Java 使用 PrintWriter 和 OutputStream

Using PrintWriter and OutputStream

提问by Random

I am creating a project with struts and I have a problem using Jasper IReports. I want to export some info into a pdf file and I keep getting the java.lang.IllegalStateException: getOutputStream() has already been call... Exception due to openning a ServletOutputStream in my code when the page already opens a PrintWriter.

我正在使用 struts 创建一个项目，但在使用 Jasper IReports 时遇到了问题。我想将一些信息导出到 pdf 文件中，但我不断收到 java.lang.IllegalStateException: getOutputStream() has been call... 由于在页面已经打开 PrintWriter 时在我的代码中打开 ServletOutputStream 的异常。

The code is in the model (so it is not in the jsp, it's in a java file), as it follows:

代码在模型中（所以它不在jsp中，而是在java文件中），如下所示：

    public void handle(HttpServletResponse res, Connection connection, String path)throws Exception{
    ServletOutputStream out = null;
    try {

        JasperDesign jasperDesign = JRXmlLoader.load(path);
        JasperReport jasperReport = JasperCompileManager.compileReport(jasperDesign);
        byte[] bytes = JasperRunManager.runReportToPdf(jasperReport, null, connection);
        res.setContentType("application/pdf");
        res.setContentLength(bytes.length);
        out = res.getOutputStream();
        out.write(bytes, 0, bytes.length);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        out.flush();
        out.close();
    }

I have checked the connection, the path and the HttpServletResponse and are all working fine.

我已经检查了连接、路径和 HttpServletResponse 并且一切正常。

I'm very newbie with Jasper Reports as well as with coding stuff into PDF so you can -correctly- suposse that I have a minimal idea of what I am doing here and that, obviously my code is copy/pasted from somewhere through the net.

我是 Jasper Reports 以及将内容编码为 PDF 的新手，因此您可以 - 正确地 - 假设我对我在这里所做的事情知之甚少，显然我的代码是通过网络从某处复制/粘贴的.

I have tried to use PrintWriter instead of OutputStream, transforming bytes into a String and using the PrintWriter.append(String) method (allthought is not String is CharSequence), but it doesn't extract the data into the PDF.

我尝试使用 PrintWriter 而不是 OutputStream，将字节转换为 String 并使用 PrintWriter.append(String) 方法（allthought is not String is CharSequence），但它不会将数据提取到 PDF 中。

I have also tried to get the PrintWriter, close it to open the OutputStream (didn't work) or flush it (neither).

我还尝试获取 PrintWriter，关闭它以打开 OutputStream（不起作用）或刷新它（两者都没有）。

Any help with a solution to use any out that could show the data in a pdf would be great. Thanks a lot!

任何有关使用任何可以在 pdf 中显示数据的解决方案的帮助都会很棒。非常感谢！

采纳答案by simonlord

Would be useful to see the stack trace.

查看堆栈跟踪会很有用。

You might try running a sanity check first though: Modify that code to simply write a static string (hello world) to the ServletOutputStream and set content type to text/html. As that should work fine:

不过，您可以先尝试运行健全性检查：修改该代码以简单地将静态字符串（hello world）写入 ServletOutputStream 并将内容类型设置为 text/html。因为这应该可以正常工作：

public void handle(HttpServletResponse res, Connection connection, String path)throws Exception{
ServletOutputStream out = null;
try {
    byte[] bytes = "hello world".getBytes();
    res.setContentType("text/html");
    res.setContentLength(bytes.length);
    out = res.getOutputStream();
    out.write(bytes, 0, bytes.length);
} catch (Exception e) {
    e.printStackTrace();
} finally {
    out.flush();
    out.close();
}

HTH

HTH

回答by Jim Rush

Some ideas:

一些想法：

• PrintWriter isn't going to work if you are working with a binary stream (PDF are binary)
• The illegal state might occur if there is client side timeout or disconnect. A packet trace of the process will tell you a lot (even if you can't read them well). Look at WireShark or what is available for your platform. Its worth your time to learn at least a little bit about what happens at the wire level.
• Make sure the data you are getting back from the report generate is actually a pdf. Write it to a file and attempt to open.
• Some situations need you to set the http length header before writing to the stream otherwise they give up when the data starts to show. Might be necessary here.

• 如果您使用的是二进制流（PDF 是二进制的），则 PrintWriter 将无法工作
• 如果客户端超时或断开连接，则可能会出现非法状态。该过程的数据包跟踪会告诉您很多信息（即使您不能很好地阅读它们）。查看 WireShark 或适用于您的平台的内容。值得您花时间至少了解一点有关线路级别发生的事情。
• 确保您从生成的报告中返回的数据实际上是 pdf。将其写入文件并尝试打开。
• 某些情况需要您在写入流之前设置 http 长度标头，否则它们会在数据开始显示时放弃。这里可能需要。

回答by Random

Own answer:

自己的回答：

I have put in the path a jrxml that actually connects to the database and gets some real data out and suddendly it worked, the PDF opened in mozilla, but the Exception keeps happening. I do not know how I can throw and exception (I have debugged and the Exception happens in the same place) and be able to see the PDF.

我在路径中放置了一个 jrxml，它实际上连接到数据库并获取了一些真实数据，并且突然它起作用了，在 mozilla 中打开了 PDF，但异常不断发生。我不知道如何抛出和异常（我已经调试过并且异常发生在同一个地方）并且能够看到 PDF。

So I can only keep searching for what actually happens here. I will answer with anything I find (probably on monday).

所以我只能继续寻找这里实际发生的事情。我会用我找到的任何东西来回答（可能在星期一）。

Thanks simonlord and Jim Rush for your help! :)

感谢 simonlord 和 Jim Rush 的帮助！:)

Edit: By the way, here is the stacktrace (it's in Spanish, if needed I will translate anything you don't understand): Edit again: Seems I didn't copy the '1' in the 15th-Jan-2010... could create confusion about a trace from the 5th-Jan insetad. Corrected.

编辑：顺便说一下，这是堆栈跟踪（它是西班牙语的，如果需要，我会翻译您不理解的任何内容）：再次编辑：似乎我没有在 2010 年 1 月 15 日复制“1”。 . 可能会对 1 月 5 日插图中的痕迹造成混淆。更正。

15-ene-2010 13:47:03 org.apache.catalina.core.ApplicationDispatcher invoke
GRAVE: El Servlet.service() para servlet jsp lanzó una excepción
java.lang.IllegalStateException: getOutputStream() ya ha sido llamado para esta respuesta
    at org.apache.catalina.connector.Response.getWriter(Response.java:607)
    at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:196)
    at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
    at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
    at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
    at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:171)
    at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:116)
    at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:76)
    at org.apache.jsp.pages.inicio2_jsp._jspService(inicio2_jsp.java:300)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:679)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:497)
    at org.apache.struts.chain.commands.servlet.PerformForward.handleAsInclude(PerformForward.java:141)
    at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:92)
    at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
    at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
    at java.lang.Thread.run(Unknown Source)
15-ene-2010 13:47:03 org.apache.struts.chain.commands.AbstractExceptionHandler execute
ADVERTENCIA: Unhandled exception
org.apache.jasper.JasperException: getOutputStream() ya ha sido llamado para esta respuesta
    at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:460)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:367)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:679)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:497)
    at org.apache.struts.chain.commands.servlet.PerformForward.handleAsInclude(PerformForward.java:141)
    at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:92)
    at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
    at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
    at java.lang.Thread.run(Unknown Source)
15-ene-2010 13:47:03 org.apache.struts.chain.commands.ExceptionCatcher postprocess
ADVERTENCIA: Exception from exceptionCommand 'servlet-exception'
org.apache.jasper.JasperException: getOutputStream() ya ha sido llamado para esta respuesta
    at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:460)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:367)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:679)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:497)
    at org.apache.struts.chain.commands.servlet.PerformForward.handleAsInclude(PerformForward.java:141)
    at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:92)
    at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
    at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
    at java.lang.Thread.run(Unknown Source)
15-ene-2010 13:47:03 org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() para servlet action lanzó excepción
java.lang.IllegalStateException: getOutputStream() ya ha sido llamado para esta respuesta
    at org.apache.catalina.connector.Response.getWriter(Response.java:607)
    at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:196)
    at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
    at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
    at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
    at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:171)
    at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:116)
    at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:76)
    at org.apache.jsp.pages.inicio2_jsp._jspService(inicio2_jsp.java:300)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:679)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:584)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:497)
    at org.apache.struts.chain.commands.servlet.PerformForward.handleAsInclude(PerformForward.java:141)
    at org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:92)
    at org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
    at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
    at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
    at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
    at java.lang.Thread.run(Unknown Source)

回答by BalusC

How exactly is the code invoked? Judging from the stacktrace it look like that you're running the Java class with the handlemethod using scriptletsinside a JSP file (the inicio2.jspto be precise). After that the Java class has written the report to the OutputStream, the JSP file would continue with outputting the remnant of the file itself (including whitespace!), which would implicitly invoke the getWriter()to write it to response. Exactly that would cause an IllegalStateExceptionas you're facing now when the getOutputStream()is already been called before in the Java class.

代码究竟是如何调用的？从堆栈跟踪来看，您正在handle使用JSP 文件中的scriptlet方法运行 Java 类（inicio2.jsp准确地说）。在 Java 类将报告写入 之后，OutputStreamJSP 文件将继续输出文件本身的剩余部分（包括空格！），这将隐式调用 将getWriter()其写入响应。没错，它会造成IllegalStateException你所面对现在当getOutputStream()是已经在Java类之前调用。

It's good that Java code is been placed in a Java class, but that doesn't mean that you may still use JSP to invoke it. The JSP should not contain any single line of Java code. JSP itself is as being a view technology part of the output. To fix this all, just have a Struts action class (or a HttpServlet) which you can invoke by a HTML <form>or <a>.

将 Java 代码放在 Java 类中是件好事，但这并不意味着您仍然可以使用 JSP 来调用它。JSP 不应包含任何单行 Java 代码。JSP 本身作为输出的视图技术部分。要解决这一切，只需拥有一个 Struts 操作类（或HttpServlet），您可以通过 HTML<form>或<a>.