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一 点睛
虽然EhCache已经能够适用很多应用场景,但是由于EhCache是进程内的缓存框架,在集群模式下时,各应用服务器之间的缓存都是独立的,因此在不同服务器的进程间会存在缓存不一致的情况。即使EhCache提供了集群环境下的缓存同步策略,但是同步依然需要一定的时间,短暂的缓存不一致依然存在。
在一些要求高一致性(任何数据变化都能及时的被查询到)的系统和应用中,就不能再使用EhCache来解决了,这个时候使用集中式缓存是个不错的选择,因此本篇将介绍如何在Spring Boot的缓存支持中使用Redis进行数据缓存。
二 实战
1 新增依赖
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.21</version>
</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-cache</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-redis</artifactId>
</dependency>
</dependencies>
2 实体类
package com.didispace.domain;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import java.io.Serializable;
/**
* @author 程序猿DD
* @version 1.0.0
* @date 16/3/21 下午3:35.
* @blog http://blog.didispace.com
*/
@Entity
public class User implements Serializable {
@Id
@GeneratedValue
private Long id;
@Column(nullable = false)
private String name;
@Column(nullable = false)
private Integer age;
public User(){}
public User(String name, Integer age) {
this.name = name;
this.age = age;
}
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;
}
}
3 数据访问
package com.didispace.domain;
import org.springframework.cache.annotation.CacheConfig;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.data.jpa.repository.JpaRepository;
@CacheConfig(cacheNames = "users")
public interface UserRepository extends JpaRepository<User, Long> {
@Cacheable(key = "#p0")
User findByName(String name);
@CachePut(key = "#p0.name")
User save(User user);
}
4 启动类
package com.didispace;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
@SpringBootApplication
@EnableCaching
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
5 application.properties配置
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect
spring.jpa.properties.hibernate.hbm2ddl.auto=create-drop
spring.jpa.properties.hibernate.show_sql=true
spring.redis.host=localhost
spring.redis.port=6379
spring.redis.pool.max-idle=8
spring.redis.pool.min-idle=0
spring.redis.pool.max-active=8
spring.redis.pool.max-wait=-1
6 测试类
package com.didispace;
import com.didispace.domain.User;
import com.didispace.domain.UserRepository;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.cache.CacheManager;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(Application.class)
public class ApplicationTests {
@Autowired
private UserRepository userRepository;
@Autowired
private CacheManager cacheManager;
@Before
public void before() {
userRepository.save(new User("AAA", 10));
}
@Test
public void test() throws Exception {
User u1 = userRepository.findByName("AAA");
System.out.println("第一次查询:" + u1.getAge());
User u2 = userRepository.findByName("AAA");
System.out.println("第二次查询:" + u2.getAge());
u1.setAge(20);
userRepository.save(u1);
User u3 = userRepository.findByName("AAA");
System.out.println("第三次查询:" + u3.getAge());
}
}
三 测试结果
Hibernate: insert into user (age, name) values (?, ?)
第一次查询:10
第二次查询:10
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.name as name3_0_0_ from user user0_ where user0_.id=?
Hibernate: update user set age=?, name=? where id=?
第三次查询:20
可以看到,我们的第三次查询获得了正确的结果!同时,我们的第一次查询也不是通过select查询获得的,因为在初始化数据的时候,调用save方法时,就已经将这条数据加入了redis缓存中,因此后续的查询就直接从redis中获取了。