Combining dynamic. NET Twain and jetty for Web-based TWAIN file scanning

Web page TWAIN scanning is implemented through a combination of techniques, see the Flowchart:

Preparatory work

Read:

• How to call the C # interface in a Java application via Jni4net

• Use jetty to build Java Websocket Server for image transmission

How to Run

1. Run Java application in Eclipse, select Uimain
   When this window is started, the Websocket server has been initialized for completion.

• Load: Load local picture

• Send: Push the picture to the Web client

• Scan: Scans files via scanner, automatically sends images to web client

2. Select a scanner source in Chrome
   

3. Show TWAIN scanned file images
   

Twain Web Scanning Process parsing

Start by importing all the relevant libraries (DLLs & jars) into the Eclipse project:

Combining the code for two articles in preparation, create a class sourcemanager:

Package com.data;import java.awt.event.actionevent;import java.awt.event.actionlistener;import  java.io.file;import java.util.arraylist; import javatwain. Dotnetscanner;import javatwain. Ijavaproxy;import javatwain. inativeproxy; import javax.swing.timer; import com.server.wshandler;import  com.util.imageutil; import net.sf.jni4net.bridge; public class sourcemanager  implements inativeproxy {    private ijavaproxy mscanner;     private String[] mSources;    private ScanAction  Mscanaction;     public sourcemanager ()  {         inittwain ();         mscanaction = new  scanaction ();     }     private void inittwain ()  {        try {             bridge.init ();             Bridge.loadandregisterassemblyfrom (New java.io.file ("Libs\\jni\\javatwain.j4n.dll"));         }        catch  (Exception e)  {            e.printstacktrace ();         }         mscanner  = new dotnetscanner ();         Mscanner.registerlistener (This);        msources =  Mscanner.getsources ();    }     public string[]  Getsources ()  {        rEturn msources;    }     public synchronized void  acquireimage (Int index)  {        mscanaction.setindex ( index);         mscanaction.start ();    }       @Override     public boolean notify (String message,  string value)  {        ArrayList<WSHandler>  sessions = wshandler.getallsessions ();         for   (wshandler session : sessions)  {             session.sendimage (Imageutil.getimagebytes (New file (value)));         }         return true;     }  &nbsP;  public class scanaction {        private  int mindex;        private int mdelay =  1;        private Timer mTimer;          public scanaction ()  {             mtimer = new timer (Mdelay, mtaskperformer);             mtimer.setrepeats (False);         }         private actionlistener  mtaskperformer = new actionlistener ()  {              @Override              public void actionperforMed (actionevent evt)  {                 mscanner.acquireimage (Mindex);                 actionlistener taskperformer = new actionlistener ()  {                      @Override                      public void actionperformed (ACTIONEVENT&NBSP;EVT)  {                          mscanner.closesource ();                     }                 };                 int delay = 1;                  timer timer = new timer (delay,  Taskperformer);                 timer.setrepeats (False);                 timer.start ();             }         };         public  void setindex (Int index)  {             mIndex = index;        }          public&nbSp;void start ()  {             Mtimer.start ();         }    }}

The Java Websocket server communicates with the JavaScript client through JSON.

To send JSON data using Java creation:

Jsonobject jsonobj = new Jsonobject (); Jsonarray Jsonarray = new Jsonarray (); string[] sources = msourcemanager.getsources (), if (sources! = null) {for (String source:sources) {Jsonarray.    Add (new jsonprimitive (source)); }} jsonobj.add (Msg.msg_sources, Jsonarray); String s = jsonobj.tostring (); try {session.getremote (). sendstring (s);} catch (IOException e) {//TODO auto-generated catch block E.printstack Trace ();}

Parsing JSON data using Java parsing:

Public void onmessage (string message)  {         Jsonparser parser = new jsonparser ();         Boolean isjson = true;        jsonelement element  = null;        try {             element =  parser.parse (message);         }        catch  (jsonparseexception  e)  {            system.out.println (" exception:  " + e);             isjson = false;        }          if  (isjson&Nbsp;&& element != null)  {             jsonobject obj = element.getasjsonobject ();             element = obj.get (msg.msg_message);             if  (element != null)  {                 switch  ( Element.getasstring ())  {                 case Msg.MSG_SOURCE:                     int index = obj.get (Msg.MSG_INDEX). Getasint ();                     msourcemanager.acquireimaGE (Index);                     break;                 }            }         }         system.out.println (" message:  " + message);     }

Use JavaScript to create a send JSON data:

var json = {};json. Message = Msg_source;json. Index = I;var msg = json.stringify (JSON); Ws.send (msg);

Parsing JSON data using JavaScript parsing:

Ws.onmessage = function (evt) {var data = Evt.data;        var json = json.parse (data);        var value = json[msg_sources];    Showsources (value); }

Create a class scanaction, where you create a Timerthat runs in the UI thread to handle the scan event:

public class scanaction {        private int  mindex;        private int mdelay = 1;         private Timer mTimer;          public scanaction ()  {             mtimer = new timer (Mdelay, mtaskperformer);             mtimer.setrepeats (false);         }          private actionlistener mtaskperformer =  new actionlistener ()  {             @Override             public void  Actionperformed (ActionevenT EVT)  {                 mscanner.acquireimage (Mindex);                 actionlistener taskperformer = new actionlistener ()  {                       @Override                      public void actionperformed (ACTIONEVENT EVT)  {                          mscanner.closesource ();                     }                 };                 int delay = 1;                  timer timer = new timer (Delay, taskperformer);                 timer.setrepeats ( False);                 Timer.start ();            }         };         public void  Setindex (Int index)  {            mindex  = index;        }          public void sTart ()  {            mtimer.start ();         }    }

Once the data scan is complete, it can be sent to the Web page:

public boolean Notify (String message, String value) {arraylist<wshandler> sessions = Wshandler.getallsession        S ();        for (Wshandler session:sessions) {session.sendimage (imageutil.getimagebytes (new File));    } return true; }