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基于spring-boot搭建根据依赖 + 配置初始化zookeeper client框架

一、目标

  1. 根据指定加载顺序和yml配置生成可用的zookeeper客户端(支持curator、zkClient、zookeeper native client)
  2. 抽象出zookeeper的一些通用基本操作: 增加节点、删除节点、修改节点、给指定节点、孩子节点添加监听器

二、使用到的技术点

  • Spring 事件驱动模型、ImportBeanDefinitionRegistrar、FactoryBean、InitializingBean、DisposableBean

  • 通过BeanDefinition设置bean自动装配的类型以及手动不需要自动装配的属性

  • 观察者设计模式、适配器设计模式、代理设计模式

  • jdk1.8接口实现默认方法特性

  • SpringBoot自动装配、SPI特性

三、缺点

  • 实例化客户端单一，每个客户端目前只提供一种初始化策略。后续若版本升级，可添加策略者模式，根据用户配置的参数来决定使用哪种初始化api。目前初始化策略api详细如下:

    客户端类型 使用初始化api 备注
    org.apache.curator.framework.CuratorFramework org.apache.curator.framework.CuratorFrameworkFactory#newClient(String connectString, RetryPolicy retryPolicy) 无
    org.I0Itec.zkclient.ZkClient org.I0Itec.zkclient.ZkClient#ZkClient(String zkServers, int sessionTimeout, int connectionTimeout, ZkSerializer zkSerializer) 无
    org.apache.zookeeper.ZooKeeper org.apache.zookeeper.ZooKeeper#ZooKeeper(String connectString, int sessionTimeout, Watcher watcher) 无

  • 没有完全覆盖三个客户端对zookeeper的操作的api

四、开发中遇到的问题

  1. ZookeeperClientFactoryBean循环依赖(**这里我设置了此bean的名字为:zookeeperClientProcessor **)

    The dependencies of some of the beans in the application context form a cycle:

┌─────┐
|  zookeeperClientProcessor
└─────┘

    出现此原因大概是因为: ZookeeperClientFactoryBean内部维护的beanzookeeperClient提供了set方法，在autowireMode为AUTOWIRE_BY_TYPE时spring会自动为这个属性进行byType装配。具体规则可参考: Spring自动装配注意事项

  2. 在初始化ZKClientlistener时，因为listener是@Import注解导入的，所以它会被spring当成一个bean处理，会去校验所以被@Bean注解标识的方法，进而会去获取所有的参数值、返回值，若返回值的类型在classpath中找不到会抛出'java.lang.NoClassDefFoundError' exception.。这其实就是jdk反射获取方法时抛出的异常。eg如下: 在ZKClientInitListener中获取initZKClient()方法时，当检测到方法的返回值是ZkClient, 若当前的classpath中无ZkClient的依赖，则会报上述错误信息。解决方法就是把方法返回值改成void，传入引用进去， 如下述的第二段java代码的initZKClient方法核心就是不要让jvm编译时去校验方法参数和返回值)

     @Order(2)
 public class ZKClientInitListener implements ApplicationListener<ZookeeperClientInitEvent> {
 
     private Logger logger = LoggerFactory.getLogger(ZKClientInitListener.class);
 
     private Environment environment;
 
     public ZKClientInitListener(Environment environment) {
         this.environment = environment;
     }
 
     public void onApplicationEvent(ZookeeperClientInitEvent event) {
         Object resource = event.getSource();
         if (resource instanceof ZookeeperClientFactoryBean) {
             try {
                 ZookeeperClientFactoryBean factoryBean = (ZookeeperClientFactoryBean) resource;
                 if (!ObjectUtils.isEmpty(factoryBean.getObject())) {
                     logger.warn("Zookeeper client has been initialized, stop initialization ZKClient ");
                     return;
                 }
 
                 if (logger.isInfoEnabled()) {
                     logger.info("Try to load class {}", Constants.ZK_CLIENT_CLASS);
                 }
 
                 ZKClient zookeeperClient = new ZKClient();
                 zookeeperClient.setClient(initZKClient());
 
                 factoryBean.setZookeeperClient(zookeeperClient);
 
             } catch (Exception e) {
                 e.printStackTrace();
             }
         }
     }
 
     private ZkClient initZKClient() {
         ZkClient zkClient = null;
         try {
             Class zkClientClazz = Class.forName(Constants.ZK_CLIENT_CLASS);
             Constructor zkClientConstructor = zkClientClazz.getConstructor(
                     String.class,
                     int.class,
                     int.class,
                     ZkSerializer.class);
             String zookeeperHost = ValidataUtil.validAndGet(
                     environment,
                     Constants.ZOOKEEPER_HOST,
                     String.class);
 
             int sessionTime = ValidataUtil.validAndGet(
                     environment,
                     Constants.ZOOKEEPER_ZK_CLIENT_SESSION_TIME,
                     int.class);
 
             int connectionTimeOut = ValidataUtil.validAndGet(
                     environment,
                     Constants.ZOOKEEPER_ZK_CLIENT_CONNECTION_TIME_OUT,
                     int.class);
 
             String zkSerializerClassValue = ValidataUtil.validAndGet(
                     environment,
                     Constants.ZOOKEEPER_ZK_SERIALIZER_CLASS,
                     String.class);
             // Check config class exist。
             Class zkSerializerClass = Class.forName(zkSerializerClassValue);
             ZkSerializer zkSerializer = (ZkSerializer) zkSerializerClass.getConstructor().newInstance();
 
             zkClient = (ZkClient) zkClientConstructor.newInstance(zookeeperHost, sessionTime, connectionTimeOut, zkSerializer);
 
         } catch (ClassNotFoundException e) {
             logger.warn("Not found {} class, please import zkclient dependency", Constants.ZK_CLIENT_CLASS);
             e.printStackTrace();
         } catch (NoSuchMethodException e) {
             e.printStackTrace();
         } catch (IllegalAccessException e) {
             e.printStackTrace();
         } catch (InstantiationException e) {
             e.printStackTrace();
         } catch (InvocationTargetException e) {
             e.printStackTrace();
         }
 
         return zkClient;
     }
 
 }

    改动后:

       @Order(2)
   public class ZKClientInitListener implements ApplicationListener<ZookeeperClientInitEvent> {
   
       private Logger logger = LoggerFactory.getLogger(ZKClientInitListener.class);
   
       private Environment environment;
   
       public ZKClientInitListener(Environment environment) {
           this.environment = environment;
       }
   
       public void onApplicationEvent(ZookeeperClientInitEvent event) {
           Object resource = event.getSource();
           if (resource instanceof ZookeeperClientFactoryBean) {
               try {
                   ZookeeperClientFactoryBean factoryBean = (ZookeeperClientFactoryBean) resource;
                   if (!ObjectUtils.isEmpty(factoryBean.getObject())) {
                       logger.warn("Zookeeper client has been initialized, stop initialization ZKClient ");
                       return;
                   }
   
                   if (logger.isInfoEnabled()) {
                       logger.info("Try to load class {}", Constants.ZK_CLIENT_CLASS);
                   }
   
                   initZKClient(factoryBean);
   
               } catch (Exception e) {
                   e.printStackTrace();
               }
           }
       }
   
       private void initZKClient(ZookeeperClientFactoryBean factoryBean) {
           ZkClient zkClient = null;
           try {
               Class zkClientClazz = Class.forName(Constants.ZK_CLIENT_CLASS);
               Constructor zkClientConstructor = zkClientClazz.getConstructor(
                       String.class,
                       int.class,
                       int.class,
                       ZkSerializer.class);
               String zookeeperHost = ValidataUtil.validAndGet(
                       environment,
                       Constants.ZOOKEEPER_HOST,
                       String.class);
   
               int sessionTime = ValidataUtil.validAndGet(
                       environment,
                       Constants.ZOOKEEPER_ZK_CLIENT_SESSION_TIME,
                       int.class);
   
               int connectionTimeOut = ValidataUtil.validAndGet(
                       environment,
                       Constants.ZOOKEEPER_ZK_CLIENT_CONNECTION_TIME_OUT,
                       int.class);
   
               String zkSerializerClassValue = ValidataUtil.validAndGet(
                       environment,
                       Constants.ZOOKEEPER_ZK_SERIALIZER_CLASS,
                       String.class);
               // Check config class exist。
               Class zkSerializerClass = Class.forName(zkSerializerClassValue);
               ZkSerializer zkSerializer = (ZkSerializer) zkSerializerClass.getConstructor().newInstance();
   
               zkClient = (ZkClient) zkClientConstructor.newInstance(zookeeperHost, sessionTime, connectionTimeOut, zkSerializer);
   
               ZKClient zookeeperClient = new ZKClient();
               zookeeperClient.setClient(zkClient);
               factoryBean.setZookeeperClient(zookeeperClient);
           } catch (ClassNotFoundException e) {
               logger.warn("Not found {} class, " +
                   "if you want to initialize zkclient then you should import zkclient dependency",
                   Constants.ZK_CLIENT_CLASS);
               e.printStackTrace();
           } catch (NoSuchMethodException e) {
               e.printStackTrace();
           } catch (IllegalAccessException e) {
               e.printStackTrace();
           } catch (InstantiationException e) {
               e.printStackTrace();
           } catch (InvocationTargetException e) {
               e.printStackTrace();
           }
       }
   
   }

  3. ZookeeperClient接口中的抽象出来的重载方法中若参数名包含其他jar包的类型时，若使用其中一个重载方法运行程序，编译会报错。 eg:

    default void watchChildrenNode(String parentPath, IZkChildListener iZkChildListener) throws Exception {

}

default void watchChildrenNode(String parentPath, Watcher watcher) throws Exception {

}

    当在使用zookeeperClient.watchChildrenNode方法时，若当前的项目只添加了原生客户端的依赖，依赖如下:

    <dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.6</version>
</dependency>

    那么项目启动不了，会报org.I0Itec.zkclient.IZkChildListener找不到的错误。

五、约定

  • zookeeper的默认加载顺序为: curator、zkClient、zookeeper原生客户端
  • curator客户端的初始化目前只提供重试的实例化策略，即采用如下api: 
    public static CuratorFramework newClient(String connectString, RetryPolicy retryPolicy)
  • zkClient客户端初始化目前只支持如下api实例化: 
    public ZkClient(String zkServers, int sessionTimeout, int connectionTimeout)
  • zookeeper原生客户端目前只支持如下api实例化: 
    public ZooKeeper(String connectString, int sessionTimeout, Watcher watcher)

六、初始化客户端

6.1 初始化curator client

  1. 添加curator client和spring-boot-zookeeper-client-starter的依赖

    <!-- 添加至repositories标签中 -->
<dependency>
    <groupId>com.eugene.sumarry</groupId>
    <artifactId>spring-boot-zookeeper-client-starter</artifactId>
    <version>0.0.1</version>
</dependency>

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>2.10.0</version>
</dependency>

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>2.10.0</version>
</dependency>

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-client</artifactId>
    <version>2.10.0</version>
</dependency>

<!-- 添加至project标签中, 若使用mvn clean compile命令一直连接不上服务器时，可将协议改成http。然后重试，
 若两者皆不行，那就多试几次吧。 国外网站嘛，大家都懂~~~-->
<repositories>
    <repository>
        <id>github</id>
        <name>avengerEug</name>
        <url>https://raw.github.com/AvengerEug/maven-repository/master</url>
    </repository>
</repositories>

  2. yml或properties文件中添加如下配置:

    zookeeper:
  host: 192.168.111.146:2181
  curator:
    sleep-ms-between-retries: 5000
    retry-time: 2

  3. spring boot入口中添加如下注解

    @EnableZookeeperClient

6.2 初始化ZkClient

  1. 添加ZkClient和spring-boot-zookeeper-client-starter的依赖

    <!-- 添加至repositories标签中 -->
<dependency>
    <groupId>com.eugene.sumarry</groupId>
    <artifactId>spring-boot-zookeeper-client-starter</artifactId>
    <version>0.0.1</version>
</dependency>

<dependency>
    <groupId>com.101tec</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.10</version>
</dependency>	

<!-- 添加至project标签中, 若使用mvn clean compile命令一直连接不上服务器时，可将协议改成http。然后重试，
 若两者皆不行，那就多试几次吧。 国外网站嘛，大家都懂~~~-->
<repositories>
    <repository>
        <id>github</id>
        <name>avengerEug</name>
        <url>https://raw.github.com/AvengerEug/maven-repository/master</url>
    </repository>
</repositories>

  2. yml或properties文件中添加如下配置:

    zookeeper:
  host: 192.168.111.146:2181
  zk-client:
    session-time: 10000
    connection-timeout: 10000
    zk-serializer-class: org.I0Itec.zkclient.serialize.SerializableSerializer

  3. spring boot入口中添加如下注解

    @EnableZookeeperClient

6.3 初始化zookeeper原生客户端

  1. 添加zookeeper和spring-boot-zookeeper-client-starter的依赖

    <!-- 添加至repositories标签中 -->
<dependency>
    <groupId>com.eugene.sumarry</groupId>
    <artifactId>spring-boot-zookeeper-client-starter</artifactId>
    <version>0.0.1</version>
</dependency>

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.6</version>
</dependency>

<!-- 添加至project标签中, 若使用mvn clean compile命令一直连接不上服务器时，可将协议改成http。然后重试，
 若两者皆不行，那就多试几次吧。 国外网站嘛，大家都懂~~~-->
<repositories>
    <repository>
        <id>github</id>
        <name>avengerEug</name>
        <url>https://raw.github.com/AvengerEug/maven-repository/master</url>
    </repository>
</repositories>

  2. 新建ZookeeperInitWatcher.java类，并实现org.apache.zookeeper.Watcher接口作为默认监听器。如下:

    package com.eugene.sumarry.springbootstudy.watch;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ZookeeperInitWatcher implements Watcher {

    private final static Logger logger = LoggerFactory.getLogger(ZookeeperInitWatcher.class);

    @Override
    public void process(WatchedEvent watchedEvent) {
        logger.info("Zookeeper native client init successful");
    }
}

  3. yml或properties文件中添加如下配置:

    zookeeper:
  host: 192.168.111.146:2181
  native-client:
    session-time: 10000
    watcher-class: com.eugene.sumarry.springbootstudy.watch.ZookeeperInitWatcher

  4. spring boot入口中添加如下注解

    @EnableZookeeperClient

6.4 如何操作zookeeper

  • 将使用spring常用@Autowired注解注入

    @Service
public class UserService {
    @Autowired
    private ZookeeperClient zookeeperClient
    
    public void createEphNode() {
        try {
            // 创建临时节点
            zookeeperClient.createEphNode("/test", "value");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

  • 使用spring上下文获取

    AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.java);
ZookeeperClient zookeeperClient = context.getBean(ZookeeperClient.class);
try {
    zookeeperClient.createEphNode("/test", "value");
} catch (Exception e) {
    e.printStackTrace();
}

  • 具体的api参考ZookeeperClient类

    public interface ZookeeperClient {
    String createPerNode(String var1) throws Exception;

    String createPerNode(String var1, String var2) throws Exception;

    String createPerSeqNode(String var1) throws Exception;

    String createPerSeqNode(String var1, String var2) throws Exception;

    String createEphNode(String var1) throws Exception;

    String createEphNode(String var1, String var2) throws Exception;

    String createEphSeqNode(String var1) throws Exception;

    String createEphSeqNode(String var1, String var2) throws Exception;

    void deleteNode(String var1) throws Exception;

    Stat changeNode(String var1, String var2) throws Exception;

    List<String> findChildren(String var1) throws Exception;

    default void watchDesignationNodeUsingCurator(String path, CuratorWatcher curatorWatcher) throws Exception {
    }

    default void watchTreeCacheNodeUsingCurator(String parentPath, TreeCacheListener treeCacheListener) throws Exception {
    }

    default void watchChildrenNodeUsingCurator(String parentPath, PathChildrenCacheListener pathChildrenCacheListener) throws Exception {
    }

    default void watchDesignationNodeUsingZKClient(String path, IZkDataListener iZkDataListener) throws Exception {
    }

    default void watchChildrenNodeUsingZKClient(String parentPath, IZkChildListener iZkChildListener) throws Exception {
    }

    default void watchChildrenNodeUsingNative(String parentPath, Watcher watcher) throws Exception {
    }

    default void watchDesignationNodeUsingNative(String path, Watcher watcher) throws Exception {
    }

    default <T> T checkExist(String path) throws Exception {
        return null;
    }

    void close() throws InterruptedException;
}

6.5 注意

  • 同上述约定，三种客户端的加载顺序为curator, zkclient, native client。若上述的依赖包都存在，则会按照如下顺序初始化客户端

    curator、zkClient、zookeeper原生客户端

  • 因为springboot中内嵌了sl4j的绑定器和具体的日志实现类(log4j)，而zookeeper原生客户端的jar包也包含了sl4j和log4j。所以建议修改zookeeper的jar包依赖如下(去除zookeeper jar包中依赖的日志体系):

    <!-- 添加至repositories标签中 -->
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.6</version>
    <exclusions>
        <exclusion>
            <artifactId>log4j</artifactId>
            <groupId>log4j</groupId>
        </exclusion>
        <exclusion>
            <artifactId>slf4j-api</artifactId>
            <groupId>org.slf4j</groupId>
        </exclusion>
        <exclusion>
            <artifactId>slf4j-log4j12</artifactId>
            <groupId>org.slf4j</groupId>
        </exclusion>
    </exclusions>
</dependency>

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内部抽象出zookeeper的一些通用基本操作: 增加节点、删除节点、修改节点、给指定节点、孩子节点添加监听器等操作。

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