Question

JavaEE API附带了HttpServletResponseWrapper，引用javadoc，“提供了一个方便的HttpServletResponse接口实现，可以由希望调整Servlet响应的开发人员进行子类化。”没有子类化，这个类只是将所有调用传递给包装的响应对象。请求有一个类似的包装器。

有人能指出我提供这些类的有用子类实现的任何实用程序库吗？特别是，我正在寻找响应包装器的子类，它捕获写入的响应（作为String，byte []，无论什么是合适的）并通过API方法公开它。

我自己写了一个相当半生不熟的版本，但坦率地说，我不应该这样做，而是宁可把它扔掉，也不要使用现成的版本。

Answer 1

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

SiteMesh
DWR也使用它

原始回答：

JavaWorld Filter code with Servlet 2.3 model中有一篇经典文章。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);
  }
}

代码有点陈旧（2001年6月！），但它很好地展示了用法。

Answer 2

过去我曾使用spring框架中提供的对象。特别是，这应该有效：http://static.springsource.org/spring/docs/2.0.x/api/org/springframework/mock/web/MockHttpServletRequest.html

寻找HttpServletResponseWrapper的捕获impl

2 个答案: