【Mybatis02】快速入门

1.通过demo来快速入门

1.1环境准备
在pom.xml中添加依赖

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.jay</groupId>
    <artifactId>mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>

    
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>
</project>

1.2全局配置文件
全局配置文件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>
	<!-- 和Spring整合后environment配置都会被干掉 -->
    <environments default="development">
        <environment id="development">
      	  <!-- 使用jdbc事务管理，目前由mybatis来管理 -->
            <transactionManager type="JDBC" />
            <!-- 数据库连接池，目前由mybatis来管理 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatisdb?characterEncoding=utf8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
    <!--关联映射文件-->
	<mappers>
		<mapper resource="com/jay/mapper/UserMapper.xml"></mapper>
    </mappers>
</configuration>  

其中<mappers>用来引入一个或多个映射文件
1.3编写pojo对象

/**
 * 为什么id要用Integer类型？因为包装类型： 初始值为null
 * 而基本数据类型：本身的值0就是一个状态
 *
 */

    public class User {
        private Integer id;
        private String username;
        private String password;
        private String sex;
        private String address;
    
       set、get方法省略...
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    ", sex='" + sex + '\'' +
                    ", address='" + address + '\'' +
                    '}';
        }
    }

1.4编写映射文件

<?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="com.jay.dao.UserDao">
    <select id="findAll" resultType="com.jay.domain.User">
        select * from user
    </select>
</mapper>

上面的属性：

1. <select>：执行数据库查询的标签
2. id：唯一标识
3. resultType：返回结果的类型

1.5测试程序

public class TestCustomFrame {

    @Test
    public void test(){
        //获取配置文件的输入流对象
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("SqlMapConfig.xml");
        //创建SqlSessionFactoryBuilder对象
        SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
        //创建SqlSessionFactory对象
        SqlSessionFactory sessionFactory = sqlSessionFactoryBuilder.build(inputStream);
        //获取sqlSession对象
        SqlSession sqlSession = sessionFactory.openSession();
        //执行sql语句
        List list = sqlSession.selectList("com.itheima.dao.UserDao.findAll");
        //遍历结果集
        for (Object o : list) {
            System.out.println(o);
        }
        //关闭资源
        sqlSession.close();
    }
}