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
{ 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
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
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
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> 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 getParameterMap() { log.info("走了getParameterMap"); return super.getParameterMap(); } @Override public Enumeration 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> nameVals = doParameter(); List 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> 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>(); for (String nameVal : nameVals) { String name = nameVal.split("=")[0]; String val = nameVal.split("=")[1]; if (map.containsKey(name)) { List vals = map.get(name); vals.add(val); map.put(name, vals); } else { List vals = new ArrayList(); 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。
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：
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0133技术站。
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