├── README.md
└── java-lock
    ├── .classpath
    ├── .project
    ├── .settings
        ├── org.eclipse.jdt.core.prefs
        └── org.eclipse.m2e.core.prefs
    ├── pom.xml
    ├── src
        └── main
        │   └── java
        │       └── com
        │           └── lock
        │               ├── OrderNumGenerator.java
        │               └── service
        │                   ├── Lock.java
        │                   ├── OrderService.java
        │                   ├── ZookeeperAbstractLock.java
        │                   └── ZookeeperDistrbuteLock.java
    └── target
        └── classes
            ├── META-INF
                ├── MANIFEST.MF
                └── maven
                │   └── com.itmayiedu
                │       └── java-lock
                │           ├── pom.properties
                │           └── pom.xml
            └── com
                └── itmayiedu
                    ├── OrderNumGenerator.class
                    └── service
                        ├── Lock.class
                        ├── OrderService.class
                        ├── ZookeeperAbstractLock.class
                        ├── ZookeeperDistrbuteLock$1.class
                        └── ZookeeperDistrbuteLock.class


/README.md:
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 1 | # java-lock
 2 | java版本的用Zookeeper实现的分布式锁
 3 | 
 4 | 代码已经测过，可以直接使用！
 5 | 
 6 | #业务场景
 7 | 
 8 | 在分布式情况，生成全局订单号ID
 9 | 
10 | 生成订单号方案
11 | 
12 | 1.	使用时间戳
13 | 
14 | 2.	使用UUID
15 | 
16 | 3.	推特 (Twitter) 的 Snowflake 算法——用于生成唯一 ID
17 | 
18 | #产生问题
19 | 
20 | 在分布式(集群)环境下，每台JVM不能实现同步，在分布式场景下使用时间戳生成订单号可能会重复
21 | 
22 | #分布式情况下，怎么解决订单号生成不重复
23 | 
24 | 1.	使用分布式锁
25 | 
26 | 2.	提前生成好，订单号，存放在redis取。获取订单号，直接从redis中取。
27 | 
28 | #使用分布式锁生成订单号技术
29 | 
30 | 1.使用数据库实现分布式锁
31 | 
32 | 缺点:性能差、线程出现异常时，容易出现死锁
33 | 
34 | 2.使用redis实现分布式锁
35 | 
36 | 缺点:锁的失效时间难控制、容易产生死锁、非阻塞式、不可重入
37 | 
38 | 3.使用zookeeper实现分布式锁
39 | 
40 | 实现相对简单、可靠性强、使用临时节点，失效时间容易控制
41 | 
42 | 什么是分布式锁
43 | 
44 | 分布式锁一般用在分布式系统或者多个应用中，用来控制同一任务是否执行或者任务的执行顺序。在项目中，部署了多个tomcat应用，在执行定时任务时就会遇到同一任
45 | 
46 | 务可能执行多次的情况，我们可以借助分布式锁，保证在同一时间只有一个tomcat应用执行了定时任务
47 | 
48 | #使用Zookeeper实现分布式锁
49 | 
50 | #Zookeeper实现分布式锁原理
51 | 
52 | 使用zookeeper创建临时序列节点来实现分布式锁，适用于顺序执行的程序，大体思路就是创建临时序列节点，找出最小的序列节点，获取分布式锁，程序执行完成之后此序列节点消失，通过watch来监控节点的变化，从剩下的节点的找到最小的序列节点，获取分布式锁，执行相应处理，依次类推……
53 | 
54 | 


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/java-lock/.classpath:
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 1 | <?xml version="1.0" encoding="UTF-8"?>
 2 | <classpath>
 3 | 	<classpathentry kind="src" output="target/classes" path="src/main/java">
 4 | 		<attributes>
 5 | 			<attribute name="optional" value="true"/>
 6 | 			<attribute name="maven.pomderived" value="true"/>
 7 | 		</attributes>
 8 | 	</classpathentry>
 9 | 	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
10 | 		<attributes>
11 | 			<attribute name="maven.pomderived" value="true"/>
12 | 		</attributes>
13 | 	</classpathentry>
14 | 	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
15 | 		<attributes>
16 | 			<attribute name="optional" value="true"/>
17 | 			<attribute name="maven.pomderived" value="true"/>
18 | 		</attributes>
19 | 	</classpathentry>
20 | 	<classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
21 | 		<attributes>
22 | 			<attribute name="maven.pomderived" value="true"/>
23 | 		</attributes>
24 | 	</classpathentry>
25 | 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/J2SE-1.5">
26 | 		<attributes>
27 | 			<attribute name="maven.pomderived" value="true"/>
28 | 		</attributes>
29 | 	</classpathentry>
30 | 	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
31 | 		<attributes>
32 | 			<attribute name="maven.pomderived" value="true"/>
33 | 		</attributes>
34 | 	</classpathentry>
35 | 	<classpathentry kind="output" path="target/classes"/>
36 | </classpath>
37 | 


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/java-lock/.project:
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 1 | <?xml version="1.0" encoding="UTF-8"?>
 2 | <projectDescription>
 3 | 	<name>java-lock</name>
 4 | 	<comment></comment>
 5 | 	<projects>
 6 | 	</projects>
 7 | 	<buildSpec>
 8 | 		<buildCommand>
 9 | 			<name>org.eclipse.jdt.core.javabuilder</name>
10 | 			<arguments>
11 | 			</arguments>
12 | 		</buildCommand>
13 | 		<buildCommand>
14 | 			<name>org.eclipse.m2e.core.maven2Builder</name>
15 | 			<arguments>
16 | 			</arguments>
17 | 		</buildCommand>
18 | 	</buildSpec>
19 | 	<natures>
20 | 		<nature>org.eclipse.jdt.core.javanature</nature>
21 | 		<nature>org.eclipse.m2e.core.maven2Nature</nature>
22 | 	</natures>
23 | </projectDescription>
24 | 


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/java-lock/.settings/org.eclipse.jdt.core.prefs:
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1 | eclipse.preferences.version=1
2 | org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.5
3 | org.eclipse.jdt.core.compiler.compliance=1.5
4 | org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
5 | org.eclipse.jdt.core.compiler.source=1.5
6 | 


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/java-lock/.settings/org.eclipse.m2e.core.prefs:
--------------------------------------------------------------------------------
1 | activeProfiles=
2 | eclipse.preferences.version=1
3 | resolveWorkspaceProjects=true
4 | version=1
5 | 


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/java-lock/pom.xml:
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 1 | <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 2 |   <modelVersion>4.0.0</modelVersion>
 3 |   <groupId>com.itmayiedu</groupId>
 4 |   <artifactId>java-lock</artifactId>
 5 |   <version>0.0.1-SNAPSHOT</version>
 6 |   <dependencies>
 7 | 		<dependency>
 8 | 			<groupId>com.101tec</groupId>
 9 | 			<artifactId>zkclient</artifactId>
10 | 			<version>0.10</version>
11 | 		</dependency>
12 | 	</dependencies>
13 |   
14 | </project>


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/java-lock/src/main/java/com/lock/OrderNumGenerator.java:
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 1 | package com.lock;
 2 | 
 3 | import java.text.SimpleDateFormat;
 4 | import java.util.Date;
 5 | 
 6 | //生成订单号规则 使用时间戳+业务id
 7 | public class OrderNumGenerator {
 8 | 	// 业务ID
 9 | 	private static int count = 0;
10 | 
11 | 	// 生成订单号
12 | 	public String getNumber() {
13 | 		try {
14 | 			Thread.sleep(200);
15 | 		} catch (Exception e) {
16 | 			// TODO: handle exception
17 | 		}
18 | 		SimpleDateFormat simpt = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss");
19 | 		return simpt.format(new Date()) + "-" + ++count;
20 | 
21 | 	}
22 | 
23 | }
24 | 


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/java-lock/src/main/java/com/lock/service/Lock.java:
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 1 | package com.lock.service;
 2 | 
 3 | 
 4 | // lock 锁 定义分布式锁
 5 | public interface Lock {
 6 | 
 7 | 	 //获取锁
 8 | 	 public void getLock();
 9 | 	 //释放锁
10 | 	 public void unLock();
11 | }
12 | 


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/java-lock/src/main/java/com/lock/service/OrderService.java:
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 1 | package com.lock.service;
 2 | 
 3 | import java.util.concurrent.locks.Lock;
 4 | import java.util.concurrent.locks.ReentrantLock;
 5 | 
 6 | import com.itmayiedu.OrderNumGenerator;
 7 | 
 8 | // 订单生成调用业务逻辑
 9 | public class OrderService implements Runnable {
10 | 	// 生成订单号
11 | 	OrderNumGenerator orderNumGenerator = new OrderNumGenerator();
12 | 	// 重入锁
13 | 	// private Lock lock = new ReentrantLock();
14 | 	private com.itmayiedu.service.Lock lock = new ZookeeperDistrbuteLock();
15 | 
16 | 	public void run() {
17 | 		try {
18 | 			// 上锁
19 | 			lock.getLock();
20 | 			// synchronized (this) {
21 | 			// 模拟用户生成订单号
22 | 			getNumber();
23 | 		} catch (Exception e) {
24 | 			e.printStackTrace();
25 | 		} finally {
26 | 			// 釋放鎖資源
27 | 			lock.unLock();
28 | 		}
29 | 	}
30 | 
31 | 	public void getNumber() {
32 | 		String number = orderNumGenerator.getNumber();
33 | 		System.out.println(Thread.currentThread().getName() + ",##number:" + number);
34 | 	}
35 | 
36 | 	public static void main(String[] args) {
37 | 		System.out.println("##模拟生成订单号开始...");
38 | 
39 | 		for (int i = 0; i < 100; i++) {
40 | 			new Thread(new OrderService()).start();
41 | 		}
42 | 	}
43 | 
44 | }
45 | 


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/java-lock/src/main/java/com/lock/service/ZookeeperAbstractLock.java:
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 1 | package com.lock.service;
 2 | 
 3 | import java.util.concurrent.CountDownLatch;
 4 | 
 5 | import org.I0Itec.zkclient.ZkClient;
 6 | 
 7 | //重构重复代码，将重复代码交给子类执行
 8 | public abstract class ZookeeperAbstractLock implements Lock {
 9 | 	// zk连接地址
10 | 	private static final String CONNECTSTRING = "127.0.0.1:2181";
11 | 	// 创建zk连接
12 | 	protected ZkClient zkClient = new ZkClient(CONNECTSTRING);
13 | 	protected static final String PATH = "/lock";
14 | 	protected CountDownLatch countDownLatch = null;
15 | 
16 | 	public void getLock() {
17 | 		if (tryLock()) {
18 | 			System.out.println("###获取锁成功#####");
19 | 		} else {
20 | 			// 等待
21 | 			waitLock();
22 | 			// 重新获取锁
23 | 			getLock();
24 | 		}
25 | 	}
26 | 
27 | 	// 是否获取锁成功,成功返回true 失败返回fasle
28 | 	abstract Boolean tryLock();
29 | 
30 | 	// 等待
31 | 	abstract void waitLock();
32 | 
33 | 	public void unLock() {
34 | 		if (zkClient != null) {
35 | 			zkClient.close();
36 | 		  System.out.println("释放锁资源");
37 | 		}
38 | 	}
39 | 
40 | }
41 | 


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/java-lock/src/main/java/com/lock/service/ZookeeperDistrbuteLock.java:
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 1 | package com.lock.service;
 2 | 
 3 | import java.util.concurrent.CountDownLatch;
 4 | 
 5 | import org.I0Itec.zkclient.IZkDataListener;
 6 | 
 7 | public class ZookeeperDistrbuteLock extends ZookeeperAbstractLock {
 8 | 
 9 | 	@Override
10 | 	Boolean tryLock() {
11 | 		try {
12 | 			zkClient.createEphemeral(PATH);
13 | 			return true;
14 | 		} catch (Exception e) {
15 | 			return false;
16 | 		}
17 | 
18 | 	}
19 | 
20 | 	@Override
21 | 	void waitLock() {
22 | 
23 | 		// 使用事件监听，获取到节点被删除，
24 | 		IZkDataListener iZkDataListener = new IZkDataListener() {
25 | 			// 当节点被删除
26 | 			public void handleDataDeleted(String dataPath) throws Exception {
27 | 				if (countDownLatch != null) {
28 | 					// 唤醒
29 | 					countDownLatch.countDown();
30 | 				}
31 | 
32 | 			}
33 | 
34 | 			// 当节点发生改变
35 | 			public void handleDataChange(String dataPath, Object data) throws Exception {
36 | 
37 | 			}
38 | 		};
39 | 
40 | 		// 注册节点信息
41 | 		zkClient.subscribeDataChanges(PATH, iZkDataListener);
42 | 		if (zkClient.exists(PATH)) {
43 | 			// 创建信号量
44 | 			countDownLatch = new CountDownLatch(1);
45 | 			try {
46 | 				// 等待
47 | 				countDownLatch.await();
48 | 			} catch (Exception e) {
49 | 
50 | 			}
51 | 
52 | 		}
53 | 		// 删除事件通知
54 | 		zkClient.unsubscribeDataChanges(PATH, iZkDataListener);
55 | 	}
56 | 
57 | }
58 | 


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/java-lock/target/classes/META-INF/MANIFEST.MF:
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1 | Manifest-Version: 1.0
2 | Built-By: Administrator
3 | Build-Jdk: 1.8.0_101
4 | Created-By: Maven Integration for Eclipse
5 | 
6 | 


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/java-lock/target/classes/META-INF/maven/com.itmayiedu/java-lock/pom.properties:
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1 | #Generated by Maven Integration for Eclipse
2 | #Sat Mar 03 22:27:12 CST 2018
3 | version=0.0.1-SNAPSHOT
4 | groupId=com.itmayiedu
5 | m2e.projectName=java-lock
6 | m2e.projectLocation=F\:\\itmayiedujiangke2018-02-24\\java-lock
7 | artifactId=java-lock
8 | 


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/java-lock/target/classes/META-INF/maven/com.itmayiedu/java-lock/pom.xml:
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 1 | <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 2 |   <modelVersion>4.0.0</modelVersion>
 3 |   <groupId>com.itmayiedu</groupId>
 4 |   <artifactId>java-lock</artifactId>
 5 |   <version>0.0.1-SNAPSHOT</version>
 6 |   <dependencies>
 7 | 		<dependency>
 8 | 			<groupId>com.101tec</groupId>
 9 | 			<artifactId>zkclient</artifactId>
10 | 			<version>0.10</version>
11 | 		</dependency>
12 | 	</dependencies>
13 |   
14 | </project>


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