ACL 可以指 Access Control List（访问控制列表），它是一种网络安全技术，用于控制数据包在网络设备上的流动。ACL 可以根据预先设定的规则，允许或者拒绝数据包通过网络设备，从而实现对网络流量的精细控制。
在 ZooKeeper 中，ACL 是 Access Control List（访问控制列表）的缩写，它用于控制对 ZooKeeper 节点的访问权限。ACL 可以通过预定义的规则来限制对 ZooKeeper 节点的读取、写入和管理权限。这样可以确保 ZooKeeper 中的数据得到安全地存储和访问。ACL 在 ZooKeeper 中扮演着重要的安全角色，可以帮助管理者控制对 ZooKeeper 节点的访问权限。
本文将介绍怎样通过 ZooKeeper 类中的 getACL 和 seACL 方法来控制节点的 ACL。
Stat setACL(String path, List<ACL> acl, int version) 如果存在给定路径的节点，且给定版本与该节点的版本一致，则为该节点设置 ACL。如果不存在具有给定路径的节点，则会抛出错误代码为 KeeperException.NoNode 的 KeeperException。如果给定的版本与节点的版本不匹配，将抛出错误代码为 KeeperException.BadVersion 的 KeeperException。
void setACL(String path, List<ACL> acl, int version, AsyncCallback.StatCallback cb, Object ctx) setACL 方法的异步版本
参数说明：
path - 节点路径
acl - ACL 列表
versin - 节点版本
cb - 回调接口
ctx - 上下文，用于向回调传递扩展数据
List<ACL> getACL(String path, Stat stat) 返回给定路径节点的 ACL 和状态。如果不存在具有给定路径的节点，则会抛出错误代码为 KeeperException.NoNode 的 KeeperException。
void getACL(String path, Stat stat, AsyncCallback.ACLCallback cb, Object ctx) getACL 方法的异步版本
参数说明：
path - 节点路径
stat - 如果不为空，节点的状态将被复制到此参数中。
cb - 回调接口
ctx - 上下文，用于向回调传递扩展数据
下面通过实例演示同步设置/获取ACL以及异步设置/获取ACL的用法，代码如下：
package com.hxstrive.zookeeper;
import com.alibaba.fastjson.JSONObject;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
/**
* 设置节点ACL
* @author hxstrive.com
*/
public class SetACLNode {
private static ZooKeeper zooKeeper;
@Before
public void init() throws Exception {
zooKeeper = new ZooKeeper("127.0.0.1:2181", 2000, new Watcher() {
public void process(WatchedEvent watchedEvent) {
System.out.println("触发了 " + watchedEvent.getType() + " 事件");
}
});
// 如果节点不存在，则创建节点
Stat stat = zooKeeper.exists("/setACL_node", false);
if(null == stat) {
String nodeName = zooKeeper.create("/setACL_node", "init value".getBytes(),
ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
System.out.println("nodeName = " + nodeName);
}
}
/**
* 同步判断节点是否存在
*/
@Test
public void syncDemo() throws Exception {
Stat stat = zooKeeper.setACL("/setACL_node", ZooDefs.Ids.OPEN_ACL_UNSAFE, -1);
System.out.println(JSONObject.toJSONString(stat));
// 获取 ACL
Stat newStat = new Stat();
List<ACL> aclList = zooKeeper.getACL("/setACL_node", newStat);
System.out.println("newStat = " + JSONObject.toJSONString(newStat));
for(ACL acl : aclList) {
System.out.println(JSONObject.toJSONString(acl));
}
//输出：
//触发了 None 事件
//nodeName = /setACL_node
//{"aversion":1,"ctime":1703939758594,"cversion":0,"czxid":220,"dataLength":10,
// "ephemeralOwner":0,"mtime":1703939758594,"mzxid":220,"numChildren":0,"pzxid":220,"version":0}
//newStat = {"aversion":2,"ctime":1703939758594,"cversion":0,"czxid":220,"dataLength":10,
// "ephemeralOwner":0,"mtime":1703939758594,"mzxid":220,"numChildren":0,"pzxid":220,"version":0}
//{"id":{"id":"anyone","scheme":"world"},"perms":31}
}
/**
* 异步判断节点是否存在
*/
@Test
public void asyncDemo() throws Exception {
Map<String,String> extData = new HashMap<>();
extData.put("code", "C100");
extData.put("title", "这是标题");
CountDownLatch countDownLatch = new CountDownLatch(1);
zooKeeper.setACL("/setACL_node", ZooDefs.Ids.OPEN_ACL_UNSAFE, -1,
new AsyncCallback.StatCallback() {
@Override
public void processResult(int i, String s, Object o, Stat stat) {
System.out.println("i = " + i);
System.out.println("s = " + s);
System.out.println("o = " + o);
System.out.println("stat = " + JSONObject.toJSONString(stat));
countDownLatch.countDown();
}
}, extData);
countDownLatch.await();
// 获取ACL
CountDownLatch countDownLatch2 = new CountDownLatch(1);
Stat newStat = new Stat();
zooKeeper.getACL("/setACL_node", newStat, new AsyncCallback.ACLCallback() {
@Override
public void processResult(int i, String s, Object o, List<ACL> list, Stat stat) {
System.out.println("i = " + i);
System.out.println("s = " + s);
System.out.println("o = " + o);
System.out.println("list = " + JSONObject.toJSONString(list));
System.out.println("stat = " + JSONObject.toJSONString(stat));
countDownLatch2.countDown();
}
}, extData);
countDownLatch2.await();
//输出：
//触发了 None 事件
//i = 0
//s = /setACL_node
//o = {code=C100, title=这是标题}
//stat = {"aversion":3,"ctime":1703939758594,"cversion":0,"czxid":220,"dataLength":10,"ephemeralOwner":0,
// "mtime":1703939758594,"mzxid":220,"numChildren":0,"pzxid":220,"version":0}
//i = 0
//s = /setACL_node
//o = {code=C100, title=这是标题}
//list = [{"id":{"id":"anyone","scheme":"world"},"perms":31}]
//stat = {"aversion":3,"ctime":1703939758594,"cversion":0,"czxid":220,"dataLength":10,"ephemeralOwner":0,
// "mtime":1703939758594,"mzxid":220,"numChildren":0,"pzxid":220,"version":0}
}
}
