java在filter中修改一个http请求出入参内容

水深无声 2022-09-05 01:45 172阅读 0赞

response保存了请求的返回信息,里面有个outputstream,你要返回给页面的流,都在这个地方保存.   
之前遇到一个问题,想把outputstream修改一下.因为这是个输出流,想要改这个里面的东西不是这么简单的.   
sun为我们提供了这么一个工具HttpServletResponseWrapper抽象类,利用这个类的子类把servletresponse包装一下,在过滤器中使用,就可以去除response的文件流,对其作出修改.给出一个实现:

import javax.servlet.ServletOutputStream;
    import javax.servlet.WriteListener;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpServletResponseWrapper;
    import java.io.*;
    
    /**
     * ResponseWrapper
     *
     * @author wuweifeng
     * @version 1.0
     * @date 2021-08-16
     */
    public class ResponseWrapper extends HttpServletResponseWrapper {
        /**
         * ByteArrayOutputStream
         */
        private ByteArrayOutputStream buffer;
        /**
         * ServletOutputStream
         */
        private ServletOutputStream out;
        /**
         * writer
         */
        private PrintWriter writer;
    
        /**
         * ResponseWrapper
         */
        public ResponseWrapper(HttpServletResponse resp) throws IOException {
            super(resp);
            buffer = new ByteArrayOutputStream();//真正存储数据的流
            out = new WrapperOutputStream(buffer);
            writer = new PrintWriter(new OutputStreamWriter(buffer, this.getCharacterEncoding()));
        }
    
        //重载父类获取outputstream的方法
        @Override
        public ServletOutputStream getOutputStream() throws IOException {
            return out;
        }
    
        //重载父类获取writer的方法
        @Override
        public PrintWriter getWriter() throws UnsupportedEncodingException {
            return writer;
        }
    
        //重载父类获取flushBuffer的方法
        @Override
        public void flushBuffer() throws IOException {
            if (out != null) {
                out.flush();
            }
            if (writer != null) {
                writer.flush();
            }
        }
    
        @Override
        public void reset() {
            buffer.reset();
        }
    
        /**
         * 获取response的字符串
         */
        public String getContent() throws IOException {
            flushBuffer();//将out、writer中的数据强制输出到WapperedResponse的buffer里面，否则取不到数据
            return new String(buffer.toByteArray());
        }
    
        //内部类，对ServletOutputStream进行包装
        private class WrapperOutputStream extends ServletOutputStream {
            /**
             * ByteArrayOutputStream
             */
            private ByteArrayOutputStream bos;
    
            /**
             * WrapperOutputStream
             */
            WrapperOutputStream(ByteArrayOutputStream stream) {
                bos = stream;
            }
    
            @Override
            public void write(int b) {
                bos.write(b);
            }
    
            @Override
            public boolean isReady() {
                return false;
            }
    
            @Override
            public void setWriteListener(WriteListener writeListener) {
    
            }
        }
    }

然后在你的过滤器中这么使用:

public class UserFilter implements Filter {
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            HttpServletResponse resp = (HttpServletResponse) servletResponse;
    
            ResponseWrapper mResp = new ResponseWrapper(resp);// 包装响应对象 resp 并缓存响应数据
            filterChain.doFilter(servletRequest, mResp);
    
            String content = mResp.getContent();//response流的内容
            System.out.println(content);
    
    
            //此处可以对content做处理,然后再把content写回到输出流中
            servletResponse.setContentLength(-1);
    
            PrintWriter out = servletResponse.getWriter();
    
            out.write(content);
    
            out.flush();
    
            out.close();
        }
    }

关于入参request的，如果只是key-value型的，对应客户端是form那种传过来的，在filter里直接获取没事。但如果是application/json型的，如果这个输入流被提前读取了，则后续真正的controller就取不到了，也需要做个包装类。

import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import java.io.BufferedReader;
    import java.io.ByteArrayInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.util.Collections;
    import java.util.Enumeration;
    import java.util.HashMap;
    import java.util.Map;
    import javax.servlet.ReadListener;
    import javax.servlet.ServletInputStream;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;
    
    import static com.alibaba.fastjson.util.IOUtils.UTF8;
    
    public class RequestWrapper extends HttpServletRequestWrapper {
        /**
         * log
         */
        private static final Logger log = LoggerFactory.getLogger(RequestWrapper.class);
        /**
         * application/json型的入参
         */
        private final String body;
        /**
         * key-value型所有的入参
         */
        private Map<String, String[]> params = new HashMap<>();
    
    
        public RequestWrapper(HttpServletRequest request) {
            super(request);
            this.params.putAll(request.getParameterMap());
            StringBuilder stringBuilder = new StringBuilder();
            BufferedReader bufferedReader = null;
            InputStream inputStream = null;
            try {
                inputStream = request.getInputStream();
                if (inputStream != null) {
                    bufferedReader = new BufferedReader(new InputStreamReader(inputStream, UTF8));
                    char[] charBuffer = new char[512];
                    int bytesRead;
                    while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
                        stringBuilder.append(charBuffer, 0, bytesRead);
                    }
                }
            } catch (IOException ex) {
                log.error("requestBody read error ignore,message:" + ex.getMessage());
            } finally {
                if (inputStream != null) {
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        log.error("requestBody inputStream close error,ignore");
                    }
                }
                if (bufferedReader != null) {
                    try {
                        bufferedReader.close();
                    } catch (IOException e) {
                        log.error("requestBody bufferedReader close error,ignore");
                    }
                }
            }
            body = stringBuilder.toString();
        }
    
        @Override
        public ServletInputStream getInputStream() throws IOException {
            final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes(UTF8));
            ServletInputStream servletInputStream = new ServletInputStream() {
                @Override
                public boolean isFinished() {
                    return false;
                }
    
                @Override
                public boolean isReady() {
                    return false;
                }
    
                @Override
                public void setReadListener(ReadListener readListener) {
                }
    
                @Override
                public int read() throws IOException {
                    return byteArrayInputStream.read();
                }
            };
            return servletInputStream;
    
        }
    
        @Override
        public BufferedReader getReader() throws IOException {
            return new BufferedReader(new InputStreamReader(this.getInputStream(), UTF8));
        }
    
        public String getBody() {
            return this.body;
        }
    
        @Override
        public String getParameter(String name) {
            String[] values = params.get(name);
            if (values == null || values.length == 0) {
                return null;
            }
            return values[0];
        }
    
        @Override
        public String[] getParameterValues(String name) {
            return params.get(name);
        }
    
    
        @Override
        public Enumeration<String> getParameterNames() {
            return Collections.enumeration(params.keySet());
        }
    
    }