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為了多次讀取ServletInputStream引發(fā)的一系列問題

更新時(shí)間：2021年10月26日 10:15:00 作者：JAVA道人

這篇文章主要介紹了為了多次讀取ServletInputStream引發(fā)的一系列問題，具有很好的參考價(jià)值，希望對大家有所幫助。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教

多次讀取ServletInputStream引發(fā)的問題

因?yàn)榉?wù)器和app之間傳輸方式是JSON

格式如下

{
 head:null
body:null
token:xxxxxxxxxxxxxxxxxxxxx
}

所以想在服務(wù)端寫個(gè)攔截器或者filter先讀取token，來驗(yàn)證身份.但是如果前置攔截，那么在springMVC里的參數(shù)控制器就會讀取不到，導(dǎo)致@RequestBody 這個(gè)注解的參數(shù)不起作用.

原因在于ServletInputStream已經(jīng)在前置攔截器里讀取過一次，在接下來的ArgumentHandler里讀取的時(shí)候就不能再讀了，導(dǎo)致取不到數(shù)據(jù)而無法賦值.

于是寫了下面的filter來讓ServletInputStream來多次讀取

先寫個(gè)request

public class MyHttpRequest extends HttpServletRequestWrapper {
 private static Logger log=Logger.getLogger(MyHttpRequest.class);
    private  byte[] bytes;
    /**
     * @param request {@link javax.servlet.http.HttpServletRequest} object.
     * @throws IOException 
     */
    public MyHttpRequest(HttpServletRequest request) throws IOException {
        super(request);
        bytes= IOUtils.toByteArray( request.getInputStream());      
    }
 
    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
        return new DelegatingServletInputStream(byteArrayInputStream);
    }
    @Override
    public BufferedReader getReader() throws IOException {
     return new BufferedReader(new InputStreamReader(getInputStream()));
    }

以上內(nèi)容是先讀取出來，然后放到一個(gè)byte[]里，以后每次拿流的時(shí)候就可以再新建一個(gè)關(guān)于Byte[]的流.

然后再寫一個(gè)filter

public class MyFilter implements Filter{ 
 @Override
 public void destroy() {    
 }
 
 @Override
 public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
   throws IOException, ServletException {
  HttpServletRequest request=(HttpServletRequest) req;
  MyHttpRequest myrequest=new MyHttpRequest(request);
  chain.doFilter(myrequest, res);  
 }
 
 @Override
 public void init(FilterConfig arg0) throws ServletException {  
 } 
}

在web.xml里配置一下，試試效果，非常不錯(cuò).可以多次讀取了，

但是，我去

在post請求下，request.getParamter這種東西又不起作用了.

原因在于我們重寫的那個(gè)request是默認(rèn)調(diào)用父類的super.getparamter方法，而super.getparamter又依賴于super.getInputStream，但是在我們重寫的request里的構(gòu)造方法里，第一句話就老request注入到super里，然后下一句話就把老的request的流給讀了，導(dǎo)致我們調(diào)用super.getparameter的時(shí)候遇到了一個(gè)空的流。

解決思路：自己解決

package com.hrhs.jyj.filter; 
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map; 
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper; 
import org.apache.commons.io.IOUtils;
import org.apache.log4j.Logger;
import org.springframework.mock.web.DelegatingServletInputStream;
 
public class MyHttpRequest extends HttpServletRequestWrapper {
 private static Logger log = Logger.getLogger(MyHttpRequest.class);
 private byte[] bytes;
 private String body;
 private Map<String, List<String>> map;
 private int readMap=0;
 private String queryString;
 /**
  * @param request
  *            {@link javax.servlet.http.HttpServletRequest} object.
  * @throws IOException
  */
 public MyHttpRequest(HttpServletRequest request) throws IOException {
  super(request);
  bytes = IOUtils.toByteArray(request.getInputStream());
  queryString = request.getQueryString();
  
 }
 
 @Override
 public ServletInputStream getInputStream() throws IOException {
  final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
  return new DelegatingServletInputStream(byteArrayInputStream);
 }
 
 @Override
 public BufferedReader getReader() throws IOException {
  return new BufferedReader(new InputStreamReader(getInputStream()));
 }
 
 @Override
 public String getParameter(String name) {
  log.info("走了getParameter");
  return super.getParameter(name);
 }
 
 @Override
 public Map<String, String[]> getParameterMap() {
  log.info("走了getParameterMap");
  return super.getParameterMap();
 }
 
 @Override
 public Enumeration<String> getParameterNames() {
  log.info("走了getParameterNames");
  return super.getParameterNames();
 }
 //暫時(shí)先改寫這一個(gè),其他的也可以修改
 @Override
 public String[] getParameterValues(String name) {
  log.info("走了getParameterValues");
  try {
   Map<String, List<String>> nameVals = doParameter();
   List<String> list = nameVals.get(name);
   if(list!=null&&list.size()>0){
    return list.toArray(new String[]{});
   }
  } catch (UnsupportedEncodingException e) {
   e.printStackTrace();
  }
  return new String[]{};
 }
 //這里獲取所有參數(shù)值的map
 public Map<String, List<String>> doParameter() throws UnsupportedEncodingException {
  if(readMap==0){
   //這里把post里的參數(shù)和地址欄參數(shù)結(jié)合到一起,然后解析
   body = new String(bytes, getCharacterEncoding())+"&"+queryString;
   String[] nameVals = body.split("&");
   map = new HashMap<String, List<String>>();
   for (String nameVal : nameVals) {
    String name = nameVal.split("=")[0];
    String val = nameVal.split("=")[1];
    if (map.containsKey(name)) {
     List<String> vals = map.get(name);
     vals.add(val);
     map.put(name, vals);
    } else {
     List<String> vals = new ArrayList<String>();
     vals.add(val);
     map.put(name, vals);
    }
   }
   readMap=1;
  }
  return map;  
 }
}

ServletInputStream重復(fù)讀取問題

本來是想實(shí)現(xiàn)tomcat的acess_log打印post請求參數(shù)。吐槽一下，tomcat功能和nginx差了好幾條街。網(wǎng)上找了個(gè)方法，用tomcat的filter來實(shí)現(xiàn)。

但是，寫filter的時(shí)候，發(fā)現(xiàn)了ServletInputStream重復(fù)讀取問題。

網(wǎng)上找個(gè)幾個(gè)方法，都不能直接用。綜合網(wǎng)上的資料，根據(jù)自己的理解，終于能完美運(yùn)行了。

直接貼代碼了，親測能用

首先要寫個(gè)BufferHttpServletRequestWrapper類，用來復(fù)制HttpServletRequest request。

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader; 
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
 
public class BufferHttpServletRequestWrapper extends HttpServletRequestWrapper { 
 private final byte[] body; 
 public BufferHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
  super(request);
  InputStream is = request.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte buff[] = new byte[ 1024 ];
        int read;
        while( ( read = is.read( buff ) ) > 0 ) {
            baos.write( buff, 0, read );
        }
        body = baos.toByteArray();
 }
 
 @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();
   }
  };
 } 
}

然后filter實(shí)現(xiàn)如下：

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
 
/**
 * Servlet Filter implementation class PostDataDumperFilter
 */
 
public class PostDataDumperFilter implements Filter {
 
 private FilterConfig filterConfig = null;
 
    /**
     * Default constructor. 
     */
    public PostDataDumperFilter() {
        // TODO Auto-generated constructor stub
    }
 
 /**
  * @see Filter#destroy()
  */
 public void destroy() {
  this.filterConfig = null; 
 }
 
 /**
  * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
  */
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
  if (filterConfig == null) 
   return;
  //備份HttpServletRequest
  ServletRequest requestWrapper = null;  
        if(request instanceof HttpServletRequest) {  
            requestWrapper = new BufferHttpServletRequestWrapper((HttpServletRequest) request);  
        }
  //使用流
  InputStream reader = requestWrapper.getInputStream();
  ByteArrayOutputStream byteOutput = new ByteArrayOutputStream(100);
  int i =0;
  byte [] b = new byte[100];
  while((i = reader.read(b))!= -1){
   byteOutput.write(b, 0, i);
  }
  request.setAttribute("post", new String(byteOutput.toByteArray()));
  // pass the request along the filter chain
  if(null == requestWrapper){
   chain.doFilter(request, response);
  } else {  
            chain.doFilter(requestWrapper, response);  
        }
 }
 
 /**
  * @see Filter#init(FilterConfig)
  */
 public void init(FilterConfig fConfig) throws ServletException {
  this.filterConfig = fConfig;
 } 
}

好了，就寫到這里。以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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