Mybatis学习笔记（一）入门案例.md

Mybatis学习笔记（一）入门案例

一、环境搭建

1. Mybatis的环境搭建

   （数据库创建略过）

   第一步：创建Maven工程并导入坐标Pom.xml

    <?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.greyson</groupId>
        <artifactId>day91_mybatis</artifactId>
        <version>1.0-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <dependencies>
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.4.1</version>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.46</version>
            </dependency>
    
            <dependency>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
                <version>1.2.17</version>
            </dependency>
    
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
        </dependencies>
    
    </project>
   

   第二步：创建实体类和Dao的接口（略）

   第三步： 创建Mybatis的主配置文件 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>
        <environments default="mysql">
            <!--configure mysql-->
            <environment id="mysql">
                <!--configure transaction type-->
                <transactionManager type="JDBC"></transactionManager>
                <!--configure datasource-->
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/eesy"/>
                    <property name="username" value="root"/>
                    <property name="password" value="HotteMYSQL"/>
                </dataSource>
            </environment>
        </environments>
    
        <!--Specified mapping location-->
        <mappers>
            <mapper resource="com/greyson/dao/IUserDao.xml"/>
        </mappers>
    </configuration>
   

   第四步：创建映射配置文件IUserDao.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.greyson.dao.IUserDao">
        <select id="findAll" resultType="com.greyson.domain.User">
            select * from user
        </select>
    </mapper>
   

2. 环境搭建的注意事项

   • Mybatis中把持久层的操作接口名称和映射文件都叫做：Mapper，所以 IUserDao 和 IUserMapper 是一样的
   • Mybatis 的映射配置文件位置必须和 dao 接口的包结构一致
   • 映射配置文件的 mapper 标签 namespace 属性的取值必须是 dao 接口的全限定类名
   • 映射配置文件的操作配置（select），id 属性的取值必须是 dao 接口的方法名

   遵从以上规则，开发中则无须再写 dao 的实现类。

3. 编写测试类MyBatisTest

    public class MybatisTest{
    
        /**
         * Getting started case
         * @param args
         */
        public static void main(String[] args) throws Exception {
            // 1. Read configuration file
            InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
            // 2. Create SqlSessionFactory
            SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
            SqlSessionFactory factory = builder.build(in);
            // 3. Use factory generate SqlSession Object
            SqlSession session = factory.openSession();
            // 4. Use SqlSession generate proxy object of DAO interface
            IUserDao userDao = session.getMapper(IUserDao.class);
            // 5. Use proxy object execution
            List<User> userList = userDao.findAll();
            for (User user : userList) {
                System.out.println(user);
            }
            // 6. Release resources
            session.close();
            in.close();
    
        }
    }
   

4. 文件结构（补充）

   

5. 测试结果