WebSocket连接问题：Error during WebSocket handshake: Unexpected response code: 200

WebSocket connection to ‘ws://localhost:8080/bidingRecord’ failed: Error during WebSocket handshake: Unexpected response code: 200

翻译：WebSocket握手过程中出错：意外响应代码：200

代码实现
pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.0.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

<groupId>com.dtdream</groupId>
<artifactId>web-socket</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>web-socket</name>

<properties>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.16.2</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-websocket</artifactId>
        <version>5.0.9.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>
</project>
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code
1、注入ServerEndpointExporter（使用SpringBoot时使用？）

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;

/**
 * @desc:
 * @author: admin
 * @date: 2020/06/02
 **/
@Configuration
public class WebSocketConfig {

    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }
}
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2、WebSocket连接服务

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.concurrent.CopyOnWriteArraySet;

/**
 * @desc: WebSocket服务
 * @author: admin
 * @date: 2020/06/02
 **/
@Component
@ServerEndpoint("/bidingRecord")
@Slf4j
public class WebSocket {

    private Session session;
    private static CopyOnWriteArraySet<WebSocket> webSockets = new CopyOnWriteArraySet<>();

    /**
     * 建立连接
     * @param session
     */
    @OnOpen
    public void onOpen(Session session) {
        this.session = session;
        webSockets.add(this);
        log.info("【新建连接】，连接总数:{}", webSockets.size());
    }

    /**
     * 断开连接
     */
    @OnClose
    public void onClose(){
        webSockets.remove(this);
        log.info("【断开连接】，连接总数:{}", webSockets.size());
    }

    /**
     * 接收到信息
     * @param message
     */
    @OnMessage
    public void onMessage(String message){
        log.info("【收到】，客户端的信息:{}，连接总数:{}", message, webSockets.size());
    }

    /**
     * 发送消息
     * @param message
     */
    public void sendMessage(String message){
        log.info("【广播发送】，信息:{}，总连接数:{}", message, webSockets.size());
        for (WebSocket webSocket : webSockets) {
            try {
                webSocket.session.getBasicRemote().sendText(message);
            } catch (IOException e) {
                log.info("【广播发送】，信息异常:{}", e.fillInStackTrace());
            }
        }
    }
}
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以上代码写出来的demo，已可以实现WebSocket的连接，但是为什么会出现握手出错的问题呢？

解决思路
1、查阅网上的资料
以上代码写出来的demo是可以本地访问的，但是我把这些代码加到项目中就不好使了。网上的资料基本在说实现上的问题，尝试后跟资料中提供的一些信息也不一样，就没得到解决。

2、猜想原因
由于我们使用的是域名访问，我开始猜测是反向代理中没设置WebSocket连接的相关配置。结果问了下运维，运维说我们没用反向代理，尴尬了。

3、询问有经验的老师
整不出来，就问当初给我WebSocket的demo的老师，老师很有经验，让我原始代码给他，他也很快定位到了问题的位置，大概就在过滤器的位置，让后让我打点日志看看，具体什么原因。机智的我把这块过滤器代码拷贝到我的demo中，结果发现本地原本可以访问的WebSocket连接，现在也不好使了，而且报的是相同的错误。当时，真是第一次替Bug感到高兴，太好了，基本问题就定位在这个过滤器上了。

过滤器代码

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

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


/**
 * @desc:
* @author: admin
 * @date: 2020/06/02
 **/
@Slf4j
@Component
class ApiFilter 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 requestURI = request.getRequestURI();
        if(!requestURI.startsWith("/api") && !requestURI.equals("/index.html")) {
            request.getRequestDispatcher("/index.html").forward(request, response);
        }else {
            filterChain.doFilter(servletRequest,servletResponse);
        }
    }

    @Override
    public void destroy() {
    }
}
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看过上面代码你会发现，我的请求"/bidingRecord"会被转发走，而不会到达WebSocket的连接处。不信，你可以先加上这块过滤器的代码Debug一下，到这里会转发走，就会报上文中的错误。所以，问题就这样解决了，将WebSocket的请求URI配置上，不被转发走即可。

修改过的过滤器代码

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

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


/**
 * @desc:
* @author: admin
 * @date: 2020/06/02
 **/
@Slf4j
@Component
class ApiFilter 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 requestURI = request.getRequestURI();
        if(!requestURI.startsWith("/api") && !requestURI.equals("/index.html")
                // 配置WebSocket连接不被转发即可
                && !requestURI.equals("/bidingRecord")) {
            request.getRequestDispatcher("/index.html").forward(request, response);
        }else {
            filterChain.doFilter(servletRequest,servletResponse);
        }
    }

    @Override
    public void destroy() {
    }
}
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总结
WebSocket连接未真正到达连接节点处，请求发出中间为什么没到到达连接的节点，是解决问题的关键。