Zookeeper学习(十)：ZooKeeper 实现分布式队列

1.分布式队列的架构

2.向队列中提交数据流程

3.从队列中取数据流程

队列的组成

package com.jike.queue;


import java.util.Collections;
import java.util.Comparator;
import java.util.List;




import org.I0Itec.zkclient.ExceptionUtil;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.exception.ZkNoNodeException;

public class DistributedSimpleQueue<T> {

	protected final ZkClient zkClient;//用于操作zookeeper集群
	protected final String root;//代表根节点

	protected static final String Node_NAME = "n_";//顺序节点的名称
	


	public DistributedSimpleQueue(ZkClient zkClient, String root) {
		this.zkClient = zkClient;
		this.root = root;
	}
    
	//获取队列的大小
	public int size() {
		/**
		 * 通过获取根节点下的子节点列表
		 */
		return zkClient.getChildren(root).size();
	}
	
    //判断队列是否为空
	public boolean isEmpty() {
		return zkClient.getChildren(root).size() == 0;
	}
	
	/**
	 * 向队列提供数据
	 * @param element
	 * @return
	 * @throws Exception
	 */
    public boolean offer(T element) throws Exception{
    	
    	//构建数据节点的完整路径
    	String nodeFullPath = root .concat( "/" ).concat( Node_NAME );
        try {
        	//创建持久的节点，写入数据
            zkClient.createPersistentSequential(nodeFullPath , element);
        }catch (ZkNoNodeException e) {
        	zkClient.createPersistent(root);
        	offer(element);
        } catch (Exception e) {
            throw ExceptionUtil.convertToRuntimeException(e);
        }
        return true;
    }


    //从队列取数据
	@SuppressWarnings("unchecked")
	public T poll() throws Exception {
		
		try {

			List<String> list = zkClient.getChildren(root);
			if (list.size() == 0) {
				return null;
			}
			//将队列安装由小到大的顺序排序
			Collections.sort(list, new Comparator<String>() {
				public int compare(String lhs, String rhs) {
					return getNodeNumber(lhs, Node_NAME).compareTo(getNodeNumber(rhs, Node_NAME));
				}
			});
			
			/**
			 * 将队列中的元素做循环，然后构建完整的路径，在通过这个路径去读取数据
			 */
			for ( String nodeName : list ){
				
				String nodeFullPath = root.concat("/").concat(nodeName);	
				try {
					T node = (T) zkClient.readData(nodeFullPath);
					zkClient.delete(nodeFullPath);
					return node;
				} catch (ZkNoNodeException e) {
					// ignore
				}
			}
			
			return null;
			
		} catch (Exception e) {
			throw ExceptionUtil.convertToRuntimeException(e);
		}

	}

	
	private String getNodeNumber(String str, String nodeName) {
		int index = str.lastIndexOf(nodeName);
		if (index >= 0) {
			index += Node_NAME.length();
			return index <= str.length() ? str.substring(index) : "";
		}
		return str;

	}

}

发送的消息对象封装

package com.jike.queue;

import java.io.Serializable;

public class User implements Serializable {
	
	String name;
	String id;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	
	

}

Zookeeper构建分布式队列测试

package com.jike.queue;

import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;

public class TestDistributedSimpleQueue {

	public static void main(String[] args) {
		
		
		ZkClient zkClient = new ZkClient("192.168.1.105:2181", 5000, 5000, new SerializableSerializer());
		DistributedSimpleQueue<User> queue = new DistributedSimpleQueue<User>(zkClient,"/Queue");
		
		User user1 = new User();
		user1.setId("1");
		user1.setName("xiao wang");
		
		User user2 = new User();
		user2.setId("2");
		user2.setName("xiao wang");		
		
		try {
			queue.offer(user1);
			queue.offer(user2);
			User u1 = (User) queue.poll();
			User u2 = (User) queue.poll();
			
			if (user1.getId().equals(u1.getId()) && user2.getId().equals(u2.getId())){
				System.out.println("Success!");
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
	
}