The Request request body is repackaged to solve the problem that the request body can only be obtained once

问题

在mvc架构中,Interfaces are often intercepted to do some permission checks,A common practice is to add interceptors or filters,which will be obtained in advancepost请求体,获取之后,controllerThe problem that the parameters on the method can no longer be obtained.

解决方案

定义一个ServletInputStreamWrapper

ServletInputStreamWrapper is to re-wrap the request body into 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

The purpose here is to repackage the new onerequest,And to be passed into the new request,因此,Using filters is the best option,Interceptors are more cumbersome to do this.实现 getInputStream() 、getContentLength() 、getContentLengthLong() 方法.在getInputStream()The method return is what we defined in the previous stepServletInputStreamWrapper,The new request body is passed in the constructorbyte[]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requestThe wrapper object is passed into the filter chain
        filterChain.doFilter(requestWrapper, servletResponse);
    }

    @Override
    public void destroy() {
    

    }
 
}