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。