java使用Filter过滤器对Response返回值进行修改

傷城~ 2022-06-10 12:13 888阅读 0赞

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

<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>