解决post请求无法获取到值的问题

ppandrr

已于 2023-08-29 08:14:09 修改

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分类专栏： bug 文章标签： bug

于 2023-08-21 16:29:03 首次发布

本文链接：https://blog.youkuaiyun.com/ppandrr/article/details/132410205

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这里写目录标题

项目场景：
问题描述
原因分析：
解决方案：

项目场景：

最近写了一个拦截器，要对拦截器里的参数进行抓取和校验。

问题描述

使用request.getParameter(String )时无法获取到参数。只能获取到get方法的请求，但是获取不到拦截器里的post请求。

原因分析：

原因是request.getParamers(String) 方法获取post请求时，需要确保请求头中设置了正确的 Content-Type，例如 application/x-www-form-urlencoded 或 multipart/form-data。如果请求头中的 Content-Type 不正确，服务器可能无法正确解析请求体中的参数。

解决方案：

第1种方案：

如果要解决，可以试着将Content-Type进行修改。[看情况]

第2种方案：

如果Content-Type传输格式必须为除上面两种外的其他格式，可以试着用流的方式来传输。[不推荐]

String body = "";
StringBuilder stringBuilder = new StringBuilder();
BufferedReader bufferedReader = null;
InputStream inputStream = null;
try {
    inputStream = request.getInputStream();
    if (inputStream != null) {
        bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        char[] charBuffer = new char[128];
        int bytesRead = -1;
        while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
            stringBuilder.append(charBuffer, 0, bytesRead);
        }
    } else {
        stringBuilder.append("");
    }
} catch (IOException ex) {
    e.printStackTrace();
} finally {
    if (inputStream != null) {
        try {
            inputStream.close();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
    if (bufferedReader != null) {
        try {
            bufferedReader.close();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}
body = stringBuilder.toString();

上面就是使用流的方式来读取post的参数。之所以不推荐，是因为这种流读取的方式是有缺陷的。

众所周知，流只能被读取一次，如果在拦截器中被读取了，那么在@RequestBody时是会报错的

request的输入流只能读取一次，那么这是为什么呢？
那是因为流对应的是数据，数据放在内存中，有的是部分放在内存中。read 一次标记一次当前位置（mark position），第二次read就从标记位置继续读（从内存中copy）数据。所以这就是为什么读了一次第二次是空了。怎么让它不为空呢？只要inputstream 中的pos 变成0就可以重写读取当前内存中的数据。javaAPI中有一个方法public void reset() 这个方法就是可以重置pos为起始位置，但是不是所有的IO读取流都可以调用该方法！ServletInputStream是不能调用reset方法，这就导致了只能调用一次getInputStream()。
摘自：https://blog.youkuaiyun.com/sdut406/article/details/81369983

第3种方案：

那么有什么办法可以用户解决呢？上面这篇博客中提到了解决方案，就是重写HttpServletRequestWrapper把request保存下来，然后通过过滤器把保存下来的request再填充进去，这样就可以多次读取request了。步骤如下所示：

①写一个类，继承HttpServletRequestWrapper

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.*;

public class RequestWrapper extends HttpServletRequestWrapper {
    private final String body;

    public RequestWrapper(HttpServletRequest request) {
        super(request);
        StringBuilder stringBuilder = new StringBuilder();
        BufferedReader bufferedReader = null;
        InputStream inputStream = null;
        try {
            inputStream = request.getInputStream();
            if (inputStream != null) {
                bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                char[] charBuffer = new char[128];
                int bytesRead = -1;
                while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
                    stringBuilder.append(charBuffer, 0, bytesRead);
                }
            } else {
                stringBuilder.append("");
            }
        } catch (IOException ex) {

        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bufferedReader != null) {
                try {
                    bufferedReader.close();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        body = stringBuilder.toString();
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes());
        ServletInputStream servletInputStream = new ServletInputStream() {
            @Override
            public boolean isFinished() {
                return false;
            }
            @Override
            public boolean isReady() {
                return false;
            }
            @Override
            public void setReadListener(ReadListener readListener) {
            }
            @Override
            public int read() throws IOException {
                return byteArrayInputStream.read();
            }
        };
        return servletInputStream;

    }

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

    public String getBody() {
        return this.body;
    }

}

②写个过滤器Filter，用来把request传递下去


import com.miniprogram.web.douyin.config.RequestWrapper;

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

@Component
@WebFilter(urlPatterns = "/*",filterName = "channelFilter")
public class ChannelFilter implements Filter {

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

    }
 
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        ServletRequest requestWrapper = null;
        if(servletRequest instanceof HttpServletRequest) {
            requestWrapper = new RequestWrapper((HttpServletRequest) servletRequest);
        }
        if(requestWrapper == null) {
            filterChain.doFilter(servletRequest, servletResponse);
        } else {
            filterChain.doFilter(requestWrapper, servletResponse);
        }
    }
 
    @Override
    public void destroy() {

    }
}

③在拦截器中使用上面写好的类

package com.miniprogram.web.douyin.interceptor;

import com.alibaba.fastjson.JSON;
import com.miniprogram.api.douyin.user.req.DyuserReq;
import com.miniprogram.common.auth.VisitLimitCount;
import com.miniprogram.common.cache.RedisCache;
import com.miniprogram.common.config.InterceptorConfigMap;
import com.miniprogram.common.config.InterceptorUrlConfig;
import com.miniprogram.common.douyin.SearchEngineMapConstants;
import com.miniprogram.common.response.Response;
import com.miniprogram.common.session.*;
import com.miniprogram.common.utils.DateUtil;
import com.miniprogram.dao.common.UserLoginEntity.Users;
import com.miniprogram.service.douyin.users.UsersService;
import com.miniprogram.web.douyin.config.RequestWrapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Component("authSecurityInterceptor")
public class AuthSecurityInterceptor extends HandlerInterceptorAdapter {
    private Logger logger = LoggerFactory.getLogger(AuthSecurityInterceptor.class);

    @Autowired
    private UsersService douYinUsersService;
    @Autowired
    private RedisCache redisCache;
    @Autowired
    private VisitLimitCount visitLimitCount;

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        try {
            RequestWrapper requestWrapper = new RequestWrapper(httpServletRequest);
            String body = requestWrapper.getBody();
            System.out.println(body);
            return true;
        }catch (Exception e){
            logger.error("权限判断出错",e);
        }
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
    }
}

④记得在启动类中注册拦截器

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.MultipartConfigFactory;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@SpringBootApplication
@ServletComponentScan  //注册过滤器注解
@Configuration
public class WebApplication {

    public static void main(String[] args) {
        SpringApplication.run(WebApplication.class, args);
    }
}

问题解决，仅供参考