mybatis 基本用法

先进行全局配置 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">
<!--mybatis的主配置文件-->
<configuration>
    <!--配置环境-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置数据源(连接池)-->
            <dataSource type="POOLED">
                <!--配置连接数据库4个基本信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/eesy_mybatis?serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="nimahaoma49"/>
            </dataSource>
        </environment>
    </environments>

    <!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>

</configuration>

首先定义好一个User类，和数据库里的user表相对应

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

定义一个QueryVo类用于对象封装的查询

package com.itheima.domain;

public class QueryVo {
    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

定义好一个用来操作数据库的接口IUserDao

package com.itheima.dao;

import com.itheima.domain.QueryVo;
import com.itheima.domain.User;

import java.util.List;

public interface IUserDao {
    /*
    * 查询所有操作
    * */
    List<User> findAll();

    /*
    * 保存一条记录并返回id（直接将id赋给对应的属性）
    * */
    void saveUser(User user);

    /*
    * 更新用户
    * */
    void updateUser(User user);

    /*
    * 删除用户
    * */
    void deleteUser(Integer userId);

    /*
    * 根据Id查询User
    * */
    User findById(Integer userId);

    /*
    * 模糊查询
    * */
    List<User> findByName(String username);

    /*
    * 查询User总数
    * */
    int findTotal();

    /*
    *  根据queryVo查询中的条件查询用户
    * */
    List<User> findByVo(QueryVo vo);
}

编写 IUserDao.xml ,配置接口的各类操作(重点)

<?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.itheima.dao.IUserDao">

    <!--当表列名和实体类的属性名不同时，配置列名和实体类属性名的对应关系,同时，要把下面使用这个配置的resultType改成resultMap-->
    <resultMap id="userMap" type="com.itheima.domain.User">
        <!--主键字段的对应-->
        <id property="id" column="id"></id>
        <!--非主键字段的对应-->
        <result property="username" column="username"></result>
        <result property="address" column="address"></result>
        <result property="sex" column="sex"></result>
        <result property="birthday" column="birthday"></result>
    </resultMap>

    <!--配置查询所有-->
    <select id="findAll" resultMap="userMap">
        select id as id,username as username, address as address,sex as sex, birthday as birthday
        from user;
    </select>

    <!--保存一条记录-->
    <insert id="saveUser" parameterType="com.itheima.domain.User">
        <!--插入后，获取插入数据的id keyColumn对应表的列名，keyProperty对应实体类的属性-->
        <selectKey keyColumn="id" keyProperty="id" resultType="int" order="AFTER">
            select last_insert_id();
        </selectKey>
        insert into user(username,address,sex,birthday)
        values(#{username},#{address},#{sex},#{birthday});
    </insert>


    <!--更新用户-->
    <update id="updateUser" parameterType="com.itheima.domain.User">
        update user set
        username=#{username},address=#{address},sex=#{sex},birthday=#{birthday}
        where id=#{id};
    </update>

    <!--删除用户-->
    <delete id="deleteUser" parameterType="Integer">
        delete from user where id = #{userId}
    </delete>

    <!--根据id查询User-->
    <select id="findById" parameterType="int" resultType="com.itheima.domain.User">
        select * from user
        where id = #{id};
    </select>

    <!--根据username模糊查询User-->
    <select id="findByName" parameterType="String" resultType="com.itheima.domain.User">
        select * from user where username like #{username}
    </select>

    <!--获取用户的总记录条数-->
    <select id="findTotal" resultType="int">
        select count(*) from user ;
    </select>

    <!--根据queryVo的条件查询用户-->
    <select id="findByVo" parameterType="com.itheima.domain.QueryVo" resultType="com.itheima.domain.User">
        select * from user
        where username like #{user.username};
    </select>
</mapper>

 

使用(测试)前的准备工作 

　　 private InputStream in = null;
    private SqlSession session = null;
    private IUserDao userDao = null;

    @Before //用于测试前执行
    public void init()throws Exception{
        //1.读取配置文件
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SQLSessionFactory对象
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //3.使用工厂生成SqlSession对象
        session = factory.openSession();
        //4.使用SqlSession创建Dao接口的代理对象
        userDao = session.getMapper(IUserDao.class);
    }
    @After //用于测试后执行
    public void destory() throws IOException {
        //6.提交事务，释放资源
        session.commit();
        session.close();
        in.close();
    }

测试

@Test
    public void testFindAll()throws Exception{
        //5.使用代理对象执行方法
        List<User>users = userDao.findAll();
        for(User user:users)
            System.out.println(user);
    }

    @Test
    public void testSave() throws IOException {
        User user = new User();
        user.setUsername("mybatis testsave3");
        user.setAddress("北京市顺义区3");
        user.setSex("男");
        user.setBirthday(new Date());

        System.out.println(user);
        //5.使用代理对象执行方法
        userDao.saveUser(user);
        System.out.println(user);
    }

    @Test
    public void testUpdate(){
        User user = new User();
        user.setId(50);
        user.setUsername("mybatis testUpdate");
        user.setAddress("北京市顺义区");
        user.setSex("女");
        userDao.updateUser(user);
    }

    @Test
    public void testDelete(){
        userDao.deleteUser(48);
    }

    @Test
    public void testFindById(){
        User user = userDao.findById(50);
        System.out.println(user);
    }

    @Test
    public void testFindByName(){
        List<User> users = userDao.findByName("%王%");
        for(User user:users)
            System.out.println(user);
    }

    @Test
    public void testFindTotal(){
        int count = userDao.findTotal();
        System.out.println(count);
    }

    @Test
    public void testFindByVo(){
        QueryVo vo = new QueryVo();
        User user = new User();
        user.setUsername("%王%");
        vo.setUser(user);
        List<User> users = userDao.findByVo(vo);
        for(User user1:users)
            System.out.println(user1);
    }