Request请求体重新封装，解决请求体只能获取一次的问题

问题

在mvc架构中，经常会对接口进行拦截做一些权限校验，常用做法就是加入拦截器或过滤器，其中会提前获取post请求体，获取之后，controller方法上的参数就无法再获取的问题。

解决方案

定义一个ServletInputStreamWrapper

ServletInputStreamWrapper 是为了重新将请求体包装到HttpServletRequestWrapper中

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import java.io.IOException;

public class ServletInputStreamWrapper extends ServletInputStream {
    private byte[] data;
    private int idx = 0;

    public ServletInputStreamWrapper(byte[] data) {
        if (data == null) {
            data = new byte[0];
        }

        this.data = data;
    }

    public int read() throws IOException {
        return this.idx == this.data.length ? -1 : this.data[this.idx++] & 255;
    }

    @Override
    public boolean isFinished() {
        return false;
    }

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

    @Override
    public void setReadListener(ReadListener readListener) {

    }
}

定义一个过滤器，并对request进行包装

这里的目的就是为了重新包装新的request，并且要传入到新的请求中，因此，使用过滤器是最好的选择，拦截器完成此操作比较麻烦。实现 getInputStream() 、getContentLength() 、getContentLengthLong() 方法。在getInputStream()方法返回则是我们上一步定义的ServletInputStreamWrapper，构造方法中传入新请求体的byte[]即可。

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;

/**
 * 过滤器
 */
@Component
@WebFilter(filterName = "outAuthFilter", urlPatterns = {"/outer/*"})
public class OutAuthFilter implements Filter {
 
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
 
        String requestBody = "";
        try {
            InputStream stream = request.getInputStream();
            if (stream != null) {
                requestBody = StreamUtils.copyToString(stream, Charset.forName("UTF-8"));
            }
        } catch (IOException e) {
            //requestBody里面没有数据
            System.out.println("requestBody里面没有数据");
            return;
        }

        String newRequestBody ="{\"id\":\"1\",\"text\":\"新包装的JSON数据\"}";
     
        final byte[] reqBodyBytes = newRequestBody.getBytes();
        //对request进行重新包装
        HttpServletRequestWrapper requestWrapper = new HttpServletRequestWrapper(request) {
            @Override
            public ServletInputStream getInputStream() throws IOException {
                return new ServletInputStreamWrapper(reqBodyBytes);
            }

            @Override
            public int getContentLength() {
                return reqBodyBytes.length;
            }

            @Override
            public long getContentLengthLong() {
                return reqBodyBytes.length;
            }
        };
		// 将新request包装对象传入过滤器链中
        filterChain.doFilter(requestWrapper, servletResponse);
    }

    @Override
    public void destroy() {

    }
 
}