ServletRequest中getReader()和getInputStream()只能调用一次的解决方法

ServletRequest中getReader()和getInputStream()只能调用一次的解决办法
最近使用spring mvc做项目，数据格式是json，有一个功能是实现记录请求的参数，而请求的参数是整个RequestBody，Controller里是用过@RequestBody获取的。实现方法是通过一个Filter读取整个RequestBody并记录。但是这时就遇到一个问题，ServletRequest的getReader()和getInputStream()两个方法只能被调用一次，而且不能两个都调用。那么如果Filter中调用了一次，在Controller里面就不能再调用了。查看了下ServletRequest的说明，如下：

    /**     * Retrieves the body of the request as binary data using     * a {@link ServletInputStream}.  Either this method or      * {@link #getReader} may be called to read the body, not both.     *     * @returna {@link ServletInputStream} object containing     * the body of the request     *     * @exception IllegalStateException  if the {@link #getReader} method     *  has already been called for this request     *     * @exception IOException    if an input or output exception occurred     *     */    public ServletInputStream getInputStream() throws IOException;     /**     * Retrieves the body of the request as character data using     * a <code>BufferedReader</code>.  The reader translates the character     * data according to the character encoding used on the body.     * Either this method or {@link #getInputStream} may be called to read the     * body, not both.     *      *     * @returna <code>BufferedReader</code>     *containing the body of the request     *     * @exception UnsupportedEncodingException if the character set encoding     * used is not supported and the      *text cannot be decoded     *     * @exception IllegalStateException   if {@link #getInputStream} method     * has been called on this request     *     * @exception IOException  if an input or output exception occurred     *     * @see #getInputStream     *     */    public BufferedReader getReader() throws IOException;

两个方法都注明方法只能被调用一次，由于RequestBody是流的形式读取，那么流读了一次就没有了，所以只能被调用一次。既然是因为流只能读一次的原因，那么只要将流的内容保存下来，就可以实现反复读取了。

实现方法：先将RequestBody保存为一个byte数组，然后通过Servlet自带的HttpServletRequestWrapper类覆盖getReader()和getInputStream()方法，使流从保存的byte数组读取。然后再Filter中将ServletRequest替换为ServletRequestWrapper。代码如下：

BodyReaderHttpServletRequestWrapper类包装ServletRequest，将流保存为byte[]，然后将getReader()和getInputStream()方法的流的读取指向byte[]

import java.io.BufferedReader;import java.io.ByteArrayInputStream;import java.io.IOException;import java.io.InputStreamReader;import javax.servlet.ServletInputStream;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper;import jodd.JoddDefault;import jodd.io.StreamUtil;public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {private final byte[] body;public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {super(request);body = StreamUtil.readBytes(request.getReader(), JoddDefault.encoding);}@Overridepublic BufferedReader getReader() throws IOException {return new BufferedReader(new InputStreamReader(getInputStream()));}@Overridepublic ServletInputStream getInputStream() throws IOException {final ByteArrayInputStream bais = new ByteArrayInputStream(body);return new ServletInputStream() {@Overridepublic int read() throws IOException {return bais.read();}};}}

在Filter中将ServletRequest替换为ServletRequestWrapper

public class HttpServletRequestReplacedFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {//Do nothing}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {ServletRequest requestWrapper = null;if(request instanceof HttpServletRequest) {requestWrapper = new BodyReaderHttpServletRequestWrapper((HttpServletRequest) request);}if(null == requestWrapper) {chain.doFilter(request, response);} else {chain.doFilter(requestWrapper, response);}}@Overridepublic void destroy() {//Do nothing}}

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