[Java知识库]Java WebSocketClient 同步返回数据，建立长链接这一篇就够用了。

1. Maven 坐标引入依赖

# Java-WebSocket 坐标
<!-- https://mvnrepository.com/artifact/org.java-websocket/Java-WebSocket -->
<dependency>
    <groupId>org.java-websocket</groupId>
    <artifactId>Java-WebSocket</artifactId>
    <version>1.5.1</version>
</dependency>

2. WebSocketClient 帮助类，建立长链接实现单例模式，连接断开自动重连机制，代码可以直接使用。

import org.java_websocket.enums.ReadyState;
import org.java_websocket.handshake.ServerHandshake;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.URI;
import java.net.URISyntaxException;

/**
 * websocket client 客户端端控制
 */
public class WebSocketClient extends org.java_websocket.client.WebSocketClient {

    private static final Logger logger = LoggerFactory.getLogger(WebSocketClient.class);
    
    // 复制请留意，该位置url需要进行更改
    private static String wsUrl = "ws://127.0.0.1:10080//";

    private static WebSocketClient instance;

    private int sendFlag = 0;
    private String result = null;

    static {
        try {
            instance = new WebSocketClient(wsUrl);
            instance.connect();
        } catch (URISyntaxException e) {
            e.printStackTrace();
        }
    }

    // 获取到当前实例
    public static WebSocketClient getInstance(){
       try{
           if(instance != null){
               if(instance.getReadyState() == ReadyState.NOT_YET_CONNECTED
                       || instance.getReadyState() == ReadyState.CLOSED){
                   if(instance.isClosed()){
                       instance.reconnect();
                   }
               }
           }else{
               instance = new WebSocketClient(wsUrl);
               instance.connect();
           }
       }catch (Exception ex){
           instance = null;
           logger.error(" websocket 构建实例出现问题！！" + ex);
       }
       return instance;
    }

    // 发送字符串消息
    public String sendStr(String text){
        synchronized(this){
            sendFlag = 1;
            this.send(text);
            // int i = 1;
            while(sendFlag != 0){
                logger.debug(" 等待返回值中 =============== " + sendFlag);
                // if(i >= 10000)break;
                // i++;
            }
            return result;
        }
    }


    private WebSocketClient(String url) throws URISyntaxException {
        super(new URI(url));
    }

    @Override
    public void onOpen(ServerHandshake serverHandshake) {
        logger.debug(" ws 服务正常打开！！");
    }

    @Override
    public void onMessage(String s) {
        result = s;
        sendFlag = 0;
        logger.debug(" ws 接收服务器推送的消息！！" + s);
    }

    @Override
    public void onClose(int i, String s, boolean b) {
        result = null;
        sendFlag = 0;
        logger.debug(" ws 客户端正常关闭！！");
    }

    @Override
    public void onError(Exception e) {
        result = null;
        sendFlag = 0;
        logger.debug(" ws 客户端连接出现错误！！");
    }
}

3. 在任意位置调用

// 构建实例
private WebSocketClient wsClient = WebSocketClient.getInstance();

// 发送消息 接收返回值
// result 会同步返回数据，可以直接进行使用。
String result = wsClient.sendStr("hello ws server!!");

微笑的java

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