mybatis快速入门

1. 开发步骤

①添加MyBatis的坐标

②创建user数据表

③编写User实体类

④编写映射⽂件UserMapper.xml

⑤编写核⼼⽂件SqlMapConfig.xml

⑥编写测试类

 

2. 环境搭建

1)导⼊MyBatis的坐标和其他相关坐标

<properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.encoding>UTF-8</maven.compiler.encoding> <java.version>1.8</java.version> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target>
</properties>
<!--mybatis坐标-->
<dependency>
 <groupId>org.mybatis</groupId>
 <artifactId>mybatis</artifactId>
 <version>3.4.5</version>
</dependency>
<!--mysql驱动坐标-->
<dependency> 
 <groupId>mysql</groupId> 
 <artifactId>mysql-connector-java</artifactId> 
 <version>5.1.6</version> 
 <scope>runtime</scope>
</dependency>
<!--单元测试坐标-->
<dependency> 
 <groupId>junit</groupId> 
 <artifactId>junit</artifactId> 
 <version>4.12</version> 
 <scope>test</scope>
</dependency>
<!--⽇志坐标-->
<dependency> 
 <groupId>log4j</groupId> 
 <artifactId>log4j</artifactId> 
 <version>1.2.12</version>
</dependency>

2) 创建user数据表

 

3) 编写User实体

public class User { 
 private int id; 
 private String username; 
 private String password;
 //省略get个set⽅法
}

4)编写UserMapper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">
<mapper namespace="userMapper"> 
 <select id="findAll" resultType="com.lagou.domain.User"> 
 select * from User 
 </select>
</mapper>

5) 编写MyBatis核⼼⽂件

<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN“
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration> 
 <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:///test"/> 
 <property name="username" value="root"/>
 <property name="password" value="root"/> 
 </dataSource> 
 </environment> 
 </environments> 
 
 <mappers>
 <mapper resource="com/lagou/mapper/UserMapper.xml"/>
 </mappers>
</configuration>

6） 编写测试代码

//加载核⼼配置⽂件
InputStream resourceAsStream =
Resources.getResourceAsStream("SqlMapConfig.xml");
//获得sqlSession⼯⼚对象
SqlSessionFactory sqlSessionFactory = new 
 SqlSessionFactoryBuilder().build(resourceAsStream);
//获得sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
//执⾏sql语句
List<User> userList = sqlSession.selectList("userMapper.findAll");
//打印结果
System.out.println(userList);
//释放资源
sqlSession.close();

3. MyBatis的增删改查操作

MyBatis的插⼊数据操作

1)编写UserMapper映射⽂件

<mapper namespace="userMapper">

<insert id="add" parameterType="com.lagou.domain.User">

insert into user values(#{id},#{username},#{password})

</insert>

</mapper>

2)编写插⼊实体User的代码

InputStream resourceAsStream =

Resources.getResourceAsStream("SqlMapConfig.xml");

SqlSessionFactory sqlSessionFactory = new

SqlSessionFactoryBuilder().build(resourceAsStream);

SqlSession sqlSession = sqlSessionFactory.openSession();

int insert = sqlSession.insert("userMapper.add", user);

System.out.println(insert);

//提交事务

sqlSession.commit();

sqlSession.close();

3)插⼊操作注意问题

• 插⼊语句使⽤insert标签

• 在映射⽂件中使⽤parameterType属性指定要插⼊的数据类型

•Sql语句中使⽤#{实体属性名}⽅式引⽤实体中的属性值•插⼊操作使⽤的API是sqlSession.insert(“命名空间.id”,实体对象);

•插⼊操作涉及数据库数据变化，所以要使⽤sqlSession对象显示的提交事务，即sqlSession.commit()

 

MyBatis的修改数据操作

1)编写UserMapper映射⽂件

<mapper namespace="userMapper">

<update id="update" parameterType="com.lagou.domain.User">

update user set username=#{username},password=#{password} where id=#

{id}

</update>

</mapper>

2)编写修改实体User的代码

InputStream resourceAsStream =

Resources.getResourceAsStream("SqlMapConfig.xml");

SqlSessionFactory sqlSessionFactory = new

SqlSessionFactoryBuilder().build(resourceAsStream);

SqlSession sqlSession = sqlSessionFactory.openSession();

int update = sqlSession.update("userMapper.update", user);

System.out.println(update);

sqlSession.commit();

sqlSession.close();

3)修改操作注意问题

• 修改语句使⽤update标签

• 修改操作使⽤的API是sqlSession.update(“命名空间.id”,实体对象);

 

MyBatis的删除数据操作

1)编写UserMapper映射⽂件

<mapper namespace="userMapper">

<delete id="delete" parameterType="java.lang.Integer">

delete from user where id=#{id}

</delete>

</mapper>

2)编写删除数据的代码InputStream resourceAsStream =

Resources.getResourceAsStream("SqlMapConfig.xml");

SqlSessionFactory sqlSessionFactory = new

SqlSessionFactoryBuilder().build(resourceAsStream);

SqlSession sqlSession = sqlSessionFactory.openSession();

int delete = sqlSession.delete("userMapper.delete",3);

System.out.println(delete);

sqlSession.commit();

sqlSession.close();

3)删除操作注意问题

• 删除语句使⽤delete标签

•Sql语句中使⽤#{任意字符串}⽅式引⽤传递的单个参数

•删除操作使⽤的API是sqlSession.delete(“命名空间.id”,Object);