Java中使用etcd，包括基本的set、get、超时设置，watch监听等

<dependency>
                <groupId>com.ibm.etcd</groupId>
                <artifactId>etcd-java</artifactId>
                <version>0.0.13</version>
            </dependency>

import com.ibm.etcd.api.KeyValue;
import com.ibm.etcd.client.kv.KvClient;

import java.util.List;

/**
 * @author wuweifeng wrote on 2019-12-09
 * @version 1.0
 */
public interface IConfigCenter {
    /**
     * 存入key，value
     */
    void put(String key, String value);

    /**
     * 存入key、value，和租约id
     */
    void put(String key, String value, long leaseId);

    /**
     * 存入key、value，和过期时间，单位是秒
     */
    void putAndGrant(String key, String value, long ttl);

    /**
     * 根据key，获取value
     */
    String get(String key);

    /**
     * 获取指定前缀的所有key-value
     */
    List<KeyValue> getPrefix(String key);

    /**
     * 监听key
     */
    KvClient.WatchIterator watch(String key);

    /**
     * 监听前缀为key的
     */
    KvClient.WatchIterator watchPrefix(String key);

    /**
     * 自动续约
     * @param frequencySecs 续约频率，最小是4秒，默认是5秒
     * @param minTtl 最小存活时间，最小是2秒，默认是10秒
     * @return 返回leaseId
     */
    long keepAlive(String key, String value, int frequencySecs, int minTtl) throws Exception;

    /**
     * 判断剩余的过期时间
     */
    long timeToLive(long leaseId);
}

import com.google.protobuf.ByteString;
import com.ibm.etcd.api.KeyValue;
import com.ibm.etcd.api.LeaseGrantResponse;
import com.ibm.etcd.api.RangeResponse;
import com.ibm.etcd.client.KvStoreClient;
import com.ibm.etcd.client.kv.KvClient;
import com.ibm.etcd.client.lease.LeaseClient;
import com.ibm.etcd.client.lease.PersistentLease;
import com.ibm.etcd.client.lock.LockClient;

import org.springframework.util.CollectionUtils;

import java.util.List;
import java.util.concurrent.ExecutionException;

import static java.util.concurrent.TimeUnit.SECONDS;

/**
 * etcd客户端
 *
 * @author wuweifeng wrote on 2019-12-06
 * @version 1.0
 */
public class JdEtcdClient implements IConfigCenter {

    private KvClient kvClient;
    private LeaseClient leaseClient;
    private LockClient lockClient;

    public JdEtcdClient(KvStoreClient kvStoreClient) {
        this.kvClient = kvStoreClient.getKvClient();
        this.leaseClient = kvStoreClient.getLeaseClient();
        this.lockClient = kvStoreClient.getLockClient();
    }

    @Override
    public void put(String key, String value) {
        kvClient.put(ByteString.copyFromUtf8(key), ByteString.copyFromUtf8(value)).sync();
    }

    @Override
    public void put(String key, String value, long leaseId) {
        kvClient.put(ByteString.copyFromUtf8(key), ByteString.copyFromUtf8(value), leaseId).sync();
    }

    @Override
    public void putAndGrant(String key, String value, long ttl) {
        LeaseGrantResponse lease = leaseClient.grant(ttl).sync();
        put(key, value, lease.getID());
    }

    @Override
    public String get(String key) {
        RangeResponse rangeResponse = kvClient.get(ByteString.copyFromUtf8(key)).sync();
        List<KeyValue> keyValues = rangeResponse.getKvsList();
        if (CollectionUtils.isEmpty(keyValues)) {
            return null;
        }
        return keyValues.get(0).getValue().toStringUtf8();
    }

    @Override
    public List<KeyValue> getPrefix(String key) {
        RangeResponse rangeResponse = kvClient.get(ByteString.copyFromUtf8(key)).asPrefix().sync();
        return rangeResponse.getKvsList();
    }

    @Override
    public KvClient.WatchIterator watch(String key) {
        return kvClient.watch(ByteString.copyFromUtf8(key)).start();
    }

    @Override
    public KvClient.WatchIterator watchPrefix(String key) {
        return kvClient.watch(ByteString.copyFromUtf8(key)).asPrefix().start();
    }

    @Override
    public long keepAlive(String key, String value, int frequencySecs, int minTtl) throws Exception {
        //minTtl秒租期，每frequencySecs秒续约一下
        PersistentLease lease = leaseClient.maintain().leaseId(SystemClock.now()).keepAliveFreq(frequencySecs).minTtl(minTtl).start();
        long newId = lease.get(3L, SECONDS);
        put(key, value, newId);
        return newId;
    }

    @Override
    public long timeToLive(long leaseId) {
        try {
            return leaseClient.ttl(leaseId).get().getTTL();
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
            return 0L;
        }
    }
}

 /**
     * @param endPoints 如https://127.0.0.1:2379 有多个时逗号分隔
     */
    public static JdEtcdClient build(String endPoints) {
        return new JdEtcdClient(EtcdClient.forEndpoints(endPoints).withPlainText().build());
    }