如何构建可重复读取inputStream的request
作者:bjo2008cn 时间:2023-09-18 02:32:56
构建可重复读取inputStream的request
我们知道,request的inputStream只能被读取一次,多次读取将报错,那么如何才能重复读取呢?答案之一是:增加缓冲,记录已读取的内容。
代码如下所示:
import lombok.extern.log4j.Log4j2;
import org.springframework.mock.web.DelegatingServletInputStream;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;
/**
* request wrapper: 可重复读取request.getInputStream
*/
@Log4j2
public class RepeatedlyReadRequestWrapper extends HttpServletRequestWrapper {
private static final int BUFFER_START_POSITION = 0;
private static final int CHAR_BUFFER_LENGTH = 1024;
/**
* input stream 的buffer
*/
private final String body;
/**
* @param request {@link javax.servlet.http.HttpServletRequest} object.
*/
public RepeatedlyReadRequestWrapper(HttpServletRequest request) {
super(request);
StringBuilder stringBuilder = new StringBuilder();
InputStream inputStream = null;
try {
inputStream = request.getInputStream();
} catch (IOException e) {
log.error("Error reading the request body…", e);
}
if (inputStream != null) {
try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream))) {
char[] charBuffer = new char[CHAR_BUFFER_LENGTH];
int bytesRead;
while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
stringBuilder.append(charBuffer, BUFFER_START_POSITION, bytesRead);
}
} catch (IOException e) {
log.error("Fail to read input stream",e);
}
} else {
stringBuilder.append("");
}
body = stringBuilder.toString();
}
@Override
public ServletInputStream getInputStream() throws IOException {
final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes());
return new DelegatingServletInputStream(byteArrayInputStream);
}
}
接下来,需要一个对应的Filter.
代码如下所示:
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
public class RepeatlyReadFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
//Do nothing
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
if (request instanceof HttpServletRequest) {
request = new RepeatedlyReadRequestWrapper((HttpServletRequest) request);
}
chain.doFilter(request, response);
}
@Override
public void destroy() {
//Do nothing
}
}
最后,需要在web.xml中,增加该Filter的配置(略)。
request中inputStream多次读取
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
编写rHttpServletRequestWrapper子类,用来处理请求数据
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.Enumeration;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import lombok.extern.slf4j.Slf4j;
@Slf4j
public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper
{
private final byte[] body;
public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException
{
super(request);
Enumeration<String> e = request.getHeaderNames();
while (e.hasMoreElements())
{
String name = (String) e.nextElement();
String value = request.getHeader(name);
log.debug("HttpServletRequest头信息:{}-{}", name, value);
}
body = HttpHelper.getBodyString(request).getBytes(Charset.forName("UTF-8"));
}
@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 boolean isFinished()
{
return false;
}
@Override
public boolean isReady()
{
return false;
}
@Override
public void setReadListener(ReadListener listener)
{
}
@Override
public int read() throws IOException
{
return bais.read();
}
};
}
@Override
public String getHeader(String name)
{
return super.getHeader(name);
}
@Override
public Enumeration<String> getHeaderNames()
{
return super.getHeaderNames();
}
@Override
public Enumeration<String> getHeaders(String name)
{
return super.getHeaders(name);
}
}
调用
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException
{
HttpServletRequest httpRequest = (HttpServletRequest) request;
HttpServletResponse httpResponse = (HttpServletResponse) response;
ServletRequest requestWrapper = null;
requestWrapper = new BodyReaderHttpServletRequestWrapper(httpRequest);
//数据读取处理
//...
//将requestWrapper专递给后面的过滤器
filterChain.doFilter(requestWrapper, httpResponse);
}
来源:https://blog.csdn.net/bjo2008cn/article/details/53888923
标签:可重复读取,inputStream,request
![](/images/zang.png)
![](/images/jiucuo.png)
猜你喜欢
Android 沉浸式改变小米魅族状态栏颜色的实例代码
2023-11-18 15:13:16
![](https://img.aspxhome.com/file/2023/5/125395_0s.png)
Java结构型设计模式之享元模式示例详解
2022-05-16 21:41:10
![](https://img.aspxhome.com/file/2023/9/66059_0s.png)
TC 集群Seata1.6高可用架构源码解析
2022-04-18 05:02:34
![](https://img.aspxhome.com/file/2023/1/75801_0s.png)
Android使用gallery和imageSwitch制作可左右循环滑动的图片浏览器
2021-08-31 22:49:45
![](https://img.aspxhome.com/file/2023/6/139426_0s.gif)
Android Support Palette使用详解
2023-04-05 15:47:24
![](https://img.aspxhome.com/file/2023/4/108264_0s.jpg)
c#中(int)、int.Parse()、int.TryParse、Convert.ToInt32的区别详解
2023-01-26 04:59:46
java使用动态代理来实现AOP(日志记录)的实例代码
2023-11-28 22:34:45
![](https://img.aspxhome.com/file/2023/2/60262_0s.jpg)
user32.dll 函数说明小结
2021-10-13 12:19:21
Android实现加载广告图片和倒计时的开屏布局
2023-04-29 13:54:45
将java项目打包成exe可执行文件的完整步骤
2021-11-10 03:48:04
![](https://img.aspxhome.com/file/2023/4/122324_0s.png)
Kotlin语言编程Regex正则表达式实例详解
2023-06-22 02:06:29
Spring创建bean对象三种方式代码实例
2023-02-04 08:53:33
![](https://img.aspxhome.com/file/2023/6/70526_0s.png)
解决Android 沉浸式状态栏和华为虚拟按键冲突问题
2023-10-15 14:08:14
![](https://img.aspxhome.com/file/2023/4/125404_0s.png)
Android网格布局GridView学习使用
2023-02-07 15:03:13
![](https://img.aspxhome.com/file/2023/2/96752_0s.png)
跨域解决方案Jsonp原理解析
2023-11-07 18:48:05
解决springboot URL带有斜杠的转义字符百分之2F导致的400错误
2022-05-08 07:27:32
![](https://img.aspxhome.com/file/2023/3/75703_0s.png)
Android创建简单发送和接收短信应用
2022-01-04 18:31:08
![](https://img.aspxhome.com/file/2023/0/106820_0s.png)
Java 判断字符串中是否包含中文的实例详解
2023-11-06 13:17:18
![](https://img.aspxhome.com/file/2023/3/58913_0s.png)
SpringCloud服务网关Gateway的使用教程详解
2021-05-29 20:53:39
![](https://img.aspxhome.com/file/2023/3/132193_0s.png)
编写Java代码对HDFS进行增删改查操作代码实例
2023-07-08 11:46:42