Request的Body只能读取一次解决方法

旧城等待， 2022-12-21 14:52 300阅读 0赞

## request只能读取一次 ##

#### 之前我在拦截器中获取request里面的参数值，处理完之后回到控制器发现取不出来了，原因很简单：因为是流。想想看，java中的流也是只能读一次，因为读完之后，position就到末尾了。 ####

### 办法 ###

#### 一、需要一个类继承HttpServletRequestWrapper，该类继承了ServletRequestWrapper并实现了HttpServletRequest， ####

#### 因此它可作为request在FilterChain中传递。 ####

#### 该类需要重写getReader和getInputStream两个方法，并在返回时将读出的body数据重新写入。 ####

#### 二、需要一个Filter筛选目标urlPattern，调用第一个类的同时，将第一个类写入FilterChain中代替原本的Request。 ####

package com.bonc.util;
    
    import javax.servlet.ReadListener;
    import javax.servlet.ServletInputStream;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;
    import java.io.*;
    
    public class BodyReaderRequestWrapper extends HttpServletRequestWrapper {
        private final String body;
    
        /**
         *
         * @param request
         */
        public BodyReaderRequestWrapper(HttpServletRequest request) throws IOException{
            super(request);
            StringBuilder sb = new StringBuilder();
            InputStream ins = request.getInputStream();
            BufferedReader isr = null;
            try{
                if(ins != null){
                    isr = new BufferedReader(new InputStreamReader(ins));
                    char[] charBuffer = new char[128];
                    int readCount = 0;
                    while((readCount = isr.read(charBuffer)) != -1){
                        sb.append(charBuffer,0,readCount);
                    }
                }else{
                    sb.append("");
                }
            }catch (IOException e){
                throw e;
            }finally {
                if(isr != null) {
                    isr.close();
                }
            }
    
            sb.toString();
            body = sb.toString();
        }
    
        @Override
        public BufferedReader getReader() throws IOException {
            return new BufferedReader(new InputStreamReader(this.getInputStream()));
        }
    
        @Override
        public ServletInputStream getInputStream() throws IOException {
            final ByteArrayInputStream byteArrayIns = new ByteArrayInputStream(body.getBytes());
            ServletInputStream servletIns = 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 byteArrayIns.read();
                }
            };
            return  servletIns;
        }
    }

package com.bonc.bitwd.filter;
    
    import com.bonc.util.BodyReaderRequestWrapper;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    public class BodyReaderRequestFilter implements Filter{
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
    
        }
    
        @Override
        public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException {
            HttpServletRequest request = (HttpServletRequest)req;
            HttpServletResponse response = (HttpServletResponse)res;
            BodyReaderRequestWrapper requestWrapper  = new BodyReaderRequestWrapper(request);
            if(requestWrapper == null){
                filterChain.doFilter(request,response);
            }else {
                filterChain.doFilter(requestWrapper,response);
            }
        }
    
        @Override
        public void destroy() {
    
        }
    }