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

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在自己的类的帮助下包含一个JSP页面CharArrayWriterResponse implementing HttpServletResponseWrapper.

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),但此解决方案不再起作用.

到目前为止我发现了什么:

在调用我的类request.getRequestDispatcher(jsp).include()上面的例子后调用Tomcat .getWriter()CharArrayWriterResponse

在WebLogic getWriter()中不再被调用,这就是它不再起作用的原因.

经过一些调试后,我发现在WebLogic中,如果我覆盖它,getWriter()则只getOutputStream()调用它. getWriter()在Weblogic上没有调用一次,因此必须在Tomcat和WebLogic的底层实现上有所不同.

问题是,getOutputStream()我认为不可能include()在单独的流或其他内容中获得调用的响应,并将其转换为String以用于构建包含HTML的最终JSON.

有人已经解决了这个问题,并且能够提供一种工作解决方案,以便以编程方式将JSP与WebLogic结合使用吗？

有谁知道另一个解决方案来实现我的目标？

谢谢你的建议.

---

解

请参阅此处的工作示例

暗示

我在Tomcat和新的Weblogic解决方案之间发现了一个不同之处:对于后者,我不可能直接包含JSPF,而不再getWriter()是Tomcat .

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WriterOutputStream从 apache commons-io 使用，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，但我已经用一个简单的文件进行了测试，我相信它是有效的。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>"}