一、客户端脚本

1.1、客户端连接

cd /usr/local/services/zookeeper/zookeeper-3.4.13/bin

##连接本地Zookeeper服务器

sh zkCli.sh

##连接主机server1上的zookeeper服务

sh zkCli.sh -server server1:2181

1.2、CRUD操作

创建

##语法：create [-s] [-e] path data acl

create /zk-temp "tmp"

说明：-s / -e分别制定节点特性：顺序或临时节点。默认情况下，创建的是持久节点。

读取

##获取节点子节点列表，语法：ls path [watch]

ls /zk-temp

##获取节点数据，语法：get path [watch]

get /zk-temp

更新

##语法：set path data [version]

set /zk-temp "zk"

删除

##语法：delete path [version]

delete /zk-temp

二、Java客户端API

2.1、创建会话

创建会话Java代码



package zookeeper.javaapi;

import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.ZooKeeper;

public class CreateSession implements Watcher {
private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

public void process(WatchedEvent event) {

    System.out.println("Receive watched event：" + event);

    if (Event.KeeperState.SyncConnected == event.getState()) {

        connectedSemaphore.countDown();

    }

}

public static void main(String[] args) throws Exception{

    ZooKeeper zooKeeper = new ZooKeeper("server1:2181",1000,new CreateSession());

    System.out.println(zooKeeper.getState());

    try {

    	connectedSemaphore.await();

    } catch(InterruptedException e) {

    	e.printStackTrace();

    }

    System.out.println("Zookeeper session established.");

}


}

![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707134733773-503584414.png)

2.2、创建节点

2.2.1、同步创建节点

方法：String create(final String path, byte data[], List acl, CreateMode createMode)

参数说明：

同步创建节点Java代码



package zookeeper.javaapi;

import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.CreateMode;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.Watcher.Event.KeeperState;


import org.apache.zookeeper.ZooDefs.Ids;


import org.apache.zookeeper.ZooKeeper;

/**
ZooKeeper API创建节点，使用同步(sync)接口。


*/


public class Sync_Create_Usage implements Watcher {

private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

public static void main(String[] args) throws Exception{
 ZooKeeper zookeeper = new ZooKeeper("server1:2181", 5000, new Sync_Create_Usage());

 connectedSemaphore.await();

 //创建临时节点

 String path1 = zookeeper.create("/zk-test-ephemeral-", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

 System.out.println("Success create znode: " + path1);

 //临时顺序节点

 String path2 = zookeeper.create("/zk-test-ephemeral-", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);

 System.out.println("Success create znode: " + path2);

 //阻塞线程，查看临时节点创建结果

 Thread.sleep( Integer.MAX_VALUE );


}


public void process(WatchedEvent event) {


if (KeeperState.SyncConnected == event.getState()) {


connectedSemaphore.countDown();


}


}


}

2.2.2、异步创建节点

方法：void create(final String path, byte data[], List acl, CreateMode createMode, StringCallback cb, Object ctx)

参数说明：

异步创建节点Java代码



package zookeeper.javaapi;

import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.AsyncCallback;


import org.apache.zookeeper.CreateMode;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.ZooKeeper;


import org.apache.zookeeper.Watcher.Event.KeeperState;


import org.apache.zookeeper.ZooDefs.Ids;

/**
ZooKeeper API创建节点，使用异步(Async)接口。


*/


public class Async_Create_Usage implements Watcher {


private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

public static void main(String[] args) throws Exception {


ZooKeeper zookeeper = new ZooKeeper("server1:2181", 5000, new Async_Create_Usage());


System.out.println(zookeeper.getState());


connectedSemaphore.await();
 //创建临时节点

 zookeeper.create("/zk-test-demo-", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL,

         new IStringCallback(), "I am context. ");

 //创建临时节点

 zookeeper.create("/zk-test-demo-", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL,

         new IStringCallback(), "I am context. ");

 //阻塞线程，查看临时节点创建结果

 zookeeper.create("/zk-test-demo-", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL,

         new IStringCallback(), "I am context. ");

 Thread.sleep(Integer.MAX_VALUE);


}
public void process(WatchedEvent event) {


if (KeeperState.SyncConnected == event.getState()) {


connectedSemaphore.countDown();


}


}


}
class IStringCallback implements AsyncCallback.StringCallback {


public void processResult(int rc, String path, Object ctx, String name) {


System.out.println("Create path result: [" + rc + ", " + path + ", " + ctx + ", real path name: " + name);


}


}

![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707152913115-60968538.png)
![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707152849873-1815609224.png)

2.2.3、回调函数方法说明

方法：void processResult(int rc, String path, Object ctx, String name)

参数说明：

2.3、删除节点

2.3.1、同步删除节点

方法：public void delete(final String path, int version)

参数说明：

同步删除节点Java代码



package zookeeper.javaapi;

import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.CreateMode;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.Watcher.Event.EventType;


import org.apache.zookeeper.Watcher.Event.KeeperState;


import org.apache.zookeeper.ZooDefs.Ids;


import org.apache.zookeeper.ZooKeeper;

public class Sync_Delete_Usage implements Watcher {


private static CountDownLatch connectedSemaphore = new CountDownLatch(1);


private static ZooKeeper zookeeper;
public static void main(String[] args) throws Exception {

    String path = "/zk-delete-demo";

    zookeeper = new ZooKeeper("server1:2181", 5000, new Sync_Delete_Usage());

    connectedSemaphore.await(); 

    //同步创建持久节点 /zk-delete-demo

    zookeeper.create(path, "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

    System.out.println("success create znode: " + path);

    //同步创建持久节点 /zk-delete-demo/test

    zookeeper.create(path + "/test", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

    System.out.println("success create znode: " + path + "/test");

    //删除非叶子节点将报错

    try {

    	zookeeper.delete(path, -1);

    } catch (Exception e) {

        System.out.println("fail to delete znode: " + path);

    }

    //删除叶子节点 /zk-delete-demo/test

    zookeeper.delete(path + "/test", -1);

    System.out.println("success delete znode: " + path + "/c1");

    //删除叶子节点 /zk-delete-demo

    zookeeper.delete(path, -1);

    System.out.println("success delete znode: " + path);

    Thread.sleep(Integer.MAX_VALUE);

}

public void process(WatchedEvent event) {

    if (KeeperState.SyncConnected == event.getState()) {

        if (EventType.None == event.getType() && null == event.getPath()) {

            connectedSemaphore.countDown();

        }

    }

}


}

![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707161503791-943167895.png)

2.3.2、异步删除节点

方法：public void delete(final String path, int version, VoidCallback cb, Object ctx)

参数说明：

异步删除节点Java代码



package zookeeper.javaapi;

import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.AsyncCallback;


import org.apache.zookeeper.CreateMode;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.ZooKeeper;


import org.apache.zookeeper.Watcher.Event.EventType;


import org.apache.zookeeper.Watcher.Event.KeeperState;


import org.apache.zookeeper.ZooDefs.Ids;

public class Async_Delete_Usage implements Watcher {


private static CountDownLatch connectedSemaphore = new CountDownLatch(1);


private static ZooKeeper zookeeper;
public static void main(String[] args) throws Exception {

    String path = "/zk-delete-demo";

    zookeeper = new ZooKeeper("server1:2181", 5000, new Async_Delete_Usage());

    connectedSemaphore.await();

    //同步创建持久节点 /zk-delete-demo

    zookeeper.create(path, "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

    System.out.println("success create znode: " + path);

    //同步创建持久节点 /zk-delete-demo/test

    zookeeper.create(path + "/test", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

    System.out.println("success create znode: " + path + "/test");

    //删除非叶子节点将报错

    zookeeper.delete(path, -1, new IVoidCallback(), null);

    //删除叶子节点 /zk-delete-demo/test

    zookeeper.delete(path + "/test", -1, new IVoidCallback(), null);

    //删除叶子节点 /zk-delete-demo

    zookeeper.delete(path, -1, new IVoidCallback(), null);        

    Thread.sleep(Integer.MAX_VALUE);

}

public void process(WatchedEvent event) {

    if (KeeperState.SyncConnected == event.getState()) {

        if (EventType.None == event.getType() && null == event.getPath()) {

            connectedSemaphore.countDown();

        }

    }

}


}
class IVoidCallback implements AsyncCallback.VoidCallback {


public void processResult(int rc, String path, Object ctx) {


System.out.println(rc + ", " + path + ", " + ctx);


}


}

![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707165818262-1510544827.png)

2.4、获取节点

2.4.1、同步获取节点列表

方法：

List getChildren(final String path, Watch watcher)

List getChildren(String path, boolean watch)

List getChildren(final String path, Watch watcher, Stat stat)

List getChildren(String path, boolean watch, Stat stat)

参数说明：

同步获取节点列表Java代码



package zookeeper.javaapi;

import java.util.List;


import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.CreateMode;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.ZooKeeper;


import org.apache.zookeeper.Watcher.Event.EventType;


import org.apache.zookeeper.Watcher.Event.KeeperState;


import org.apache.zookeeper.ZooDefs.Ids;

public class Sync_Update_Usage implements Watcher {


private static CountDownLatch connectedSemaphore = new CountDownLatch(1);


private static ZooKeeper zookeeper = null;
public static void main(String[] args) throws Exception {

    String path = "/zk-update-demo";

    zookeeper = new ZooKeeper("server1:2181", 5000, new Sync_Update_Usage());

    connectedSemaphore.await();

    //同步创建持久节点 /zk-delete-demo

    zookeeper.create(path, "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

    System.out.println("success create znode: " + path);

    //同步创建持久节点 /zk-delete-demo/test_1

    zookeeper.create(path + "/test_1", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

    System.out.println("success create znode: " + path + "/test_1");

    //同步获取节点，同时使用默认Watcher

    List<String> childrenList = zookeeper.getChildren(path, true);

    System.out.println(childrenList);

    //同步创建持久节点 /zk-delete-demo/test_2

    zookeeper.create(path + "/test_2", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

    System.out.println("success create znode: " + path + "/test_2");

    Thread.sleep(3000);

    //同步创建持久节点 /zk-delete-demo/test_3

    zookeeper.create(path + "/test_3", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

    System.out.println("success create znode: " + path + "/test_3");

    Thread.sleep(Integer.MAX_VALUE);

}

public void process(WatchedEvent event) {

    if (KeeperState.SyncConnected == event.getState()) {

        if (EventType.None == event.getType() && null == event.getPath()) {

            connectedSemaphore.countDown();

        } else if (event.getType() == EventType.NodeChildrenChanged) {

            try {

                //Watcher通知是一次性的，一旦触发一次通知后，该Watcher就失效了

                //因此客户端需要反复注册Watcher，即程序中在process里面再次注册了Watcher，否则将无法获取之后该节点的变动通知

                System.out.println("ReGet Child:" + zookeeper.getChildren(event.getPath(), true));

            } catch (Exception e) {

            }

        }

    }

}


}

![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707171557000-1963604897.png)

2.4.2、异步获取节点列表

方法：

void getChildren(final String path, Watch watcher, ChildrenCallback cb, Object ctx)

void getChildren(String path, boolean watch, ChildrenCallback cb, Object ctx)

void getChildren(final String path, Watch watcher, ChildrenCallback cb, Object ctx, Stat stat)

void getChildren(String path, boolean watch, ChildrenCallback cb, Object ctx, Stat stat)

参数说明：

异步获取节点列表Java代码



package zookeeper.javaapi;

import java.util.List;


import java.util.concurrent.CountDownLatch;


import org.apache.zookeeper.AsyncCallback;


import org.apache.zookeeper.CreateMode;


import org.apache.zookeeper.WatchedEvent;


import org.apache.zookeeper.Watcher;


import org.apache.zookeeper.Watcher.Event.EventType;


import org.apache.zookeeper.Watcher.Event.KeeperState;


import org.apache.zookeeper.ZooDefs.Ids;


import org.apache.zookeeper.ZooKeeper;


import org.apache.zookeeper.data.Stat;

public class Async_Update_Usage implements Watcher {


private static CountDownLatch connectedSemaphore = new CountDownLatch(1);


private static ZooKeeper zookeeper = null;
public static void main(String[] args) throws Exception {

    String path = "/zk-get-demo";

    zookeeper = new ZooKeeper("server1:2181", 5000, new Async_Update_Usage());

    connectedSemaphore.await();

    zookeeper.create(path, "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

    System.out.println("success create znode: " + path);

    zookeeper.create(path + "/test_1", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

    System.out.println("success create znode: " + path + "/test_1");

    //异步获取节点，使用默认Watcher

    zookeeper.getChildren(path, true, new IChildren2Callback(), null);

    zookeeper.create(path + "/test_2", "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

    System.out.println("success create znode: " + path + "/test_2");

    Thread.sleep(Integer.MAX_VALUE);

}

public void process(WatchedEvent event) {

    if (KeeperState.SyncConnected == event.getState()) {

        if (EventType.None == event.getType() && null == event.getPath()) {

            connectedSemaphore.countDown();

        } else if (event.getType() == EventType.NodeChildrenChanged) {

            try {

                System.out.println("ReGet Child:" + zookeeper.getChildren(event.getPath(), true));

            } catch (Exception e) {

            }

        }

    }

}


}
class IChildren2Callback implements AsyncCallback.Children2Callback {


public void processResult(int rc, String path, Object ctx, List children, Stat stat) {


System.out.println("Get Children znode result: [response code: " + rc + ", param path: " + path + ", ctx: "


+ ctx + ", children list: " + children + ", stat: " + stat);


}


}

![](https://img2018.cnblogs.com/blog/1659331/201907/1659331-20190707174315216-1862803024.png)

说明：stat对象中记录了一个节点的基本属性信息，例如节点创建时的事务ID、最后一次修改的事务ID和节点数据内容的长度等。有时候，我们不仅需要获取节点最新的子节点列表，还要获取这个节点最新的节点状态信息。对于这种情况，我们可以将一个旧的stat变量传入API接口，该stat变量会在方法执行过程中，被来自服务器响应的新stat对象替换；

妈呀！写着好累，剩下的介绍下方法，代码就不贴了，大同小异。

2.4.3、同步获取节点数据

同步方法：

byte[] getData(final String path, Watcher watcher, Stat stat);

byte[] getData(String path, boolean watch, Stat stat);

异步方法：

void getData(String path, boolean watch, DataCallback cb, Object ctx);

void getData(String path, boolean watch, DataCallback cb, Object ctx);

参数说明：

说明：客户端在获取一个节点的数据内容时，可进行watcher注册，一旦该节点的状态发生变更，那么zookeeper服务端就会向客户端发送一NodeDataChanged(EventType.NodeDataChanged)的事件通知。注意，节点数据内容或者节点版本的变化都被看做是zookeeper节点的变化，都会触发NodeDataChanged通知。

2.5、更新节点

同步方法：

Stat setData(final String path, byte data[], int version);

异步方法：

void setData(final String path, byte data[], int version, StatCallback cb, Object ctx);

参数说明：

说明：在调用更新操作的时候，就可以添加version这个参数，该参数可以对应于CAS原理中的“预期值”，表明是针对该数据版本进行更新的；在zookeeper中，数据版本都是从0开始计数的，所以严格的讲，“-1”并不是一个合法的数据版本，它仅仅是一个标识符，如果客户端传入的版本参数是“-1”，就是告诉zookeeper服务器，客户端需要基于数据的最新版本进行更新操作。如果对zookeeper数据节点的更新操作没有原子性要求，那么就可以使用“-1”。

2.6、检测节点是否存在

同步方法：

Stat exists(final String path, Watcher watcher);

Stat exists(String path, boolean watch);

异步方法：

void exists(final String path, Watcher watcher, StatCallback cb, Object ctx);

void exists(String path, boolean watch, StatCallback cb, Object ctx);

参数说明：

说明：无论指定节点是否存在，通过调用exists()接口都可以注册watcher；exists()接口中注册的watcher，能够对节点创建、节点删除和节点数据更新事件进行监听；对于指定节点的子节点的各种变化，都不会通知客户端。

2.7、权限控制

方法：

void addAuthInfo(String scheme, byte auth[]);

参数说明：

说明：对于节点的权限，当一个客户端为一个节点添加权限信息的时候，该权限信息是添加到了该节点的叶子节点上，操作这些授权节点需要权限信息；但如果操作该父节点，是不需要权限的。

参考资料

参考书籍：从Paxos到Zookeeper：分布式一致性原理与实践

作者：
DeepInThought

出处：
https://www.cnblogs.com/DeepInThought

本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。

【6】Zookeeper脚本及API的更多相关文章

Linux -- 基于zookeeper的java api(二)
Linux -- 基于zookeeper的java api(二) 写一个关于基于集群的zookeeper的自定义实现HA 基于客户端和监控器:使用监控的方法查看每个注册过的节点的状态来做出操作. Wa ...
Linux -- 基于zookeeper的java api(一)
Linux -- 基于zookeeper的java api 首先启动你所有的 zkService.sh 查看状态:检查是否启动正确 [root@hu-hadoop2 ~]# zkServer.sh s ...
ZooKeeper客户端原生API的使用以及ZkClient第三方API的使用
这两部分内容的介绍主要讲的是节点及节点内容和子节点的操作,并且讲解的节点的事件监听以及ACL授权 ZooKeeper客户端原生API的使用百度网盘地址: http://pan.baidu.com/s ...
zookeeper的java api操作
zookeeper的java api操作创建会话: Zookeeper(String connectString,int sessionTimeout,Watcher watcher) Zookee ...
【分布式】Zookeeper使用--Java API
一.前言上一篇博客我们通过命令行来操作Zookeper的客户端和服务端并进行相应的操作,这篇主要介绍如何通过API(JAVA)来操作Zookeeper. 二.开发环境配置首先打开Zookeeper ...
(原) 1.3 zookeeper脚本使用
本文为原创文章,转载请注明出处,谢谢 zookeeper自带脚本使用 1.进入zookeeper客户端找到安装目录下的bin目录,执行以下脚本(中括号标示被必填) ./zkCli.sh -time ...
Zookeeper Java客户端API的使用
1. 原生api 具体查看下面github代码 2. ZkClient ZkClient是Github上一个开源的ZooKeeper客户端.ZkClient在ZooKeeper原生 A ...
JDK1.7新特性(3):java语言动态性之脚本语言API
简要描述:其实在jdk1.6中就引入了支持脚本语言的API.这使得java能够很轻松的调用其他脚本语言.具体API的使用参考下面的代码: package com.rampage.jdk7.chapte ...
Zookeeper（二）Zookeeper原理与API应用
一 Zookeeper概述 1.1 概述 Zookeeper是Google的Chubby一个开源的实现.它是一个针对大型分布式系统的可靠协调系统,提供的功能包括:配置维护.名字服务. 分布式同步.组服 ...

随机推荐

部署 --- Nginx
Nginx介绍简介: Nginx是由伊戈尔.塞索耶夫开发的,在04年10月开源的一款高性能HTTP和反向代理服务器. 因为它的稳定性好,功能丰富,有示例配置文件和较低的系统资源消耗而闻名同时也是一 ...
Centos7 yum源配置及关闭防火墙
清理源 #yum clean all更新源缓存 #yum makecache更新源 #yum update 设置主机名: #hostnamectl set-hostname 查看防火墙状态 #syst ...
IDEA注释模板
(1)Getter和Setter 生成代码的同时注释添加新模板输入模板生产代码: 其实就是InteliJ Default默认模板上面我们添加了生产注释,Getter的生成代码就是默认模板的. Ge ...
spring的控制器如何获取参数
1.控制器代码获取参数的注解 @RequestParam(name="name", required=false, defaultValue="World") ...
使用js加载器动态加载外部js、css文件
let MiniSite = new Object(); /** * 判断浏览器 */ MiniSite.Browser = { ie: /msie/.test(window.navigator.us ...
spring使用注解的方式创建bean ，将组件加入容器中
第一种使用@Bean的方式 1.创建一个bean package com.springbean; public class Person { private String name; private ...
类型限定符volatile
目录类型限定符volatile 强制内存读取禁止编译优化注意:volatile不能够保证线程同步 volatile bool flag; volatile int a; 添加volatile限定 ...
[LuoguP3064][USACO12DEC]伊斯坦布尔的帮派Gangs of Istanbull(加强版)_线段树_贪心
伊斯坦布尔的帮派Gangs of Istanbull 题目链接:https://www.luogu.org/problem/P3064 数据范围:略. 题解: 这个题其实分为两问,第一问是$YES$. ...
Python Excel文件的读写操作(xlwt xlrd xlsxwriter)
转:https://www.cnblogs.com/ultimateWorld/p/8309197.html Python语法简洁清晰,作为工作中常用的开发语言还是很强大的(废话). python关于 ...
MySQL中的InnoDB中产生的死锁深究
查考地址:https://blog.csdn.net/loophome/article/details/79867174 待研究中.....

【6】Zookeeper脚本及API

一、客户端脚本

1.1、客户端连接

1.2、CRUD操作

二、Java客户端API

2.1、创建会话

2.2、创建节点

2.2.1、同步创建节点

2.2.2、异步创建节点

2.2.3、回调函数方法说明

2.3、删除节点

2.3.1、同步删除节点

2.3.2、异步删除节点

2.4、获取节点

2.4.1、同步获取节点列表

2.4.2、异步获取节点列表

2.4.3、同步获取节点数据

2.5、更新节点

2.6、检测节点是否存在

2.7、权限控制

参考资料

【6】Zookeeper脚本及API的更多相关文章

随机推荐

热门专题