最近打算在之前的项目APP接口里面加入验证签名的功能，实现思路很简单，就是通过添加filter的方式，在filter中读取所有的请求参数，然后验证客户端传过来的SIGN值跟服务端生成的SIGN值是否一致。
目前的接口里面参数有K=V格式的，也有JSON格式的，对于前者在filter中通过HttpServletRequest.getParameterMap就可以直接获取。但是对于JSON参数，我们需要从request的inputStream中读取，当然这也不复杂，几行代码就可以搞定了。
但是当我完成filter中的代码，在进行调试的时候，发现原来controller中通过@RequestBody获取JSON参数的接口抛出“Required request body is missing”的错误。刚开始还以为参数传的有问题，查阅相关资料才明白inputStream的数据只能读取一次，从inputStream中读取过数据之后，后续再从inputStream中就不能再读取到数据了。然后就继续在网上翻资料，有的说需要自己重写HttpServletRequestWrapper，有的说通过spring自带的ContentCachingRequestWrapper就可以，我是一个比较懒的人，如果有现成好用的我才懒得自己写呢，先试试看。
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper((HttpServletRequest) request);
String body = IOUtils.toString(request.getInputStream(),request.getCharacterEncoding());
//TODO 验证签名
chain.doFilter(requestWrapper, response);
}
然而并没有什么用 WTF ... 查看ContentCachingRequestWrapper源码发现它也只是把inputStream的数据读取出来存到cachedContent里面了，后面仍然不能再次读取inputStream, 但是我看网上有几个都说这样可以，后来才发现他们是在 chain.doFilter(requestWrapper, response)之后再通过requestWrapper.getContentAsByteArray方法获取数据，或者在filter中读取了inputstream之后，在controller接口方法中使用requestWrapper.getContentAsByteArray方法再获取数据，这样就不能使用@RequestBody自动注入参数了，这显然不是我想要的。
看来还得自己动手，我们要做的就是读取了inputStream之后，再将数据写回去，具体实现如下：
package com.spbd.core.web.filter;
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);
loadBody(request);
}
private void loadBody(HttpServletRequest request) throws IOException{
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) {
}
}
}
https://github.com/sergewu/demo
参考文档：
https://www.jianshu.com/p/9b717551ee44
https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/util/ContentCachingRequestWrapper.html
最后附上ContentCachingRequestWrapper的源码：
/*
* Copyright 2002-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
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;
/**
* {@link javax.servlet.http.HttpServletRequest} wrapper that caches all content read from
* the {@linkplain #getInputStream() input stream} and {@linkplain #getReader() reader},
* and allows this content to be retrieved via a {@link #getContentAsByteArray() byte array}.
*
* Used e.g. by {@link org.springframework.web.filter.AbstractRequestLoggingFilter}.
*
* @author Juergen Hoeller
* @author Brian Clozel
* @since 4.1.3
* @see ContentCachingResponseWrapper
*/
public class ContentCachingRequestWrapper extends HttpServletRequestWrapper {
private static final String FORM_CONTENT_TYPE = "application/x-www-form-urlencoded";
private final ByteArrayOutputStream cachedContent;
private final Integer contentCacheLimit;
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);
this.contentCacheLimit = null;
}
/**
* Create a new ContentCachingRequestWrapper for the given servlet request.
* @param request the original servlet request
* @param contentCacheLimit the maximum number of bytes to cache per request
* @since 4.3.6
* @see #handleContentOverflow(int)
*/
public ContentCachingRequestWrapper(HttpServletRequest request, int contentCacheLimit) {
super(request);
this.cachedContent = new ByteArrayOutputStream(contentCacheLimit);
this.contentCacheLimit = contentCacheLimit;
}
@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 getParameterMap() {
if (this.cachedContent.size() == 0 && isFormPost()) {
writeRequestParametersToCachedContent();
}
return super.getParameterMap();
}
@Override
public Enumeration 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 form = super.getParameterMap();
for (Iterator nameIterator = form.keySet().iterator(); nameIterator.hasNext(); ) {
String name = nameIterator.next();
List values = Arrays.asList(form.get(name));
for (Iterator 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.
* The returned array will never be larger than the content cache limit.
* @see #ContentCachingRequestWrapper(HttpServletRequest, int)
*/
public byte[] getContentAsByteArray() {
return this.cachedContent.toByteArray();
}
/**
* Template method for handling a content overflow: specifically, a request
* body being read that exceeds the specified content cache limit.
*
The default implementation is empty. Subclasses may override this to
* throw a payload-too-large exception or the like.
* @param contentCacheLimit the maximum number of bytes to cache per request
* which has just been exceeded
* @since 4.3.6
* @see #ContentCachingRequestWrapper(HttpServletRequest, int)
*/
protected void handleContentOverflow(int contentCacheLimit) {
}
private class ContentCachingInputStream extends ServletInputStream {
private final ServletInputStream is;
private boolean overflow = false;
public ContentCachingInputStream(ServletInputStream is) {
this.is = is;
}
@Override
public int read() throws IOException {
int ch = this.is.read();
if (ch != -1 && !this.overflow) {
if (contentCacheLimit != null && cachedContent.size() == contentCacheLimit) {
this.overflow = true;
handleContentOverflow(contentCacheLimit);
}
else {
cachedContent.write(ch);
}
}
return ch;
}
}
}