MyBatis(3.2.3) - hello world

Posted 2020-06-17

1. 创建数据表（mysql）：

DROP TABLE IF EXISTS `department`;
CREATE TABLE `department` (
  `did` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `dept_name` varchar(127) DEFAULT NULL,
  `address` varchar(127) DEFAULT NULL,
  `tel` varchar(16) DEFAULT NULL,
  PRIMARY KEY (`did`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

 

2. 新建 Maven 工程，配置 Maven 依赖：

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.2.3</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.22</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.14.4</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.5</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.5</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.8.1</version>
    </dependency>
</dependencies>

View Code

 

3. JavaBean：

package com.huey.hello.mybatis.beans;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Department {
    private int did;
    private String deptName;
    private String address;
    private String tel;
}

 

3. Mapper 接口：

package com.huey.hello.mybatis.mapper;

import com.huey.hello.mybatis.beans.Department;

public interface DepartmentMapper {

    public int insertDepartment(Department department);
    
    public Department getDepartmentById(int did);
    
}

 

4. 配置映射文件：

<?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">

<!--注意：此处的命名空间是 DepartmentMapper 的全限定类名-->
<mapper namespace="com.huey.hello.mybatis.mapper.DepartmentMapper">

    <!-- ResultMaps 被用来将 SQL SELECT 语句的结果集映射到 JavaBean 的属性中 -->
    <resultMap type="Department" id="deptMap">
        <!-- 映射主键 -->
        <id property="did" column="did" />
        <!-- 映射普通字段 -->
        <result property="deptName" column="dept_name"/>
        <result property="address" column="address"/>
        <result property="tel" column="tel"/>
    </resultMap>

    <!-- 添加部门记录 -->
    <!-- id 名称需要与 DepartmentMapper 中的方法签名一致 -->
    <!-- Department 这一别名在 mybatis-config.xml 中配置 -->
    <insert id="insertDepartment" parameterType="Department">
        insert into department(did, dept_name, address, tel)
        values(#{did}, #{deptName}, #{address}, #{tel})
    </insert>
    
    <!-- 根据 ID 查询部门记录 -->
    <select id="getDepartmentById" parameterType="int" resultMap="deptMap">
        select * from department where did=#{did}
    </select>

</mapper>

 

5. 配置 mybatis-config.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>

    <!-- 设置别名 -->
    <typeAliases>
        <typeAlias type="com.huey.hello.mybatis.beans.Department" alias="Department" />
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 配置数据源 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>

    <!-- mapper 对应的 xml 配置文件 -->
    <mappers>
        <mapper resource="com/huey/hello/mybatis/mapper/DepartmentMapper.xml" />
    </mappers>
    
</configuration>

 

6. 创建 SqlSessionFactory 单例类：

package com.huey.hello.mybatis.utils;

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;

public class MyBatisSqlSessionFactory {

    private static SqlSessionFactory sqlSessionFactory;
    
    /**
     * 加载 mybatis-config.xml，创建 SqlSessionFactory 实例
     * 每个数据库环境应该就只有一个 SqlSessionFactory 对象实例
     * 所以使用单例模式只创建一个 SqlSessionFactory 实例
     * @return
     */
    public synchronized static SqlSessionFactory getSqlSessionFactory() {
        if (sqlSessionFactory == null) {
            InputStream inputStream;
            try {
                inputStream = Resources.getResourceAsStream("mybatis-config.xml");
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
                throw new RuntimeException(e.getCause());
            }
        }
        return sqlSessionFactory;
    }
    
    public static SqlSession openSqlSession() {
        return getSqlSessionFactory().openSession();
    }
}

 

7. 业务逻辑：

package com.huey.hello.mybatis.serv;

import org.apache.ibatis.session.SqlSession;

import com.huey.hello.mybatis.beans.Department;
import com.huey.hello.mybatis.mapper.DepartmentMapper;
import com.huey.hello.mybatis.utils.MyBatisSqlSessionFactory;

public class DepartmentService {
    
    public int createDepartment(Department department) {
        int result = 0;
        /**
         * SqlSession 对象实例不是线程安全的，并且不被共享。
         * 每一个线程应该有它自己的 SqlSession 实例。
         * 所以 SqlSession 的作用域最好就是其所在方法的作用域。
         * 从 Web 应用程序角度上看，SqlSession 应该存在于 request 级别作用域上。
         */
        SqlSession sqlSession = MyBatisSqlSessionFactory.openSqlSession();
        try {
            DepartmentMapper deptMapper = sqlSession.getMapper(DepartmentMapper.class);
            result = deptMapper.insertDepartment(department);
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return result;
    }
    
    public Department getDepartmentById(int did) {
        Department department = null;
        SqlSession sqlSession = MyBatisSqlSessionFactory.openSqlSession();
        try {
            DepartmentMapper deptMapper = sqlSession.getMapper(DepartmentMapper.class);
            department = deptMapper.getDepartmentById(did);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return department;
    }

}

 

8. 单元测试：

package com.huey.hello.mybatis.serv;

import org.junit.Test;

import com.huey.hello.mybatis.beans.Department;

public class DepartmentServiceTest {
    
    DepartmentService deptService = new DepartmentService();
    
    @Test
    public void testCreateDepartment() {
        Department department = new Department(1001, "研发部", "XX 路 YY 号", "010-55551234");
        deptService.createDepartment(department);
    }
    
    @Test
    public void testGetDepartmentById() throws Exception {
        int did = 1001;
        Department department = deptService.getDepartmentById(did);
        if (department != null) {
            System.out.println(department);
        }
    }

}