JFreeChart Struts2组件报IllegalStateException

在s2sh框架中应用了JFreeChart 组件，使用了struts2-jfreechart -plugin，jfreechart 生 成图片的时候在服务器后台会产生如下的错误，

但是图片却能够正常的显示出来。

严重: Servlet.service() for servlet default threw exception java.lang.IllegalStateException at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:407) at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:770) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:505) at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395) 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.Http11AprProcessor.process(Http11AprProcessor.java:859) at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:574) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2018) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:651) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:676) at java.lang.Thread.run(Thread.java:595)

这个问题困扰了我很久，当请求JFreeChart 图片时突然中断或者第一次请求图片还没完 成就发生第二次请求时就会抛出这个异常。
网上解释说是产生图片过程中发生了io异常,修改struts plugins包里ChartResult.java 源文件。

... HttpServletResponse response = ServletActionContext.getResponse(); //OutputStream os = response.getOutputStream();//原来是这么写的 OutputStream os = null; try { os = response.getOutputStream();//挪到try里面 // check the type to see what kind of output we have to produce if ("png".equalsIgnoreCase(type)) { response.setContentType("image/png"); ChartUtilities.writeChartAsPNG(os, chart, getIntValueFromString(width), getIntValueFromString(height)); } else if ("jpg".equalsIgnoreCase(type) || "jpeg".equalsIgnoreCase(type)) { response.setContentType("image/jpg"); } else throw new IllegalArgumentException(type + " is not a supported render type (only JPG and PNG are)."); } catch (IOException e) {//加上异常捕获 } finally { if (os != null) os.flush(); } ...

经测试问题依旧存在 ，查看struts2源码采用如下办法解决，在 org.apache.struts2.dispatcher.Dispatcher 770行左右：

try { // WW-1977: Only put errors in the request when code is a 500 error if (code == HttpServletResponse.SC_INTERNAL_SERVER_ERROR) { // send a http error response to use the servlet defined error handler // make the exception availible to the web.xml defined error page request.setAttribute("javax.servlet.error.exception", e); // for compatibility request.setAttribute("javax.servlet.jsp.jspException", e); } // send the error response response.sendError(code, e.getMessage()); } catch (IOException e1) { // we're already sending an error, not much else we can do if more stuff breaks } catch (IllegalStateException e2) { //添加IllegalStateException 异常捕捉 }

就哦了。