Zookeeper(3)-使用ZooKeeper作为配置中心

ZooKeeper作为配置中心
现在我们大多数应用都是采用的是分布式开发的应用，搭建到不同的服务器上，我们的配置文件，同一个应用程序的配置文件一样，还有就是多个程序存在相同的配置。当我们配置文件中有个配置属性需要改变，我们需要改变每个程序的配置属性，这样会很麻烦的去修改配置。而现在可以使用SpringCloud提供的配置中心，或者使用zookeeper来实现配置中心。

如何使用Zookeeper作为配置中心？
我们可以清除的了解ZooKeeper的Znode节点提供了一个Watcher，我们可以通过该方法来实现配置改变，来通知所有客户端配置的变化，并赋值。

如何存储配置信息呢
其实我们可以把key作为znode的节点名称，value则可以使用znode的数据域来储存，从而达成一个key-value的形式来存储配置信息。

下面是Zookeeper作为配置中心的代码
ConfigServer主要是对配置的读取，配置信息的写入，获取全部配置信息

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.data.Stat;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ConfigServer extends ConnectWatcher{
private String rootPath="/config";
public ConfigServer(){
this.connect();
}
//写入配置信息
public void write(String key,String value){
try {
Stat stat=this.zooKeeper.exists(rootPath+"/"+key,false);
if(stat!=null){
this.zooKeeper.setData(rootPath+"/"+key,value.getBytes(),-1);
}else{
this.zooKeeper.create(rootPath+"/"+key,value.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public Map<String,String> getAllConfig(){
Map<String,String> resultMap=new HashMap<String, String>();
try {
List<String> paths=this.zooKeeper.getChildren(rootPath,false);
for (String path:paths
) {
System.out.println(path);
String value=new String(this.zooKeeper.getData(rootPath+"/"+path,false,null));
resultMap.put(path,value);
}
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
return resultMap;
}
public void createRoot(){
try {
this.zooKeeper.create("/config",null, ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public String readConfig(String key, Watcher watcher){
byte[] bytes=null;
try {
bytes=this.zooKeeper.getData(rootPath+"/"+key,watcher,null);
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
return new String(bytes);
}

}

configClient主要是相当于我们每台服务器上对于配置中心的配置属性的监控
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;

import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.CountDownLatch;

public class ConfigClient implements Watcher {
private ConfigServer configServer=new ConfigServer();
private CountDownLatch countDownLatch=new CountDownLatch(1);
public void process(WatchedEvent watchedEvent) {
String path=watchedEvent.getPath();
if(watchedEvent.getType()== Event.EventType.NodeDataChanged){
this.updateConfig(path);
}
}
public void updateConfig(String path){

System.out.println(configServer.readConfig(path.substring(path.lastIndexOf("/")+1),this));
}
public void getAllConfig(){
Map<String,String> map=configServer.getAllConfig();
Iterator<String> keys=map.keySet().iterator();
while (keys.hasNext()){
String key=keys.next();
String value=map.get(key);
System.out.println("key:"+key+" value:"+value);
}
}

}

connectWatcher主要是用来创建ZK的连接及关闭
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

public class ConnectWatcher implements Watcher{
private final static String ZK_HOST="47.106.132.60:2181,47.106.132.60:2182,47.106.132.60:2183";
private final static int SESSION_TIME_OUT=3000;
private CountDownLatch countDownLatch=new CountDownLatch(1);
ZooKeeper zooKeeper;
public void process(WatchedEvent watchedEvent) {
if(watchedEvent.getState()== Event.KeeperState.SyncConnected){
countDownLatch.countDown();
}
}
public void connect(){
try {
zooKeeper=new ZooKeeper(ZK_HOST,SESSION_TIME_OUT,this);
countDownLatch.await();
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}

public void close(){
try {
this.zooKeeper.close();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

测试类
import org.junit.Test;

import java.util.concurrent.CountDownLatch;

public class Main {
public static void main(String[] args) {
CountDownLatch countDownLatch=new CountDownLatch(1);
ConfigClient configClient=new ConfigClient();
configClient.updateConfig("jdbc.url");
try {
countDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Test
public void addConfig(){
ConfigServer configServer=new ConfigServer();
configServer.createRoot();
configServer.write("jdbc.url","com.mysql.jdbc.Driver");
configServer.write("jdbc.password","1234");
configServer.close();
}
@Test
public void updateConfig(){
ConfigServer configServer=new ConfigServer();
configServer.write("jdbc.url","com.mysql.jdbc.update.test2");
configServer.close();
}
}

————————————————
版权声明：本文为CSDN博主「恋旧uni」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/qq_30756815/article/details/80611166