Zookeeper系列四：Zookeeper實現分散式鎖、Zookeeper實現配置中心

摘要： 一、Zookeeper實現分散式鎖 分散式鎖主要用於在分散式環境中保證資料的一致性。 包括跨程序、跨機器、跨網路導致共享資源不一致的問題。 1. 分散式鎖的實現思路 說明： 這種實現會有一個缺點，即當有很多程序在等待鎖的時候，在釋放鎖的時候會有很多程序就過來...

一、Zookeeper實現分散式鎖

分散式鎖主要用於在分散式環境中保證資料的一致性。

包括跨程序、跨機器、跨網路導致共享資源不一致的問題。

1. 分散式鎖的實現思路

說明：

這種實現會有一個缺點，即當有很多程序在等待鎖的時候，在釋放鎖的時候會有很多程序就過來爭奪鎖，這種現象稱為 “驚群效應”

2. 分散式鎖優化後的實現思路

3. Zookeeper分散式鎖的程式碼實現

準備工作：

1）安裝Zookeeper，具體參考我前面的我文章 ofollow,noindex" target="_blank">Zookeeper系列一：Zookeeper介紹、Zookeeper安裝配置、ZK Shell的使用

2）新建一個maven專案ZK-Demo,然後在pom.xml裡面引入相關的依賴

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

3.1 Zookeeper分散式鎖的核心程式碼實現

實現邏輯參考“ 2. 分散式鎖優化後的實現思路 ”中的流程圖

package com.study.demo.lock;

import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

import org.I0Itec.zkclient.IZkDataListener;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
* 
* @Description: Zookeeper分散式鎖的核心程式碼實現
* @author leeSmall
* @date 2018年9月4日
*
*/
public class DistributedLock implements Lock {
private static Logger logger = LoggerFactory.getLogger(DistributedLock.class);

private static final String ZOOKEEPER_IP_PORT = "192.168.152.130:2181";
private static final String LOCK_PATH = "/LOCK";

private ZkClient client = new ZkClient(ZOOKEEPER_IP_PORT, 4000, 4000, new SerializableSerializer());

private CountDownLatch cdl;

private String beforePath;// 當前請求的節點前一個節點
private String currentPath;// 當前請求的節點

// 判斷有沒有LOCK目錄，沒有則建立
public DistributedLock() {
if (!this.client.exists(LOCK_PATH)) {
this.client.createPersistent(LOCK_PATH);
}
}

public void lock() {
//嘗試去獲取分散式鎖失敗
if (!tryLock()) {
//對次小節點進行監聽
waitForLock();
lock();
} 
else {
logger.info(Thread.currentThread().getName() + " 獲得分散式鎖！");
}
}

public boolean tryLock() {
// 如果currentPath為空則為第一次嘗試加鎖，第一次加鎖賦值currentPath
if (currentPath == null || currentPath.length() <= 0) {
// 建立一個臨時順序節點
currentPath = this.client.createEphemeralSequential(LOCK_PATH + '/', "lock");
System.out.println("---------------------------->" + currentPath);
}

// 獲取所有臨時節點並排序，臨時節點名稱為自增長的字串如：0000000400
List<String> childrens = this.client.getChildren(LOCK_PATH);
//由小到大排序所有子節點
Collections.sort(childrens);
//判斷建立的子節點/LOCK/Node-n是否最小,即currentPath,如果當前節點等於childrens中的最小的一個就佔用鎖
if (currentPath.equals(LOCK_PATH + '/' + childrens.get(0))) {
return true;
} 
//找出比建立的臨時順序節子節點/LOCK/Node-n次小的節點,並賦值給beforePath
else {
int wz = Collections.binarySearch(childrens, currentPath.substring(6));
beforePath = LOCK_PATH + '/' + childrens.get(wz - 1);
}

return false;
}

//等待鎖,對次小節點進行監聽
private void waitForLock() {
IZkDataListener listener = new IZkDataListener() {
public void handleDataDeleted(String dataPath) throws Exception {
logger.info(Thread.currentThread().getName() + ":捕獲到DataDelete事件！---------------------------");
if (cdl != null) {
cdl.countDown();
}
}

public void handleDataChange(String dataPath, Object data) throws Exception {

}
};

// 對次小節點進行監聽,即beforePath-給排在前面的的節點增加資料刪除的watcher
this.client.subscribeDataChanges(beforePath, listener);
if (this.client.exists(beforePath)) {
cdl = new CountDownLatch(1);
try {
cdl.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
this.client.unsubscribeDataChanges(beforePath, listener);
}

//完成業務邏輯以後釋放鎖
public void unlock() {
// 刪除當前臨時節點
client.delete(currentPath);
}

// ==========================================
public void lockInterruptibly() throws InterruptedException {

}

public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
return false;
}

public Condition newCondition() {
return null;
}
}

3.2 在業務裡面使用分散式鎖

package com.study.demo.lock;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.Lock;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
* 
* @Description: 在業務裡面使用分散式鎖
* @author leeSmall
* @date 2018年9月4日
*
*/
public class OrderServiceImpl implements Runnable {
private static OrderCodeGenerator ong = new OrderCodeGenerator();

private Logger logger = LoggerFactory.getLogger(OrderServiceImpl.class);
// 同時併發的執行緒數
private static final int NUM = 10;
// 按照執行緒數初始化倒計數器,倒計數器
private static CountDownLatch cdl = new CountDownLatch(NUM);

private Lock lock = new DistributedLock();

// 建立訂單介面
public void createOrder() {
String orderCode = null;

//準備獲取鎖
lock.lock();
try {
// 獲取訂單編號
orderCode = ong.getOrderCode();
} catch (Exception e) {
// TODO: handle exception
} finally {
//完成業務邏輯以後釋放鎖
lock.unlock();
}

// ……業務程式碼

logger.info("insert into DB使用id：=======================>" + orderCode);
}


public void run() {
try {
// 等待其他執行緒初始化
cdl.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// 建立訂單
createOrder();
}

public static void main(String[] args) {
for (int i = 1; i <= NUM; i++) {
// 按照執行緒數迭代例項化執行緒
new Thread(new OrderServiceImpl()).start();
// 建立一個執行緒，倒計數器減1
cdl.countDown();
}
}
}

工具類：

package com.study.demo.lock;

import java.text.SimpleDateFormat;
import java.util.Date;

public class OrderCodeGenerator {
// 自增長序列
private static int i = 0;

// 按照“年-月-日-小時-分鐘-秒-自增長序列”的規則生成訂單編號
public String getOrderCode() {
Date now = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
return sdf.format(now) + ++i;
}

}

二、Zookeeper實現配置中心

1. 首先在zookeeper裡面建立一個Jdbc的節點，在下面分別建立4個子節點/Jdbc/url、/Jdbc/uname、/Jdbc/password、/Jdbc/driver

create /Jdbc ''
create /Jdbc/url jdbc.mysql://192.168.152.1/dbspread 
create /Jdbc/uname root
create /Jdbc/password 123456
create /Jdbc/driver com.mysql.jdbc.Driver

注意：/Jdbc/url這個節點的值是錯的 

2. 新建一個zkdemo的maven的web專案

專案結構如下：

2.1 在pom.xml檔案裡面引入下面依賴：

<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.study.demo</groupId>
<artifactId>zkdemo</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>zkdemo Maven Webapp</name>
<url>http://maven.apache.org</url>

<properties>
<spring.version>4.3.8.RELEASE</spring.version>
</properties>

<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>

<dependency>
<groupId>org.apache.zookeeper</groupId>
<artifactId>zookeeper</artifactId>
<version>3.4.10</version>
</dependency>

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

<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-framework</artifactId>
<version>4.0.0</version>
</dependency>
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-recipes</artifactId>
<version>4.0.0</version>
</dependency>

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-catalina</artifactId>
<version>7.0.39</version>
</dependency>

<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>

<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<version>2.7.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.41</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>

<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.1</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.1</version>
</dependency>

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>

</dependencies>
<build>
<finalName>zkdemo</finalName>
</build>
</project>

2.2 新建一個zookeeper配置中心類,從zookeeper動態獲取資料庫配置

package com.study.demo.config;

import java.util.List;
import java.util.Properties;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.TreeCache;
import org.apache.curator.framework.recipes.cache.TreeCacheEvent;
import org.apache.curator.framework.recipes.cache.TreeCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.WebApplicationContext;

import com.zaxxer.hikari.HikariDataSource;

/**
* 
* @Description: zookeeper配置中心類,從zookeeper動態獲取資料庫配置
* @author leeSmall
* @date 2018年9月10日
*
*/
public class ZookeeperConfigurerCentral {
//curator客戶端
private CuratorFramework zkClient;

//curator事件監聽
private TreeCache treeCache;

//zookeeper的ip和埠
private String zkServers;

//zookeeper上的/Jdbc路徑
private String zkPath;

//超時設定
private int sessionTimeout;

//讀取zookeeper上的資料庫配置檔案放到這裡
private Properties props;

public ZookeeperConfigurerCentral(String zkServers, String zkPath, int sessionTimeout) {
this.zkServers = zkServers;
this.zkPath = zkPath;
this.sessionTimeout = sessionTimeout;
this.props = new Properties();

//初始化curator客戶端
initZkClient();
//從zookeeper的Jdbc節點下獲取資料庫配置存入props
getConfigData();
//對zookeeper上的資料庫配置檔案所在節點進行監聽，如果有改變就動態重新整理props
addZkListener();
}

//初始化curator客戶端
private void initZkClient() {
zkClient = CuratorFrameworkFactory.builder().connectString(zkServers).sessionTimeoutMs(sessionTimeout)
.retryPolicy(new ExponentialBackoffRetry(1000, 3)).build();
zkClient.start();
}

//從zookeeper的Jdbc節點下獲取資料庫配置存入props
private void getConfigData() {
try {
List<String> list = zkClient.getChildren().forPath(zkPath);
for (String key : list) {
String value = new String(zkClient.getData().forPath(zkPath + "/" + key));
if (value != null && value.length() > 0) {
props.put(key, value);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}

//對zookeeper上的資料庫配置檔案所在節點進行監聽，如果有改變就動態重新整理props
private void addZkListener() {
TreeCacheListener listener = new TreeCacheListener() {
public void childEvent(CuratorFramework client, TreeCacheEvent event) throws Exception {
if (event.getType() == TreeCacheEvent.Type.NODE_UPDATED) {
getConfigData();
WebApplicationContext ctx = ContextLoader.getCurrentWebApplicationContext();
HikariDataSource dataSource = (HikariDataSource) ctx.getBean("dataSource");
System.out.println("================"+props.getProperty("url"));
dataSource.setJdbcUrl(props.getProperty("url"));
dataSource.setUsername(props.getProperty("uname"));
dataSource.setPassword(props.getProperty("password "));
dataSource.setDriverClassName(props.getProperty("driver "));
}
}
};

treeCache = new TreeCache(zkClient, zkPath);
try {
treeCache.start();
treeCache.getListenable().addListener(listener);
} catch (Exception e) {
e.printStackTrace();
}
}

public Properties getProps() {
return props;
}

public void setZkServers(String zkServers) {
this.zkServers = zkServers;
}

public void setZkPath(String zkPath) {
this.zkPath = zkPath;
}

public void setSessionTimeout(int sessionTimeout) {
this.sessionTimeout = sessionTimeout;
}
}

2.3 新建一個載入props裡面的資料庫配置的類

package com.study.demo.config;

import java.util.Properties;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;

/**
* 
* @Description: 載入props裡面的資料庫配置,這個類等價於以前在xml檔案裡面的配置：
* <context:property-placeholder location="classpath:config/jdbc_conf.properties"/>
* @author leeSmall
* @date 2018年9月10日
*
*/
public class ZookeeperPlaceholderConfigurer extends PropertyPlaceholderConfigurer {
private ZookeeperConfigurerCentral zkConfigurerCentral;

@Override
protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
throws BeansException {
System.out.println(zkConfigurerCentral.getProps());
super.processProperties(beanFactoryToProcess, zkConfigurerCentral.getProps());
}

public void setzkConfigurerCentral(ZookeeperConfigurerCentral zkConfigurerCentral) {
this.zkConfigurerCentral = zkConfigurerCentral;
}
}

2.4 在/zkdemo/src/main/webapp/WEB-INF/config/applicationContext.xml配置2.2和2.3新建的兩個主類

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

<context:annotation-config />

<context:component-scan base-package="com.study.demo" />

<!--通過建構函式注入zkServers、sessionTimeout、zkPath從zookeeper動態獲取資料庫配置-->
<bean id="zkConfigurerCentral" class="com.study.demo.config.ZookeeperConfigurerCentral">
<constructor-arg name="zkServers" value="192.168.152.130:2181" />
<constructor-arg name="sessionTimeout" value="1000" />
<constructor-arg name="zkPath" value="/Jdbc" />
</bean>

<!--這個類等價於以前在xml檔案裡面的配置：
<context:property-placeholder location="classpath:config/jdbc_conf.properties"/>載入
props裡面的資料庫配置
-->
<bean id="zkPlaceholderConfigurer" class="com.study.demo.config.ZookeeperPlaceholderConfigurer">
<property name="zkConfigurerCentral" ref="zkConfigurerCentral" />
<property name="ignoreUnresolvablePlaceholders" value="true" />
<property name="order" value="1" />
</bean>

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource">
<ref bean="dataSource" />
</property>
</bean>

<bean id="dataSource" class="com.zaxxer.hikari.HikariDataSource"
destroy-method="shutdown">
<property name="driverClassName" value="${driver}" />
<property name="jdbcUrl" value="${url}" />
<property name="username" value="${uname}" />
<property name="password" value="${password}" />

<!-- 連線只讀資料庫時配置為true， 保證安全 -->
<property name="readOnly" value="false" />
<!-- 等待連線池分配連線的最大時長（毫秒），超過這個時長還沒可用的連線則發生SQLException， 預設:30秒 -->
<property name="connectionTimeout" value="30000" />
<!-- 一個連線idle狀態的最大時長（毫秒），超時則被釋放（retired），預設:10分鐘 -->
<property name="idleTimeout" value="600000" />
<!-- 一個連線的生命時長（毫秒），超時而且沒被使用則被釋放（retired），預設:30分鐘，建議設定比資料庫超時時長少30秒，參考MySQL 
wait_timeout引數（show variables like '%timeout%';） -->
<property name="maxLifetime" value="1800000" />
<!-- 連線池中允許的最大連線數。預設值：10；推薦的公式：((core_count * 2) + effective_spindle_count) -->
<property name="maximumPoolSize" value="15" />
</bean>
</beans>

2.5 在com.study.demo.controller新建測試類

測試類1：

package com.study.demo.controller;

import java.io.Serializable;

public class OrderModel implements Serializable {
private static final long serialVersionUID = 1L;

private int orderId;
private int brandId;

public int getOrderId() {
return orderId;
}

public void setOrderId(int orderId) {
this.orderId = orderId;
}

public int getBrandId() {
return brandId;
}

public void setBrandId(int brandId) {
this.brandId = brandId;
}

}

View Code

測試類2：

package com.study.demo.controller;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;

@Repository
public class OrderDao {
@Autowired
private JdbcTemplate jdbcTemplate;

public OrderModel findById() {
String sql = "select * from tbl_order where order_id = 1";
return jdbcTemplate.queryForObject(sql, new RowMapper<OrderModel>() {
public OrderModel mapRow(ResultSet rs, int rowNum) throws SQLException {
OrderModel payment = new OrderModel();
payment.setOrderId(rs.getInt("order_id"));
payment.setBrandId(rs.getInt("brand_id"));
return payment;
}
});
}
}

View Code

測試類3：

package com.study.demo.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class OrderService {
@Autowired
private OrderDao dao;

public OrderModel getById() {
return dao.findById();
}
}

View Code

測試類4：

package com.study.demo.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class OrderController {
@Autowired
private OrderService service;

@ResponseBody
@RequestMapping(value = "/test", method = RequestMethod.GET)
public String test() {
OrderModel p = service.getById();
return p.getBrandId() + "";
}
}

View Code

2.6 其他附加配置和資料庫指令碼

/zkdemo/src/main/webapp/WEB-INF/config/log4j.properties

log4j.rootLogger=INFO,console
log4j.logger.org.apache.zookeeper=DEBUG
log4j.logger.org.apache.curator=DEBUG
log4j.logger.java.lang.Exception=INFO


log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%d{MM-dd HH:mm:ss.SSS} [%c:%p] %m%n

View Code

/zkdemo/src/main/webapp/WEB-INF/config/spring-mvc.xml

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

<mvc:default-servlet-handler />
<mvc:annotation-driven
content-negotiation-manager="contentNegotiationManager" />

<context:component-scan base-package="com.study.demo">
<context:include-filter type="annotation"
expression="org.springframework.stereotype.Controller" />
<context:exclude-filter type="annotation"
expression="org.springframework.stereotype.Service" />
</context:component-scan>

<bean id="stringHttpMessageConverter"
class="org.springframework.http.converter.StringHttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<bean class="org.springframework.http.MediaType">
<constructor-arg index="0" value="text" />
<constructor-arg index="1" value="plain" />
<constructor-arg index="2" value="UTF-8" />
</bean>
</list>
</property>
</bean>
<bean id="mappingJacksonHttpMessageConverter"
class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" />

<bean
class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
<list>
<ref bean="stringHttpMessageConverter" />
<ref bean="mappingJacksonHttpMessageConverter" />
</list>
</property>
</bean>

<bean id="contentNegotiationManager"
class="org.springframework.web.accept.ContentNegotiationManagerFactoryBean">
<property name="mediaTypes">
<map>
<entry key="html" value="text/html" />
<entry key="pdf" value="application/pdf" />
<entry key="xsl" value="application/vnd.ms-excel" />
<entry key="xml" value="application/xml" />
<entry key="json" value="application/json" />
</map>
</property>
<property name="defaultContentType" value="text/html" />
</bean>

<bean id="viewResolver"
class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
<property name="order" value="0" />
<property name="contentNegotiationManager" ref="contentNegotiationManager" />

<property name="viewResolvers">
<list>
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver" />
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="prefix" value="/WEB-INF/pages/" />
<property name="suffix" value=".jsp"></property>
</bean>
</list>
</property>

<property name="defaultViews">
<list>
<bean
class="org.springframework.web.servlet.view.json.MappingJackson2JsonView">
<property name="extractValueFromSingleKeyModel" value="true" />
</bean>
</list>
</property>
</bean>
</beans>

View Code

/zkdemo/src/main/webapp/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

<display-name>zkdemo</display-name>
<description>Zookeeper Demo Application</description>

<!--============================================================== -->
<!-- Context parameters definition -->
<!--============================================================== -->
<context-param>
<param-name>webAppRootKey</param-name>
<param-value>zkdemo.root</param-value>
</context-param>
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/config/log4j.properties</param-value>
</context-param>
<context-param>
<param-name>log4jRefreshInterval</param-name>
<param-value>60000</param-value>
</context-param>

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/config/applicationContext.xml</param-value>
</context-param>

<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/config/spring-mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>


<!--============================================================== -->
<!-- Listener definition -->
<!--============================================================== -->
<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>

<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>


<!--============================================================== -->
<!-- Filter definition -->
<!--============================================================== -->
<filter>
<filter-name>characterEncodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<!--============================================================== -->
<!-- Web Session definition -->
<!--============================================================== -->
<session-config>
<session-timeout>20</session-timeout>
</session-config>


<!--============================================================== -->
<!-- Redirect page definition -->
<!--============================================================== -->
<error-page>
<error-code>403</error-code>
<location>/403.jsp</location>
</error-page>
<error-page>
<error-code>404</error-code>
<location>/404.jsp</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/500.jsp</location>
</error-page>


<!--============================================================== -->
<!-- First page definition -->
<!--============================================================== -->
<welcome-file-list>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>

</web-app>

View Code

資料庫指令碼：

CREATE TABLE `tbl_order` (
`order_id` int(11) NOT NULL AUTO_INCREMENT COMMENT '訂單id',
`brand_id` int(11) DEFAULT NULL COMMENT '品牌id',
PRIMARY KEY (`order_id`)
) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 COMMENT='訂單表';INSERT INTO tbl_order VALUES('1','1')

2.7 啟動專案在瀏覽器輸入地址http://localhost:8080/zkdemo/test檢視效果

可以看到報錯了，這是因為我們之前設定了錯誤的url

create /Jdbc/url jdbc.mysql://192.168.152.1/dbspread 

修改url為正確的

set /Jdbc/url jdbc:mysql://192.168.152.1:3306/dbspread

再次輸入地址訪問檢視效果：

http://localhost:8080/zkdemo/test

可以看到在沒有重啟服務的情況下，可以正常訪問獲取到值了，這是因為zookeeper的資料庫的配置動態重新整理到服務了！