mybatis前期项目搭建做准备工作

1.新建maven项目

2.导入mybatis依赖和静态资源导出

<!--导入依赖-->
    <dependencies>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!--Mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <!--Junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.1</version>
        </dependency>

        <!--Log4j-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

        <!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.10</version>
        </dependency>

        <!--Ehcache-->
        <dependency>
            <groupId>org.mybatis.caches</groupId>
            <artifactId>mybatis-ehcache</artifactId>
            <version>1.1.0</version>
        </dependency>
    </dependencies>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <!--在build中配置Resource来防止我们资源导出失败的问题-->
    <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>

3.连接数据库

在resources目录下新建db.properties文件

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8
username=root
password=root

配置mybatis核心配置文件mybatis-config.xml

<?xml version="1.0" encoding="UTF8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--引入外部配置文件-->
    <properties resource="db.properties">
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    </properties>

    <!--给实体类起别名-->
    <typeAliases>
        <package name="com.my.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--每一个Mapper.xml都需要在Mybatis核心配置文件中注册-->
    <mappers>
        <mapper resource="com/my/dao/UserMapper.xml"/>
    </mappers>
</configuration>

4.创建mybatis工具类MybatisUtils拿到操作数据库的SqlSession

//SqlSessionFactory → SqlSession
public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;

    //获取SqlSessionFactory对象
    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream =  Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例
    //SqlSession 提供了在数据库执行 SQL 命令所需的所有方法

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

5.创建数据库对应的实体类

package com.my.pojo;

import org.apache.ibatis.type.Alias;

//实体类
public class User {

    private int id;
    private String name;
    private String pwd;

    public User() {
    }

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

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

6.创建接口类

package com.my.dao;

import com.my.pojo.User;

import java.util.List;
import java.util.Map;

public interface UserDao {
    //查询全部用户
    List<User> getUserList();
    //根据id查询用户
    User getUserById(int id);
    //插入数据
    int insertUser(User user);
    //更新数据
    int updateUser(User user);
    //删除数据
    int deleteUserById(int id);

}

7.创建对应的Mapper

<?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.my.dao.UserDao">
    <!--查询全部用户-->
    <select id="getUserList" resultType="user">
        select * from user
    </select>
    <!--根据id查询用户-->
    <select id="getUserById" parameterType="int" resultType=" User">
        select * from user where id = #{id}
    </select>
    <!--插入数据-->
    <insert id="insertUser" parameterType="com.my.pojo.User">
        insert into user (id,name,pwd)
        values (#{id},#{name},#{pwd});
    </insert>
    <!--更新数据-->
    <update id="updateUser" parameterType="com.my.pojo.User">
        update user
        set name = #{name},pwd = #{pwd}
        where id = #{id};
    </update>
    <!--删除数据-->
    <delete id="deleteUserById" parameterType="int">
        delete from user where id = #{id}
    </delete>


</mapper>

8.测试

package com.my.dao;

import com.my.pojo.User;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import com.my.util.MybatisUtils;

import java.util.List;


public class UserTest {
    @Test
    public void test(){
        //1、获得SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        //方式一：getWrapper
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> userList = userDao.getUserList();
        //方式二
        //List<User> userList = sqlSession.selectList("com.my.dao.UserDao.getUserList");


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

        //关闭sqlSession
        sqlSession.close();
    }

}

9.后面的可以从mybatis官网补充

https://mybatis.org/mybatis-3/zh/dynamic-sql.html