2.1 mybatis_HelloWorld01（原生编程）

朱雀 2022-06-01 10:51 157阅读 0赞

学习mybatis可以跟着官网文档学习http://www.mybatis.org/mybatis-3/configuration.html\#properties

mybatis\_HelloWorld有两种写法，方法二见[2.2 mybatis\_HelloWorld02（接口式编程）][2.2 mybatis_HelloWorld02] ，现在普遍用第二种写法：接口式编程

我们先来看第一种写法：

步骤：

1.  导入jar包
2.  配置全局配置文件mybatis-config.xml
3.  配置映射文件xxxMapper.xml

1. 目录结构：

![Image 1][]

![Center][]

2. 完整代码：

Employee.java

package com.mybatis.bean;
    
    public class Employee {
    	private Integer id;
    	private String lastName;
    	private String email;
    	private String gender;
    	public Integer getId() {
    		return id;
    	}
    	public void setId(Integer id) {
    		this.id = id;
    	}
    	public String getLastName() {
    		return lastName;
    	}
    	public void setLastName(String lastName) {
    		this.lastName = lastName;
    	}
    	public String getEmail() {
    		return email;
    	}
    	public void setEmail(String email) {
    		this.email = email;
    	}
    	public String getGender() {
    		return gender;
    	}
    	public void setGender(String gender) {
    		this.gender = gender;
    	}
    	@Override
    	public String toString() {
    		return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + "]";
    	}
    
    	
    
    }

全局配置文件mytatis-config.xml：

<?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>
    
    	
    	<settings>  
            <setting name="logImpl" value="STDOUT_LOGGING"/>  
        </settings> 
        
      
      <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"/>
            <property name="username" value="root"/>
            <property name="password" value="shapolang"/>
          </dataSource>
        </environment>
      </environments>
      
      
      <mappers>
        <mapper resource="com/mybatis/bean/EmployeeMapper.xml"/>
      </mappers>
    </configuration>

配置映射文件EmployeeMapper.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.mybatis.bean.EmployeeMapper">
      <select id="selectEmployee" resultType="com.mybatis.bean.Employee">
        select id,last_name lastName,email,gender from tbl_employee where id = #{id}
      </select>
    </mapper>

测试文件testMabatis.java

package test;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.Reader;
    
    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.Test;
    import com.mybatis.bean.Employee;
    /*
     * 1.根据xml配置文件（全局配置文件）创建一个SqlSessionFactory对象
     *  有数据源一些运行环境信息
     * 2.sql映射文件：配置了每一个sql，以及sql的封装规则等
     * 3.将sql映射文件注册在全局配置文件中
     * 4.写代码：
     *	1）根据全局配置文件得到SqlSessionFactory;
     *      2）使用sqlSession工厂，获取sqlSesssion对象使用它来进行增删改查
     *	       一个sqlSession就是代表和数据库一次对话，用完关闭
     *	3)使用sql的唯一标识符来告诉MyBatis执行那个sql。sql都是保存在sql映射文件中的。
     */
    public class testMybatis{
    	
    	@Test
    	public void test() throws IOException {
    		String resource = "mybatis-config.xml";
    		InputStream inputStream = Resources.getResourceAsStream(resource);
    		SqlSessionFactory sf =new SqlSessionFactoryBuilder().build(inputStream);
    	
    		//创建一个SqlSession实例，能直接执行已经映射sql语句
    		//session.selectOne(sql的唯一标识,执行sql要用的参数);
    		SqlSession session = sf.openSession();		
    		try {
    			Employee emp = session.selectOne(
    				"com.mybatis.bean.EmployeeMapper.selectEmployee", 1);
    			System.out.println(emp);
    		} finally {
    			session.close();
    		}
    		}
    }

控制台打印显示：（控制台打印sql语句需要设置，见[MyBatis3 用log4j在控制台输出 SQL][MyBatis3 _log4j_ SQL]）

==>  Preparing: select id,last_name lastName,email,gender from tbl_employee where id = ? 
    ==> Parameters: 1(Integer)
    <==    Columns: id, lastName, email, gender
    <==        Row: 1, aa, aa@qq.com, 1
    <==      Total: 1
    Employee [id=1, lastName=aa, email=aa@qq.com, gender=1]

[2.2 mybatis_HelloWorld02]: http://blog.csdn.net/yiguang_820/article/details/79180279
[Image 1]: 
[Center]: /images/20220601/316e86a76b7440bd9048bcb63fc0f596.png
[MyBatis3 _log4j_ SQL]: http://blog.csdn.net/yiguang_820/article/details/79176195