RequestBody只能读取一次的问题

一、为什么只能读一次

原因很简单：因为是流。想想看，java中的流也是只能读一次，因为读完之后，position就到末尾了。

二、解决办法

思路：第一次读的时候，把流数据暂存起来。后面需要的时候，直接把暂存的数据返回出去。

实现逻辑：

自定义一个HttpServletRequestWrapper，覆写getInputStream()和getReader()方法。
增加一个Filter，在doFilter()中启用自定义的Wrapper

三、代码

1、自定义的Wrapper

import javax.servlet.ReadListener;

import javax.servlet.ServletInputStream;

import javax.servlet.ServletRequest;

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.InputStream;

import java.io.InputStreamReader;

import java.nio.charset.Charset;

public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {

    private final byte[] body;

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {

        super(request);

        String sessionStream = getBodyString(request);

        body = sessionStream.getBytes(Charset.forName("UTF-8"));

    }

    private String getBodyString(ServletRequest request) throws IOException {

        StringBuilder sb = new StringBuilder();

        InputStream ins = request.getInputStream();

        try (BufferedReader isr = new BufferedReader(new InputStreamReader(ins, Charset.forName("UTF-8")));) {

            String line = "";

            while ((line = isr.readLine()) != null) {

                sb.append(line);

            }

        } catch (IOException e) {

            throw e;

        }

        return sb.toString();

    }

    @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 int read() throws IOException {

                return bais.read();

            }

            @Override

            public boolean isFinished() {

                return bais.available() == 0;

            }

            @Override

            public boolean isReady() {

                return true;

            }

            @Override

            public void setReadListener(ReadListener readListener) {

            }

        };

    }

}

2、加个Filter来启用wrapper

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.annotation.WebFilter;

import javax.servlet.http.HttpServletRequest;

import java.io.IOException;

// 启用Filter需要在Springboot的启动类加@ServletComponentScan

@WebFilter(filterName = "bodyReaderFilter", urlPatterns = "/*")

public class BodyReaderFilter implements Filter {

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;

        ServletRequest requestWrapper = new BodyReaderHttpServletRequestWrapper(httpServletRequest);

        filterChain.doFilter(requestWrapper, servletResponse);

    }

    @Override

    public void destroy() {

    }

}

巴特西

RequestBody只能读取一次的问题

一、为什么只能读一次

二、解决办法

三、代码

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