1.CURD操作

第一步：创建maven工程并导入坐标

<?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.itheima</groupId>
    <artifactId>day02_eesy_01mybatisCURD</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>

    </dependencies>

</project>

第二步：创建实体类和dao的接口

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;

    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 + '\'' +
                '}';
    }
}

package com.itheima.dao;

import com.itheima.domain.User;

import java.util.List;

public interface IUserDao {

    List<User> findAll();

    void saveUser(User user);

    void updateUser(User user);

    void deleteUser(Integer userId);
}

第三步：创建Mybatis的主配置文件

<?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">

<!-- mybatis的主配置文件 -->
<configuration>
    <!-- 配置环境 -->
    <environments default="mysql">
        <!-- 配置mysql环境 -->
        <environment id="mysql">
            <!-- 事物类型 -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源（连接池） -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/eesy_mybatis" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>
    <!-- 指定映射配置文件的位置，映射配置文件指的是dao独立的配置文件-->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>
</configuration>

第四步：创建映射配置文件

<?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">

    <!-- 配置查询所有 -->
    <select id="findAll" resultType="com.itheima.domain.User">
        select  *  from  user;
    </select>

    <insert id="saveUser" parameterType="com.itheima.domain.User">
        insert into user(username,address,sex,birthday) values(#{username},#{address},#{sex},#{birthday});
    </insert>

    <update id="updateUser" parameterType="com.itheima.domain.User">
        update user set username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id=#{id};
    </update>
    
    <delete id="deleteUser" parameterType="Integer">
        delete  from user where id=#{uid};
    </delete>
</mapper>

第五歩：测试程序

package com.itheima.test;

import com.itheima.dao.IUserDao;
import com.itheima.domain.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 MybatisTest {
    private InputStream in;
    private SqlSession sqlSession;
    private IUserDao userDao;

    @Before
    public void init() throws IOException {
        // 1.读取文件
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        // 2.创建SqlSessionFactory工厂
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        // 3.使用工厂生产SQLSession对象
        sqlSession = factory.openSession();
        // 4.使用SQLSession创建Dao接口的代理对象
        userDao = sqlSession.getMapper(IUserDao.class);
    }

    @After
    public void destroy() throws IOException {
        // 提交事务
        sqlSession.commit();
        // 关闭资源
        sqlSession.close();
        in.close();
    }

    /**
     * 查询所有用户
     */
    @Test
    public void findAll() throws IOException {

        List<User> users = userDao.findAll();
        for (User user : users) {
            System.out.println(user);
        }
    }

    /**
     * 保存（插入）用户
     */
    @Test
    public void testSave() {
        User user = new User();
        user.setUsername("mybatis saveuser");
        user.setAddress("beijing");
        user.setSex("男");
        user.setBirthday(new Date());
        userDao.saveUser(user);
    }

    /**
     * 更新用户信息
     */
    @Test
    public void testUpdate(){
        User user = new User();
        user.setId(50);
        user.setUsername("mybatis updateUser");
        user.setAddress("beijing");
        user.setSex("女");
        user.setBirthday(new Date());

        userDao.updateUser(user);
    }

    /**
     * 删除方法
     */
    @Test
    public void testDelete(){
        userDao.deleteUser(48);
    }

}

2.OGNL表达式

Object Graphic Navigation Language
对象     图         导航           语言
它是通过对象的取值方法来获取数据。在写法上把get给省略了。
比如：我们获取用户的名称
类中的写法：user.getUsername();
OGNL表达式写法：user.username

mybatis中为什么能直接写username,而不用user.呢：
因为在parameterType中已经提供了属性所属的类，所以此时不需要写对象名