Spring和SpringDataJpa整合的乐观锁与悲观锁详情

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发布于 2019-09-12 09:46:25

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发布于 2019-09-12 09:46:25

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Spring整合SpringDataJpa的乐观锁与悲观锁详情

一、概述

上一篇《Spring和SpringDataJpa整合详解》介绍了Spring如何结合Spring-data-jpa进行数据库访问操作。这一篇介绍下springmvc环境下spring-data-jpa如何进行乐观锁、悲观锁的使用。

悲观锁和乐观锁的概念：

悲观锁：就是独占锁，不管读写都上锁了。传统的关系型数据库里边就用到了很多这种锁机制，比如行锁，表锁等，读锁，写锁等，都是在做操作之前先上锁。Java中synchronized和ReentrantLock等独占锁就是悲观锁思想的实现。
乐观锁：不上锁，读取的时候带版本号，写入的时候带着这个版本号，如果不一致就失败，乐观锁适用于多读的应用类型，因为写多的时候会经常失败。

代码可以在Spring组件化构建https://www.pomit.cn/java/spring/spring.html中的JpaLock组件中查看，并下载。

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二、环境配置

本文假设你已经引入Spring必备的一切了，已经是个Spring项目了,如果不会搭建，可以打开这篇文章看一看《Spring和Spring Mvc 5整合详解》。

2.1 maven依赖

和上一篇《Spring和SpringDataJpa整合详解》的配置一样，

使用Spring-data-jpa需要引入spring-data-jpa，因为是非Springboot项目，我们不能通过starter引入，需要引入spring-data-jpa、javax.transaction-api、hibernate-core。

<?xml version="1.0"?>
<project
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>cn.pomit</groupId>
		<artifactId>SpringWork</artifactId>
		<version>0.0.1-SNAPSHOT</version>
	</parent>
	<artifactId>JpaLock</artifactId>
	<packaging>jar</packaging>
	<name>JpaLock</name>
	<url>http://maven.apache.org</url>
	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-orm</artifactId>
		</dependency>
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
		</dependency>
		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
		</dependency>
		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-dbcp2</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.data</groupId>
			<artifactId>spring-data-jpa</artifactId>
			<version>2.0.10.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>javax.transaction</groupId>
			<artifactId>javax.transaction-api</artifactId>
			<version>1.2</version>
		</dependency>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-core</artifactId>
			<version>5.2.17.Final</version>
			<scope>compile</scope>
			<exclusions>
				<exclusion>
					<artifactId>jboss-transaction-api_1.2_spec</artifactId>
					<groupId>org.jboss.spec.javax.transaction</groupId>
				</exclusion>
			</exclusions>
		</dependency>
	</dependencies>
	<build>
		<finalName>JpaLock</finalName>
	</build>
</project>

父模块可以在https://www.pomit.cn/spring/SpringWork/pom.xml获取。

2.2 Spring配置

需要配置数据源、jdbcTemplate、entityManagerFactory、transactionManager和jpa:repositories。

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jpa="http://www.springframework.org/schema/data/jpa"
	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/tx 
                    http://www.springframework.org/schema/tx/spring-tx.xsd
                    http://www.springframework.org/schema/aop 
                    http://www.springframework.org/schema/aop/spring-aop.xsd
                    http://www.springframework.org/schema/context      
                    http://www.springframework.org/schema/context/spring-context.xsd
                    http://www.springframework.org/schema/data/jpa
     				http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

	<context:annotation-config />
	<context:component-scan base-package="cn.pomit.springwork.springdatajpa">
	</context:component-scan>

	<bean id="annotationPropertyConfigurerJpaLock"
		class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
		<property name="order" value="1" />
		<property name="ignoreUnresolvablePlaceholders" value="true" />
		<property name="locations">
			<list>
				<value>classpath:db.properties</value>
			</list>
		</property>
	</bean>


	<bean id="dataSource" class="org.apache.commons.dbcp2.BasicDataSource"
		destroy-method="close">
		<property name="driverClassName" value="${db.dirverClass}"></property>
		<property name="url" value="${db.url}" />
		<property name="username" value="${db.username}" />
		<property name="password" value="${db.password}" />

		<property name="initialSize" value="1" />
		<property name="minIdle" value="1" />
		<property name="maxTotal" value="20" />

		<property name="validationQuery" value="SELECT 1" />
		<property name="testWhileIdle" value="true" />
		<property name="testOnBorrow" value="false" />
		<property name="testOnReturn" value="false" />
	</bean>

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

	<bean id="entityManagerFactory"
		class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
		<property name="dataSource" ref="dataSource"></property>
		<property name="packagesToScan" value="cn.pomit.springwork.springdatajpa.domain"></property>
		<property name="jpaVendorAdapter">
			<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
				<property name="databasePlatform" value="org.hibernate.dialect.MySQL5Dialect">
			</property>
			</bean>
		</property>
	</bean>
	<jpa:repositories base-package="cn.pomit.springwork.springdatajpa.dao" />
	
	<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
		<property name="entityManagerFactory" ref="entityManagerFactory" />
	</bean>
	<!-- 使用annotation定义事务 -->
	<tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true" />
</beans>

这里面，需要注意的是：

entityManagerFactory，是实体和数据库选择信息。
jpa:repositories，指明Spring-data-jpa的repositories地址。就是我们的数据库交互层。
transactionManager，事务处理器。
tx:annotation-driven:开启事务注解。

db.properties中存放数据库的地址端口等连接信息。

db.properties：

db.url=jdbc:mysql://127.0.0.1:3306/boot?useUnicode=true&characterEncoding=utf8&serverTimezone=UTC
db.username=cff
db.password=123456
db.dirverClass=com.mysql.cj.jdbc.Driver

三、悲观锁

悲观锁在数据库的访问中使用，表现为：前一次请求没执行完，后面一个请求就一直在等待。

3.1 Dao层

数据库要实现悲观锁，就是将sql语句带上for update即可。 for update 是行锁

在Jpa的Repository这一层，直接在方法上加上@Lock(LockModeType.PESSIMISTIC_WRITE)，就实现了悲观锁。

UserInfoDao :

package cn.pomit.springwork.springdatajpa.dao;

import javax.persistence.LockModeType;

import org.springframework.data.jpa.repository.Lock;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

import cn.pomit.springwork.springdatajpa.domain.UserInfo;

@Repository
public interface UserInfoDao extends CrudRepository<UserInfo, String> {
	@Lock(LockModeType.PESSIMISTIC_WRITE)
	UserInfo findByUserName(String userName);
}

注意加上@Repository注解。实体要加上@Entity和@Table注解。

3.2 Service层

更新数据库前，先调用findByUserName方法，使用上面的配置的悲观锁锁定表记录，然后再更新。

UserInfoService ：

package cn.pomit.springwork.springdatajpa.service;

import javax.transaction.Transactional;

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

import cn.pomit.springwork.springdatajpa.dao.UserInfoDao;
import cn.pomit.springwork.springdatajpa.domain.UserInfo;

@Service
public class UserInfoService {
	@Autowired
	UserInfoDao userInfoDao;

	public void delete(String userName) {
		userInfoDao.deleteById(userName);
	}

        public void save(UserInfo entity) {
		userInfoDao.save(entity);
	}

	@Transactional
	public UserInfo getUserInfoByUserNamePessimistic(String userName) {
		return userInfoDao.findByUserName(userName);
	}
	
	@Transactional
	public void updateWithTimePessimistic(UserInfo entity, int time) throws InterruptedException {		
		UserInfo userInfo = userInfoDao.findByUserName(entity.getUserName());
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}
		Thread.sleep(time * 1000L);

		userInfoDao.save(userInfo);
	}
	
	@Transactional
	public void updatePessimistic(UserInfo entity) {
		UserInfo userInfo = userInfoDao.findByUserName(entity.getUserName());
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}

		userInfoDao.save(userInfo);
	}
}

3.3 测试Web层

可以先调用/update/{time}接口，延迟执行，然后马上调用/update接口，会发现，/update接口一直在等待/update/{time}接口执行完成。

JpaPessLockRest :

package cn.pomit.springwork.springdatajpa.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import cn.pomit.springwork.springdatajpa.domain.UserInfo;
import cn.pomit.springwork.springdatajpa.service.UserInfoService;

/**
 * 测试悲观锁
 * 
 * @author fufei
 *
 */
@RestController
@RequestMapping("/jpapesslock")
public class JpaPessLockRest {

	@Autowired
	UserInfoService userInfoService;

	@RequestMapping(value = "/detail/{name}", method = { RequestMethod.GET })
	public UserInfo detail(@PathVariable("name") String name) {
		return userInfoService.getUserInfoByUserNamePessimistic(name);
	}

	@RequestMapping(value = "/save")
	public String save(@RequestBody UserInfo userInfo) throws InterruptedException {
		userInfoService.save(userInfo);
		return "0000";
	}

	@RequestMapping(value = "/update/{time}")
	public String update(@RequestBody UserInfo userInfo, @PathVariable("time") int time) throws InterruptedException {
		userInfoService.updateWithTimePessimistic(userInfo, time);

		return "0000";
	}

	@RequestMapping(value = "/update")
	public String update(@RequestBody UserInfo userInfo) throws InterruptedException {
		userInfoService.updatePessimistic(userInfo);
		return "0000";
	}
}

四、乐观锁

数据库访问dao层还是3.1那个dao。

4.1 实体添加@Version

UserInfo实体增加字段version，并添加注解@Version。当然，数据库也要加上version字段，普通字段就行，别设置成主键自增啥的。

@Version
private Integer version;

4.2 Service层

service层我们做一下简单的调整。更新数据库前，先调用findById方法，查询出当前的版本号，然后再更新。

UserInfoService ：

package cn.pomit.springwork.springdatajpa.service;

import javax.transaction.Transactional;

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

import cn.pomit.springwork.springdatajpa.dao.UserInfoDao;
import cn.pomit.springwork.springdatajpa.domain.UserInfo;

@Service
public class UserInfoService {
	@Autowired
	UserInfoDao userInfoDao;

	public UserInfo getUserInfoByUserName(String userName) {
		return userInfoDao.findById(userName).orElse(null);
	}

	public void save(UserInfo entity) {
		userInfoDao.save(entity);
	}
	@Transactional
	public void updateWithTimeOptimistic(UserInfo entity, int time) throws InterruptedException {		
		UserInfo userInfo = userInfoDao.findById(entity.getUserName()).orElse(null);
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}
		Thread.sleep(time * 1000L);

		userInfoDao.save(userInfo);
	}

	public void delete(String userName) {
		userInfoDao.deleteById(userName);
	}
	@Transactional
	public void updateOptimistic(UserInfo entity) {
		UserInfo userInfo = userInfoDao.findById(entity.getUserName()).orElse(null);
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}

		userInfoDao.save(userInfo);
	}


}

4.2 测试Web层

可以先调用/update/{time}接口，延迟执行，然后马上调用/update接口，会发现，/update接口不会等待/update/{time}接口执行完成，读取完版本号能够成功更新数据，但是/update/{time}接口等待足够时间以后，更新的时候会报错，因为它的版本和数据库的已经不一致了。

JpaOptiLockRest ：

package cn.pomit.springwork.springdatajpa.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import cn.pomit.springwork.springdatajpa.domain.UserInfo;
import cn.pomit.springwork.springdatajpa.service.UserInfoService;

/**
 * 测试乐观锁
 * @author fufei
 *
 */
@RestController
@RequestMapping("/jpalock")
public class JpaOptiLockRest {

	@Autowired
	UserInfoService userInfoService;

	@RequestMapping(value = "/detail/{name}", method = { RequestMethod.GET })
	public UserInfo detail(@PathVariable("name") String name) {
		return userInfoService.getUserInfoByUserName(name);
	}

	@RequestMapping(value = "/save")
	public String save(@RequestBody UserInfo userInfo) throws InterruptedException {
		userInfoService.save(userInfo);
		return "0000";
	}

	@RequestMapping(value = "/update/{time}")
	public String update(@RequestBody UserInfo userInfo, @PathVariable("time") int time) throws InterruptedException {
		userInfoService.updateWithTimeOptimistic(userInfo, time);

		return "0000";
	}

	@RequestMapping(value = "/update")
	public String update(@RequestBody UserInfo userInfo) throws InterruptedException {
		userInfoService.updateOptimistic(userInfo);
		return "0000";
	}
}

五、过程中用到的完整实体和Service

UserInfo：

package cn.pomit.springwork.springdatajpa.domain;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Version;

@Entity
@Table(name = "user_info_test")
public class UserInfo {
	@Id
	@Column(name = "user_name")
	private String userName;
	private String passwd;
	private String name;
	private String mobile;
	private String valid;
	@Version
	private Integer version;

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public String getUserName() {
		return userName;
	}

	public void setPasswd(String passwd) {
		this.passwd = passwd;
	}

	public String getPasswd() {
		return passwd;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setMobile(String mobile) {
		this.mobile = mobile;
	}

	public String getMobile() {
		return mobile;
	}

	public void setValid(String valid) {
		this.valid = valid;
	}

	public String getValid() {
		return valid;
	}

}

UserInfoService :

package cn.pomit.springwork.springdatajpa.service;

import javax.transaction.Transactional;

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

import cn.pomit.springwork.springdatajpa.dao.UserInfoDao;
import cn.pomit.springwork.springdatajpa.domain.UserInfo;

@Service
public class UserInfoService {
	@Autowired
	UserInfoDao userInfoDao;

	public UserInfo getUserInfoByUserName(String userName) {
		return userInfoDao.findById(userName).orElse(null);
	}

	public void save(UserInfo entity) {
		userInfoDao.save(entity);
	}
	@Transactional
	public void updateWithTimeOptimistic(UserInfo entity, int time) throws InterruptedException {		
		UserInfo userInfo = userInfoDao.findById(entity.getUserName()).orElse(null);
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}
		Thread.sleep(time * 1000L);

		userInfoDao.save(userInfo);
	}

	public void delete(String userName) {
		userInfoDao.deleteById(userName);
	}
	@Transactional
	public void updateOptimistic(UserInfo entity) {
		UserInfo userInfo = userInfoDao.findById(entity.getUserName()).orElse(null);
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}

		userInfoDao.save(userInfo);
	}

	@Transactional
	public UserInfo getUserInfoByUserNamePessimistic(String userName) {
		return userInfoDao.findByUserName(userName);
	}
	
	@Transactional
	public void updateWithTimePessimistic(UserInfo entity, int time) throws InterruptedException {		
		UserInfo userInfo = userInfoDao.findByUserName(entity.getUserName());
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}
		Thread.sleep(time * 1000L);

		userInfoDao.save(userInfo);
	}
	
	@Transactional
	public void updatePessimistic(UserInfo entity) {
		UserInfo userInfo = userInfoDao.findByUserName(entity.getUserName());
		if (userInfo == null)
			return;

		if (!StringUtils.isEmpty(entity.getMobile())) {
			userInfo.setMobile(entity.getMobile());
		}
		if (!StringUtils.isEmpty(entity.getName())) {
			userInfo.setName(entity.getName());
		}

		userInfoDao.save(userInfo);
	}
}

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原始发表：2019-07-29 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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