How to upload a screenshot using html2canvas?

Question

Using html2canvas how can I save a screen shot to an object? I\'ve been exploring the demos, and see that the function to generate the screenshot is generated as follows:

Answer 1

//Here I am using html2Canvas to capture screen and Java websockets to transfer data to server
//Limitation:Supported on latest browsers and Tomcat
Step1)Client Side : webSock.html  
   
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Send MSG




Step2)Server Side   
File 1)   
package Arun.Work;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

import javax.servlet.http.HttpServletRequest;

import org.apache.catalina.websocket.MessageInbound;
import org.apache.catalina.websocket.WsOutbound;

/**
 * Need tomcat-koyote.jar on class path, otherwise has compile error
 * "the hierarchy of the type ... is inconsistent"
 * 
 * @author Arun
 * 
 */
public class MyInBound extends MessageInbound {

    private String name;

    private WsOutbound myoutbound;

    private String targetLocation;

    public MyInBound(HttpServletRequest httpSerbletRequest, String targetLocation) {
        this.targetLocation = targetLocation;
    }

    @Override
    public void onOpen(WsOutbound outbound) {
        System.out.println("Web Socket Opened..");
        /*this.myoutbound = outbound;
        try {
            this.myoutbound.writeTextMessage(CharBuffer.wrap("Web Socket Opened.."));

        } catch (Exception e) {
            throw new RuntimeException(e);
        }*/

    }

    @Override
    public void onClose(int status) {
        System.out.println("Close client");
        // remove from list
    }

    @Override
    protected void onBinaryMessage(ByteBuffer arg0) throws IOException {
        System.out.println("onBinaryMessage Data");
        try {
            writeToFileNIOWay(new File(targetLocation), arg0.toString() + "\n");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {

            //this.myoutbound.flush();
        }
    }// end of onBinaryMessage

    @Override
    protected void onTextMessage(CharBuffer inChar) throws IOException {
        System.out.println("onTextMessage Data");
        try {

            writeToFileNIOWay(new File(targetLocation), inChar.toString() + "\n");

        } catch (Exception e) {
            e.printStackTrace();
        } finally {

            //this.myoutbound.flush();
        }
    }// end of onTextMessage

    public void writeToFileNIOWay(File file, String messageToWrite) throws IOException {
        System.out.println("Data Location:"+file+"            Size:"+messageToWrite.length());
        //synchronized (this){

          byte[] messageBytes = messageToWrite.getBytes();
          RandomAccessFile raf = new RandomAccessFile(file, "rw");
          raf.seek(raf.length());
          FileChannel fc = raf.getChannel();
          MappedByteBuffer mbf = fc.map(FileChannel.MapMode.READ_WRITE, fc.position(), messageBytes.length);
          mbf.put(messageBytes);
         fc.close();
        //}


    }//end of method

    /*
     * //Working Fine public void writeToFileNIOWay(File file, String
     * messageToWrite) throws IOException { byte[] messageBytes =
     * messageToWrite.getBytes(Charset.forName("ISO-8859-1")); RandomAccessFile
     * raf = new RandomAccessFile(file, "rw"); raf.seek(raf.length());
     * FileChannel fc = raf.getChannel(); MappedByteBuffer mbf =
     * fc.map(FileChannel.MapMode.READ_WRITE, fc.position(),
     * messageBytes.length);
     * 
     * mbf.put(messageBytes); fc.close(); }
     */
}


File 2)     
package Arun.Work;

import java.io.File;
import java.util.concurrent.ConcurrentHashMap;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.apache.catalina.websocket.StreamInbound;
import org.apache.catalina.websocket.WebSocketServlet;

/**
 * WebSocketServlet is contained in catalina.jar. It also needs servlet-api.jar
 * on build path
 * 
 * @author Arun
 * 
 */
@WebServlet("/wsocket")
public class MyWebSocketServlet extends WebSocketServlet {

    private static final long serialVersionUID = 1L;

    // for new clients, 
    private static ConcurrentHashMap clients = new ConcurrentHashMap();

    @Override
    protected StreamInbound createWebSocketInbound(String protocol, HttpServletRequest httpServletRequest) {

        // Check if exists
        HttpSession session = httpServletRequest.getSession();

        // find client
        StreamInbound client = clients.get(session.getId());
        if (null != client) {
            return client;

        } else {
            System.out.println(" session.getId() :"+session.getId());
            String targetLocation = "C:/Users/arsingh/Desktop/AnupData/DATA/"+session.getId();
            System.out.println(targetLocation);
            File fs=new File(targetLocation);
            boolean bool=fs.mkdirs();
            System.out.println(" Folder created :"+bool);
            client = new MyInBound(httpServletRequest,targetLocation+"/Output.txt");
            clients.put(session.getId(), client);
        }

        return client;
    }

    /*public StreamInbound getClient(String sessionId) {
        return clients.get(sessionId);
    }

    public void addClient(String sessionId, StreamInbound streamInBound) {
        clients.put(sessionId, streamInBound);
    }*/
}