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

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    {        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//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();            }//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()    {    }}

配置很简单：

spring boot：

 /**     * 配置过滤器，这里过滤器主要是对返回值做后继处理     *      * @return     */    @Bean    public FilterRegistrationBean someFilterRegistration()    {        FilterRegistrationBean registration = new FilterRegistrationBean();        registration.setFilter(new ResponseFilter());// 配置一个返回值加密过滤器        registration.addUrlPatterns("/*");        registration.addInitParameter("paramName", "paramValue");        registration.setName("responseFilter");        return registration;    }

spring mvc 下直接在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>