解决request.getParameter() 、 request.getInputStream()和request.getReader()只能使用一次的问题

青旅半醒 2022-07-12 02:03 612阅读 0赞

**问题**：在使用SpringMVC拦截器获取POST请求中的JSON信息的时候,使用request.getReader()方法获取JSON信息后,POST请求就不往下走了,

**原因**：

1. 一个Reader对象在被读取完成后，将无法被再次读取，始终返回-1；

2. POST也是一种流,所以使用Reader方法后,POST请求返回true也不往下走了

解决方案:使用HttpServletRequestWrapper来包装HttpServletRequest，在BodyReaderHttpServletRequestWrapper中初始化读取request的Reader数据，以byte\[\]形式缓存在其中，然后在Filter中将request转换为包装过的request；代码如下：

public class HttpServletRequestReplacedFilter implements Filter {  
        @Override  
        public void destroy() {  
      
        }  
      
        @Override  
        public void doFilter(ServletRequest request, ServletResponse response,  
                FilterChain chain) throws IOException, ServletException {  
      
            ServletRequest requestWrapper = null;  
            if (request instanceof HttpServletRequest) {  
                HttpServletRequest httpServletRequest = (HttpServletRequest) request;  
                System.out.println(httpServletRequest.getContentType());
                System.out.println(httpServletRequest.getContextPath());
                System.out.println(httpServletRequest.getRemoteHost());
                System.out.println(httpServletRequest.getMethod());
                if ("POST".equals(httpServletRequest.getMethod().toUpperCase())  
                        ) {  
                	//&& httpServletRequest.getContentType().equalsIgnoreCase(  
               // "application/json")
                    requestWrapper = new BodyReaderHttpServletRequestWrapper(  
                            (HttpServletRequest) request);  
                }  
            }  
      
            if (requestWrapper == null) {  
                chain.doFilter(request, response);  
            } else {  
                chain.doFilter(requestWrapper, response);   
            }  
        }  
      
        @Override  
        public void init(FilterConfig arg0) throws ServletException {  
      
        }  
      
    }

public class BodyReaderHttpServletRequestWrapper extends  
            HttpServletRequestWrapper {  
          
        private final byte[] body;  
      
        public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {  
            super(request);  
            Enumeration e = request.getHeaderNames()   ;    
             while(e.hasMoreElements()){    
                 String name = (String) e.nextElement();    
                 String value = request.getHeader(name);    
                     
             }    
            body = HttpHelper.getBodyString(request).getBytes(Charset.forName("UTF-8"));  
        }  
      
        @Override  
        public BufferedReader getReader() throws IOException {  
            return new BufferedReader(new InputStreamReader(getInputStream()));  
        }  
      
        @Override  
        public ServletInputStream getInputStream() throws IOException {  
      
            final ByteArrayInputStream bais = new ByteArrayInputStream(body);  
      
            return new ServletInputStream() {  
                @Override  
                public int read() throws IOException {  
                    return bais.read();  
                }  
            };  
        }  
      
        @Override  
        public String getHeader(String name) {  
            return super.getHeader(name);  
        }  
      
        @Override  
        public Enumeration<String> getHeaderNames() {  
            return super.getHeaderNames();  
        }  
      
        @Override  
        public Enumeration<String> getHeaders(String name) {  
            return super.getHeaders(name);  
        }  
          
    }

public class HttpHelper {  
        /** 
         * 获取请求Body 
         * 
         * @param request 
         * @return 
         */  
        public static String getBodyString(ServletRequest request) {  
            StringBuilder sb = new StringBuilder();  
            InputStream inputStream = null;  
            BufferedReader reader = null;  
            try {  
                inputStream = request.getInputStream();  
                reader = new BufferedReader(new InputStreamReader(inputStream, Charset.forName("UTF-8")));  
                String line = "";  
                while ((line = reader.readLine()) != null) {  
                    sb.append(line);  
                }  
            } catch (IOException e) {  
                e.printStackTrace();  
            } finally {  
                if (inputStream != null) {  
                    try {  
                        inputStream.close();  
                    } catch (IOException e) {  
                        e.printStackTrace();  
                    }  
                }  
                if (reader != null) {  
                    try {  
                        reader.close();  
                    } catch (IOException e) {  
                        e.printStackTrace();  
                    }  
                }  
            }  
            return sb.toString();  
        }  
    }

web.xml配置文件

<filter>  
    	    <filter-name>HttpServletRequestReplacedFilter</filter-name>  
    	    <filter-class>com.xxx.xxx.xxx.xxx.util.HttpServletRequestReplacedFilter</filter-class>  
    
    
    
    
    	</filter>  
    	<filter-mapping>  
    	    <filter-name>HttpServletRequestReplacedFilter</filter-name>  
    	    <url-pattern>/*</url-pattern>  
    	</filter-mapping>

这样运行的时候就会先走Filter再走springmvc的拦截器了,就可以多次读取了