java - 寻找 HttpServletResponseWrapper 的捕获实现

Question

JavaEE API 附带了 HttpServletResponseWrapper，引用 javadoc 的话，“提供了 HttpServletResponse 接口(interface)的一个方便的实现，可以由希望调整来自 Servlet 的响应的开发人员子类化。”在没有子类化的情况下，此类只是将所有调用传递给包装的响应对象。有一个类似的请求包装器。

任何人都可以指出任何提供这些类的有用子类实现的实用程序库吗？特别是，我正在寻找响应包装器的子类，它捕获书面响应(作为字符串、byte[]，任何合适的)并通过 API 方法公开它。

我自己写了一个半生不熟的版本，但坦率地说，我不应该这样做，我宁愿扔掉它并使用现成的。

Answer 1

我不知道有任何实现，即使 gzip 示例可以通过写入 ByteArrayOutputStream 轻松调整。您还可以通过查看其他响应包装器实现来获取想法:

• SiteMesh
• DWR也用它

原答案:

JavaWorld有经典文章Filter code with Servlet 2.3 model .您可以找到包装请求和响应的示例:

• Compression the response

  public class CompressionResponseWrapper extends HttpServletResponseWrapper {
    protected ServletOutputStream stream = null;
    protected PrintWriter writer = null;
    protected int threshold = 0;
    protected HttpServletResponse origResponse = null;
    public CompressionResponseWrapper(HttpServletResponse response) {
  super(response);
  origResponse = response;
    }
    public void setCompressionThreshold(int threshold) {
  this.threshold = threshold;
    }
    public ServletOutputStream createOutputStream() throws IOException {
  return (new CompressionResponseStream(origResponse));
    }
    public ServletOutputStream getOutputStream() throws IOException {
  if (writer != null) {
    throw new IllegalStateException("getWriter() has already been " +
                                    "called for this response");
  }
  if (stream == null) {
    stream = createOutputStream();
  }
  ((CompressionResponseStream) stream).setCommit(true);
  ((CompressionResponseStream) stream).setBuffer(threshold);
  return stream;
    }
    public PrintWriter getWriter() throws IOException {
  if (writer != null) {
    return writer;
  }
  if (stream != null) {
    throw new IllegalStateException("getOutputStream() has already " +
                                    "been called for this response");
  }
  stream = createOutputStream();
  ((CompressionResponseStream) stream).setCommit(true);
  ((CompressionResponseStream) stream).setBuffer(threshold);
  writer = new PrintWriter(stream);
  return writer;
    }
  }
  

• Handling file upload

  public class MultipartWrapper extends HttpServletRequestWrapper {
    MultipartRequest mreq = null;
    public MultipartWrapper(HttpServletRequest req, String dir)
                                   throws IOException {
  super(req);
  mreq = new MultipartRequest(req, dir);
    }
    // Methods to replace HSR methods
    public Enumeration getParameterNames() {
  return mreq.getParameterNames();
    }
    public String getParameter(String name) {
  return mreq.getParameter(name);
    }
    public String[] getParameterValues(String name) {
  return mreq.getParameterValues(name);
    }
    public Map getParameterMap() {
  Map map = new HashMap();
  Enumeration enum = getParameterNames();
  while (enum.hasMoreElements()) {
    String name = (String) enum.nextElement();
    map.put(name, mreq.getParameterValues(name));
  }
  return map;
    }
    // Methods only in MultipartRequest
    public Enumeration getFileNames() {
  return mreq.getFileNames();
    }
    public String getFilesystemName(String name) {
  return mreq.getFilesystemName(name);
    }
    public String getContentType(String name) {
  return mreq.getContentType(name);
    }
    public File getFile(String name) {
  return mreq.getFile(name);
    }
  }
  

代码有点旧(2001 年 6 月!)，但它很好地演示了用法。