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：
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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 */@Log4j2public 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：
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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
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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;@Slf4jpublic 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
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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); } |
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服务器之家。
原文链接：https://blog.csdn.net/bjo2008cn/article/details/53888923
