第一个Mybatis项目

第一个Mybatis项目

1、环境搭建

1.1、创建测试数据库

create database mybatis;
use mybatis;
create table user(
    id int not null primary key ,
    name varchar(20) not null ,
    pwd varchar(20) not null 
);
insert into user(id, name, pwd) VALUES (1,'tom', '123456');
insert into user(id, name, pwd) VALUES (2,'sam', '123456');
insert into user(id, name, pwd) VALUES (3,'smith', '123456');

1.2、创建maven项目

导入maven依赖（pom.xml）

1. mysql-connector-java（Java连接数据库）
2. mybatis（Mybatis框架）
3. junit（测试）

<dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

2、构建SqlSessionFactory

2.1、从 XML 中构建SqlSessionFactory

1. 创建mybatis-config.xml（Mybatis核心配置文件）

<?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="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/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!--注册mapper-->
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    </mappers>
</configuration>

XML 配置文件中包含了对 MyBatis 系统的核心设置：

• 获取数据库连接实例的数据源（DataSource）
• 决定事务作用域和控制方式的事务管理器（TransactionManager）

1. 创建SqlSessionFactory（这里是java代码）

   String resource = "mybatis-config.xml";//配置文件路径
   InputStream inputStream = Resources.getResourceAsStream(resource);
   SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
   

   注意：建议将这里提取成工具类，提高代码复用性

2.2、不使用XML构建SqlSessionFactory

如果你更愿意直接从 Java 代码而不是 XML 文件中创建配置，或者想要创建你自己的配置建造器，MyBatis 也提供了完整的配置类，提供了所有与 XML 文件等价的配置项。

DataSource dataSource = BlogDataSourceFactory.getBlogDataSource();
TransactionFactory transactionFactory = new JdbcTransactionFactory();
Environment environment = new Environment("development", transactionFactory, dataSource);
Configuration configuration = new Configuration(environment);
configuration.addMapper(BlogMapper.class);//注册mapper
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

3、编写代码

3.1、User实体类

package com.mybatis.example;

public class User {
    private int id;
    private String name;
    private String pwd;

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public User() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

3.2、DAO接口

public interface UserMapper {
    List<User> getUserList();
}

3.3、创建UserMapper类

public interface UserMapper {
    List<User> getUserList();
}

3.4、UserMapper.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.mybatis.example.UserMapper">
    <select id="getUserList" resultType="com.mybatis.example.User">
        select * from mybatis.user;
    </select>
</mapper>

3.5、MyTest测试类

public class MyTest {

    @Test
    public void test01() {
        //1. 获取SqlSessionFactory
        String resource = "mybatis-config.xml";//配置文件路径
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2. 获取sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        
        //3. 测试
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }

        //4. 关闭sqlSession
        sqlSession.close();
    }
}

创建图：

第一个Mybatis项目创建成功！

Mybatis官方文档（中文）：https://mybatis.net.cn/