MyBatis练习——使用MyBatis查询所有职员信息

实现要求：

使用MyBatis查询所有职员信息

create table employee(
	id int not null auto_increment,
	name varchar(255) not null,
	gender varchar(2) null,
	position varchar(255) null, -- 岗位
	nationality varchar(255) null, -- 国籍
	primary key(id)
);

实现思路：

在上一个项目基础上，在src/main/resources下面创建MyBatis的配置文件mybatis-config.xml。

mybatis-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>
	<!-- 设置包的别名 -->
	<typeAliases>
		<package name="jack.mybatis.simple.model" />
	</typeAliases>
	<environments default="development">
		<!--定义数据源，默认使用第一个 -->
		<environment id="development">
			<transactionManager type="JDBC">
				<!-- 事务处理方式 -->
				<property name="" value="" />
			</transactionManager>
			<!-- 每个environment元素定义的环境id -->
			<dataSource type="UNPOOLED">
				<!-- 数据源配置 -->
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql://localhost:3306/db_mybatis" />
				<property name="username" value="root" />
				<property name="password" value="root" />
			</dataSource>
		</environment>
	</environments>
	<!--映射 -->
	<mappers>
		<mapper resource="jack/mybatis/simple/mapper/EmployeeMapper.xml" />
	</mappers>
</configuration>

在src/main/java下创建一个基础的包jack.mybatis.simple，在这个包下面再创建model包。根据数据库表employee，在model包下创建实体类Employee。

Employee.java

package jack.mybatis.simple.model;

public class Employee {
	private int id;
	private String name;
	private String gender;
	private String position;
	private String nationality;
	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 getGender() {
		return gender;
	}
	public void setGender(String gender) {
		this.gender = gender;
	}
	public String getPosition() {
		return position;
	}
	public void setPosition(String position) {
		this.position = position;
	}
	public String getNationality() {
		return nationality;
	}
	public void setNationality(String nationality) {
		this.nationality = nationality;
	}
	public Employee(int id, String name, String gender, String position, String nationality) {
		super();
		this.id = id;
		this.name = name;
		this.gender = gender;
		this.position = position;
		this.nationality = nationality;
	}
	public Employee() {
		super();
	}
	@Override
	public String toString() {
		return "Employee [id=" + id + ", name=" + name + ", gender=" + gender + ", position=" + position
				+ ", nationality=" + nationality + "]";
	}

}

在src/main/resources下面创建jack/mybatis/simple/mapper目录，再在该目录下面创建与实体类Employee对应的映射文件EmployeeMapper.xml文件。

<?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">
<!-- Employee类的映射 -->
<mapper namespace="jack.mybatis.simple.model">
	<select id="selectAll" resultMap="Employee">
		select * from employee
	</select>
</mapper>

配置Log4j。

# 全局配置
log4j.rootLogger=ERROR, stdout
# MyBatis日志配直
log4j.logger.mapper=TRACE
# 控制台输出配置
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

编写测试代码查询所有职员的信息。

package test;

import java.io.IOException;
import java.io.Reader;
import java.util.List;

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.BeforeClass;
import org.junit.Test;

import jack.mybatis.simple.model.Employee;

public class EmployeeTest {
	private static SqlSessionFactory sqlSessionFactory;

	/* 完成mybatis配置的加载，创建得到SqlSessionFactory */
	@BeforeClass
	public static void init() {
		try {
			Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
			sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
			reader.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/* 获取SqlSession对象，用于调用方法得到数据 */
	@Test
	public void testSelectAll() {
		SqlSession sqlSession = sqlSessionFactory.openSession();
		try {
			List<Employee> selectList = sqlSession.selectList("selectAll");
			for (Employee employee : selectList) {
				System.out.println(employee.toString());
			}
		} finally {
			// 不要忘记关闭sqlSession
			sqlSession.close();
		}
	}
}