Mybatis的拓展

末蓝、 2021-09-11 03:10 352阅读 0赞

### 文章目录 ###

*   *  ResultMap复杂使用
     *   *  对象关系
         *  pom.xml
         *  准备数据库表
         *  准备实体类
         *   *  UserInfo.java
             *  UserExtra.java
         *  一对一
         *   *  需求
             *  改造UserInfo类
             *  创建One21.xml
             *  引入sqlMapConfig.xml
             *  创建One21Mapper接口
             *  测试类
     *  Mybatis的缓存
     *   *  一级缓存
         *  二级缓存

## ResultMap复杂使用 ##

### 对象关系 ###

分为一对一和一对多，分别使用resultMap提供的不同方案来处理：

一对一：使用association + javaType

一对多：使用collection + ofType

### pom.xml ###

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>2.4.2</version>
    		<relativePath/> 
    	</parent>
    	<groupId>cn.tedu</groupId>
    	<artifactId>mybatis</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<name>mybatis</name>
    	<description>Demo project for Spring Boot</description>
    	<properties>
    		<java.version>1.8</java.version>
    	</properties>
    	<dependencies>
    		<dependency>
    			<groupId>org.mybatis.spring.boot</groupId>
    			<artifactId>mybatis-spring-boot-starter</artifactId>
    			<version>2.1.4</version>
    		</dependency>
    
    		<dependency>
    			<groupId>mysql</groupId>
    			<artifactId>mysql-connector-java</artifactId>
    			<scope>runtime</scope>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-test</artifactId>
    			<scope>test</scope>
    		</dependency>
    	</dependencies>
    
    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.springframework.boot</groupId>
    				<artifactId>spring-boot-maven-plugin</artifactId>
    			</plugin>
    		</plugins>
    	</build>
    
    </project>

### 准备数据库表 ###

create table user_info(
    	id int primary key auto_increment,
    	user_name varchar(100),
    	user_addr varchar(200),
    	user_age int);
    insert into user_info values(null,'韩梅梅','上海',20);
    insert into user_info values(null,'王海涛','北京',30);
    insert into user_info values(null,'张慎政','河南',10);
    
    create table user_extra(
    	id int primary key auto_increment,
    	user_id int,
    	work varchar(100),
    	salary double);
    insert into user_extra values(null,'1','程序员',100000);
    insert into user_extra values(null, '2','教师',1000);
    insert into user_extra values(null, '3','CTO',100000);

### 准备实体类 ###

#### UserInfo.java ####

package cn.tedu.pojo;
    //描述user_info表
    public class UserInfo { 
    	private int id;
    	private String userName;
    	private int userAge;
    	private String userAddr;
    	
    	public int getId() { 
    		return id;
    	}
    	public void setId(int id) { 
    		this.id = id;
    	}
    	public String getUserName() { 
    		return userName;
    	}
    	public void setUserName(String userName) { 
    		this.userName = userName;
    	}
    	public int getUserAge() { 
    		return userAge;
    	}
    	public void setUserAge(int userAge) { 
    		this.userAge = userAge;
    	}
    	public String getUserAddr() { 
    		return userAddr;
    	}
    	public void setUserAddr(String userAddr) { 
    		this.userAddr = userAddr;
    	}
    	@Override
    	public String toString() { 
    		return "UserInfo [id=" + id + ", userName=" + userName + ", userAge=" + userAge + ", userAddr=" + userAddr
    				+ "]";
    	}
    
    }

#### UserExtra.java ####

package cn.tedu.pojo;
    //描述user_extra表
    public class UserExtra { 
    	private int id;
    	private int userId;
    	private String work;
    	private double salary;
    	
    	public int getId() { 
    		return id;
    	}
    	public void setId(int id) { 
    		this.id = id;
    	}
    	public int getUserId() { 
    		return userId;
    	}
    	public void setUserId(int userId) { 
    		this.userId = userId;
    	}
    	public String getWork() { 
    		return work;
    	}
    	public void setWork(String work) { 
    		this.work = work;
    	}
    	public double getSalary() { 
    		return salary;
    	}
    	public void setSalary(double salary) { 
    		this.salary = salary;
    	}
    	@Override
    	public String toString() { 
    		return "UserExtra [id=" + id + ", userId=" + userId + ", work=" + work + ", salary=" + salary + "]";
    	}
    }

### 一对一 ###

#### 需求 ####

user\_extra 和 user\_info表是一对一的关系

根据用户查询一对一关系的用户扩展信息，使用association + javaType描述关联表的信息

#### 改造UserInfo类 ####

package cn.tedu.pojo;
    import java.util.List;
    public class UserInfo { 
    	private int id;
    	private String userName;
    	private String userAddr;
    	private int userAge;
    	
    	**//一对一
    	private UserExtra userExtra;
    	
    	public UserExtra getUserExtra() { 
    		return userExtra;
    	}
    	public void setUserExtra(UserExtra userExtra) { 
    		this.userExtra = userExtra;
    	}**
    	public int getId() { 
    		return id;
    	}
    	public void setId(int id) { 
    		this.id = id;
    	}
    	public String getUserName() { 
    		return userName;
    	}
    	public void setUserName(String userName) { 
    		this.userName = userName;
    	}
    	public String getUserAddr() { 
    		return userAddr;
    	}
    	public void setUserAddr(String userAddr) { 
    		this.userAddr = userAddr;
    	}
    	public int getUserAge() { 
    		return userAge;
    	}
    	public void setUserAge(int userAge) { 
    		this.userAge = userAge;
    	}
    	
    	**@Override
    	public String toString() { 
    		return "UserInfo [id=" + id + ", userName=" + userName + ", userAddr=" + userAddr + ", userAge=" + userAge
    				+ ", userExtra=" + userExtra + "]";
    	}**
    	
    }

#### 创建One21.xml ####

<?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="cn.tedu.mapper.One21Mapper">
    
    	<resultMap type="UserInfo" id="One21RM">
    		
    		<id column="id" property="id"/>
    		<result column="user_name" property="userName"/>
    		<result column="user_age" property="userAge"/>
    		<result column="user_addr" property="userAddr"/>
    		**
    			<association property="userExtra"  javaType="UserExtra">
    				<id column="id" property="id"/>
    				<result column="user_id" property="userId"/>
    				<result column="work" property="work"/>
    				<result column="salary" property="salary"/>
    			</association>**
    	</resultMap>
    
    	
    	<select id="One21" resultMap="One21RM">
    		select * from user_info a,user_extra b
    		where a.id=b.user_id and a.id=#{ id} 
    	</select>
    
    </mapper>

#### 引入sqlMapConfig.xml ####

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
    
    
     <configuration>
     
     	
      	<typeAliases>
     		<typeAlias type="cn.tedu.pojo.Dept" alias="Dept"/>
     		<typeAlias type="cn.tedu.pojo.Emp" alias="Emp"/>
     		<typeAlias type="cn.tedu.pojo.UserInfo" alias="UserInfo"/>
     		<typeAlias type="cn.tedu.pojo.UserExtra" alias="UserExtra"/>
     	</typeAliases>
     	
     	<environments default="test">
     		<environment id="test">
     			<transactionManager type="JDBC"></transactionManager>
     			<dataSource type="POOLED">
     				<property name="driver" value="com.mysql.jdbc.Driver"/> 
    				<property name="url" value="jdbc:mysql://localhost:3306/mybatisdb?characterEncoding=utf8&serverTimezone=Asia/Shanghai" /> 
    				<property name="username" value="root"/> 
    				<property name="password" value="root"/> 
     			</dataSource>
     		</environment>
     	</environments>
     
     <mappers>
     	<mapper resource="mappers/UserMapper.xml"/>
     	<mapper resource="mappers/DeptMapper.xml"/>
     	<mapper resource="mappers/EmpMapper.xml"/>
     	<mapper resource="mappers/UserInfoMapper.xml"/>
     	<mapper resource="mappers/One21.xml"/>
     </mappers>
     
     </configuration>

#### 创建One21Mapper接口 ####

package cn.tedu.mapper;
    
    import cn.tedu.pojo.UserInfo;
    
    public interface One21Mapper { 
    	UserInfo One21(int userId);
    }

#### 测试类 ####

package cn.tedu.test;
    //测试 一对一
    
    import java.io.IOException;
    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;
    import org.junit.jupiter.api.BeforeEach;
    import org.junit.jupiter.api.Test;
    
    import ch.qos.logback.core.net.ssl.SSL;
    import cn.tedu.mapper.One21Mapper;
    import cn.tedu.pojo.UserInfo;
    
    public class TestOne21 { 
    	private SqlSession session ;
    	@BeforeEach
    	public void init() throws IOException { 
    		InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    		SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
    		session = factory.openSession();
    // session = factory.openSession(true);//开启自动提交
    	}
    	@Test
    	public void One21() { 
    		One21Mapper mapper = session.getMapper(One21Mapper.class);
    		UserInfo info = mapper.One21(2);
    //UserInfo [id=2, userName=王海涛, userAge=30, userAddr=北京, userExtra=UserExtra [id=2, userId=2, work=教师, salary=1000.0]]
    		System.out.println(info);
    	}
    	
    }

## Mybatis的缓存 ##

### 一级缓存 ###

### 二级缓存 ###