MyBatis——（2）MyBatis_HelloWorld

思路：
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，获取到sqlSession对象使用他来执行增删改查一个sqlSession就是代表和数据库的一次会话，用完关闭
3）、使用sql的唯一标志来告诉MyBatis执行哪个sql。sql都是保存在sql映射文件中的。

创建一个Employee数据表

创建一个Employee类

package com.atguigu.mybatis.bean;

public class Employee {
	
	private Integer id;
	private String lastName;
	private String email;
	private String gendar;
	
	
	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 gendar;
	}
	public void setGender(String gender) {
		this.gendar = gender;
	}
	@Override
	public String toString() {
		return "Employee [id=" + id + ", lastName=" + lastName + ", email="
				+ email + ", gender=" + gendar + "]";
	}
}

按照思路我们来实现如下代码

1：在conf文件夹中写一个mybatis-config.xml全局配置文件，并在MyBatisTest测试类中创建一个SqlSessionFactory对象

<?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>
	<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="zlj18059008512" />
			</dataSource>
		</environment>
	</environments>
	<!-- 将我们写好的sql映射文件（EmployeeMapper.xml）一定要注册到全局配置文件（mybatis-config.xml）中 -->
	<mappers>
		<mapper resource="EmployeeMapper.xml" />
	</mappers>
</configuration>

public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}

2,3：写一个sql映射文件，并且要把该文件注入到全局配置文件（mybatis-config.xml）中

<?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.atguigu.mybatis.dao.EmployeeMapper">
<!-- 
namespace:名称空间;指定为接口的全类名
id：唯一标识
resultType：返回值类型
#{id}：从传递过来的参数中取出id值

public Employee getEmpById(Integer id);
 -->
	<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee">
		select id,lastName,email,gendar from Employee where id = #{id}
	</select>
</mapper>

4：在MyBatisTest测试类中写演示代码

package com.atstudying.mybatis.test;
import java.io.IOException;
import java.io.InputStream;
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.atstudying.mybatis.bean.Employee;
import com.atstudying.mybatis.dao.EmployeeMapper;
public class MyBatisTest {
	

	public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}


	@Test
	public void test() throws IOException {

		// 2、获取sqlSession实例，能直接执行已经映射的sql语句
		// sql的唯一标识：statement Unique identifier matching the statement to use.
		// 执行sql要用的参数：parameter A parameter object to pass to the statement.
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			Employee employee = openSession.selectOne(
					"com.atguigu.mybatis.dao.EmployeeMapper.getEmpById", 1);
			System.out.println(employee);
		} finally {
			openSession.close();
		}

	}
}

查询结果