request.getInputStream()只能获取一次的问题

问题

在使用HTTP协议实现应用间接口通信时，服务端读取客户端请求过来的数据，会用到request.getInputStream()，第一次读取的时候可以读取到数据，但是接下来的读取操作都读取不到数据

原因

一个InputStream对象在被读取完成后，将无法被再次读取，始终返回-1；

InputStream并没有实现reset方法（可以重置首次读取的位置），无法实现重置操作；

解决方法（缓存读取到的数据）

使用request、session等来缓存读取到的数据,这种方式很容易实现，只要setAttribute和getAttribute就行；

使用HttpServletRequestWrapper来包装HttpServletRequest，在MAPIHttpServletRequestWrapper中初始化读取request的InputStream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：

package com.paddypower.financials.market.management.rest.logging;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.apache.commons.io.IOUtils;

public class LoggerFilter implements Filter {

private Auditor auditor;

public void destroy() {
// Nothing to do
}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
ResettableStreamHttpServletRequest wrappedRequest = new ResettableStreamHttpServletRequest(
(HttpServletRequest) request);
// wrappedRequest.getInputStream().read();
String body = IOUtils.toString(wrappedRequest.getReader());
auditor.audit(wrappedRequest.getRequestURI(),wrappedRequest.getUserPrincipal(), body);
wrappedRequest.resetInputStream();
chain.doFilter(wrappedRequest, response);

}

public void init(FilterConfig arg0) throws ServletException {
// Nothing to do
}

private static class ResettableStreamHttpServletRequest extends
HttpServletRequestWrapper {

private byte[] rawData;
private HttpServletRequest request;
private ResettableServletInputStream servletStream;

public ResettableStreamHttpServletRequest(HttpServletRequest request) {
super(request);
this.request = request;
this.servletStream = new ResettableServletInputStream();
}

public void resetInputStream() {
servletStream.stream = new ByteArrayInputStream(rawData);
}

@Override
public ServletInputStream getInputStream() throws IOException {
if (rawData == null) {
rawData = IOUtils.toByteArray(this.request.getReader());
servletStream.stream = new ByteArrayInputStream(rawData);
}
return servletStream;
}

@Override
public BufferedReader getReader() throws IOException {
if (rawData == null) {
rawData = IOUtils.toByteArray(this.request.getReader());
servletStream.stream = new ByteArrayInputStream(rawData);
}
return new BufferedReader(new InputStreamReader(servletStream));
}

private class ResettableServletInputStream extends ServletInputStream {

private InputStream stream;

@Override
public int read() throws IOException {
return stream.read();
}
}
}

public void setAuditor(Auditor auditor) {
this.auditor = auditor;
}

}