MyBatis框架学习(二)-MyBatis入门案例

前言:这次我们学习一个MyBatis的入门案列,需求主要是初步了解MyBatis如何连接数据库,以及如何实现简单的CRUD操作.

一、准备开发环境

1.将所需要的jar包,添加到环境中

2.创建一个数据库db.sql并且创建一个student的表结构

3.创建一个配置文件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>
	<!-- 开启驼峰命名法规则,create_time 就等于createTime  -->
	<settings>
		<setting name="mapUnderscoreToCamelCase" value="true"/>
	</settings>
	<!-- 默认引用那个数据库环境 -->
	<environments default="development">
		<environment id="development">
			<!-- 事务管理方式 -->
			<transactionManager type="JDBC" />
			<!-- 数据库连接四要素 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis" />
				<property name="username" value="root" />
				<property name="password" value="root" />
			</dataSource>
		</environment>
	</environments>
	<!-- SQL的映射文件 -->
	<mappers>
		<mapper resource="com/dqsy/mybatis/xml/StudentMapper.xml" />
	</mappers>
</configuration>

4.我们创建一个映射文件StudentMapper.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.dqsy.mybatis.xml.StudentMapper">
<!--  
	id:表示一个SQL句柄,相当于JDBC中的statement
	parametaerType:输入参数的类型,在SQL语句中,通过占位符#{}来接受参数
	resultType:SQL操作的返回结果类型
-->
  <!-- 单个查询 -->
  <select id="getStudentById" parameterType="java.lang.Integer" 
  resultType="com.dqsy.mybatis.entity.Student">
    select id,name,age,create_time from student where id=#{id}
  </select>
  <!-- 查询列表 -->
  <select id="getStudentList" resultType="com.dqsy.mybatis.entity.Student">
  	select id,name,age,create_time from student
  </select>
  <!-- 添加学生 注意在这传参是java里的参数 而不是数据库里的字段名-->
  <select id="addStudent" parameterType="com.dqsy.mybatis.entity.Student">
  	insert into student(name,age,create_time) values(#{name}, #{age}, #{createTime})
  </select>
  <!-- 删除学生 -->
  <select id="delStudent" parameterType="java.lang.Integer">
  	delete from student where id = #{id}
  </select>
  <!-- 修改学生的数据 -->
  <select id="uptStudent" parameterType="com.dqsy.mybatis.entity.Student">
  	update student set name=#{name}, age=#{age}, create_time=#{createTime} where id=#{id}
  </select>
</mapper>

5.创建一个Student的实体类,并生成getset方法和toString方法

package com.dqsy.mybatis.entity;

import java.util.Date;

public class Student {
	
	private int id;
	private String name;
	private int age;
	private Date createTime;
	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 int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public Date getCreateTime() {
		return createTime;
	}
	public void setCreateTime(Date createTime) {
		this.createTime = createTime;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", age=" + age + ", createTime=" + createTime + "]";
	}
	
}

6.我们先暂时常见一个MainTest的测试方法

package com.dqsy.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 com.dqsy.mybatis.entity.Student;

public class MainTest {

	public static void main(String[] args) throws IOException {
		//1.读取配置文件
		String configFile = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(configFile);
		//2.通过SqlSessionFactoryBuilder建立sqlSessionFactory
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		//3.通过sqlSessionFactory创建sqlSession
		SqlSession sqlSession = sqlSessionFactory.openSession();
		//4.通过sqlSession接口方法开执行数据库
		Student stu = sqlSession.selectOne("com.dqsy.mybatis.xml.StudentMapper.getStudentById", 1);
		//5.测试
		System.out.println(stu);
		//6.关闭sqlSession
		sqlSession.close();
	}

}

输出的结果为:

7.上面的这个测试方法为Main方法,有点麻烦,我可以可以写一个Junit Test来测试,实现我们简单的CRUD首先我们写一个IStudentDao的接口

package com.dqsy.mybatis.dao;

import java.util.List;

import com.dqsy.mybatis.entity.Student;

public interface IStudentDao {
	
	public Student getStudentById(int id);
	public List<Student> getStudentList();
	public void addStudent(Student stu);
	public void delStudent(int id);
	public void uptStudent(Student stu);
}

8.实现这个接口IStudentDaoImpl

package com.dqsy.mybatis.dao.impl;

import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import com.dqsy.mybatis.dao.IStudentDao;
import com.dqsy.mybatis.entity.Student;

public class IStudentDaoImpl implements IStudentDao {
	//通过构造方法把sqlSessionFactory加载进来
	private SqlSessionFactory sqlSessionFactory;
	public IStudentDaoImpl(SqlSessionFactory sqlSessionFactory){
		this.sqlSessionFactory = sqlSessionFactory;
	}
	@Override
	public Student getStudentById(int id) {
		// TODO Auto-generated method stub
		SqlSession  sqlSession = sqlSessionFactory.openSession();
		Student stu = sqlSession.selectOne("com.dqsy.mybatis.xml.StudentMapper.getStudentById", id);
		sqlSession.close();
		return stu;
	}

	@Override
	public List<Student> getStudentList() {
		// TODO Auto-generated method stub
		SqlSession  sqlSession = sqlSessionFactory.openSession();
		List<Student> stus = sqlSession.selectList("com.dqsy.mybatis.xml.StudentMapper.getStudentList");
		sqlSession.close();
		return stus;
	}

	@Override
	public void addStudent(Student stu) {
		// TODO Autoerated method stub
		SqlSession  sqlSession = sqlSessionFactory.openSession();
		int rows = sqlSession.insert("com.dqsy.mybatis.xml.StudentMapper.addStudent", stu);
		System.out.println("行数"+rows);
		sqlSession.commit();
		sqlSession.close();
	}
	@Override
	public void delStudent(int id) {
		// TODO Auto-generated method stub
		SqlSession  sqlSession = sqlSessionFactory.openSession();
		int rows = sqlSession.delete("com.dqsy.mybatis.xml.StudentMapper.delStudent", id);
		System.out.println("行数"+rows);
		sqlSession.commit();
		sqlSession.close();	
	}
	@Override
	public void uptStudent(Student stu) {
		// TODO Auto-generated method stub
		SqlSession  sqlSession = sqlSessionFactory.openSession();
		int rows = sqlSession.update("com.dqsy.mybatis.xml.StudentMapper.uptStudent", stu);
		System.out.println("行数"+rows);
		sqlSession.commit();
		sqlSession.close();
	}
}

9.然后就是测试文件了

package com.dqsy.mybatis.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

import com.dqsy.mybatis.dao.IStudentDao;
import com.dqsy.mybatis.dao.impl.IStudentDaoImpl;
import com.dqsy.mybatis.entity.Student;

public class MyBatisTest {
	private SqlSessionFactory sqlSessionFactory;
	@Before
	public void init() throws IOException{
		//1.读取配置文件
				String configFile = "mybatis-config.xml";
				InputStream inputStream = Resources.getResourceAsStream(configFile);
				//2.通过SqlSessionFactoryBuilder建立sqlSessionFactory
				 sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
	}
	@Ignore
	@Test
	public void TestGetStudentById(){
		IStudentDao stuDao = new IStudentDaoImpl(sqlSessionFactory);
		System.out.println(stuDao.getStudentById(1));
	}
	@Ignore
	@Test
	public void TestGetStudentList(){
		IStudentDao stuDao = new IStudentDaoImpl(sqlSessionFactory);
		List<Student> stus = stuDao.getStudentList();
		for(Student stu: stus){
			System.out.println(stu);
		}	
	}
	//@Ignore
	@Test
	public void TestAddStudent(){
		IStudentDao stuDao = new IStudentDaoImpl(sqlSessionFactory);
		Student stu = new Student();
		stu.setName("王巍");
		stu.setAge(25);
		stu.setCreateTime(new Date());
		stuDao.addStudent(stu);
	}
	@Ignore
	@Test
	public void TestDelStudent(){
		IStudentDao stuDao = new IStudentDaoImpl(sqlSessionFactory);
		stuDao.delStudent(1);
	}
	@Test
	public void TestUptStudent(){
		IStudentDao stuDao = new IStudentDaoImpl(sqlSessionFactory);
		Student stu = new Student();
		stu.setId(5);
		stu.setName("可鑫");
		stu.setAge(28);
		stu.setCreateTime(new Date());
		stuDao.uptStudent(stu);
	}
}

10.在这呢结果我就不一一截图了,我们来看看数据库

二、总结

通过这个简单的案例我们已经基本了解MyBatis的使用,以及它的配置文件,让一个简单的项目跑起来了,一个接口方法对应一个SQL语句,这就是MyBatis的简单之处,下节我们将继续学习,MyBatis的各项配置以及常见的、复杂的用法。