Struts Web应用程序中的JasperReport错误

时间：2011-04-04 12:44:27

标签： jasper-reports ireport netbeans6.8

我在基于Struts的Web应用程序中使用JasperReport，其中包含NetBeans 6.8和IReport插件3.7.4。我在动作类中收到以下错误：

java.lang.NullPointerException
    at java.io.ObjectInputStream$PeekInputStream.read(ObjectInputStream.java:2266)
    at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2279)
    at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2750)
    at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:780)
    at java.io.ObjectInputStream.<init>(ObjectInputStream.java:280)
    at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:188)
    at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:381)
    at net.sf.jasperreports.engine.JasperRunManager.runReportToPdfStream(JasperRunManager.java:186)
    at com.bspl.psys.ilp.action.ReportAppLinkAction.execute(ReportAppLinkAction.java:65)
    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425)
    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97)
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:332)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:233)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
    at java.lang.Thread.run(Thread.java:619)

我在动作类中使用了以下代码：

public ActionForward execute(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

         StringWriter stringWriter = new StringWriter();
         PrintWriter printWriter = new PrintWriter(stringWriter);
         ServletOutputStream servletOutputStream = response.getOutputStream();
         InputStream reportStream = getServlet().getServletConfig().getServletContext().getResourceAsStream("SampleReport.jasper");

         try {

            Class.forName("com.mysql.jdbc.Driver").newInstance();
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/SampleDB?user=common&password=common");

            JasperRunManager.runReportToPdfStream(reportStream, servletOutputStream,new HashMap());

            connection.close();
            response.setContentType("application/pdf");
            response.reset();
            reportStream.close();
            servletOutputStream.flush();
            servletOutputStream.close();

        }  catch (Exception ex) {

            ex.printStackTrace(printWriter);
            response.setContentType("text/plain");
            response.getOutputStream().print(stringWriter.toString());
        }

          return null;
    }

请建议我哪里出错了。我第一次使用JasperReport并且在我的智慧结束时:(

更新

我认为问题出在报告本身。即使是简单的代码也会出错：

try {
  Class.forName("com.mysql.jdbc.Driver").newInstance();
  connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/SampleDB?user=common&password=common);
  JasperFillManager.fillReportToFile("D:/dropbox/report/SampleReport.jasper",new HashMap(), connection);
  System.out.println("Done!");
} catch (Exception ex) {
  ex.printStackTrace(printWriter);
  response.setContentType("text/plain");
  response.getOutputStream().print(stringWriter.toString());
}
return null;
}

这次出现了不同的错误消息：

java.lang.NullPointerException
at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:63)
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:402)
at net.sf.jasperreports.engine.JasperFillManager.fillReportToFile(JasperFillManager.java:188)
at net.sf.jasperreports.engine.JasperFillManager.fillReportToFile(JasperFillManager.java:94)
at com.bspl.psys.ilp.action.ReportAppLinkAction.execute(ReportAppLinkAction.java:84)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97)
at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:332)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:233)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
at java.lang.Thread.run(Thread.java:619)

但是当我在IReport设计器中查看报告时，预览会正确显示。请帮忙。启动报告只需要太长时间。

1 个答案:

答案 0 :(得分：0)

警告：我不是struts开发人员（更多JSF 1.2 / 2.0）：

JasperReports非常挑剔并且在错误上非常冗长，除非您专门将其配置为静默行为。空指针异常通常来自你不期望的地方（图像/简单文本等......），不幸的是，有时你会在“loadObject”或“fillReport”调用中得到错误信息。

尝试将其分解为一系列步骤，并在调试器中查看它以确切地看到它失败的位置。一旦你将它拆散，这可能是一个明智的选择。删除所有图像等...并运行一个空白报告（字面意思是一个问候世界），以确保NPE不在报告中，并且您的框架可以正常工作。一旦你将它分成几部分就可以很容易地进行调试。

通常，您可以使用以下方法检查每个步骤：

//load == classloader (I'm inside JBoss so I have to explicitly define it)
//This is pseudo code pulled from my test environment

JasperReport report = JasperCompileManager.compileReport(load.getResourceAsStream("yourpackage/report.jrxml"));
JasperPrint print = JasperFillManager.fillReport(report, new Map<String, Object>(), java.sql.Connection);      
JasperExportManager.exportReportToPdfStream(print, outStream);

我真的不建议在生产环境中编译（使用print是最好的方法），但是我遇到了一系列类加载问题（JBoss相关），NPE由图像和其他细节引起的错误和由报告中的各种坏脚本。

在框架内进行测试，您会很快发现问题。 Jasper可以说是Java上最好的报告软件（它非常详细）但调试非常令人生气。

通过将其分解为步骤，可以更轻松地进行调试并查看NPE实际存在的位置。您使用的代码似乎没问题：我将我的钱放在报告中的空流或资源中（可能是图像）。

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