SpringBoot项目中，拦截器获取Post方法的请求body

一、遇到的问题

拦截器（interceptor）中通过request获取的流读出body数据后，

request.getInputStream();

controller方法接收body时出现报错

Resolved [org.springframework.http.converter.HttpMessageNotReadableException: I/O error while reading input message; nested exception is java.io.IOException: Stream closed]

二、解决方法

1. 创建HttpServletRequest包装类

• 继承HttpServletRequestWapper类

package chances.epg.user.filter;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.nio.charset.Charset;

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import chances.epg.user.util.HttpHelper;

/**
 * @author <a href="mailto:[email protected]">lanxing</a>
 *
 */
public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private final byte[] body;

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        String bodyString = HttpHelper.getBodyString(request);
        body = bodyString.getBytes(Charset.forName("UTF-8"));
    }

    @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 false;
            }

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

            @Override
            public void setReadListener(ReadListener readListener) {
            }
        };
    }
}

2. 创建过滤器

• 新建一个过滤器（Filter）,对request进行包装

package chances.epg.user.interceptor;

import java.io.IOException;

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;

/**
 * @author <a href="mailto:[email protected]">lanxing</a>
 *
 */
@WebFilter(filterName = "httpServletRequestWrapperFilter", urlPatterns = { "/*" })
public class HttpServletRequestWrapperFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        ServletRequest requestWrapper = null;
        if (request instanceof HttpServletRequest) {
            HttpServletRequest httpRequest = (HttpServletRequest) request;

            // 遇到post方法才对request进行包装
            String methodType = httpRequest.getMethod();
            // 上传文件时同样不进行包装
            String servletPath = httpRequest.getRequestURI().toString();
            if ("POST".equals(methodType) && !servletPath.contains("/material/upload")) {
                requestWrapper = new BodyReaderHttpServletRequestWrapper(
                        (HttpServletRequest) request);
            }
        }

        if (null == requestWrapper) {
            chain.doFilter(request, response);
        } else {
            chain.doFilter(requestWrapper, response);
        }

    }

    @Override
    public void destroy() {

    }
}

3. 流读取工具类

• 通过流（inputStream）获取字符串的工具类

package chances.epg.user.interceptor;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

import javax.servlet.http.HttpServletRequest;

/**
 * @author <a href="mailto:[email protected]">lanxing</a>
 *
 */
public class HttpHelper {
    public static String getBodyString(HttpServletRequest request) throws IOException {
        StringBuilder sb = new StringBuilder();
        InputStream inputStream = null;
        BufferedReader reader = null;
        try {
            inputStream = request.getInputStream();
            reader = new BufferedReader(
                    new InputStreamReader(inputStream, Charset.forName("UTF-8")));

            char[] bodyCharBuffer = new char[1024];
            int len = 0;
            while ((len = reader.read(bodyCharBuffer)) != -1) {
                sb.append(new String(bodyCharBuffer, 0, len));
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sb.toString();
    }
}

4. 拦截器中获取body数据

• 数据获取

String body = HttpHelper.getBodyString(request);

三、总结

1. 原理上目前的理解

搜索了许多类似的文章，思路都类似，以上代码是搜索的代码基础上做得一些调整，但感觉原理上的解释有一些误差

许多文章在这个问题上提到过流的复制或者说重新把数据写入到流之中，我有被这些说法误导

在我看来，这一思路的解决原理:

• 把request中的body保存在HttpServletRequest包装类的属性body中，

    private final byte[] body;

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) {
        super(request);
        String sessionStream = getBodyString(request);
        body = sessionStream.getBytes(Charset.forName("UTF-8"));
    }

• 包装类中重写了getInputStream方法,每次通过传入保存的body返回一个新的流

    @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 false;
            }

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

            @Override
            public void setReadListener(ReadListener readListener) {
            }
        };
    }

2. 流的本质其实还是只能读取一次