mybatis入门之注解版 idea（含目录结构与sql语句）

maven目录结构

1、创建一个maven项目

如果你的maven项目加载不了依赖
方法炒鸡简单 —>：maven经常报错,改改你的setting.xml

2、 配置pom文件

• mysql依赖：数据库
• mybatis依赖
• junit依赖：用于单元测试
• log4j：日志打印
• build 在mybatis中必须写，因为在编译时加载不了src/main/java下的xml等文件

<dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
    </dependencies>


    <!--在mybatis当中，必须写-->
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                    <include>**/*.yml</include>
                </includes>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                    <include>**/*.yml</include>
                </includes>
            </resource>
        </resources>
    </build>

3、创建数据库及数据库表

CREATE DATABASE mybatis;
use mybatis;
CREATE TABLE IF NOT EXISTS user (
	id int(20) not null primary key,
    name VARCHAR(50) default NULL,
    pwd VARCHAR(50) default null 
)engine=innodb;

insert into user(id,name,pwd) values
(1,'贾立桐','123123'),
(2,'李四','123456'),
(3,'王麻子','111111');

4、java类和接口

4.1 User.java实体类

• 此处省略了有参构造及无参构造，getter and setter，toString，请自己添加
• 快捷键 Alt+insert

package com.tong.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;
    
    //有参构造及无参构造
    //getter and setter
    //toString
}

4.2、UserMapper.java 接口

• 使用Select注解查询
• @pram

package com.tong.dao;

import com.tong.pojo.User;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface UserMapper {
    @Select("select * from user")
    List<User> getUserList();
}

5、mybatis相关配置

4.1、db.properties文件

• url后的mybatis为数据库名

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis
username=root
password=这里填你自己的密码

4.2、mybatis_config.xml文件

• settings标签中配置了日志类型，此处选择为STDOUT_LOGGING
• environments 标签中配置mybatis环境，可创建多个环境environment ，在environments标签中的default来选中环境
• dataSource 配置数据源
• mappers 标签通过class将UserMapper接口注册到Mybatis中

<?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>
    <properties resource="db.properties"/>
    
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
    <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 class="com.tong.dao.UserMapper"/>
    </mappers>
</configuration>

5、 测试（5步）

5.1、MybatisUtils.java

1. 读取配置文件
2. 创建SqlSessionFactory工厂
3. 使用工厂生产sqlSession对象

package com.tong.util;

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 java.io.IOException;
import java.io.InputStream;

public class MybatisUtils {
    //创建一个工厂
    private static SqlSessionFactory sqlSessionFactory = null;
    static {
        try {
            InputStream in = Resources.getResourceAsStream("mybatis_config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

5.2、UserMapperTest.java

4. 使用sqlSession创建DAO接口的代理对像
5. 使用代理对象执行方法

package com.tong.dao;

import com.tong.pojo.User;
import com.tong.util.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.Before;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    private SqlSession session;
    private UserMapper userMapper;
    
    @Before
    public void init(){
        session = MybatisUtils.getSqlSession();
    }

    @Test
    public void getAll(){

        try {
            userMapper = session.getMapper(UserMapper.class);
            List<User> list = userMapper.getUserList();
            for (User user:list) {
                System.out.println(user);
            }
        }finally {
            session.close();
        }
    }
}