mybatis用法

1.导入依赖

<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>3.5.6</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>5.3.1</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.9.6</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis-spring</artifactId>
        <version>2.0.6</version>
    </dependency>
</dependencies>

2.编写pojo类

public class User {
    private int id;
    private String name;
    private int age;
    private String gradeid;

    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 int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGradeid() {
        return gradeid;
    }

    public void setGradeid(String gradeid) {
        this.gradeid = gradeid;
    }

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

3.操作pojo类，编写操作实体类接口

public interface UserMapper {

    public List<User> selectUser();

}

4.实现接口xml: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.ld.maper.UserMapper">
    <select id="selectUser" resultType="aaa">
        select * from mysql_dong.cb_user;
    </select>
</mapper>

5.编写mybatis-config.xml配置文件

其中typeAliases是配置别名

environments配置数据库信息

mappers是注册实现接口的xml信息

其中有<mapper class="com.ld.maper.UserMapper"/> 标签，

<mapper resource="com/ld/maper/UserMapper.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">

<!--mybatis核心配置文件-->
<configuration>
    <typeAliases>
        <typeAlias type="com.ld.pojo.User"/>
    </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/mysql_dong?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com.ld.maper.UserMapper"/>
    </mappers>
</configuration>

6.实现mybatis

String resource = "mybatis-config.xml";
    SqlSession sqlSession = null;
    InputStream in;
    try {
        in = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = mapper.selectUser();

        for (int i = 0; i <users.size() ; i++) {
            System.out.println(users.get(i));
        }
    } catch (IOException e) {
        e.printStackTrace();
    }finally {
        if(sqlSession !=null){
            sqlSession.close();
        }

    }
}

注：若发现编译后target中没有编写的xml文件

在pom.xml中添加build标签，将需要编译的文件信息写入include标签中

<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>