解决HttpServletRequest无法获取@RequestBody修饰的参数

在使用springboot设计controller时我们通常会在某个请求如post中使用@RequestBody来修饰参数如：

在一些特殊场景下，我们需要在service层的代码去拿到当前上下文请求（HttpServletRequest）中的一些信息如请求体，这个时候被@RequestBody所修饰的请求是无法获取的，原因如下：
1、请求体流只能读取一次：Servlet 规范中，HttpServletRequest 的输入流 (getInputStream()) 是单向的，一旦被 @RequestBody 读取后，流就会关闭，无法再次读取。
2、@RequestBody 优先处理：Spring MVC 在处理控制器方法时，会先解析 @RequestBody，导致后续通过 HttpServletRequest 获取请求体时为空。

下面简单演示下解决方案：

一、先编写一个http工具类用来读取ServletRequest的内容

import com.alibaba.fastjson.JSON;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.List;

/**
 * http工具类
 */
@Slf4j
public class HttpUtils {
    /**
     * 从request获取body的数据
     *
     * @param request 请求
     * @return body数据字符串
     */
    public static String getBodyStr(ServletRequest request) {
        StringBuilder sb = new StringBuilder();
        try {
            try (ServletInputStream inputStream = request.getInputStream()) {
                try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8))) {
                    String line;
                    while ((line = reader.readLine()) != null) {
                        sb.append(line);
                    }
                }
            }
        } catch (Exception e) {
            log.error("get request body error: ", e);
        }
        return sb.toString();
    }

    /**
     * 从request获取body的数据，并转换成对象（适用于使用@RequestBody修饰的参数）
     *
     * @param request request 请求
     * @param clazz   对象类型
     * @return 对象
     */
    public static <T> T getBodyToObject(ServletRequest request, Class<T> clazz) {
        String bodyStr = getBodyStr(request);
        if (StringUtils.isBlank(bodyStr)) {
            return null;
        }
        return JSON.parseObject(bodyStr, clazz);
    }

    /**
     * 从request获取body的数据，并转换成集合对象（适用于使用@RequestBody修饰的参数）
     *
     * @param request request 请求
     * @param clazz   集合对象类型
     * @return 集合对象
     */
    public static <T> List<T> getBodyToList(ServletRequest request, Class<T> clazz) {
        String bodyStr = getBodyStr(request);
        if (StringUtils.isBlank(bodyStr)) {
            return null;
        }
        return JSON.parseArray(bodyStr, clazz);
    }
}

二、添加请求体复制包装器

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;
import java.nio.charset.StandardCharsets;

/**
 * 请求体复制包装器
 */
public class BodyCopyWrapper extends HttpServletRequestWrapper {
    private byte[] requestBody;

    public BodyCopyWrapper(HttpServletRequest request) throws IOException {
        super(request);
        requestBody = HttpUtils.getBodyStr(request).getBytes(StandardCharsets.UTF_8);
    }

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

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream basis = new ByteArrayInputStream(requestBody);
        return new ServletInputStream() {
            @Override
            public int read() throws IOException {
                return basis.read();
            }

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

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

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

    public void setInputStream(byte[] body) {
        this.requestBody = body;
    }
}

三、添加请求拦截器配置类

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;

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

/**
 * 请求拦截器配置类
 */
@Slf4j
@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean<RequestWrapperFilter> requestWrapperFilter() {
        FilterRegistrationBean<RequestWrapperFilter> bean = new FilterRegistrationBean<>();
        bean.setFilter(new RequestWrapperFilter());
        bean.addUrlPatterns("/*");
        bean.setOrder(Ordered.HIGHEST_PRECEDENCE);
        return bean;
    }

    public static class RequestWrapperFilter implements Filter {
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException
                , IOException {
            ServletRequest requestWrapper = null;
            if (request instanceof HttpServletRequest) {
                requestWrapper = new BodyCopyWrapper((HttpServletRequest) request);
            }
            if (null == requestWrapper) {
                log.warn("未进行request包装返回原来的request");
                chain.doFilter(request, response);
            } else {
                chain.doFilter(requestWrapper, response);
            }
        }
    }
}

四、业务代码中使用方式

HttpServletRequest request = ((ServletRequestAttributes) (RequestContextHolder.currentRequestAttributes())).getRequest();
//转对象
UserLoginDTO userLoginDTO = HttpUtils.getBodyToObject(request, UserLoginDTO.class);
//直接获取内容字符串
String bodyStr = HttpUtils.getBodyStr(request);