搭建Mybatis环境

1.导入依赖

pom.xml

<dependencies>

        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.7version>
        dependency>

        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.30version>
        dependency>

        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.12version>
            <scope>testscope>
        dependency>


    dependencies>

2.在Resource下面创建Mybatis-config.xml

并把下面内容复制进去，然后配置数据库连接信息

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <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>
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    mappers>
configuration>

3.创建Mapper接口

MyBatis中的mapper接口相当于以前的Dao但是区别在于，mapper仅仅是接口，我们不需要提供实现类。
实体类

package com.mybatis.Bean;

public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;

    public User(Integer id, String username, String password, Integer age) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.age = age;
    }

    public User() {
    }

    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 String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getAge() {
        return age;
    }

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

Mapper类

package com.mybatis.Mapper;

public interface UserMapper {

}

项目结构图

4.创建Mybatis映射文件

    <mappers>
        <mapper resource="Mappers/UserMapper.xml"/>
    mappers>

5.

MyBatis面向接口编程的两个一致:
1、映射文件的namespace要和mapper接口的全类名保持一致
2、映射文件中SQL语句的id要和mapper接口中的方法名一致

public interface UserMapper {

    int insertUser();

}

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mybatis.Mapper.UserMapper">

    <insert id="insertUser">
        insert into user values (null,"cc","123445",20);
    insert>
mapper>