java使用Filter过滤器对Response返回值进行修改

有时候在开发过程中会有这样一个场景，有时需要对返回的数据进行处理。比如加密啊，添加某些标记啊等等。这种情况我们可以通过过滤器去处理。

过滤器是什么就不介绍了，百度一下，你就知道。

看看代码吧：

返回值输出代理类：这个类主要是为了吧Response里面的返回值获取到，因为直接Response没有提供直接拿到返回值的方法。所以要通过代理来取得返回值

自定义response包装类ResponseWrapper：

package com.channel.filter;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
* 返回值输出代理类
*
* @Title: ResponseWrapper
* @Description:
* @author kokJuis
* @date 上午9:52:11
*/
public class ResponseWrapper extends HttpServletResponseWrapper
{

private ByteArrayOutputStream buffer;

private ServletOutputStream out;

public ResponseWrapper(HttpServletResponse httpServletResponse)
{
super(httpServletResponse);
buffer = new ByteArrayOutputStream();
out = new WrapperOutputStream(buffer);
}

@Override
public ServletOutputStream getOutputStream()
throws IOException
{
return out;
}

@Override
public void flushBuffer()
throws IOException
{
if (out != null)
{
out.flush();
}
}

public byte[] getContent()
throws IOException
{

4000
flushBuffer();
return buffer.toByteArray();
}

class WrapperOutputStream extends ServletOutputStream
{
private ByteArrayOutputStream bos;

public WrapperOutputStream(ByteArrayOutputStream bos)
{
this.bos = bos;
}

@Override
public void write(int b)
throws IOException
{
bos.write(b);
}

@Override
public boolean isReady()
{

// TODO Auto-generated method stub
return false;

}

@Override
public void setWriteListener(WriteListener arg0)
{

// TODO Auto-generated method stub

}
}

}

过滤器类：

package com.channel.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;

import com.channel.util.RsaEncryptUtil;

/**
* 返回值输出过滤器，这里用来加密返回值
*
* @Title: ResponseFilter
* @Description:
* @author kokJuis
* @date 上午9:52:42
*/
public class ResponseFilter implements Filter
{

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
throws IOException, ServletException
{
ResponseWrapper wrapperResponse = new ResponseWrapper((HttpServletResponse)response);//转换成代理类
// 这里只拦截返回，直接让请求过去，如果在请求前有处理，可以在这里处理
filterChain.doFilter(request, wrapperResponse);
byte[] content = wrapperResponse.getContent();//获取返回值
<span style="white-space:pre">  </span>//判断是否有值
if (content.length > 0)
{

String str = new String(content, "UTF-8");
System.out.println("返回值:" + str);
String ciphertext = null;

try
{
//......根据需要处理返回值
}
catch (Exception e)
{
e.printStackTrace();
}
<span style="white-space:pre">      </span>//把返回值输出到客户端
ServletOutputStream out = response.getOutputStream();
out.write(ciphertext.getBytes());
out.flush();
}

}

@Override
public void init(FilterConfig arg0)
throws ServletException
{

}

@Override
public void destroy()
{

}

}

web.xml下添加配置即可

<!-- 返回值过滤器 -->
<filter>
<filter-name>responseFilter</filter-name>
<filter-class>com.im.filter.ResponseFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>responseFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>