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我门知道一个程序的瓶颈在于数据库，我门也知道内存的速度是大大快于硬盘的速度的。当我门需要重复的获取相同的数据的时候，我门一次又一次的请求数据库或者远程服务，导致大量的时间耗费在数据库查询或者远程方法的调用上，导致程序性能的恶化，这更是数据缓存要解决的问题。

spring 缓存支持

spring定义了 org.springframework.cache.CacheManager和org.springframework.cache.Cache接口来统一不同的缓存技术。其中，CacheManager是Spring提供的各种缓存技术抽象接口，Cache接口包含了缓存的各种操作（增加、删除获得缓存，我门一般不会直接和此接口打交道）

spring 支持的CacheManager

针对不同的缓存技术，需要实现不同的CacheManager ,spring 定义了如下表的CacheManager实现。

实现任意一种CacheManager 的时候，需要注册实现CacheManager的bean，当然每种缓存技术都有很多额外的配置，但配置CacheManager 是必不可少的。

声明式缓存注解

spring提供了4个注解来声明缓存规则（又是使用注解式的AOP的一个生动例子），如表。

开启声明式缓存

开启声明式缓存支持非常简单，只需要在配置类上使用@EnabelCaching 注解即可。

springBoot 的支持

在spring中国年使用缓存技术的关键是配置CacheManager 而springbok 为我门自动配置了多个CacheManager的实现。在spring boot 环境下，使用缓存技术只需要在项目中导入相关缓存技术的依赖包，并配置类使用@EnabelCaching开启缓存支持即可。

---

小例子

小例子是使用 springboot+jpa ＋cache 实现的。

实例步骤目录

• 1.创建maven项目
• 2.数据库配置
• 3.jpa配置和cache配置
• 4.编写bean 和dao层
• 5.编写service层
• 6.编写controller
• 7.启动cache
• 8.测试校验

---

1.创建maven项目

新建maven 项目pom.xml文件如下内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.us</groupId><artifactId>springboot-Cache</artifactId><version>1.0-SNAPSHOT</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.3.0.RELEASE</version></parent><properties><start-class>com.us.Application</start-class><maven.compiler.target>1.8</maven.compiler.target><maven.compiler.source>1.8</maven.compiler.source></properties><!-- Add typical dependencies for a web application --><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-cache</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>net.sf.ehcache</groupId><artifactId>ehcache</artifactId></dependency><!--db--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>6.0.5</version></dependency><dependency><groupId>com.mchange</groupId><artifactId>c3p0</artifactId><version>0.9.5.2</version><exclusions><exclusion><groupId>commons-logging</groupId><artifactId>commons-logging</artifactId></exclusion></exclusions></dependency></dependencies></project>

2.数据库配置

在src/main/esouces目录下新建application.properties 文件，内容为数据库连接信息，如下： 
application.properties

ms.db.driverClassName=com.mysql.jdbc.Driver
ms.db.url=jdbc:mysql://localhost:3306/cache?prepStmtCacheSize=517&cachePrepStmts=true&autoReconnect=true&useUnicode=true&characterEncoding=utf-8&useSSL=false&allowMultiQueries=true
ms.db.username=root
ms.db.password=xxxxxx
ms.db.maxActive=500

新建DBConfig.java 配置文件，配置数据源

package com.us.example.config;/*** Created by yangyibo on 17/1/13.*/
import java.beans.PropertyVetoException;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import com.mchange.v2.c3p0.ComboPooledDataSource;@Configuration
public class DBConfig {@Autowiredprivate Environment env;@Bean(name="dataSource")public ComboPooledDataSource dataSource() throws PropertyVetoException {ComboPooledDataSource dataSource = new ComboPooledDataSource();dataSource.setDriverClass(env.getProperty("ms.db.driverClassName"));dataSource.setJdbcUrl(env.getProperty("ms.db.url"));dataSource.setUser(env.getProperty("ms.db.username"));dataSource.setPassword(env.getProperty("ms.db.password"));dataSource.setMaxPoolSize(20);dataSource.setMinPoolSize(5);dataSource.setInitialPoolSize(10);dataSource.setMaxIdleTime(300);dataSource.setAcquireIncrement(5);dataSource.setIdleConnectionTestPeriod(60);return dataSource;}
}

数据库设计，数据库只有一张Person表，设计如下：

3.jpa配置

spring－data－ jpa 配置文件如下：

package com.us.example.config;import java.util.HashMap;
import java.util.Map;import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;/*** Created by yangyibo on 17/1/13.*/@Configuration
@EnableJpaRepositories("com.us.example.dao")
@EnableTransactionManagement
@ComponentScan
public class JpaConfig {@Autowiredprivate DataSource dataSource;@Beanpublic EntityManagerFactory entityManagerFactory() {HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();factory.setJpaVendorAdapter(vendorAdapter);factory.setPackagesToScan("com.us.example.bean");factory.setDataSource(dataSource);Map<String, Object> jpaProperties = new HashMap<>();jpaProperties.put("hibernate.ejb.naming_strategy","org.hibernate.cfg.ImprovedNamingStrategy");jpaProperties.put("hibernate.jdbc.batch_size",50);factory.setJpaPropertyMap(jpaProperties);factory.afterPropertiesSet();return factory.getObject();}@Beanpublic PlatformTransactionManager transactionManager() {JpaTransactionManager txManager = new JpaTransactionManager();txManager.setEntityManagerFactory(entityManagerFactory());return txManager;}
}

4.编写bean 和dao层

实体类 Person.java

package com.us.example.bean;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;/*** Created by yangyibo on 17/1/13.*/
@Entity
@Table(name = "Person")
public class Person {@Id@GeneratedValueprivate Long id;private String name;private Integer age;private String address;public Person() {super();}public Person(Long id, String name, Integer age, String address) {super();this.id = id;this.name = name;this.age = age;this.address = address;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}}

dao层，PersonRepository.java

package com.us.example.dao;import com.us.example.bean.Person;
import org.springframework.data.jpa.repository.JpaRepository;/*** Created by yangyibo on 17/1/13.*/
public interface PersonRepository extends JpaRepository<Person, Long> {}

5.编写service层

service 接口

package com.us.example.service;import com.us.example.bean.Person;/*** Created by yangyibo on 17/1/13.*/
public  interface DemoService {public Person save(Person person);public void remove(Long id);public Person findOne(Person person);}

实现：(重点，此处加缓存)

package com.us.example.service.Impl;import com.us.example.bean.Person;
import com.us.example.dao.PersonRepository;
import com.us.example.service.DemoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;/*** Created by yangyibo on 17/1/13.*/
@Service
public class DemoServiceImpl implements DemoService {@Autowiredprivate PersonRepository personRepository;@Override//@CachePut缓存新增的或更新的数据到缓存,其中缓存名字是 people 。数据的key是person的id@CachePut(value = "people", key = "#person.id")public Person save(Person person) {Person p = personRepository.save(person);System.out.println("为id、key为:"+p.getId()+"数据做了缓存");return p;}@Override//@CacheEvict 从缓存people中删除key为id 的数据@CacheEvict(value = "people")public void remove(Long id) {System.out.println("删除了id、key为"+id+"的数据缓存");//这里不做实际删除操作}@Override//@Cacheable缓存key为person 的id 数据到缓存people 中,如果没有指定key则方法参数作为key保存到缓存中。@Cacheable(value = "people", key = "#person.id")public Person findOne(Person person) {Person p = personRepository.findOne(person.getId());System.out.println("为id、key为:"+p.getId()+"数据做了缓存");return p;}}

6.编写controller

为了测试方便请求方式都用了get

package com.us.example.controller;
import com.us.example.bean.Person;
import com.us.example.service.DemoService;
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.ResponseBody;
import org.springframework.web.bind.annotation.RestController;/*** Created by yangyibo on 17/1/13.*/
@RestController
public class CacheController {@Autowiredprivate DemoService demoService;//http://localhost:8080/put?name=abel&age=23&address=shanghai@RequestMapping("/put")public Person put(Person person){return demoService.save(person);}//http://localhost:8080/able?id=1@RequestMapping("/able")@ResponseBodypublic Person cacheable(Person person){return demoService.findOne(person);}//http://localhost:8080/evit?id=1@RequestMapping("/evit")public String  evit(Long id){demoService.remove(id);return "ok";}}

7.启动cache

启动类中要记得开启缓存配置。

package com.us.example;import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;import static org.springframework.boot.SpringApplication.*;/*** Created by yangyibo on 17/1/13.*/@ComponentScan(basePackages ="com.us.example")
@SpringBootApplication
@EnableCaching
public class Application {public static void main(String[] args) {ConfigurableApplicationContext run = run(Application.class, args);}}

8.测试校验

检验able：

启动Application 类，启动后在浏览器输入：http://localhost:8080/able?id=1（首先要在数据库中初始化几条数据。）

控制台输出： 
“为id、key为:1数据做了缓存“ 此时已经为此次查询做了缓存，再次查询该条数据将不会出现此条语句，也就是不查询数据库了。

检验put

在浏览器输入：http://localhost:8080/put?name=abel&age=23&address=shanghai（向数据库插入一条数据，并将数据放入缓存。）

此时控制台输出为该条记录做了缓存：

然后再次调用able 方法，查询该条数据，将不再查询数据库，直接从缓存中读取数据。

测试evit

在浏览器输入：http://localhost:8080/evit?id=1（将该条记录从缓存中清楚，清除后，在次访问该条记录，将会重新将该记录放入缓存。）

控制台输出：

切换缓存

1.切换为EhCache作为缓存

pom.xml 文件中添加依赖

<dependency><groupId>net.sf.ehcache</groupId><artifactId>ehcache</artifactId></dependency>

在resource 文件夹下新建ehcache的配置文件ehcache.xml 内容如下，此文件spring boot 会自动扫描

<?xml version="1.0" encoding="UTF-8"?>
<ehcache><!--切换为ehcache 缓存时使用-->
<cache name="people" maxElementsInMemory="1000" />
</ehcache>

2.切换为Guava作为缓存

只需要在pom中添加依赖

     <dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>18.0</version></dependency>

3.切换为redis作为缓存

请看下篇博客

本文参考：《JavaEE开发的颠覆者：Spring Boot实战 》

本文源代码：https://github.com/527515025/springBoot.git

 

见：http://blog.csdn.net/u012373815/article/details/54564076