java代码实现 websocket结合opcua实现订阅返回给前端

好的，这里是一个简单的Java代码示例，可以使用Java语言和Spring框架实现WebSocket结合OPC UA实现订阅并返回数据给前端：

// 导入相关依赖
import org.eclipse.milo.opcua.sdk.client.api.subscriptions.UaMonitoredItem;
import org.eclipse.milo.opcua.sdk.client.subscriptions.OpcUaSubscription;
import org.eclipse.milo.opcua.sdk.client.subscriptions.UaSubscription;
import org.eclipse.milo.opcua.stack.core.types.builtin.DataValue;
import org.eclipse.milo.opcua.stack.core.types.structured.EndpointDescription;
import org.eclipse.milo.opcua.stack.core.types.structured.MonitoredItemCreateRequest;
import org.eclipse.milo.opcua.stack.core.types.structured.MonitoredItemCreateResult;
import org.eclipse.milo.opcua.stack.core.types.structured.ReadValueId;
import org.springframework.messaging.simp.SimpMessagingTemplate;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.WebSocketSession;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CompletableFuture;

@Component
public class OpcUaWebSocketSubscriptionHandler {
    
    // 注入WebSocket消息发送模板
    private final SimpMessagingTemplate simpMessagingTemplate;
    
    // 保存已订阅的OPC UA监控项
    private final List<UaMonitoredItem> monitoredItemList = new ArrayList<>();
    
    // OPC UA连接信息
    private final EndpointDescription endpoint;
    
    // WebSocket会话对象
    private WebSocketSession webSocketSession;
    
    // OPC UA订阅对象
    private UaSubscription subscription;
    
    // 构造函数
    public OpcUaWebSocketSubscriptionHandler(SimpMessagingTemplate simpMessagingTemplate) {
        this.simpMessagingTemplate = simpMessagingTemplate;
        
        // TODO: 初始化OPC UA连接信息
    }
    
    // 处理WebSocket订阅请求
    public void handleWebSocketSubscription(WebSocketSession session, String nodeId) {
        this.webSocketSession = session;
        
        // 创建OPC UA订阅
        CompletableFuture<UaSubscription> future = createOpcUaSubscription();
        future.thenAccept(subscription -> {
            this.subscription = subscription;
            
            // 创建OPC UA监控项
            CompletableFuture<MonitoredItemCreateResult> monitoredItemFuture = createOpcUaMonitoredItem(nodeId);
            monitoredItemFuture.thenAccept(result -> {
                if (result.getStatusCode().isGood()) {
                    UaMonitoredItem monitoredItem = result.getMonitoredItem();
                    monitoredItemList.add(monitoredItem);
                }
            });
        });
    }
    
    // 处理WebSocket取消订阅请求
    public void handleWebSocketUnsubscription(WebSocketSession session, String nodeId) {
        if (this.webSocketSession != null && webSocketSession.equals(session)) {
            for (UaMonitoredItem monitoredItem : monitoredItemList) {
                if (monitoredItem.getReadValueId().getNodeId().getIdentifier().toString().equals(nodeId)) {
                    subscription.removeItem(monitoredItem);
                    monitoredItemList.remove(monitoredItem);
                    break;
                }
            }
        }
    }
    
    // 创建OPC UA订阅
    private CompletableFuture<UaSubscription> createOpcUaSubscription() {
        CompletableFuture<UaSubscription> future = new CompletableFuture<>();
        
        // 创建OPC UA订阅
        OpcUaSubscription subscription = new OpcUaSubscription(this.endpoint.getClient(), 1000.0);
        subscription.addNotificationListener(this::onSubscriptionValue);
        subscription.addStatusListener(this::onSubscriptionStatusChanged);
        subscription.setPublishingEnabled(true);
        subscription.setLifetimeCount(1000);
        subscription.setMaxKeepAliveCount(10);
        subscription.setPriority((byte) 0);
        
        // 启动OPC UA订阅
        CompletableFuture<Void> future1 = subscription.connect();
        future1.thenAccept(v -> {
            if (subscription.getSession().isPresent()) {
                future.complete(subscription);
            }
        });
        
        return future;
    }
    
    // 创建OPC UA监控项
    private CompletableFuture<MonitoredItemCreateResult> createOpcUaMonitoredItem(String nodeId) {
        CompletableFuture<MonitoredItemCreateResult> future = new CompletableFuture<>();
        
        // 创建OPC UA监控项
        ReadValueId readValueId = new ReadValueId(
            new NodeId(0, nodeId),
            AttributeId.Value.uid(), null, QualifiedName.NULL_VALUE);
        MonitoredItemCreateRequest request = new MonitoredItemCreateRequest(
            readValueId,
            MonitoringMode.Reporting,
            new MonitoringParameters(
                0.0,
                10.0,
                null,
                10,
                true
            )
        );
        
        // 添加OPC UA监控项
        CompletableFuture<List<MonitoredItemCreateResult>> future1 = subscription.createMonitoredItems(
            TimestampsToReturn.Both,
            Lists.newArrayList(request)
        );
        future1.thenAccept(resultList -> {
            if (resultList.size() > 0) {
                future.complete(resultList.get(0));
            }
        });
        
        return future;
    }
    
    // 处理OPC UA订阅值变化事件
    private void onSubscriptionValue(UaMonitoredItem item, DataValue value) {
        String nodeId = item.getReadValueId().getNodeId().getIdentifier().toString();
        String message = value.getValue().getValue().toString();
        simpMessagingTemplate.convertAndSendToUser(
            webSocketSession.getId(),
            "/topic/opcua/value/" + nodeId,
            message
        );
    }
    
    // 处理OPC UA订阅状态变化事件
    private void onSubscriptionStatusChanged(UaSubscription subscription, StatusCode statusCode) {
        if (!statusCode.isGood()) {
            simpMessagingTemplate.convertAndSendToUser(
                webSocketSession.getId(),
                "/topic/opcua/status",
                "OPC UA subscription status changed: " + statusCode
            );
        }
    }
}

这段代码实现了WebSocket结合OPC UA实现订阅，并将数据发送给前端的功能。在代码中，我们使用了Spring框架的SimpMessagingTemplate组件，用于发送WebSocket消息。我们通过创建UaMonitoredItem对象实现对OPC UA变量值的监控，并在变量值变化时，通过SimpMessagingTemplate将变量值发送给前端。同时，我们也实现了处理WebSocket取消订阅请求的功能。