zookeeper配置中心

zookeeper配置中心

记录下学习zookeeper配置中心的内容，写的不好请指导

实际开发中我们会遇到修改一些配置文件的内容

比如数据库用户名和密码信息放在一个配置文件中，应用读取该配置文件，配置文件信息放入缓存。
若数据库的用户名和密码改变时候，还需要重新加载缓存，比较麻烦，通过 ZooKeeper可以轻松完成，当数据库发生变化时自动完成缓存同步。

设计思路：
1. 连接zookeeper服务器

2. 读取zookeeper中的配置信息，注册watcher监听器，存入本地变量

3. 当zookeeper中的配置信息发生变化时，通过watcher的回调方法捕获数据变化事件

4. 重新获取配置信息

具体代码如下：

package com.itcast.zookeeper;

import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooKeeper;

public class MyConfigCenter implements Watcher {
 // zk的连接串
 String IP = "192.168.106.129:2181";
 // 计数器对象
 CountDownLatch countDownLatch = new CountDownLatch(1);
 // 连接对象
 static ZooKeeper zooKeeper;

 // 用于本地化存储配置信息
 private String url;
 private String username;
 private String password;

 @Override
 public void process(WatchedEvent event) {
  try {
   // 捕获事件状态
   if (event.getType() == Event.EventType.None) {
    if (event.getState() == Event.KeeperState.SyncConnected) {
     System.out.println("连接成功");
     countDownLatch.countDown();
    } else if (event.getState() == Event.KeeperState.Disconnected) {
     System.out.println("连接断开!");
    } else if (event.getState() == Event.KeeperState.Expired) {
     System.out.println("连接超时!");
     // 超时后服务器端已经将连接释放，需要重新连接服务器端
     zooKeeper = new ZooKeeper("192.168.106.129:2181", 6000, new ZKConnectionWatcher());
    } else if (event.getState() == Event.KeeperState.AuthFailed) {
     System.out.println("验证失败!");
    }
    // 当配置信息发生变化时
   } else if (event.getType() == EventType.NodeDataChanged) {
    initValue();
   }
  } catch (Exception ex) {
   ex.printStackTrace();
  }

 }

 // 构造方法
 public MyConfigCenter() {
  initValue();
 }

 // 连接zookeeper服务器，读取配置信息
 public void initValue() {
  try {
   // 创建连接对象
   zooKeeper = new ZooKeeper(IP, 5000, this);
   // 阻塞线程，等待连接的创建成功
   countDownLatch.await();
   // 读取配置信息
   this.url = new String(zooKeeper.getData("/config/url", true, null));
   this.username = new String(zooKeeper.getData("/config/username", true, null));
   this.password = new String(zooKeeper.getData("/config/password", true, null));
  } catch (Exception ex) {
   ex.printStackTrace();
  }
 }

 public static void main(String[] args) {
  try {
   MyConfigCenter myConfigCenter = new MyConfigCenter();
   for (int i = 1; i <= 20; i++) {
    Thread.sleep(5000);
    System.out.println("url:" + myConfigCenter.getUrl());
    System.out.println("username:" + myConfigCenter.getUsername());
    System.out.println("password:" + myConfigCenter.getPassword());
    System.out.println("########################################");
   }
  } catch (Exception ex) {
   ex.printStackTrace();
  }
 }

 public String getUrl() {
  return url;
 }

 public void setUrl(String url) {
  this.url = url;
 }

 public String getUsername() {
  return username;
 }

 public void setUsername(String username) {
  this.username = username;
 }

 public String getPassword() {
  return password;
 }

 public void setPassword(String password) {
  this.password = password;
 }

}

通过linux上来实际查看变更的状态值

1、启动zookeeper