使用PrintWriter和OutputStream [英] Using PrintWriter and OutputStream

问题描述

我正在使用struts创建一个项目，我在使用Jasper IReports时遇到了问题。我想将一些信息导出到pdf文件中，并且我一直得到java.lang.IllegalStateException：getOutputStream（）已被调用...由于在页面已打开PrintWriter时在我的代码中打开ServletOutputStream而导致异常。

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.

代码在模型中（所以它不在jsp中，它在java文件中），如下所示：

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

    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();
    }

我检查了连接，路径和HttpServletResponse并且都运行良好。

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

我是Jasper Reports的新手以及编写PDF格式的东西，所以你可以 - 正确地 - 我对我正在做的事情一无所知在这里和那个，显然我的代码是通过网络从某处复制/粘贴的。

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.

我试图使用PrintWriter而不是OutputStream，将字节转换为字符串并使用PrintWriter.append（String）方法（allthought不是String是CharSequence），但它不会将数据提取到PDF中。

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.

我也尝试过PrintWriter，关闭它以打开OutputStream（不起作用）或刷新它（两者都没有）。

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

任何有关使用任何可以显示数据的解决方案的帮助在pdf中会很棒。
非常感谢！

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

推荐答案

查看堆栈跟踪会很有用。

Would be useful to see the stack trace.

您可能首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。因为它应该工作正常：

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:

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

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