Java.lang.reflect.InnvokationTargetException

Question

Hello everybody,
I am getting following error logs while executing my swing application.
java.lang.reflect.InnvokationTargetException
at sun.reflect.delegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Mehod:java:324)
I am trying to call some class's method using reflection principle.
All values of acces modifier, return type, method name, args are correct at run time. I don't understand why i am getting this error.
Can anybody please help me.
Thanks and regards
Girish Varde

Answer 1

I would say that this sentence is rather confusing since you get the exception nonetheless.The sentence means when I am in debug mode and check value of the actual class whose method is called, the class value is correct. It's not that the class whose method I am calling does not exist.
First I give the reference error log which you can use to locate at what point the exception is thrown.
java.lang.reflect.InvocationTargetException
     at sun.reflect.GeneratedMethodAccessor74.invoke(Unknown Source)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:324)
     at com.apsiva.commframework.server.Communicator.processRequest(Communicator.java:45)
     at com.apsiva.commframework.server.CommunicationServlet.processRequest(CommunicationServlet.java:92)
     at com.apsiva.commframework.server.CommunicationServlet.doPost(CommunicationServlet.java:30)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:763)
public class Communicator implements java.io.Serializable{
     public static final String DECENTRALIZED_MODE = "decentralizedMode";
     //applicationMode could be localMode or distributedMode or decentralizedMode
     public static final String DISTRIBUTED_MODE = "distributedMode";
     public static final String LOCAL_MODE = "localMode";
      * Communicator constructor comment.
     public Communicator() {
          super();
public Object processRequest(Request request) throws java.lang.Exception {
     Object obj = null;
     try
          String str = request.getActionCode();
          System.out.println("Printing str : " + str);
          if (str == null)
               return null;
          Class cls = ActionCodes.class;
          Field f = cls.getField(str);
          String actionClassName = (String)f.get(null);
          if (actionClassName == null)
               return null;
          cls = Class.forName(actionClassName);
          Object actionObj = cls.newInstance();
          System.out.println("Printing  actionClassName : " + actionClassName);
          Method mthd = cls.getMethod("processRequest", new Class[]{Request.class}); 
          System.out.println("Printing  mthd : " + mthd);
          obj = mthd.invoke(actionObj, new Object[]{request});   // line 45
          return obj;     
     } catch (Exception e)
          e.printStackTrace();
          throw e;
public class CommunicationServlet extends HttpServlet{
     private Communicator communicator = null;
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
     doPost(req,res);
     }//end of doGet
public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
     res.setContentType("text/html");
     Response response = null;
     OutputStream o = null;
     try{
          Request request = getSerializedRequest(req);
          //logString("The seriliazed object is: " + request.toString());
          response = (Response)processRequest(request);
          o = res.getOutputStream();
          sendSerializedResponse(o, response);
     }catch(Exception e){
          e.printStackTrace();
          try{
               if(o != null)sendSerializedResponse(o, e);
               else {
                    o = res.getOutputStream();
                    sendSerializedResponse(o, e);
          }catch(Exception ignor){
               ignor.printStackTrace();
     }//end of doPost
public Communicator getCommunicator() {
     return new Communicator();
private HashMap getParams(HttpServletRequest req){
     Enumeration enu = req.getParameterNames();     
     HashMap map = new HashMap();
     while(enu.hasMoreElements()){
          String name = (String)enu.nextElement();
          String value = req.getParameter(name);
          if(name != null && !name.equals("") && value != null){
               map.put(name, value);
          }//end of if
     }//end while
     return map;
     }//end of getParams
private Request getSerializedRequest(HttpServletRequest req) throws Exception{
     log("start getSerializedRequest()");
     Request request = null;
     try{
          ObjectInputStream oIn = new ObjectInputStream(req.getInputStream());
          Object o = oIn.readObject();
          oIn.close();
          request = (Request)o;
          return request;     
     }catch(Exception e){
          logString("CommunicationServlet cannot receive serialized object.");     
          e.printStackTrace();
          throw e;
}//end of getRequest
private void logString(Object s){
     if(s != null) System.out.println(s);
     else System.out.println("Received null object.");
public Object processRequest(Request request) throws Exception {
     return  this.getCommunicator().processRequest(request);        // line 92
private void sendSerializedResponse(OutputStream o, Object resp) throws Exception{
     if(o != null){
          ObjectOutputStream oOut = new ObjectOutputStream(o);
          oOut.writeObject(resp);
          oOut.flush();
          oOut.close();
public void setCommunicator(Communicator newCommunicator) {
     communicator = newCommunicator;
}