java - 在创建自定义 HttpServletResponse 方面需要帮助

Question

突然停滞在生成自定义 servlet 响应上。我想用预定义的替换 servlet 响应:

public class MyCustomResponse extends HttpServletResponseWrapper {
  private String customOutput;
  public MyCustomResponse(String customOutput, HttpServletResponse response) {
    super(response);
    // PrintWriter and Outputstream should stream this variable as output
    this.customOutput = customOutput;
  }

  //
  // Below I need to override something
  //
}

过滤代码如下:

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
  //
  //
  MyCustomResponse customResponse = new MyCustomResponse("Hello world!", (HttpServletResponse) response);
  chain.doFilter(request, customResponse);
}

真可惜，但我真的坚持编写这个简单的任务:(

如有任何帮助，我们将不胜感激。

更新:

我想要的只是实现自定义响应包装器，一旦将其放入过滤器链中，它就会始终以一些预定义的文本进行响应。我知道如何从 doFilter() 方法中编写自定义数据，但我希望 MyCustomResponse 对此负责 - 只需实例化并放入链中。也欢迎任何有充分理由的回答“你不能那样做，因为......”。

Answer 1

如您的评论之一所述:

"I want my custom response to return a string in response to getWriter or getOutputStream method invocation"

为此，您必须通过覆盖它们来为 getWriter() 和 getOutputStream() 提供您自己的实现。

//---

    private PrintWriter printWriter = null;
    private ServletOutputStream outputStream = null;

    public PrintWriter getWriter( ) throws IOException {

        if (this.outputStream != null) {
            throw new IllegalStateException(
                    "Cannot call getWriter( ) after getOutputStream( )");
        }

        if (this.printWriter == null) {
            // initialize printWriter
        }
        return this.printWriter;
    }

    public ServletOutputStream getOutputStream( ) throws IOException {

        if (this.printWriter != null) {
            throw new IllegalStateException(
                "Cannot call getOutputStream( ) after getWriter( )");
        }

        if (this.outputStream == null) {
            // initialize outputStream
        }
        return this.outputStream;
    }

//---