false; // Wapable lonnched

}

server.handleClient();

}

delay(10);

}

//===============================================================================

bool waitForWiFiConnection()

{

int c = 0;

//Serial.println("Waiting for WiFi to connect");

while (c < 80) {

if (WiFi.status() == WL_CONNECTED)

{

IN_ST_MODE_FLAGE = true;

return true;

}

delay(500);

Serial.print("*");

c++;

}

//Serial.println("\nWiFi connection timed out");

return false;

}

void handleRoot()

{

IPAddress ip = WiFi.softAPIP();

String ipStr = String(ip[0]) + '.' + String(ip[1]) + '.' + String(ip[2]) + '.' + String(ip[3]);

content = "<!DOCTYPE HTML>\r\n<html>ESP8266 WiFi Connectivity Setup ";

content += "<form action=\"/scan\" method=\"POST\"><input type=\"submit\" value=\"scan\"></form>";

content += ipStr;

content += "<p>";

content += st;

content += "</p><form method='get' action='setting'><label>SSID: </label><input name='ssid' length=32><input name='pass' length=64><input type='submit'></form>";

content += "</html>";

server.send(200, "text/html", content);

}

void setupAP()

{

WiFi.mode(WIFI_STA);

WiFi.disconnect();

delay(100);

int n = WiFi.scanNetworks();

//Serial.println("Scan completed");

if (n == 0)

Serial.println("No WiFi Networks found");

else {

//Serial.print(n);

Serial.println(" Networks found");

for (int i = 0; i < n; ++i) {

Serial.print(i + 1);

Serial.print(": ");

Serial.print(WiFi.SSID(i));

Serial.print(" (");

Serial.print(WiFi.RSSI(i));

Serial.print(")");

Serial.println((WiFi.encryptionType(i) == ENC_TYPE_NONE) ? " " : "*");

delay(10);

}

//Serial.println("");

st = "<ol>";

for (int i = 0; i < n; ++i) {

st += "<li>";

st += WiFi.SSID(i);

st += " (";

st += WiFi.RSSI(i);

st += ")";

st += (WiFi.encryptionType(i) == ENC_TYPE_NONE) ? " " : "*";

st += "</li>";

}

st += "</ol>";

delay(100);

WiFi.softAP("ESP-TEST", ""); // Set your desired AP name

//Serial.println("Initializing WiFi access point");

launchWeb();

//Serial.println("Over");

}

void handleSetting() {

String qsid = server.arg("ssid");

String qpass = server.arg("pass");

if (qsid.length() > 0 && qpass.length() > 0) {

//Serial.println("Clearing EEPROM");

for (int i = 0; i < 96; ++i) {

EEPROM.write(i, 0);

}

//Serial.println(qsid);

//Serial.println("");

//Serial.println(qpass);

//Serial.println("");

//Serial.println("Writing EEPROM ssid:");

for (int i = 0; i < qsid.length(); ++i) {

EEPROM.write(i, qsid[i]);

//Serial.print("Wrote: ");

//Serial.println(qsid[i]);

}

//Serial.println("Writing EEPROM pass:");

for (int i = 0; i < qpass.length(); ++i) {

EEPROM.write(32 + i, qpass[i]);

//Serial.print("Wrote: ");

//Serial.println(qpass[i]);

}

EEPROM.commit();

content = "{\"Success\":\"Saved to EEPROM... Reset to boot into new WiFi\"}";

statusCode = 200;

ESP.reset();

} else {

content = "{\"Error\":\"404 not found\"}";

statusCode = 404;

//Serial.println("Sending 404");

}

server.sendHeader("Access-Control-Allow-Origin", "*");

server.send(statusCode, "application/json", content);

}

void handleScan() {

content = "<!DOCTYPE HTML>\r\n<html><a href='/'>Go back</a></html>";

server.send(200, "text/html", content);

}

bool checkInternetConnection() {

WiFiClient client;

return client.connect("8.8.8.8", 53); // Try to connect to Google's DNS

}

void launchWeb() {

//Serial.println("");

if (WiFi.status() == WL_CONNECTED)

Serial.println("WiFi connected");

//Serial.print("Local IP: ");

//Serial.println(WiFi.localIP());

//Serial.print("SoftAP IP: ");

//Serial.println(WiFi.softAPIP());

server.on("/", HTTP_GET, handleRoot);

server.on("/scan", HTTP_GET, handleScan);

server.on("/setting", HTTP_GET, handleSetting);

server.begin();

//Serial.println("Server started");

}

Apache Cordova app issues

2021-11-07T00:22:00.005-07:00

Here I am sharing all the issues/errors which I get during Cordova mobile app development-

1-Call to undefined method mysqli_stmt::get_result

Solution: https://stackoverflow.com/questions/8321096/call-to-undefined-method-mysqli-stmtget-result

cpanel dispable mysqli and enable nd_mysqli

2- Server origin access issue (Unable to access API hosted on server)

v1=> .htaccess => added following lines

Header set Access-Control-Allow-Origin "*"

</IfModule>

3- Emulator : net not working.

First change DNS to 8.8.8.8 of the computer where avd running.

Now open android studio=> tools=>AVD manager=> select drop down arrow of the AVD(Emulator)=> click on "Cold Boot Now"

4- Add platform: cordova platform add android

cordova platform rm android

cordova platform add browser

5- Run app into emulator:

cordova build --emulator

cordova run android --emulator

To run in mobile-> cordova run or cordova run android

To browser cordova run browser

6- Biggest Issue:

i) Why am I seeing net::ERR_CLEARTEXT_NOT_PERMITTED errors in cordova 8/9.....?

ii) was unable to call API using jquery ajax : Error was cordova app ajax api call returning xhr.status 0

Solution: go to config.xml

<widget id="com.my.awesomeapp" version="1.0.0" xmlns="http://www.w3.org/ns/widgets"

xmlns:android="http://schemas.android.com/apk/res/android" xmlns:cdv="http://cordova.apache.org/ns/1.0">

this line already in config.xml but here you can see xmln:android not there so just copy xmlns:android="http://schemas.android.com/apk/res/android"

and past it there.

now past below <edit-config....>....</edit-config> into <plateform name="android"> ..../<platform> section.

<edit-config file="app/src/main/AndroidManifest.xml" mode="merge" target="/manifest/application">

</edit-config>

</platform>

for more details please check https://stackoverflow.com/questions/54752716/why-am-i-seeing-neterr-cleartext-not-permitted-errors-after-upgrading-to-cordo

7- Issue : if you want to use <script> in .html file then need to add follwoing

How to analyze windows event log

2021-11-06T23:50:00.002-07:00

Open windows event viewer-

1- Open Control Panel.

2- Click on Administrative Tools.

3- Now open Event Viewer.

In the console tree, expand Windows Logs, and then click System. The results pane lists individual system events.

Now before proceeding further we should know the event id of the event which we want to analyze. here we want to check system shut down, reboot, start etct so event id is given below-

Event ID 41: The system rebooted without cleanly shutting down first. This error occurs when the system stopped responding, crashed, or lost power unexpectedly.

Event ID 1074: Indicates that the shut down process was initiated by an app or user, or when a user initiates a restart or shutdown. Your computer records this event when an application forces your laptop to shut down or restart. This event also helps you know when a user restarted or shut down the computer from the Start menu or by using CTRL+ALT+DEL.

Event ID 6006 - The clean shut down event. This means Windows 10 was turned off correctly. It gives the message, “The Event log service was stopped.”

Event ID 6008 - Indicates a dirty/improper shutdown. Appears in the log when the previous shutdown was unexpected, e.g. due to power loss or BSoD (Bug check).you will see this event in your system log. It gives the message, “The previous system shutdown at time on date was unexpected.”

After this, we can find the particular event by Option "Filter Current logs" in the right side action tab and you can see all the logs with time for that particular event.

If you want to see more details about a specific event, in the results pane, click the event.

Oracle Network Adapter Could Not Establish The Connection Error

2021-06-17T02:10:00.005-07:00

The Network Adapter Could Not Establish The Connection Error in oracle.

Hey guys! Have you ever faced the TNS IO error saying “The network adapter could not establish the connection”? when you are trying to make a new connection in SQL Developer or logging on to the database using SQL*Plus editor. If yes then you are at the right place because here in this blog I am going to show you how you can solve this error.

So without further ado let’s proceed to solve this badass TNS error.

Step 1: Make sure your entries are correct

First of all to solve “The network adapter could not establish the connection” error, check whether you have entered the correct username and password as well as the correct Hostname and Port number. Though these are small things we cannot avoid them. After all “It’s the small things in a relationship that means the most.”

[bctt tweet=”How to solve “The network adapter could not establish the connection” error in just 2 steps” username=”RebellionRider”]

For the valid hostname and port number, you can check the Listener.ora if you have access to your server as the listener is a server process. In case you don’t have access to listener.ora file then you can check the tnsnames.ora file.

In case of Listener.ora file check for Host and Port entry in Listener tag for valid hostname and port number.

Listener.ora

And if you are using TNSnames.ora file for validating the hostname and port number then search for the entry which has the same name as your SID and then check for host and port number entry in that particular tag.

TNSnames.ora

Now try connecting. If this solves your problem then you can avoid the next step. But if “The network adapter could not establish the connection” error is still there, then don’t worry just follow the next step.

Step 2: Is your listener taking a rest?

If your problem is still there and you haven’t gotten rid of that nasty error then there is a possibility that your Listener is not running. To check whether Listener is up and running or not, simply open up your command prompt with Administrative privileges and Write

C:\> lsnrctl status

This command will show you the status of your listener. If the output of this command looks like the one shown in the picture below then it clearly means your listener is not running thus next what you have to do is to start the listener.

To start the listener you just have to write

C:\> lsnrctl start.

This will start your listener and most probably solve your problem.

Info Byte:
In case you are hav ing problems in starting your listener then try starting “OracleOraDb11g_home1TNSListener” windows service. For that open your Run Command and write services.msc this will open your service panel. Here search for the same and right click to start it.

Special thanks to Mr. Manish Sharma http://www.rebellionrider.com/ for above information.

Forget oracle database username or password

2021-06-17T01:15:00.004-07:00

Forget oracle database username or password

Recover oracle database username and password

Step-1: open sqlplus.

Step-2: type- connect / as sysdba and password will be blank so just enter.

Step-3: Now you can see SQL>

Step-4: To get all user type following query-

SQL> select username,password from dba_users;

now find the user which you have created from the shown list and reset password by following query-

SQL> alter user username identified by password;

Here username is the user for which you want to reset the password.

Create new user-

Step-1: open sqlplus.

Step-2: type- connect / as sysdba and password will be blank so just enter.

Step-3: Now you can see SQL>

Step-4 :To create new user type following query-

create user NewUserName identified by password

note: if you get "create user invalid common user or role name" error then just change the session by type following query-

alter session set "_ORACLE_SCRIPT"=true;

and try again to create user by step-4.

Step-5: Grant Previlage to oracle user (With DBA power)-

GRANT CONNECT, RESOURCE, DBA TO NewUserName;

To grant all role to user-

GRANT ALL PRIVILEGES TO NewUserName;

Export And Save Each Worksheet As Separate

2020-07-22T06:21:00.003-07:00

Export And Save Each Worksheet As Separate New Workbook In Excel

Open Visual basic editor by pressing Alt+F11
On project window at left side => right click on project => insert=>Module.
now paste below code.

Option Explicit

Sub SaveShtsAsBook()
Dim Sheet As Worksheet, SheetName$, MyFilePath$, N&
MyFilePath$ = ActiveWorkbook.Path & "\" & _
Left(ThisWorkbook.Name, Len(ThisWorkbook.Name) - 4)
With Application
.ScreenUpdating = False
.DisplayAlerts = False
' End With
On Error Resume Next '<< a folder exists
MkDir MyFilePath '<< create a folder
For N = 1 To Sheets.Count
Sheets(N).Activate
SheetName = ActiveSheet.Name
Cells.Copy
Workbooks.Add (xlWBATWorksheet)
With ActiveWorkbook
With .ActiveSheet
.Paste
.Name = SheetName
[A1].Select
End With
'save book in this folder
.SaveAs Filename:=MyFilePath _
& "\" & SheetName & ".xls"
.Close SaveChanges:=True
End With
.CutCopyMode = False
Next
End With
Sheet1.Activate
End Sub

Set CATALINA_HOME, JRE_HOME, JAVA_HOME in environment variable using command line

2020-04-26T14:10:00.002-07:00

To set CATALINA_HOME, JRE_HOME, JAVA_HOME in environment variable

To run apache tomcat server this is a basic requirement-

1- Open command Prompt=> Run as administrator

2- Now type below command one by one.
setx JAVA_HOME -m "Java/JDK_Installation_Directory_Path";
setx JRE_HOME -m "Java/JRE_Installation_Directory_Path";
setx CATALINA_HOME -m "Tomcat_Directory_Path/bin";

3-Now restart system.

4- To verify environment variable run following command one by one-
echo %JAVA_HOME%
echo %JRE_HOME%
echo %CATALINA_HOME%

Now run tomcat.(in case of installer)
or
In case of tomcat downloaded folder-
1- Open command Prompt=> Run as administrator
2- Go to tomcat directory/bin folder.
3- execute/run startup.bat
4- you will get a separate window which shows tomcat status.

Its ready to play.

Various error during maven configuration with java spring

2020-04-26T11:08:00.004-07:00

Q1- During project Creation or Maven Update or if Pom.xml showing any error or dependecy jar not loading then-

Solution: Go to User Profile Foler =>.m2=>delete .lastupate.

if you unable to find User Profile folder then follow below steps-

1-Open folder by running this text (without Quotes) in Search Explorer of Window “%USERPROFILE%.m2”.
2-After running above command, “m2” folder of maven will open. Now search for file (without Quotes) “*.lastUpdated”.
3-In this step, delete all the files found by running Step 2.
4-Now go to Eclipse project and select “Maven | Update Dependency” or “Maven | Update Project”
5-If you still facing error then close eclipse and delete .m2 folder and try again.

-----------------------------------------------------------------------------------------

Q2- Could not transfer artifact org.apache.maven.plugins:maven-surefire-plugin:pom:2.7.1 from/to central
or
ArtifactTransferException: Could not transfer artifact
or
How to create settings.xml

Solution: Create settings.xml file in User Profile Foler =>.m2 folder. ( if you are unable to fine user profile folder then see Q1 (above).

To create settings.xml file-> open notepad-> paste below code-> save as-> File Name- settings.xml. Save As Type- All and Save.

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
https://maven.apache.org/xsd/settings-1.0.0.xsd">
<localRepository>${user.home}/.m2/repository</localRepository>
<interactiveMode>true</interactiveMode>
<offline>false</offline>
</settings>

---------------------------------------------------------------------------------

Q3- tomcat:deploy: “Cannot invoke Tomcat manager: Connection refused”
Solution: Before deploying of project make sure following-
For tomcat7 or tomcat 8 do the following-

1- Project- pom.xml

<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
<configuration>
<url>http://localhost:8080/manager/text</url>
<path>/projectName</path>
<username>tomcat</username>
<password>tomcat</password>
</configuration>
</plugin>

2- TomcatDirectory\conf\ tomcat-users.xml: Add below line in

section

<role rolename="manager-gui"/>
  <role rolename="manager-status"/>
  <role rolename="manager-script"/>
  <role rolename="manager-jmx"/>
  <user username="tomcat" password="tomcat" roles="manger-gui,manager-status,manager-script,manager-jmx"/>

it will show like this-

Now run project and deploy it (Right Click on project=>Run as=>Run Configuration)

Gole:- clean install tomcat7:deploy (For first time deployment) and for next time use clean install tomcat7:redeploy.

Profile:-Leave Blank

Gole:-Default or path (if you have created settings.xml)

Create a maven project and Deloy maven project with tomcat

2020-04-26T05:40:00.002-07:00

In this tutorial we learn-
1- How to create Maven based Java web project.
2- How to deploy/run project with tomcat server.

First make sure your eclipse have installed maven plugin. if not then your need to install m2e-eclipse plugin in order to have this simple utility in Eclipse.

You can follow below link to install Maven plugin in eclipse-https://stackoverflow.com/questions/8620127/maven-in-eclipse-step-by-step-installation

1 Create Maven Project in STS ( Spring Tool Suite ).

1-Click File —> New —> Others menu, select Maven Project in the popup wizard dialog.
eclipse file new others maven project wizard dialog

2-Click Next button, check Create a simple project checkbox in the next dialog.

3-Input the spring project group id, artifact id and select packaging type with war in the next dialog.

4-Click Finish button to complete the wizard. In the left package explorer panel, you can see the project just created, the project name is just the artifact id.

5-There is an error in the pom.xml, the error message is “web.xml is missing and is set to true“, so copy below xml code into pom.xml between project xml tag.
<build>
<finalName>Deploy maven project to tomcat example</finalName>

       <plugins>
          <plugin>
             <artifactId>maven-war-plugin</artifactId>
             <version>2.3</version>
             <configuration>
               <failOnMissingWebXml>false</failOnMissingWebXml>
             </configuration>
          </plugin>
       </plugins>
</build>

6-Now right click the project name in left package explorer panel, click Maven —> Update Project menu item, then all the project error will disappear.

2. Deploy Maven Project To Tomcat.

First make sure following-
1- Tomcat is installed or have downloadd Tomcat Folder.
2-CATALINA_HOME (tomcat), JRE_HOME (jre) or JAVA_HOME (java) set in system environment veriable. (how to set environment veriable- http://hemantmenaria.blogspot.com/search/label/set%20catalina_home)
3- Need to start tomcat.

1-Before we can deploy eclipse maven project to tomcat, we need to add below user role in TOMCAT_HOME/conf/tomcat-users.xml file (Under <tomcat-users > section) as below, otherwise there will throw an unauthorized error during the maven project deploy process. Then we should restart tomcat server. When deploy war to tomcat in maven plugin, the role should be manager-scrip.

<!-- tomcat role is used to deploy maven project to tomcat in eclipse scripts.-->

<user username="admin" password="admin" roles="manager-gui"/>

2-Then add below xml in the pom.xml plugins section.

<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
<configuration>
<url>http://localhost:8080/manager/text</url>
<path>/DeployMavenToTomcat</path>

<update>true</update>

<username>tomcat</username>
<password>tomcat</password>
</configuration>
</plugin>

3-Right click the maven project, click Run As —> Run Configurations menu item.

4-Input clean install tomcat7:deploy in the Goals input text box.

5-Click Run button, when you see BUILD SUCCESS in the output console, that means the maven project has been deployed to tomcat server successfully.

6-Open a web browser, and input http://localhost:8080/manager/html, input admin / admin in the popup prompt. After you login, you can see DeployMavenToTomcat application in the application list

Convert existing Java project to Maven

2020-04-25T08:13:00.002-07:00

Convert existing Java or Spring project into Maven based Project-

Steps you need to follow-

1- Make sure your eclipse have installed maven plugin. if not then your need to install m2e-eclipse plugin in order to have this simple utility in Eclipse.

You can follow below link to install Maven plugin in eclipse-https://stackoverflow.com/questions/8620127/maven-in-eclipse-step-by-step-installation

2- Now In your eclipse just right click on Java Project and click Configure and you should see “Convert to Maven Project” option

3- You will see dialogue like this below. Just enter“Name” and you should be all set.

4- Now you can see a new file pom.xml in your project- A Project Object Model or POM is the fundamental unit of work in Maven. It is an XML file that contains information about the project and configuration details used by Maven to build the project. It also manages all the jar dependency required by your project.

5- Next, make the list of all dependency jar which you have configured in Java Build Path and add all jar dependency into pom.xml file.

6-To get maven jar dependency, go to https://mvnrepository.com/ (Maven website). Here search all jar one by one and select version.

7- Now copy the code mentioned in Maven tab (maven dependency code) and paste it into pom.xml under dependencies section as shown below.

8- One by one paste all the jar dependency in pom.xml.

9- All done, project has been converted into maven based project.

note : if you are getting any error in pom.xml then you need to update your maven. (Right click on project=> click on Maven=> Update Project; Make sure "Force Updateof Snapshots/Releases" is checked.)
--------------------------------------------------------------------------------------

Now How to compile and run the maven based project?

Step-1. Right click on project=> click on Maven=> Update Maven. Make sure "Force Update of Snapshots/Releases" is checked during project Update. (if done then skip it.)

Step-2 After updating Right click on project=> click on Run As=> Maven Install (Shown Below)

and done :)
Check on the console. if you get any compilation error like Build Failer ("no compiler is provided in this environment perhaps you are running on a jre"). then=>
Right Click on project=> Build Patah => Configure Build Path=>Select Library Tab=> Double Click on JRE System Library=>Now select Workspace default JRE option =>Finish & Apply.

Step-3 If you have faced any error in step-2 then again try to build by Right click on project=>Click on Run As=> Maven Clean and check console for a successful build.

Note:- During above steps if you still getting error or any issue or want to try all step again then first you need to delete .m2/repository from your eclipse working directory. (c:/user/username/.m2). Just close eclipse and delete .m2 folder and try again.

In case of any issue, you can watch below video-

Excel split data into multiple worksheets based on column

2017-12-07T01:11:00.002-08:00

Here VBA Code to split data into multiple worksheets based on selected column

If you have an excel sheet and want to split the data into individual multiple sheet based on column valued then the below code is best for you.

Open Visual basic editor by pressing Alt+F11
On project window at left side => right click on project => insert=>Module.
now paste below code. read comments and set your parameter.

Sub parse_data()
Dim lr As Long
Dim ws As Worksheet
Dim vcol, i As Integer
Dim icol As Long
Dim myarr As Variant
Dim title As String
Dim titlerow As Integer
vcol = 7 ''name of column on which basis you want to create saprate sheet
Set ws = Sheets("finalsheet") ''name of your master sheet which need to compile
lr = ws.Cells(ws.Rows.Count, vcol).End(xlUp).Row
title = "A1:V1" ''range of column which need to transfer into each individual sheet
titlerow = ws.Range(title).Cells(1).Row
icol = ws.Columns.Count
ws.Cells(1, icol) = "Unique"
For i = 2 To lr
On Error Resume Next
If ws.Cells(i, vcol) <> "" And Application.WorksheetFunction.Match(ws.Cells(i, vcol), ws.Columns(icol), 0) = 0 Then
ws.Cells(ws.Rows.Count, icol).End(xlUp).Offset(1) = ws.Cells(i, vcol)
End If
Next
myarr = Application.WorksheetFunction.Transpose(ws.Columns(icol).SpecialCells(xlCellTypeConstants))
ws.Columns(icol).Clear
For i = 2 To UBound(myarr)
ws.Range(title).AutoFilter field:=vcol, Criteria1:=myarr(i) & ""
If Not Evaluate("=ISREF('" & myarr(i) & "'!A1)") Then
Sheets.Add(after:=Worksheets(Worksheets.Count)).Name = myarr(i) & ""
Else
Sheets(myarr(i) & "").Move after:=Worksheets(Worksheets.Count)
End If
ws.Range("A" & titlerow & ":A" & lr).EntireRow.Copy Sheets(myarr(i) & "").Range("A1")
Sheets(myarr(i) & "").Columns.AutoFit
Next
ws.AutoFilterMode = False
ws.Activate
End Sub

=========================
now its time to run your code by pressing F5.
Done!

X-Frame-Options Header Not Set 'ClickJacking' attacks

2017-07-26T05:53:00.001-07:00

X-Frame-Options header is included in the HTTP response to protect against 'ClickJacking' attacks.

The X-Frame-Options header is used to indicate whether or not a website/browser should be allowed to open a page in frame or iframe.This will prevent website content embedded into other websites.
It protect against 'ClickJacking' attacks.

There are three options for X-Frame-Options:

SAMEORIGIN: This option will allow page to be displayed in frame on the same origin, means you can render the same website page into iframe/frame.
DENY: This option will prevent a page displaying in a frame or iframe, means no one website can render website page in frame/iframe.
ALLOW-FROM uri: This Option will allow page to be displayed only on the specified origin.if you want to allow render the page of website for a particular website then you can use this option.

Syntax:

IN HTML Page:- Type below code in head section:


       http-equiv="X-FRAME-OPTIONS" content="DENY">

IN PHP Page:-

========================================================
You can use any web developer tool to view Response headers and ensure you see

======================================================

Configuring Apache HOw to Check X-Frame-Option of a web page:
To configure Apache to send the X-Frame-Options for all pages, add below setting to your site as required:

Header always append X-Frame-Options SAMEORIGIN
Header set X-Frame-Options DENY
Header set X-Frame-Options "ALLOW-FROM https://example.com/"

======================================================

Cpanel Cron job for mysql datbase backup

2017-07-19T08:37:00.001-07:00

Cron Job: Cron Job is a time base task which will execute on a fixed time or interval (repeat after a time).

How to create a cron job in cpanel to take database backup.

Now Follow the Steps:

Step 1- First of all Create a file on your computer system and paste below code into file

[client]

user = yourCpanelUserName

password = "yourCpanelPassword"

host = localhost

save above file with .my.cnf and upload it to your server directory (like /home/Your_Domain_Directory/)

Step 2- Create a folder for backup with name of db_backup on server at same place ( /home/Your_Domain_Directory/)

Step 3-

1 -Go to Cpanel main page

2- Click on Cron Job

3- Enter email for notification regarding cron job.

4- Select Job Setting means frequency of your task /job execution.

5- Paste below line in command text box:

mysqldump --all-databases > /home/Your_Domain_Directory/db_backup/All_DB_Backup_$(date +'\%d-\%m-\%Y').sql

The above code will generate backup for your all databases in /home/Your_Domain_Directory/db_backup directory with the name of "All_DB_Backup_TodayDate". so if you set daily backup policy then it will create a backup file with current date without overriding the same file.

if you want to take backup of a particular database then at the place of --all-database you can write the name of the particular database.

Step 4 - Finally click on Add Crone Job button to save it.

Step 5 - Go to the folder /home/Your_Domain_Directory/db_backup to check your datbase backup.

httpd-xampp.conf: How to allow access to an external IP or another computer IP to mysql

2017-06-27T07:23:00.001-07:00

Access Xampp mysql from another computer:-

Open your xampp folder go to =>apache=>conf=>extra=>httpd-xampp.conf

copy below cod and past it into httpd-xampp.conf file

// How to allow a particular IP to access



    Require local
    Require ip 10.0.0.1
ErrorDocument 403 /error/XAMPP_FORBIDDEN.html.var

=====================

Note: Write the remote IP at the place of 10.0.0.1

=======================================

// How to allow anyone to access which is not safe.


    # Require local
    Require all granted
ErrorDocument 403 /error/XAMPP_FORBIDDEN.html.var

Send data from Java to PHP via Post

2015-12-03T02:23:00.000-08:00

    Here an interface between a Java and a PHP application, through we can transfer data between the two applications. Using below java code we can generate a POST request to transfer data from JAVA to PHP.

         try {
                // open a connection to the site where script written
                URL url = new URL("http://www.domainname.com/yourphppage.php");
                URLConnection con = url.openConnection();
                // activate the output
                con.setDoOutput(true);
                PrintStream ps = new PrintStream(con.getOutputStream());
                // send your parameters to your site
                ps.print("firstKey=firstValue");
                ps.print("&secondKey=secondValue");

                // we have to get the input stream in order to actually send the request
                con.getInputStream();

                // close the print stream
                ps.close();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

    We can use more complex data like array to send multiple parameters and values and In your PHP script, you can get the values like this:

    foreach ($_POST as $key => $value) {
        switch ($key) {
            case 'firstKey':
                $firstKey = $value;
                break;
            case 'secondKey':
                $secondKey = $value;
                break;
            default:
                break;
        }
    }

Enable SMTP Authentication on cpanel

2014-09-09T11:28:00.001-07:00

How do I add Email Authentication (DKIM / SPF / Text records)

To combat spam, or unwanted email, most ISPs (Internet Service Providers) and email providers (e.g. Gmail, Yahoo, Hotmail) employ sophisticated spam filters that are regularly updated. Whilst this is a good thing, it can also mean authentic emails can incorrectly get marked as spam.

Email Authentication is the effort to equip outgoing messages of the email transport system with enough verifiable information, so that recipients can recognize the nature of each incoming message automatically.

DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message that is in transit. The organization is a handler of the message, either as its originator or as an intermediary. Their reputation is the basis for evaluating whether to trust the message for further handling, such as delivery. Technically DKIM provides a method for validating a domain name identity that is associated with a message through cryptographic authentication.
Further reading: http://www.dkim.org/

Sender Policy Framework (SPF) is an open standard specifying a technical method to prevent sender address forgery. More precisely, SPF protects the envelope sender address, which is used for the delivery of messages.
Further reading: http://www.openspf.org/

Whilst no system is foolproof, agreed standards do exist and in most circumstances, there is no need to change the default settings on the Purple Dog server. You are advised to contact us first unless you are certain of what you are doing.
Records can be modified by logging in to you hosting account cpanel (e.g. www.example.com/cpanel) and navigating to email > email authentication.

=================================

Set up DKIM
DKIM helps verify the sender and integrity of a message. It allows an email system to prove that a message was not altered during transit (meaning it is not forged), and that the message came from the specified domain.

To use DKIM, click Enable.

To disable DKIM, click Disable.

Note: If a warning is displayed claiming cPanel is unable to verify that the server is an authoritative nameserver for the specified domain name and either of the following scenarios is true, then please ignore it.

The server has been changed to be the authoritative DNS server for the domain name, but the change has not yet propagated.

The server does not view itself as the authoritative DNS server, but outside servers do view it as authoritative.

Set up SPF

This function attempts to prevent spammers from sending email while forging your domain’s name as the sender (spoofing). This authentication function works by adding IP addresses to a list, specifying computers that are authorized to send mail from your domain(s). It verifies that messages sent from your domain(s) are coming from the listed server, reducing the amount of backscatter you receive.

To use SPF, click Enable.

To disable SPF, click Disable.

Note: If a warning is displayed claiming cPanel is unable to verify that the server is an authoritative nameserver for the specified domain name and either of the following scenarios is true, then please ignore it.

The server has been changed to be the authoritative DNS server for the domain name, but the change has not yet propagated.

The server does not view itself as the authoritative DNS server, but outside servers do view it as authoritative.

Advanced Settings
This section includes a number of ways to configure SPF authentication. The available options are:

Additional Hosts that send mail for your domains (A): The additional hosts specified here are automatically approved to send mail from your domain(s). You may add and remove hosts using the appropriate buttons.

Additional MX servers for your domains (MX): MX entries specified here are able to send mail from your domain(s).

Additional Ip blocks for your domains (IP4): IP addresses approved to send mail from your domain(s). Your server's main IP address is automatically included in this list. If you add IP addresses, you must use CIDR notation. (Example: 192.168.0.1/32)

Include List (INCLUDE): This feature allows you to specify additional hosts to include in your SPF settings. This is useful when sending mail with another service.

All Entry (ALL): If you select this option, the system will exclude domains not included in the lists defined above.

Overwrite Existing Entries: If you select this option, the system will overwrite existing SPF entries.

Unable to verify that this server is an authoritative name server for

2014-09-09T11:23:00.000-07:00

cpanel unable to verify authoritative nameserver

Hello

That message typically indicates the use of external name servers for the domain name associated with the account. Can you modify it's name servers at the registrar so it uses the cPanel server for hosting the DNS?

Disable right click option on web page

2014-07-22T11:03:00.000-07:00

File upload in java web through ajax Asynchronous

2014-05-12T00:36:00.001-07:00

DOWNLOAD

File upload process involves data to be sent from client side to server, in html terms this means submitting form to server side method that gets the file from request object and saves it to the server. Most of the time, it is desirable to implement file upload in ajax way without refreshing the whole page while updating the user on the progress.

It is a known fact that, it is not possible to do AJAX file uploads to server using $.ajax or XMLHttpRequest since jquery or javascript does not support file uploads for security reasons. We are now left out with two options/workarounds, to use flash or to use hidden iframe. Flash depends on a plugin to be installed on the user's browser which some people ans companies don't allow. So, out of the two options, the best option is to go for hidden iframe solution. This blog post contains an excellent article on how to do this with plain javascript.

To make the job more easier, let us use this jQuery plugin called jQuery.AjaxFileUpload.js which exactly implements the hidden iframe technique behind the scenes along with progress update and cancelling options. The logic is simple, instead of submitting the form to the server which would cause a postback, we submit the contents of the form to an iframe that is created dynamically and let the iframe communicate with the server, once the upload is complete - iframe sends the response back to the form. Steve explains this technique here in a very neat manner, so I don't want to repeat this here again.

To handle file upload in the server side, let us use Apache Commons File Upload library that makes the job very simple and easy.

1. Download all the required scripts and libraries,

2. Create a dynamic web project in Eclipse. Add the jar files to WEB-INF/lib directory and script files to WebContent folder.

2. Create a jsp file in WebContent and copy paste the below code,

01<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

02    pageEncoding="ISO-8859-1"%>

03http://www.w3.org/TR/html4/loose.dtd

04 <html>

05 <head>

`06`	`<meta` `http-equiv="Content-Type"` `content="text/html; charset=ISO-8859-1">`

`07`	`<title>Asynchronous file Upload in Java Web Application</title>`

`08`	`<script` `src="jquery-1.8.2.js"></script>`

`09`	`<script` `src="jquery.ajaxfileupload.js"></script>`

`10`	`<script` `language="Javascript">`

`11`	`$(document).ready(function(){`

`12`	`$('input[type="file"]').ajaxfileupload({`

`13`	`'action': 'UploadFile',`

`14`	`'onComplete': function(response) {`

`15`	`$('#upload').hide();`

`16`	`alert("File SAVED!!");`

17 },

`18`	`'onStart': function() {`

`19`	`$('#upload').show();`

20 }

21 });

22 });

`23`	`</script>`

24 </head>

25 <body>

26 <form>

27 <div>

`28`	`<input` `type="file"` `name="datafile"` `/>`

29

`30`	`<div` `id="upload"` `style="display:none;">Uploading..</div>`

31 </div>

32 </form>

33 </body>

34 </html>

Note that I have referenced jquery files in the head section of the html. The execution of script is very simple, whenever a file is selected using the file browse input, the script gets fired and submits the selected file to the servlet called 'UploadFile'. The action parameter takes the servlet url which handles the file upload logic in the server side. The onStart and onComplete methods are fired while the file starts to upload and after successful completion of file upload. I have used these methods to show file upload progress to the user.

3. Now let us use Apache Commons Fileupload library to handle file upload in the server side. Create a servlet and place the below code in it.

01import java.io.IOException;

02import javax.servlet.ServletException;

03import javax.servlet.annotation.WebServlet;

04import javax.servlet.http.HttpServlet;

05import javax.servlet.http.HttpServletRequest;

06import javax.servlet.http.HttpServletResponse;

07 

08import java.io.File;

09import java.util.Iterator;

10import java.util.List;

11 

12import org.apache.commons.fileupload.FileItem;

13import org.apache.commons.fileupload.FileItemFactory;

14import org.apache.commons.fileupload.FileUploadException;

15import org.apache.commons.fileupload.disk.DiskFileItemFactory;

16import org.apache.commons.fileupload.servlet.ServletFileUpload;

17/**

18 * Servlet implementation class UploadFile

19 */

20@WebServlet("/UploadFile")

21public class UploadFile extends HttpServlet {

22 private static final long serialVersionUID = 1L;

23 

24    /**

25     * Default constructor. 

26     */

27    public UploadFile() {

28        // TODO Auto-generated constructor stub

29    }

30 

31 /**

32  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

33  */

34 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

35  // TODO Auto-generated method stub

36 }

37 

38 /**

39  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

40  */

41 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

42    boolean isMultipart = ServletFileUpload.isMultipartContent(request);

43     

44         if (isMultipart) {

45          // Create a factory for disk-based file items

46          FileItemFactory factory = new DiskFileItemFactory();

47 

48          // Create a new file upload handler

49          ServletFileUpload upload = new ServletFileUpload(factory);

50   

51             try {

52              // Parse the request

53     List /* FileItem */ items = upload.parseRequest(request);

54     Iterator iterator = items.iterator();

55                 while (iterator.hasNext()) {

56                     FileItem item = (FileItem) iterator.next();

57                     if (!item.isFormField()) {

58                         String fileName = item.getName();  

59                         String root = getServletContext().getRealPath("/");

60                         File path = new File(root + "/uploads");

61                         if (!path.exists()) {

62        boolean status = path.mkdirs();

63                         }

64   

65                         File uploadedFile = new File(path + "/" + fileName);

66                         System.out.println(uploadedFile.getAbsolutePath());

67                         item.write(uploadedFile);

68                     }

69                 }

70             } catch (FileUploadException e) {

71                 e.printStackTrace();

72             } catch (Exception e) {

73                 e.printStackTrace();

74             }

75         }

76 }

77 

78}

4. Now the last step is to map the servlet to the action url we have used in index.jsp file as shown below,

01<web-app>

02  <display-name>AjaxFileUpload</display-name>

03  <servlet>

04  <servlet-name>UploadFile</servlet-name>

05  <servlet-class>com.programmingfree.fileupload</servlet-class>

06 </servlet>

07 <servlet-mapping>

08  <servlet-name>UploadFile</servlet-name>

09  <url-pattern>/UploadFile</url-pattern>

10 </servlet-mapping>

11</web-app>

That is all! Now run the application in Tomcat server and upload a file to see how it gets uploaded without refreshing the whole page.

Once the file is uploaded,

Connect two computer Using cross cable

2014-01-07T21:42:00.001-08:00

1: Make sure both computers are turned off.
2: Plug each end of the crossover cable into a network port on the back of each computer.

3: Turn both computers on (it does not matter which one you turn on first).
4: Sign-in to Windows on both computers, as you normally do.
5: Wait until both computers have fully loaded Windows and all startup programs (your mouse pointer will be the normal arrow shape and the programs that load in the system tray (usually located at the bottom right side of the screen, to the left of the time-clock) will all be there when the system is ready to use for configuration).

6. Select one of the computers to complete the rest of the process.

7. Open The Network and Sharing Centre. Click "Start," then "Control Panel," then "Network and Internet." Lastly, click "Network and Sharing Centre."

8. Double click the "Unidentified Network" icon.

If you have more than one network, this icon will be identified as "multiple networks."

9. In Network, click the information bar. Next, click on "Turn on network discovery and file sharing." If you are prompted for a password or confirmation, type it in or provide confirmation.

Note: Both PC Should be on the same network. (or you can set ip address manually like: 1st PC- 10.68.2.20, 2nd PC- 10.68.2.21. with same Subnet 255.255.255.0

Download a file in jsp

2014-01-07T21:19:00.000-08:00

<%@ page import="java.util.*,java.io.*"%>

<%

    File f = new File ("filePahtNeedToDownload"); //read file name.
    /* set content type ( word,excel,pdf,txt..etc) here we try for a pdf file */
    response.setContentType ("application/pdf");
    //setting header and the Name by which user will save the file.
    response.setHeader ("Content-Disposition", "attachment; filename=\"DownloadfileName.pdf\"");

    //retrive file name
    String name = f.getName().substring(f.getName().lastIndexOf("/") + 1,f.getName().length());


        InputStream in = new FileInputStream(f);
        ServletOutputStream outs = response.getOutputStream();


        int bit = 256;
        int i = 0;
        try {
            while ((bit) >= 0) {
                bit = in.read();
                outs.write(bit);
            }

        } catch (IOException ioe) {
            ioe.printStackTrace(System.out);
        }
        outs.flush();
        outs.close();
        in.close();
%>

Remove Shortcut Virus from Pen drive or Memory Card

2014-01-07T21:18:00.000-08:00

Open command prompt and type this command.
Note: here "g:" is drive on which you want to perform operation, so at the place of "g" write your drive label.

attrib -h -r -s /s /d g:\.

Eclipse “Failed to load JNI shared library”

2013-07-19T03:24:00.001-07:00

Problem: When I try opening Eclipse, a pop-up dialog states:

Failed to load the JNI shared library "C:/JDK/bin/client/jvm.dll"`.

Following this, Eclipse force closes.

Solution:

Working pairings of OS, JDK and Eclipse:

32-bit OS - 32-bit JDK - 32-bit Eclipse (32-bit only)
64-bit OS - 32-bit JDK - 32-bit Eclipse
64-bit OS - 64-bit JDK - 64bit Eclipse (64-bit only)

I had several JDKs and JREs installed.
Each of them had their own entry in the PATH variable, all was working more or less.
Judging from the PATH variables, some installations were completely useless, since they were never used. Of course, the "inactive" Javas could be referenced manually from within Eclipse if I needed, but I never did that, so I really did not need them. (At least I thought so at that time...)
I cleaned up the mess, deinstalled all current Java's, installed only JDK + JRE 1.7 64-bit.
One of the Eclipse 'installations' failed afterwards with the Failed to Load the JNI shared Library and a given path relative to the fresh installed JDK where it thought the jvm.dll to be.
The failing Eclipse was the only one of all my IDEs that was still a 32-bit version on my otherwise all-64-bit setup.
Adding VM arguments, like so often mentioned, in the eclipse.ini was no use in my case (because I had only the wrong JDK/JRE to relate to.)
I was also unable to find out how to check if this Eclipse was a 32-bit or 64-bit version (I could not look it up in the Task Manager, since this Eclipse 'installation' would not start up. And since it had been a while since I had set it up, I could not remember its version either.)
In case you use a newer JDK and a older JRE you might be in for trouble, too, but then it is more likely a java.lang.UnsupportedClassVersionError appears, IIRC.

2013-04-10T05:51:00.002-07:00

// How to send an email by Java application using Gmail/ Yahoo/ Hotmail

import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class sendmail {
public static void main(String[] args) {


            try{
                String host = "smtp.gmail.com";
                String from = "from@gmail.com";
                String pass = " njkgyddddshqd "; //if you are getting any error related to authentication use application specific password here.
                Properties props = System.getProperties();
                props.put("mail.smtp.starttls.enable", "true"); // added this line
                props.put("mail.smtp.host", host);
                props.put("mail.smtp.user", from);
                props.put("mail.smtp.password", pass);
                props.put("mail.smtp.port", "587");
                props.put("mail.smtp.auth", true);

                String[] to = {"to@gmail.com"}; // added this line

                Session session = Session.getDefaultInstance(props, null);
                MimeMessage message = new MimeMessage(session);
                message.setFrom(new InternetAddress(from));

                InternetAddress[] toAddress = new InternetAddress[to.length];

                // To get the array of addresses
                for( int i=0; i < to.length; i++ ) { // changed from a while loop
                    toAddress[i] = new InternetAddress(to[i]);
                }
                System.out.println(Message.RecipientType.TO);

                for( int i=0; i < toAddress.length; i++) { // changed from a while loop
                    message.addRecipient(Message.RecipientType.TO, toAddress[i]);
                }
                message.setSubject("sending in a group");
                message.setText("Welcome to JavaMail");
                Transport transport = session.getTransport("smtp");
                transport.connect(host, from, pass);
                transport.sendMessage(message, message.getAllRecipients());
                transport.close();
            }catch (MessagingException mex) {
                mex.printStackTrace();
            }
}
}

/*********************************************/

if you are getting any type of error then read below carefully

My client isn't accepting my username and password

We suggest making some adjustments in your mail client's settings so you aren't always prompted to enter your username and password. Please check the following settings in your mail client:

Make sure that you've entered your full email address (e.g. username@gmail.com)
Re-enter your password to ensure that it's correct. Keep in mind that passwords are case-sensitive.
Make sure your mail client isn't set to check for new mail too often. If your mail client checks for new messages more than once every 10 minutes, your client might repeatedly request your username and password.

Now, please follow the steps below to resolve the problem:

Open your web browser and sign in to Gmail at http://mail.google.com/mail. If you see a word verification request, type the letters in the distorted picture and finish signing in.
Close your browser and try accessing your messages in your email client again.
If you're still having problems, visit http://www.google.com/accounts/DisplayUnlockCaptcha and sign in with your Gmail username and password. If necessary, enter the letters in the distorted picture.
Click Continue.
Restart your mail client and try accessing messages in your email client again.

Note: use that application specific password at the place of original password of sender password.

read more on : http://support.google.com/mail/answer/14257

How to embed images in HTML mail using JavaMail

2012-11-03T01:51:00.001-07:00

/* How to embed images in HTML mail using JavaMail */
// Create message

Message message = new MimeMessage(session);
message.setFrom(new InternetAddress(from));
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to, false));
message.setSubject(subject);

// Add html content
// Specify the cid of the image to include in the email

String html = "Test email ";
Multipart mp = new MimeMultipart();
MimeBodyPart htmlPart = new MimeBodyPart();
htmlPart.setContent(html, "text/html");
mp.addBodyPart(htmlPart);

// add image in another part

MimeBodyPart imagePart = new MimeBodyPart();
DataSource fds = new FileDataSource(imagePath);
imagePart.setDataHandler(new DataHandler(fds));
// assign a cid to the image
imagePart.setHeader("Content-ID", "my-image-id");
mp.addBodyPart(imagePart);

message.setContent(mp);

// Send the message

Transport.send(message);

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// How to send an email by Java application using Gmail/ Yahoo/ Hotmail

if you are getting any type of error then read below carefully

My client isn't accepting my username and password

How to embed images in HTML mail using JavaMail

attrib -h -r -s /s /d g:\.