request 字节流只能读取一次

问题描述：

当我们使用拦截器或者过滤器读取和 request 的字节流之后，controller 中的 @RequestBody 报错，提示 request body 为空。

因为 request 的字节流只能读取一次，我们需要把此字节流存储起来，使其可以多次读取，利用 HttpServletRequestWrapper 对 request 进行封装。

继承 HttpServletRequestWrapper

package com.rs.shiliu.filter;

import org.springframework.util.StreamUtils;

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private byte[] requestBody = null;

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        requestBody = StreamUtils.copyToByteArray(request.getInputStream());
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        ByteArrayInputStream inputStream = new ByteArrayInputStream(requestBody);
        return new ServletInputStream() {
            @Override
            public boolean isFinished() {
                return inputStream.available() == 0;
            }

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

            @Override
            public void setReadListener(ReadListener readListener) {

            }

            @Override
            public int read() throws IOException {
                return inputStream.read();
            }
        };
    }

    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }
}

添加过滤器，替换 request

package com.rs.shiliu.filter;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

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

@Component
@WebFilter(urlPatterns = "/*")
public class BodyReaderFilter implements Filter {
    private static final Logger logger = LoggerFactory.getLogger(BodyReaderFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        ServletRequest requestWrapper = null;
        if (servletRequest instanceof HttpServletRequest) {
            requestWrapper = new BodyReaderHttpServletRequestWrapper((HttpServletRequest) servletRequest);
        }
        filterChain.doFilter(requestWrapper == null ? servletRequest : requestWrapper, servletResponse);
    }

    @Override
    public void destroy() {
        Filter.super.destroy();
    }
}