MyBatis注解之二级缓存 一 领域模型package org.fkit.domain; import java.io.Serializable; /** * CREATE TABLE tb_user ( id INT(11) NOT NULL AUTO_INCREMENT, name VARCHAR(18) DEFAULT NULL, sex CHAR(2) DEFAULT NULL, age INT(11) DEFAULT NULL, PRIMARY KEY (id) ) */ public class User implements Serializable{ private static final long serialVersionUID 1L; private Integer id; private String name; private String sex; private Integer age; public User() { super(); // TODO Auto-generated constructor stub } public User( String name, String sex, Integer age) { super(); this.name name; this.sex sex; this.age age; } public Integer getId() { return id; } public void setId(Integer id) { this.id id; } public String getName() { return name; } public void setName(String name) { this.name name; } public String getSex() { return sex; } public void setSex(String sex) { this.sex sex; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age age; } Override public String toString() { return User [id id , name name , sex sex , age age ]; } }二 会话工厂package org.fkit.factory; import java.io.InputStream; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; public class FKSqlSessionFactory { private static SqlSessionFactory sqlSessionFactory null; // 初始化创建SqlSessionFactory对象 static{ try (// 读取mybatis-config.xml文件 InputStream is Resources.getResourceAsStream(mybatis-config.xml); ){ sqlSessionFactory new SqlSessionFactoryBuilder() .build(is); } catch (Exception e) { e.printStackTrace(); } } // 获取SqlSession对象的静态方法 public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } // 获取SqlSessionFactory的静态方法 public static SqlSessionFactory getSqlSessionFactory() { return sqlSessionFactory; } }三 mapperpackage org.fkit.mapper; import org.apache.ibatis.annotations.CacheNamespace; import org.apache.ibatis.annotations.Delete; import org.apache.ibatis.annotations.Options; import org.apache.ibatis.annotations.Select; import org.apache.ibatis.cache.decorators.LruCache; import org.fkit.domain.User; CacheNamespace(evictionLruCache.class,flushInterval60000,size512, readWritetrue) public interface UserMapper { // 根据id查询User Select(SELECT * FROM TB_USER WHERE id #{id}) Options(useCachetrue) User selectUserById(Integer id); // 根据id删除User Delete(DELETE FROM TB_USER WHERE id #{id}) void deleteUserById(Integer id); }四 配置文件1 db.propertiesdrivercom.mysql.jdbc.Driver urljdbc:mysql://127.0.0.1:3306/mybatis usernameroot password1234562 log4j.xml?xml version1.0 encodingUTF-8? !DOCTYPE log4j:configuration SYSTEM log4j.dtd log4j:configuration xmlns:log4jhttp://jakarta.apache.org/log4j/ appender nameSTDOUT classorg.apache.log4j.ConsoleAppender layout classorg.apache.log4j.PatternLayout param nameConversionPattern value%5p [%t] %m%n / /layout /appender logger nameorg.fkit.mapper level valueDEBUG / /logger root level valueERROR / appender-ref refSTDOUT / /root /log4j:configuration3 mybatis-config.xml?xml version1.0 encodingUTF-8 ? !DOCTYPE configuration PUBLIC -//mybatis.org//DTD Config 3.0//EN http://mybatis.org/dtd/mybatis-3-config.dtd !-- XML 配置文件包含对 MyBatis 系统的核心设置 -- configuration properties resourcedb.properties/ !-- 指定 MyBatis 所用日志的具体实现 -- settings setting namelogImpl valueLOG4J/ !-- 开启二级缓存 -- setting namecacheEnabled valuetrue/ /settings environments defaultmysql !-- 环境配置即连接的数据库。 -- environment idmysql !-- 指定事务管理类型typeJDBC指直接简单使用了JDBC的提交和回滚设置 -- transactionManager typeJDBC/ !-- dataSource指数据源配置POOLED是JDBC连接对象的数据源连接池的实现。 -- dataSource typePOOLED property namedriver value${driver}/ property nameurl value${url}/ property nameusername value${username}/ property namepassword value${password}/ /dataSource /environment /environments !-- mappers告诉了MyBatis去哪里找持久化类的映射文件 -- mappers mapper classorg.fkit.mapper.UserMapper/ /mappers /configuration五 测试package org.fkit.test; import org.apache.ibatis.session.SqlSession; import org.fkit.domain.User; import org.fkit.factory.FKSqlSessionFactory; import org.fkit.mapper.UserMapper; public class ATwoLevelCacheTest { public static void main(String[] args) { // 使用工厂类获得SqlSession对象 SqlSession sqlSession1 FKSqlSessionFactory.getSqlSession(); // 获得UserMapping对象 UserMapper um sqlSession1.getMapper(UserMapper.class); // 查询id为1的User对象会执行select语句 User user um.selectUserById(1); System.out.println(user); // 关闭一级缓存 sqlSession1.close(); // 重新获取一级缓存 SqlSession sqlSession2 FKSqlSessionFactory.getSqlSession(); // 再次获得UserMapping对象 um sqlSession2.getMapper(UserMapper.class); // 再次查询id为1的User对象虽然现在使用的是一个新的SqlSession对象,但是二级缓存中缓存了数据所以不会执行再次select语句 User user2 um.selectUserById(1); System.out.println(user2); // 关闭SqlSession对象 sqlSession2.close(); } }六 测试结果DEBUG [main] Preparing: SELECT * FROM TB_USER WHERE id ? DEBUG [main] Parameters: 1(Integer) DEBUG [main] Total: 1 User [id1, namecakin, sex男, age18] DEBUG [main] Cache Hit Ratio [org.fkit.mapper.UserMapper]: 0.5 User [id1, namecakin, sex男, age18]