MyBatis第一个案例的优化,通过映射文件与接口进行绑定

1.创建表emp

CREATE DATABASE mybatis;
USE mybatis;
CREATE TABLE emp(
id INT(11) PRIMARY KEY AUTO_INCREMENT,
last_name VARCHAR(255),
gender CHAR(1),
email VARCHAR(255)
);

2.编写javaBean

package cn.bdqn.mybatis.been;

public class Emp {
	private Integer id;
	private String last_name;
	private String email;
	private String gender;
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getLast_name() {
		return last_name;
	}
	public void setLast_name(String last_name) {
		this.last_name = last_name;
	}
	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 "Emp [id=" + id + ", last_name=" + last_name + ", email="
				+ email + ", gender=" + gender + "]";
	}

}

　　3.编写Emp的DAO接口

package cn.bdqn.mybatis.dao;

import cn.bdqn.mybatis.been.Emp;
/**
 * 这个接口不用写实现类,是用来给empMapper.xml进行动态绑定的
 * @author Administrator
 *
 */
public interface EmpMapper {
	public Emp getEmpById(Integer id);
}

3添加需要的jar包

第一个是log4j的jar包(记录日志文件所需) 第二个是mybatis的核心jar包(必须),第三个是mysql的驱动jar包(必须)

4.创建需要的配置文件

第一个是SQL映射配置文件,所有的sql语句都写在这个配置文件里面

<?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:名称空间  值是Emp的DAO接口的全限定名称-->
<mapper namespace="cn.bdqn.mybatis.dao.EmpMapper">
<!--
id,唯一标识
resultType:返回值类型,bean的全限定名称
#{id},从传递过来的参数中取出id值,相当于换位符
public Emp getEmpById(Integer id);

id是我们接口中方法的方法名称
-->
<select id="getEmpById" resultType="cn.bdqn.mybatis.been.Emp">
select * from emp where id = #{id}
</select>
</mapper>

第二个是log4j记录日志所需

第三个是mybatis全局配置文件

<?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>
<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="admin"/>
</dataSource>
</environment>
</environments>
<!--将我们写好的SQL映射文件一定要注册到全局配置文件中  -->
<mappers>
<mapper resource="empMapper.xml"/>
</mappers>
</configuration>

　　5,最后编写测试类

package cn.bdqn.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 cn.bdqn.mybatis.been.Emp;
import cn.bdqn.mybatis.dao.EmpMapper;

public class MyBatisTest_01 {
	public static void main(String[] args) throws IOException {
		//1.获取SqlSessionFactory对象
		String resource="mybatis-config.xml";
		InputStream ras = Resources.getResourceAsStream(resource);
	SqlSessionFactory build = new	SqlSessionFactoryBuilder().build(ras);
	//2.获取SqlSession对象
	SqlSession openSession = build.openSession();

	try{
		//3.获取接口的实现类对象
		//会为接口自动创建一个代理对象,代理对象去执行增删改查方法
		EmpMapper mapper = openSession.getMapper(EmpMapper.class);
		Emp empById = mapper.getEmpById(1);
		System.out.println(empById);
	}finally{
		openSession.close();
	}

	}
}