Mybatis入门DEMO

下面将通过以下步骤说明如何使用MyBatis开发一个简单的DEMO：

步骤一：新建表STUDENTS

　　字段有： Stu_Id、Stu_Name、Stu_Age、Stu_Birthday

CREATE TABLE `student` (
`Stu_Id`  bigint(20) NOT NULL AUTO_INCREMENT ,
`Stu_Name`  varchar(30) CHARACTER SET utf8 COLLATE utf8_bin NULL DEFAULT NULL ,
`Stu_Age`  int(4) NULL DEFAULT NULL ,
`Stu_Birthday`  timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP ,
PRIMARY KEY (`Stu_Id`)
)
ENGINE=InnoDB
DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci
AUTO_INCREMENT=1
;

步骤二：新建Maven项目,添加相关的依赖包

<dependencies>
  <dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.2.2</version>
  </dependency>
  <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.22</version>
    <scope>runtime</scope>
  </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>
    <scope>runtime</scope>
  </dependency>
  <dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
    <scope>runtime</scope>
  </dependency>
  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.11</version>
    <scope>test</scope>
  </dependency>
</dependencies>

步骤三：新建mybatis-config.xml 和映射器StudentMapper.xml配置文件

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>
  <typeAliases>
    <typeAlias alias="Student" type="com.MyBatisDemo.domain.Student" />
  </typeAliases>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC" />
      <dataSource type="POOLED">
        <property name="driver" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/mybatisdemo" />
        <property name="username" value="root" />
        <property name="password" value="123123" />
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="com/MyBatisDemo/mappers/StudentMapper.xml" />
  </mappers>
</configuration>

StudentMapper.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="com.MyBatisDemo.mappers.StudentMapper">
  <resultMap type="Student" id="StudentResult">
    <id property="stuId" column="Stu_Id" />
    <result property="StuName" column="Stu_Name" />
    <result property="StuAge" column="Stu_Age" />
    <result property="StuBirthday" column="Stu_Birthday" />
  </resultMap>
 
  <select id="findStudentById" parameterType="int" resultType="Student">
     SELECT Stu_Id, Stu_Name, Stu_Age, Stu_Birthday 
         FROM STUDENT WHERE Stu_Id=#{Id}
  </select>
</mapper>

步骤四：新建建MyBatisSqlSessionFactory单例模式类

package com.MyBatisDemo.util;

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;

    public static SqlSessionFactory getSqlSessionFactory() {
        if (sqlSessionFactory == null) {
            InputStream inputStream;
            try {
                inputStream = Resources.getResourceAsStream("mybatis-config.xml");
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
                e.printStackTrace();
                throw new RuntimeException(e.getCause());
            }
        }
        return sqlSessionFactory;
    }

    public static SqlSession openSession() {
        return getSqlSessionFactory().openSession();
    }
}

步骤五：新建映射器StudentMapper 接口和 StudentService 类

StudentMapper.java

package com.MyBatisDemo.mappers;

import com.MyBatisDemo.domain.Student;

public interface StudentMapper {
    Student findStudentById(Integer id); 
}

StudentService.java

package com.MyBatisDemo.service;
import org.apache.ibatis.session.SqlSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.MyBatisDemo.domain.Student;
import com.MyBatisDemo.mappers.StudentMapper;
import com.MyBatisDemo.util.MyBatisSqlSessionFactory;

public class StudentService {
    private Logger logger = LoggerFactory.getLogger(getClass());

    public Student findStudentById(Integer studId)
    {
        SqlSession sqlSession = MyBatisSqlSessionFactory.openSession();
        try
        {
            StudentMapper studentMapper =
                sqlSession.getMapper(StudentMapper.class);
            return studentMapper.findStudentById(studId);
        }
        finally
        {
            sqlSession.close();
        }
    }
}

步骤六：新建一个JUnit 测试类来测试 StudentService

package com.MyBatisDemo;

import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import com.MyBatisDemo.domain.Student;
import com.MyBatisDemo.service.StudentService;
public class StudentServiceTest
{
    private static StudentService studentService;
    @BeforeClass
    public static void setup()
    {
        studentService = new StudentService();
    }
    @AfterClass
    public static void teardown()
    {
        studentService = null;
    }

    @Test
    public void testFindStudentById()
    {
        Student student = studentService.findStudentById(1);
        //Assert.assertNotNull(student);
        System.out.println(student);
    }
}

 首先配置了MyBatis最主要的配置文件mybatis-config.xml,里面包含了JDBC连接参数；

 配置了映射器Mapper XML配置文件文件，里面包含了SQL语句的映射。

 使用mybatis-config.xml内的信息创建了SqlSessionFactory对象。每个数据库环境应该就一个SqlSessionFactory对象实例，所以使用了单例模式只创建一个SqlSessionFactory实例。

 创建了一个映射器Mapper接口StudentMapper，其定义的方法签名和在StudentMapper.xml中定义的完全一样（即映射器Mapper接口中的方法名跟StudentMapper.xml中的id的值相同）。注意StudentMapper.xml中namespace的值被设置成com.MyBatisDemo.mappers.StudentMapper，是StudentMapper接口的完全限定名。这使我们可以使用接口来调用映射的SQL语句。