Mybatis的缓存
缓存也是为了减少java应用与数据库的交互次数，提升程序的效率
一级缓存
自带一级缓存，并且无法关闭，一直存在，存储在sqlSession中
使用同一个sqlsession进行查询操作一级缓存存在；如果有多个sqlsession那么一级缓存不存在
缓存一般争对查询，如果进行了增删改查操作，会自动的将缓存的数据清除，保证数据的一致性，一级缓存不需要设置，直接使用即可。
1.实体类
package com.shouthwind.entity;
import lombok.Data;
import java.util.List;
@Data
public class Account {
private Integer id;
private String name;
private List<Course> courses;
}
2.接口
package com.shouthwind.repository;
import com.shouthwind.entity.Account;
public interface AccountRepository {
public Account findById1(Integer id);
public Account findById(Integer id);
}
3.Mapper
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shouthwind.repository.AccountRepository">
<resultMap id="accoutMap" type="com.shouthwind.entity.Account">
<id column="aid" property="id"></id>
<result column="aname" property="name"></result>
<collection property="courses" ofType="com.shouthwind.entity.Course">
<id column="cid" property="id"></id>
<result column="cname" property="name"></result>
</collection>
</resultMap>
<select id="findById1" parameterType="java.lang.Integer" resultMap="accoutMap">
select a.id aid,a.name aname,c.id cid,c.name cname from account a,t_course c,account_course ac where a.id=#{id} and a.id=ac.aid and c.id=ac.cid
</select>
<select id="findById" parameterType="java.lang.Integer" resultType="com.shouthwind.entity.Account">
select * from account where id=#{id}
</select>
</mapper>
4.测试
二级缓存
它是Mapper级别的，无论使用多少个sqlsession都可以共享。
- 自带的二级缓存
- 第三方的ehcache二级缓存
自带的二级缓存
1.配置config.xml
<!-- 打印sql-->
<setting name="logImpl" value="STDOUT_LOGGING"/>
<!-- 延迟加载-->
<setting name="lazyLoadingEnabled" value="true"/>
<!-- 开启二级缓存-->
<setting name="cacheEnabled" value="true"/>
</settings>
2.Mapper.xml配置二级缓存
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shouthwind.repository.StudentRepository">
<cache></cache>
<resultMap id="studentMap" type="com.shouthwind.entity.Student">
<id column="sSno" property="Sno"></id>
<result column="sSname" property="Sname"></result>
<result column="sSsex" property="Ssex"></result>
<result column="sSage" property="Sage"></result>
<result column="sSdept" property="Sdept"></result>
<association property="sc" javaType="com.shouthwind.entity.Sc">
<result column="cSno" property= "Sno"></result>
<result column="cCno" property="Cno"></result>
<result column="cGrade" property="Grade"></result>
</association>
</resultMap>
<select id="findById" parameterType="java.lang.Integer" resultMap="studentMap">
select s.Sno sSno,s.Sname sSname,s.Ssex sSsex,s.Sage sSage,s.Sdept sSdept,c.Sno cSno,c.Cno cCno,c.Grade cGrade from student s,sc c where s.Sno=c.Sno and s.Sno=#{Sno}
</select>
</mapper>
3.实体类实现Serializable接口
package com.shouthwind.entity;
import lombok.Data;
import java.io.Serializable;
@Data
public class Student implements Serializable {
private Integer Sno;
private String Sname;
private String Ssex;
private Integer Sage;
private String Sdept;
private Sc sc;
}
第三方的ehcache缓存
1.配置
<!-- ehcache-->
<dependency>
<groupId>net.sf.ehcache</groupId>
<artifactId>ehcache-core</artifactId>
<version>2.4.3</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-ehcache</artifactId>
<version>1.0.0</version>
</dependency>
2.在resource小创建ehcache创建配置
<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="http://ehcache.org/ehcache.xsd">
<!-- 磁盘保存路径 -->
<diskStore path="D:\\ehcache" />
<defaultCache
maxElementsInMemory="10000"
maxElementsOndisk="10000000"
eternal="false"
overflowTodisk="true"
timetoIdleSeconds="120"
timetoLiveSeconds="120"
diskExpiryThreadIntervalSeconds="120"
memoryStoreevictionPolicy="LRU">
</defaultCache>
</ehcache>
3.config.xml中配置二级缓存
<settings>
<!-- 打印sql-->
<setting name="logImpl" value="STDOUT_LOGGING"/>
<!-- 延迟加载-->
<setting name="lazyLoadingEnabled" value="true"/>
<!-- 开启二级缓存-->
<setting name="cacheEnabled" value="true"/>
</settings>
4.Mapper.xml中配置二级缓存
<cache type="org.mybatis.caches.ehcache.EhcacheCache">
<!-- 缓存创建以后，最后一次访问的时间到失效时间-->
<property name="timetoIdleSeconds" value="3600"/>
<!-- 缓存自创建时间起自失效时间的间隔-->
<property name="timetoLiveSeconds" value="3600"/>
<!-- 缓存回收策略，LRU移除近期的最少使用的对象-->
<property name="memoryStoreevictionPolicy" value="LRU"/>
</cache>
5.实体类不需要实现序列化接口
Mybatis的动态sql可以更据不同的信息来拼接不同的sql、以适应不同的需求
1.创建实体类
package com.shouthwind.entity;
import lombok.Data;
@Data
public class People {
// private Integer Sno;
// private String Sname;
// private String Ssex;
// private Integer Sage;
// private String Sdept;
private Integer id;
private String name;
private Integer money;
}
2.创建Mapper接口和文件
package com.shouthwind.repository;
import com.shouthwind.entity.People;
import java.util.List;
public interface UserRepository {
// public int save(People people);
// public int deleteById(Integer id);
// public int update(People people);
// public People findById(Integer id);
// public List<People> findAll();
// public People findById2(int id);
// public People findByName(String name);
// public People findByIdAndName(Integer id,String name);
// public Integer count();
// public String findNameById(Integer id);
public People findByUser (People people);
}
<!-- 动态 sql-->
<select id="findByUser" parameterType="com.shouthwind.entity.People" resultType="com.shouthwind.entity.People">
select * from people
<where>
<if test="id!=null">
id=#{id}
</if>
<if test="name!=null">
and name={name}
</if>
<if test="money!=null">
and money=#{money}
</if>
</where>
</select>
4.测试
package com.shouthwind.Test;
import com.shouthwind.entity.People;
import com.shouthwind.repository.UserRepository;
import org.apache.ibatis.session.sqlSession;
import org.apache.ibatis.session.sqlSessionFactory;
import org.apache.ibatis.session.sqlSessionFactoryBuilder;
import java.io.InputStream;
public class Test7 {
public static void main(String[] args) {
InputStream inputStream = Test7.class.getClassLoader().getResourceAsstream("config.xml");
sqlSessionFactoryBuilder sqlSessionFactoryBuilder = new sqlSessionFactoryBuilder();
sqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
sqlSession sqlSession = sqlSessionFactory.openSession();
//获取实现了自定义代理接口的对象
UserRepository userRepository=sqlSession.getMapper(UserRepository.class);
People people = new People();
people.setId(1);
People result =userRepository.findByUser(people);
System.out.println(result);
}
}
if
where
- choose、when
类似swich case
代码：
<!-- 动态 sql-->
<select id="findByUser" parameterType="com.shouthwind.entity.People" resultType="com.shouthwind.entity.People">
select * from people
<where>
<choose>
<when test="id!=null">
id=#{id}
</when>
<when test="name!=null">
and name={name}
</when>
<when test="money!=null">
and money=#{money}
</when>
</choose>
</where>
</select>
-
trim
设置predix和suffix参数来完成使用
-
set用于update操作
package com.shouthwind.repository;import com.shouthwind.entity.People; import java.util.List; public interface UserRepository { // public int save(People people); // public int deleteById(Integer id); // public int update(People people); // public People findById(Integer id); // public List<People> findAll(); // public People findById2(int id); // public People findByName(String name); // public People findByIdAndName(Integer id,String name); // public Integer count(); // public String findNameById(Integer id); public People findByUser (People people); public Integer update (People people); }mapperi文件
update people
name=#{name},
money=#{money}
where id=#{id}
测试类：
package com.shouthwind.Test;
import com.shouthwind.entity.People;
import com.shouthwind.repository.UserRepository;
import org.apache.ibatis.session.sqlSession;
import org.apache.ibatis.session.sqlSessionFactory;
import org.apache.ibatis.session.sqlSessionFactoryBuilder;
import java.io.InputStream;
public class Test7 {
public static void main(String[] args) {
InputStream inputStream = Test7.class.getClassLoader().getResourceAsstream("config.xml");
sqlSessionFactoryBuilder sqlSessionFactoryBuilder = new sqlSessionFactoryBuilder();
sqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
sqlSession sqlSession = sqlSessionFactory.openSession();
//获取实现了自定义代理接口的对象
UserRepository userRepository=sqlSession.getMapper(UserRepository.class);
People people = new People();
people.setId(1);
people.setName("郝momo");
people.setMoney(55);
userRepository.update(people);
sqlSession.commit();
// People result =userRepository.findByUser(people);
// System.out.println(result);
sqlSession.close();
}
}版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 dio@foxmail.com 举报，一经查实，本站将立刻删除。
