Question

我正在努力应对以下情况：

在我们当前运行在Tomcat 7.0.64上的Web应用程序中，我们设法通过Java在自己的类CharArrayWriterResponse implementing HttpServletResponseWrapper的帮助下包含一个JSP页面。

这样做的原因是我们将生成的HTML包装成AJAX响应所需的JSON。

依赖关系：

<dependency>
     <groupId>javax</groupId>
     <artifactId>javaee-web-api</artifactId>
     <version>7.0</version>
     <scope>provided</scope>
</dependency>
<dependency>
     <groupId>javax.servlet</groupId>
     <artifactId>jstl</artifactId>
     <version>1.2</version>
</dependency>

代码示例：

// somewhere in servlet doPost()/doGet()
try (PrintWriter out = response.getWriter()) {
     out.println(getJspAsJson(request, response));
}

private static String getJspAsJson(HttpServletRequest request, HttpServletResponse response) {
    String html = getHtmlByJSP(request, response, "WEB-INF/path/to/existing.jsp");
    Gson gson = new GsonBuilder().disableHtmlEscaping().create();
    return "{\"results\":" + gson.toJson(html) + "}";
}

public static String getHtmlByJSP(HttpServletRequest request, HttpServletResponse response, String jsp) {
     CharArrayWriterResponse customResponse = new CharArrayWriterResponse(response);
     request.getRequestDispatcher(jsp).include(request, customResponse);
     return customResponse.getOutput();
}

public class CharArrayWriterResponse extends HttpServletResponseWrapper {
    private final CharArrayWriter charArray = new CharArrayWriter();

    public CharArrayWriterResponse(HttpServletResponse response) {
        super(response);
    }

    @Override
    public PrintWriter getWriter() throws IOException {
        // this is called ONLY in tomcat
        return new PrintWriter(charArray);
    }

    public String getOutput() {
        return charArray.toString();
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        // this is called ONLY in WebLogic
        return null; // don't know how to handle it
    }
}

提示：我没有考虑上面代码示例中的异常处理。

我必须将此应用程序迁移到WebLogic（12.2.1），但此解决方案不再有效。

到目前为止我发现了什么：

在调用request.getRequestDispatcher(jsp).include()之后的getWriter() CharArrayWriterResponse我的getWriter()类的getWriter()之后，在Tomcat中调用。

在WebLogic中getOutputStream()不再被调用，这就是它不再起作用的原因。

经过一些调试后，我发现在WebLogic而不是getWriter()中，如果我覆盖它，则只调用getOutputStream()。在Weblogic上不会调用include()一次，因此必须在Tomcat和WebLogic的底层实现方面存在差异。

问题在于getWriter()我认为不可能在单独的流或其他内容中获取{{1}}调用的响应，并将其转换为String以用于构建包含最终JSON的最终JSON HTML。

是否有人已经解决了这个问题，并且可以提供一个有效的解决方案，以便以编程方式将JSP与WebLogic结合使用？

有没有人知道另一种解决方案来实现我的目标？

感谢您的建议。

解决方案

参见工作示例here

提示

我发现Tomcat和新的Weblogic解决方案之间存在差异：对于后者，不可能直接包含JSPF，而Tomcat {{1}}就是这样。

解决方案是将JSPF包装在JSP文件中。

Answer 1

我这样做了：

@Override
public ServletOutputStream getOutputStream() throws IOException {
    // this is called ONLY in WebLogic
    // created a custom outputstream that wraps your charArray
    return new CustomOutputStream(this.charArray);
}

// custom outputstream to wrap charArray writer
class CustomOutputStream extends ServletOutputStream {

    private WriterOutputStream out;

    public CustomOutputStream(CharArrayWriter writer) {
        // WriterOutputStream has a constructor without charset but it's deprecated, so change the UTF-8 charset to the one you use, if needed
        this.out = new WriterOutputStream(writer, "UTF-8");
    }

    @Override
    public boolean isReady() {
        return true;
    }

    @Override
    public void setWriteListener(WriteListener writeListener) {
    }

    @Override
    public void write(int b) throws IOException {
        this.out.write(b);
        this.out.flush(); // it doesn't work without flushing
    }
}

我使用了apache commons-io中的WriterOutputStream，所以我必须包含在我的pom.xml中：

<dependency>
  <groupId>commons-io</groupId>
  <artifactId>commons-io</artifactId>
  <version>2.5</version>
</dependency>

我不知道你的jsp文件中有什么，但我用一个简单的测试，我相信它有效。我的jsp文件：

<b>Hello world</b>

<p>testing</p>

<ul>test
<li>item</li>
<li>item2</li>
</ul>

输出（在浏览器中访问servlet时）：

{"results":"<b>Hello world</b>\n\n<p>testing</p>\n\n<ul>test\n<li>item</li>\n<li>item2</li>\n</ul>"}

Answer 2

以下是我更新且工作的示例如何在实现getOutputStream()时调用getWriter()而不是HttpServletResponseWrapper时以编程方式包含JSP文件：

public class MyServletOutputStream extends ServletOutputStream {

    private final BufferedOutputStream bufferedOut;

    public MyServletOutputStream(CharArrayWriter charArray) {
        this.bufferedOut = new BufferedOutputStream(new WriterOutputStream(charArray, "UTF-8"), 16384);
    }

    @Override
    public void write(int b) throws IOException {
        this.bufferedOut.write(b);
    }

    /**
     * This is needed to get correct full content without anything missing
     */
    @Override
    public void flush() throws IOException {
        if (this.bufferedOut != null) {
            this.bufferedOut.flush();
        }
        super.flush();
    }

    @Override
    public void close() throws IOException {
        this.bufferedOut.close();
        super.close();
    }

    @Override
    public boolean isReady() {
        return true;
    }

    @Override
    public void setWriteListener(WriteListener writeListener) {
    }
}

public class CharArrayWriterResponse extends HttpServletResponseWrapper {

    private final CharArrayWriter charArray = new CharArrayWriter();
    private ServletOutputStream servletOutputStream;

    public CharArrayWriterResponse(HttpServletResponse response) {
        super(response);
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        if (servletOutputStream == null) {
            servletOutputStream = new MyServletOutputStream(this.charArray);
        }
        return servletOutputStream;
    }

    public String getOutputAndClose() {
        if (this.servletOutputStream != null) {
            try {
                // flush() is important to get complete content and not last "buffered" part missing
                this.servletOutputStream.flush()
                return this.charArray.toString();
            } finally {
                this.servletOutputStream.close()
            }
        }
        throw new IllegalStateException("Empty (null) servletOutputStream not allowed");
    }

    // not necessary to override getWriter() if getOutputStream() is used by the "application server".
}

// ...somewhere in servlet process chain e.g. doGet()/doPost()
// request/response The original servlet request/response object e.g. from doGet/doPost(HttpServletRequest request, HttpServletResponse response)
CharArrayWriterResponse customResponse = new CharArrayWriterResponse(response);
request.getRequestDispatcher("/WEB-INF/path/to/existing.jsp").include(request, customResponse);
String jspOutput = customResponse.getOutputAndClose();
// do some processing with jspOut e.g. wrap inside JSON

// customResponse.getOutputStream() is already closed by calling getOutputAndClose()

Answer 3

由于我无法弄清楚如何在评论中添加多行代码，我只是把它放在这里。我可以通过覆盖flush()类中的MyServletOutputStream方法修复issue：

// inside MyServletOutputStream class
@Override
public void flush() throws IOException {
    if (this.bufferedOut != null) {
        this.bufferedOut.flush();
    }
    super.flush();
}

RequestDispatcher在Weblogic 12c中以编程方式包含JSP的问题

解决方案

提示

3 个答案: