MyBatis第一节

1. 简介

它是一款半自动的ORM持久层框架，具有较高的SQL灵活性，支持高级映射(一对一，一对多)，动态SQL，延迟加载和缓存等特性，但它的数据库无关性较低。

2. 配置

编写全局配置文件
编写mapper映射文件
加载全局配置文件，生成SqlSessionFactory
创建SqlSession，调用mapper映射文件中的SQL语句来执行CRUD操作

3. doing

3.1 创建一个表

这就不提了

3.2 打开IDEA，创建一个maven项目

maven

3.3 导入依赖的jar包

	<dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.10</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
            <scope>test</scope>
        </dependency>
        <!-- 日志 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

3.4 创建entity

package com.qcby.entity;

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

public class User implements Serializable{

    private static final long serialVersionUID = 525400707336671154L;

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

3.5 编写mapper映射文件(编写SQL)

<?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.qcby.dao.UserDao">
    <select id="findAll" resultType="user">
        select * from userx;
    </select>
    <!--
       通过id查询
       SQL语句使用#{占位符的名称，名称可以任意}，仅限于基本数据类型和String类型
   -->
    <select id="findById" resultType="com.qcby.entity.User" parameterType="int">
        select * from userx where id = #{id};
    </select>

    <!--保存操作-->
    <insert id="insert" parameterType="com.qcby.entity.User">
        /*
        keyProperty表示要返回的属性名称
        order取值AFTER表示插入数据后的行为
        resultType表示返回值的类型
        */
        <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
            select last_insert_id();
        </selectKey>
        insert into userx (username,birthday,sex,address) values (#{username},#{birthday},#{sex},#{address})
    </insert>

    <!-- 修改 -->
    <update id="update" parameterType="com.qcby.entity.User">
        update userx set username = #{username},birthday = #{birthday},sex = #{sex},address=#{address} where id = #{id}
    </update>

    <!-- 删除 -->
    <delete id="delete" parameterType="Integer">
        delete from userx where id = #{id}
    </delete>

    <!-- 模糊查询 -->
    <select id="findByName" resultType="com.qcby.entity.User" parameterType="string">
        <!-- 第一种方式的SQL语句
        select * from user where username  like #{username}
        -->
        <!-- 第二章SQL语句的编写 强调：'%${value}%'不能修改，固定写法（不推荐使用）  -->
        select * from userx where username  like '%${value}%'
    </select>

    <!-- 具体函数的查询 -->
    <select id="findByCount" resultType="int">
        select count(*) from userx
    </select>
</mapper>

3.6 编写主配置文件

<?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>
	<!-- 别名 注意位置-->
    <typeAliases>
        <!-- 把com.qcbyjy.domain.User使用user别名来显示，别名user User USER都可以，默认是忽略大写的
        <typeAlias type="com.qcbyjy.domain.User" alias="user"/>
        -->
        <!-- 针对com.qcbyjy.domain包下的所有的类，都可以使用当前的类名做为别名 -->
        <package name="com.qcby.entity"/>
    </typeAliases>
    <!-- 配置环境们 -->
    <environments default="mysql">
        <!-- 配置具体的环境 -->
        <environment id="mysql">
            <!-- 配置事务管理类型 -->
            <transactionManager type="JDBC"/>
            <!-- 配置是否需要使用连接池，POOLED使用，UNPOOLED不使用 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///test"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 加载映射的配置文件 -->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

3.7 编写接口

package com.qcby.dao;

import com.qcby.entity.User;

import java.util.List;

public interface UserDao {
    List<User> findAll();
    public User findById(Integer userId);

    public void insert(User user);

    public void update(User user);

    public void delete(Integer userId);

    public List<User> findByName(String username);

    public Integer findByCount();
}

3.8 测试

UserTest.java

package com.qcby.demo;

import com.qcby.dao.UserDao;
import com.qcby.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

public class UserTest {
    @Test
    public void testFindAll() throws Exception {
        // 加载主配置文件，目的是构建SqlSessionFactory的对象
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 创建SqlSessionFactory对象
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        // 使用SqlSessionFactory工厂对象创建SqlSession对象
        SqlSession session = factory.openSession();
        // 通过session创建UserMapper接口的代理对象
        UserDao mapper = session.getMapper(UserDao.class);
        // 调用查询所有的方法
        List<User> list = mapper.findAll();
        // 遍历集合
        for (User user : list) {
            System.out.println(user);
        }
        // 释放资源
        session.close();
        in.close();
    }

    @Test
    public void run2() throws Exception {
        // 加载配置文件
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 构建SqlSessionFactory对象
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        // 获取到session对象
        SqlSession session = factory.openSession();
        // 查询所有的数据
        List<User> list = session.selectList("com.qcby.dao.UserDao.findAll");
        // 变量集合
        for (User user : list) {
            System.out.println(user);
        }
        // 关闭资源
        session.close();
        inputStream.close();
    }
}

运行结果：

UserTest2.java

package com.qcby.demo;

import com.qcby.dao.UserDao;
import com.qcby.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;


public class UserTest2 {
    private InputStream in;
    private SqlSession session;
    private UserDao mapper;

    @Before
    public void init() throws Exception {
        // 加载配置文件
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 创建工厂对象
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        // 创建Session对象
        session = factory.openSession();
        // 获取到代理对象
        mapper = session.getMapper(UserDao.class);
    }

    @After
    public void destory() throws IOException {
        in.close();
        session.close();
    }

    @Test
    public void testFindAll() throws Exception {
        List<User> list = mapper.findAll();
        // 遍历
        for (User user : list) {
            System.out.println(user);
        }
        in.close();
    }

    @Test
    public void testFindById() throws Exception {
        User user = mapper.findById(41);
        System.out.println(user);
        in.close();
    }

    @Test
    public void testInsert() throws Exception {
        User user = new User();
        user.setUsername("美美");
        user.setBirthday(new Date());
        user.setSex("男");
        user.setAddress("顺义");
        mapper.insert(user);
        session.commit();
        System.out.println(user.getId());
    }

    @Test
    public void testUpdate() throws Exception {
        User user = mapper.findById(41);
        user.setUsername("小凤");
        mapper.update(user);
        session.commit();
    }

    @Test
    public void testDelete() throws Exception {
        mapper.delete(48);
        session.commit();
    }

    // 第一种
/*    @Test
    public void testFindByName() throws Exception {

        List<User> list = mapper.findByName("%王%");
        for (User user : list) {
            System.out.println(user);
        }
    }*/
    // 第二种
    @Test
    public void testFindByName() throws Exception {
        List<User> list = mapper.findByName("王");
        for (User user : list) {
            System.out.println(user);
        }
    }

    @Test
    public void testFindByCount() throws Exception {
        Integer count = mapper.findByCount();
        System.out.println("总记录数：" + count);
    }
}