用java连接远程的opcDa协议获取数据怎么写代码

要连接远程OPC DA服务器并获取数据，你需要使用Java中的OPC DA客户端库。这里提供一个简单的示例代码，可以帮助你开始：

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.jinterop.dcom.common.JIException;
import org.jinterop.dcom.core.JIVariant;
import org.openscada.opc.lib.common.ConnectionInformation;
import org.openscada.opc.lib.da.AccessBase;
import org.openscada.opc.lib.da.AccessBase.OperationListener;
import org.openscada.opc.lib.da.Async20Access;
import org.openscada.opc.lib.da.Async20AccessStateListener;
import org.openscada.opc.lib.da.Item;
import org.openscada.opc.lib.da.ItemState;
import org.openscada.opc.lib.da.SyncAccess;
import org.openscada.opc.lib.da.SyncAccessStateListener;

public class OPCClient {

    // 连接信息
    private static final String CLSID = "F8582CF2-88FB-11D0-B850-00C0F0104305";
    private static final String PROG_ID = "OPC.SimaticNET";
    private static final String HOST = "192.168.0.1"; // OPC服务器的IP地址
    private static final String USERNAME = "";
    private static final String PASSWORD = "";

    // OPC项
    private static final String ITEM_NAME = "Random.Real8";
    private static final int UPDATE_RATE = 1000; // 更新速率，以毫秒为单位

    public static void main(String[] args) throws Exception {
        // 连接信息
        ConnectionInformation ci = new ConnectionInformation();
        ci.setClsid(CLSID);
        ci.setProgId(PROG_ID);
        ci.setHost(HOST);
        ci.setUser(USERNAME);
        ci.setPassword(PASSWORD);

        // 创建同步访问
        SyncAccess syncAccess = new SyncAccess(ci, UPDATE_RATE);

        // 添加状态监听器
        syncAccess.addStateListener(new SyncAccessStateListener() {
            @Override
            public void stateChanged(SyncAccess access, int state) {
                System.out.println("同步访问状态变为：" + state);
            }
        });

        // 连接到OPC服务器
        syncAccess.connect();

        // 添加项
        Item item = syncAccess.addItem(ITEM_NAME, new OperationListener() {
            @Override
            public void onError(AccessBase access, String itemId, JIException arg2) {
                System.err.println("同步访问项发生错误: " + itemId);
            }

            @Override
            public void onItemAdded(AccessBase access, String itemId) {
                System.out.println("同步访问项已添加: " + itemId);
            }

            @Override
            public void onItemRemoved(AccessBase access, String itemId) {
                System.out.println("同步访问项已移除: " + itemId);
            }
        });

        // 读取项的值
        ItemState itemState = item.read(false);
        System.out.println("同步访问项的值为：" + itemState.getValue().getObject());

        // 周期性读取项的值
        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
        scheduler.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                try {
                    ItemState itemState = item.read(false);
                    System.out.println("同步访问项的值为：" + itemState.getValue().getObject());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }, UPDATE_RATE, UPDATE_RATE, TimeUnit.MILLISECONDS);

        // 等待5秒钟
        Thread.sleep(5000);

        // 停止周期性读取
        scheduler.shutdown();

        // 断开连接
        syncAccess.disconnect();
    }
}

这里使用了OpenSCADA的OPC DA客户端库。你需要在项目中添加以下Maven依赖项：

<dependency>
    <groupId>org.openscada</groupId>
    <artifactId>org.openscada.opc.lib.da</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>org.jinterop</groupId>
    <artifactId>j-interop</artifactId>
    <version>5.0.3</version>
</dependency>
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>1.7.30</version>
</dependency>
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.30</version>
</dependency>

当你运行这个示例时，它会连接到OPC服务器并读取一个项的值。它还会周期性地读取该项的值，直到你停止它。你可以根据你的需要修改代码以读取其他项或设置其他操作监听器等。