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我門知道一個程序的瓶頸在于數據庫，我門也知道內存的速度是大大快于硬盤的速度的。當我門需要重復的獲取相同的數據的時候，我門一次又一次的請求數據庫或者遠程服務，導致大量的時間耗費在數據庫查詢或者遠程方法的調用上，導致程序性能的惡化，這更是數據緩存要解決的問題。

spring 緩存支持

spring定義了 org.springframework.cache.CacheManager和org.springframework.cache.Cache接口來統一不同的緩存技術。其中，CacheManager是Spring提供的各種緩存技術抽象接口，Cache接口包含了緩存的各種操作（增加、刪除獲得緩存，我門一般不會直接和此接口打交道）

spring 支持的CacheManager

針對不同的緩存技術，需要實現不同的CacheManager ,spring 定義了如下表的CacheManager實現。

實現任意一種CacheManager 的時候，需要注冊實現CacheManager的bean，當然每種緩存技術都有很多額外的配置，但配置CacheManager 是必不可少的。

聲明式緩存注解

spring提供了4個注解來聲明緩存規則（又是使用注解式的AOP的一個生動例子），如表。

開啟聲明式緩存

開啟聲明式緩存支持非常簡單，只需要在配置類上使用@EnabelCaching 注解即可。

springBoot 的支持

在spring中國年使用緩存技術的關鍵是配置CacheManager 而springbok 為我門自動配置了多個CacheManager的實現。在spring boot 環境下，使用緩存技術只需要在項目中導入相關緩存技術的依賴包，并配置類使用@EnabelCaching開啟緩存支持即可。

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小例子

小例子是使用 springboot+jpa ＋cache 實現的。

實例步驟目錄

• 1.創建maven項目
• 2.數據庫配置
• 3.jpa配置和cache配置
• 4.編寫bean 和dao層
• 5.編寫service層
• 6.編寫controller
• 7.啟動cache
• 8.測試校驗

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1.創建maven項目

新建maven 項目pom.xml文件如下內容如下：

<?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.數據庫配置

在src/main/esouces目錄下新建application.properties 文件，內容為數據庫連接信息，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，配置數據源

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;} }

數據庫設計，數據庫只有一張Person表，設計如下：

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.編寫bean 和dao層

實體類 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層，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.編寫service層

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);}

實現：(重點，此處加緩存)

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緩存新增的或更新的數據到緩存,其中緩存名字是 people 。數據的key是person的id@CachePut(value = "people", key = "#person.id")public Person save(Person person) {Person p = personRepository.save(person);System.out.println("為id、key為:"+p.getId()+"數據做了緩存");return p;}@Override//@CacheEvict 從緩存people中刪除key為id 的數據@CacheEvict(value = "people")public void remove(Long id) {System.out.println("刪除了id、key為"+id+"的數據緩存");//這里不做實際刪除操作}@Override//@Cacheable緩存key為person 的id 數據到緩存people 中,如果沒有指定key則方法參數作為key保存到緩存中。@Cacheable(value = "people", key = "#person.id")public Person findOne(Person person) {Person p = personRepository.findOne(person.getId());System.out.println("為id、key為:"+p.getId()+"數據做了緩存");return p;}}

6.編寫controller

為了測試方便請求方式都用了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.啟動cache

啟動類中要記得開啟緩存配置。

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.測試校驗

檢驗able：

啟動Application 類，啟動后在瀏覽器輸入：http://localhost:8080/able?id=1（首先要在數據庫中初始化幾條數據。）

控制臺輸出：?
“為id、key為:1數據做了緩存“ 此時已經為此次查詢做了緩存，再次查詢該條數據將不會出現此條語句，也就是不查詢數據庫了。

檢驗put

在瀏覽器輸入：http://localhost:8080/put?name=abel&age=23&address=shanghai（向數據庫插入一條數據，并將數據放入緩存。）

此時控制臺輸出為該條記錄做了緩存：

然后再次調用able 方法，查詢該條數據，將不再查詢數據庫，直接從緩存中讀取數據。

測試evit

在瀏覽器輸入：http://localhost:8080/evit?id=1（將該條記錄從緩存中清楚，清除后，在次訪問該條記錄，將會重新將該記錄放入緩存。）

控制臺輸出：

切換緩存

1.切換為EhCache作為緩存

pom.xml 文件中添加依賴

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

在resource 文件夾下新建ehcache的配置文件ehcache.xml 內容如下，此文件spring boot 會自動掃描

<?xml version="1.0" encoding="UTF-8"?> <ehcache><!--切換為ehcache 緩存時使用--> <cache name="people" maxElementsInMemory="1000" /> </ehcache>

2.切換為Guava作為緩存

只需要在pom中添加依賴

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

3.切換為redis作為緩存

請看下篇博客

本文參考：《JavaEE開發的顛覆者：Spring Boot實戰 》

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

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

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