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为了多次读取ServletInputStream引发的一系列问题

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这篇文章主要介绍了为了多次读取ServletInputStream引发的一系列问题，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

多次读取ServletInputStream引发的问题

因为服务器和app之间传输方式是JSON

格式如下

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{
 head:null
body:null
token:xxxxxxxxxxxxxxxxxxxxx
}

所以想在服务端写个拦截器或者filter先读取token，来验证身份.但是如果前置拦截，那么在springMVC里的参数控制器就会读取不到，导致@RequestBody 这个注解的参数不起作用.

原因在于ServletInputStream已经在前置拦截器里读取过一次，在接下来的ArgumentHandler里读取的时候就不能再读了，导致取不到数据而无法赋值.

于是写了下面的filter来让ServletInputStream来多次读取

先写个request

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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()));
    }

以上内容是先读取出来，然后放到一个byte[]里，以后每次拿流的时候就可以再新建一个关于Byte[]的流.

然后再写一个filter

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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，试试效果，非常不错.可以多次读取了，

但是，我去

在post请求下，request.getParamter这种东西又不起作用了.

原因在于我们重写的那个request是默认调用父类的super.getparamter方法，而super.getparamter又依赖于super.getInputStream，但是在我们重写的request里的构造方法里，第一句话就老request注入到super里，然后下一句话就把老的request的流给读了，导致我们调用super.getparameter的时候遇到了一个空的流。

解决思路：自己解决

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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();
 }
 //暂时先改写这一个,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[]{};
 }
 //这里获取所有参数值的map
 public Map<String, List<String>> doParameter() throws UnsupportedEncodingException {
  if(readMap==0){
   //这里把post里的参数和地址栏参数结合到一起,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重复读取问题

本来是想实现tomcat的acess_log打印post请求参数。吐槽一下，tomcat功能和nginx差了好几条街。网上找了个方法，用tomcat的filter来实现。

但是，写filter的时候，发现了ServletInputStream重复读取问题。

网上找个几个方法，都不能直接用。综合网上的资料，根据自己的理解，终于能完美运行了。

直接贴代码了，亲测能用

首先要写个BufferHttpServletRequestWrapper类，用来复制HttpServletRequest request。

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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实现如下：

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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;
  //备份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，就写到这里。以上为个人经验，希望能给大家一个参考，也希望大家多多支持米米素材网。

原文链接：https://blog.csdn.net/dmw412724/article/details/79296345