Mybatis笔记

如何获得Mybatis?

maven仓库：

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.6</version>
</dependency>

新建一个Maven项目

删除src目录

导入maven依赖

<!--导入依赖-->
<dependencies>
    <!--mysql驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.46</version>
    </dependency>
    <!--mybatis-->
    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.6</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
    
</dependencies>

编写mybatis的核心配置文件

<?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核心配置文件-->
<configuration>

  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
        <property name="username" value="username"/>
        <property name="password" value="password"/>
      </dataSource>
    </environment>
  </environments>
 <mappers>

<mapper resource="org/mybatis/example/BlogMapper.xml"/>

  </mappers>

</configuration>

编写mybatis工具类

package com.fan.Utils;

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;

//sqlSessionFactory-->工厂模式--生产sqlSession
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        //第一步：获取sqlSessionFactory对象
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream =Resources.getResourceAsStream(resource);
            sqlSessionFactory= new SqlSessionFactoryBuilder().build(inputStream);

        } catch (IOException e) {
            throw new RuntimeException(e);
        }


    }
    //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();

    }
}

编写代码

实体类

package com.fan.pojo;

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

UserMapper接口：

public interface UserMapper {
    List<User> getuserlist();
}
接口实现类由UserDaoImpl转换为一个Mapper.xml

<?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">
<!--namespace=绑定一个对应的Mapper接口-->
<mapper namespace="dao.UserDao">

    <select id="getuserList" resultType="pojo.User">
        select * from mybatis.user where id = #{id}
    </select>
</mapper>

接口实现类（UserMapper.xml）

<?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.fan.dao.UserMapper">
    <select id="getUserList" resultType="com.fan.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

测试：

public class UserDaoText {
    @Test
    public  void text(){
        SqlSession sqlSession = Mybatisutils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getuserlist();
       for (User user : userList) {
           System.out.println(user);
        }
       sqlSession.close();

    }
}
注意：
如果报这个错误

在pom.xml加入

 <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>