HttpServletRequestWrapper使用技巧（自定义session和缓存InputStream）

一、前言

　　javax.servlet.http.HttpServletRequestWrapper 是一个开发者可以继承的类，我们可以重写相应的方法来实现session的自定义以及缓存InputStream，在程序中可以多次获取request body的内容。

二、自定义seesion

import javax.servlet.http.*;

public class CustomizeHttpServletRequest extends HttpServletRequestWrapper {

public CustomizeHttpServletRequest(HttpServletRequest request) {
super(request);
this.response = response;
}

@Override
public HttpSession getSession() {
//return super.getSession(); // 默认使用的是servlet容器session管理

return this.getSession(true);
}

@Override
public HttpSession getSession(boolean create) {
Cookie[] cookies = this.getCookies();
String sessionId = "";

//这里编写自己获取session的逻辑
//既然是自定义逻辑，可以从内存中取，也可以从缓存中取。
}
}

　　也许大家都用过shiro的session管理或者spring-session，其实想要自己去实现，也是很简单的。

三、缓存InputStream

　　自定义工具类 ContentCachingRequestWrapper 

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

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.apache.commons.io.IOUtils;

public class ContentCachingRequestWrapper extends HttpServletRequestWrapper{

private byte[] body;

private BufferedReader reader;

private ServletInputStream inputStream;

public ContentCachingRequestWrapper(HttpServletRequest request) throws IOException{
super(request);
body = IOUtils.toByteArray(request.getInputStream());
inputStream = new RequestCachingInputStream(body);
}

public byte[] getBody() {
return body;
}

@Override
public ServletInputStream getInputStream() throws IOException {
if (inputStream != null) {
return inputStream;
}
return super.getInputStream();
}

@Override
public BufferedReader getReader() throws IOException {
if (reader == null) {
reader = new BufferedReader(new InputStreamReader(inputStream, getCharacterEncoding()));
}
return reader;
}

private static class RequestCachingInputStream extends ServletInputStream {

private final ByteArrayInputStream inputStream;

public RequestCachingInputStream(byte[] bytes) {
inputStream = new ByteArrayInputStream(bytes);
}
@Override
public int read() throws IOException {
return inputStream.read();
}

@Override
public boolean isFinished() {
return inputStream.available() == 0;
}

@Override
public boolean isReady() {
return true;
}

@Override
public void setReadListener(ReadListener readlistener) {
}

}

}

　　spring工具类 ContentCachingRequestWrapper 

package org.springframework.web.util;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URLEncoder;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import org.springframework.http.HttpMethod;

public class ContentCachingRequestWrapper extends HttpServletRequestWrapper {

private static final String FORM_CONTENT_TYPE = "application/x-www-form-urlencoded";

private final ByteArrayOutputStream cachedContent;

private ServletInputStream inputStream;

private BufferedReader reader;

/**
* Create a new ContentCachingRequestWrapper for the given servlet request.
* @param request the original servlet request
*/
public ContentCachingRequestWrapper(HttpServletRequest request) {
super(request);
int contentLength = request.getContentLength();
this.cachedContent = new ByteArrayOutputStream(contentLength >= 0 ? contentLength : 1024);
}

@Override
public ServletInputStream getInputStream() throws IOException {
if (this.inputStream == null) {
this.inputStream = new ContentCachingInputStream(getRequest().getInputStream());
}
return this.inputStream;
}

@Override
public String getCharacterEncoding() {
String enc = super.getCharacterEncoding();
return (enc != null ? enc : WebUtils.DEFAULT_CHARACTER_ENCODING);
}

@Override
public BufferedReader getReader() throws IOException {
if (this.reader == null) {
this.reader = new BufferedReader(new InputStreamReader(getInputStream(), getCharacterEncoding()));
}
return this.reader;
}

@Override
public String getParameter(String name) {
if (this.cachedContent.size() == 0 && isFormPost()) {
writeRequestParametersToCachedContent();
}
return super.getParameter(name);
}

@Override
public Map<String, String[]> getParameterMap() {
if (this.cachedContent.size() == 0 && isFormPost()) {
writeRequestParametersToCachedContent();
}
return super.getParameterMap();
}

@Override
public Enumeration<String> getParameterNames() {
if (this.cachedContent.size() == 0 && isFormPost()) {
writeRequestParametersToCachedContent();
}
return super.getParameterNames();
}

@Override
public String[] getParameterValues(String name) {
if (this.cachedContent.size() == 0 && isFormPost()) {
writeRequestParametersToCachedContent();
}
return super.getParameterValues(name);
}

private boolean isFormPost() {
String contentType = getContentType();
return (contentType != null && contentType.contains(FORM_CONTENT_TYPE) &&
HttpMethod.POST.matches(getMethod()));
}

private void writeRequestParametersToCachedContent() {
try {
if (this.cachedContent.size() == 0) {
String requestEncoding = getCharacterEncoding();
Map<String, String[]> form = super.getParameterMap();
for (Iterator<String> nameIterator = form.keySet().iterator(); nameIterator.hasNext(); ) {
String name = nameIterator.next();
List<String> values = Arrays.asList(form.get(name));
for (Iterator<String> valueIterator = values.iterator(); valueIterator.hasNext(); ) {
String value = valueIterator.next();
this.cachedContent.write(URLEncoder.encode(name, requestEncoding).getBytes());
if (value != null) {
this.cachedContent.write('=');
this.cachedContent.write(URLEncoder.encode(value, requestEncoding).getBytes());
if (valueIterator.hasNext()) {
this.cachedContent.write('&');
}
}
}
if (nameIterator.hasNext()) {
this.cachedContent.write('&');
}
}
}
}
catch (IOException ex) {
throw new IllegalStateException("Failed to write request parameters to cached content", ex);
}
}

/**
* Return the cached request content as a byte array.
*/
public byte[] getContentAsByteArray() {
return this.cachedContent.toByteArray();
}

private class ContentCachingInputStream extends ServletInputStream {

private final ServletInputStream is;

public ContentCachingInputStream(ServletInputStream is) {
this.is = is;
}

@Override
public int read() throws IOException {
int ch = this.is.read();
if (ch != -1) {
cachedContent.write(ch);
}
return ch;
}

@Override
public boolean isFinished() {
return is.available() == 0;
}

@Override
public boolean isReady() {
return true;
}

@Override
public void setReadListener(ReadListener readlistener) {
}

}

}

　　获取InputStream

　　1、使用自定义工具类的时候调用方法 getBody

　　2、使用spring工具类的时候调用方法 getContentAsByteArray

　　打印request中的所有请求信息，详细代码如下。

private void printRequest(HttpServletRequest request) {
String body = StringUtils.EMPTY;
try {
if (request instanceof ContentCachingRequestWrapper) {
body = new String(((ContentCachingRequestWrapper) request).getContentAsByteArray(), "UTF-8");
LOGGER.info("Request-Inputstream: " + body);
}
} catch (IOException e) {
LOGGER.error("printRequest 获取body异常...", e);
}

JSONObject requestJ = new JSONObject();
JSONObject headers = new JSONObject();
Collections.list(request.getHeaderNames())
.stream()
.forEach(name -> headers.put(name, request.getHeader(name)));
requestJ.put("headers", headers);
requestJ.put("parameters", request.getParameterMap());
requestJ.put("body", body);
requestJ.put("remote-user", request.getRemoteUser());
requestJ.put("remote-addr", request.getRemoteAddr());
requestJ.put("remote-host", request.getRemoteHost());
requestJ.put("remote-port", request.getRemotePort());
requestJ.put("uri", request.getRequestURI());
requestJ.put("url", request.getRequestURL());
requestJ.put("servlet-path", request.getServletPath());
requestJ.put("method", request.getMethod());
requestJ.put("query", request.getQueryString());
requestJ.put("path-info", request.getPathInfo());
requestJ.put("context-path", request.getContextPath());

LOGGER.info("Request-Info: " + JSON.toJSONString(requestJ, SerializerFeature.PrettyFormat));
}

　　request中的所有请求信息示例

Request-Inputstream: {
"timestamp":1539155028668,
"appId":"cmos10086e36ipz2otyy8gfqh",
"nonce":691879,
"telephone":"18736085778",
"signature":"226e734a49d513b3b1e364a06fc6f4eb5e2c425c6446ce6a7a950f1d8d6af06c"
}

Request-Info: {
"headers":{
"x-real-ip":"211.138.20.171",
"content-length":"183",
"content-encoding":"UTF-8",
"host":"221.176.66.251",
"connection":"close",
"content-type":"application/json",
"accept-encoding":"gzip,deflate",
"user-agent":"Apache-HttpClient/4.5.3 (Java/1.7.0_76)"
},
"remote-host":"172.17.20.92",
"method":"POST",
"body":"{\"timestamp\":1539155028668,\"appId\":\"cmos10086e36ipz2otyy8gfqh\",\"nonce\":691879,\"telephone\":\"18736085778\",\"signature\":\"226e734a49d513b3b1e364a06fc6f4eb5e2c425c6446ce6a7a950f1d8d6af06c\"}",
"uri":"/wmhopenapi/hevb-api/total",
"url":"http://221.176.66.251/wmhopenapi/hevb-api/total",
"servlet-path":"/hevb-api/total",
"remote-addr":"172.17.20.92",
"context-path":"/wmhopenapi",
"remote-port":49174,
"parameters":{}
}

四、在Filter中替换掉默认的Request

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.util.ContentCachingRequestWrapper;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

@Configuration
public class FilterConfig {

@Bean
public FilterRegistrationBean wmhFilterRegistration() {
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setFilter(new WmhFilter());
registration.addUrlPatterns("/*");
registration.setName("MyFilter");
registration.setOrder(1);
return registration;
}

private static class WmhFilter implements Filter {

@Override
public void init(javax.servlet.FilterConfig filterConfig) throws ServletException {

}

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
chain.doFilter(new ContentCachingRequestWrapper((HttpServletRequest) request), response);
}

@Override
public void destroy() {

}
}
}

 五、使用场景

　　个人认为，在做权限管理、用户管理、登录等场景，尤其是多系统的情况下，常常需要借助第三方的工具比如shiro，spring-session，完成权限、角色、用户、登录的管理逻辑。之前我自己也尝试过使用spring-session+redis缓存实现共享session和单点登录的逻辑。如果时间充分的话，完全可以自己去写一套session管理的工具，并应用到项目中去。

　　最近在配合其他组的同时联调接口的时候，遇到了这样的一种情况：他说request body的内容是按照我的协议来的，我后端的实现是通过@RequestBody注解拿到的一个java 对象，有一个字段值为null，很是诡异。于是我俩就纠结是谁的问题，我说他参数传的不对，他说我字段定义不对并让我打印一下Request InputStream，于是就开始寻找解决方案。我们都知道Input Sream只能获取一次，再次获取一定会抛出异常。通过寻找HttpServletRequest的子类，发现了spring提供了这样一个缓存Input Stream内容的工具类，问题迎刃而解。