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   有些场景，我们会试图获取渲染jsp以后的html，或者修改一下生成json，例如把普通的json换成跨域的jsonp。

ResponseFacade只提供了getOutStream(),但是获取不了stream的容器bytearray，不通过hacker的方式根本获取不了。Tomcat也意识到这一点，提供了HttpServletResponseWrapper帮我们解决这个问题，对于HttpServletResponseWrapper有这样的comments:

       Provides a convenient implementation of the HttpServletResponse interface

 * that can be subclassed by developers wishing to adapt the response from a

 * Servlet. This class implements the Wrapper or Decorator pattern. Methods

 * default to calling through to the wrapped response object.

我们只要在其子类添加一些逻辑就能得到我们想要的东西,用byteArrayOutSteam换掉coyoteOutStream，再通过toByteArray就能获取到html，但这得借助filter帮我们用responsewrapper在dochain()换掉reponse,

上代码吧

/**       * Creates a GenericResponseWrapper       */     public GenericResponseWrapper(final HttpServletResponse response, final OutputStream outstr) {          super(response);          this.outstr = new FilterServletOutputStream(outstr);      } /**       * Gets the outputstream.       */     public ServletOutputStream getOutputStream() {          return outstr;      }    /**       * Gets the print writer.       */     public PrintWriter getWriter() throws IOException {          if (writer == null) {              writer = new PrintWriter(new OutputStreamWriter(outstr, getCharacterEncoding()), true);          }          return writer;      }

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