struts1.2使用json时报的错误
用的ssh框架，struts1.2，在action中有

Java code

public ActionForward getComment(ActionMapping mapping, ActionForm form,
        HttpServletRequest request, HttpServletResponse response) {
    
    String messageID=request.getParameter("messageID");
    try {  
        List commentList=messageDAOImpl.getComment(messageID);
        
        JSONArray json=JSONArray.fromObject(commentList); 
        
        response.setContentType("text/json; charset=utf-8");
                PrintWriter out=response.getWriter();  
              // out.print(json);  
             // out.flush();  
    } catch (IOException e) {  
        // TODO Auto-generated catch block  
        e.printStackTrace();  
    }  
    
    return null;
    
}

不加上JSONArray json=JSONArray.fromObject(commentList)这句代码时，没有错，可以输出commentList的长度，加上时报错，如下：（这是什么错误呢）

 [日志信息] Dispatch[/getComment] to method 'getComment' returned an exception
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:274)
at org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:194)
at org.springframework.web.struts.DelegatingActionProxy.execute(DelegatingActionProxy.java:106)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.Base.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:22)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NoClassDefFoundError: net/sf/ezmorph/Morpher
at net.sf.json.util.CycleDetectionStrategy.<clinit>(CycleDetectionStrategy.java:37)
at net.sf.json.JsonConfig.<clinit>(JsonConfig.java:65)
at net.sf.json.JSONArray.fromObject(JSONArray.java:105)
at com.struts.action.GetCommentAction.getComment(GetCommentAction.java:38)
... 28 more
Caused by: java.la