Mybatis第二讲——熟悉使用XML配置SQL映射器

往期回顾：

本讲主要熟悉使用XML配置SQL映射器，熟悉常见的SQL语句：

工程目录结构：

SqlSessionFactoryUtil.java

package com.java1234.util;

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;

public class SqlSessionFactoryUtil {

	private static SqlSessionFactory sqlSessionFactory;
	public static SqlSessionFactory getSessionFactory() {
		if(sqlSessionFactory==null) {
			InputStream inputStream=null;
			try {
				inputStream=Resources.getResourceAsStream("mybatis-config.xml");
				sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		
		return sqlSessionFactory;
	}
	
	public static SqlSession openSession() {
		return getSessionFactory().openSession();
	}
}

StudentMapper.java

package com.java1234.mappers;

import java.util.List;

import com.java1234.model.Student;

public interface StudentMapper {

	public int add(Student student);
	public int delete(Integer id);
	public int update(Student student);
	public Student getStudentById(Integer id);
	public List<Student> getAllStudents();
}

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.java1234.mappers.StudentMapper">

	<insert id="add" parameterType="Student"  >
		insert into t_student values(null,#{name},#{age})
	</insert>
	
	<delete id="delete" parameterType="Integer">
	 delete from t_student where id=#{id}
	</delete>
	
	<update id="update" parameterType="Student">
	update t_student set name=#{name},age=#{age} where id=#{id}
	</update>
	
	<select id="getStudentById" parameterType="Integer" resultType="Student">
	select * from t_student where id=#{id}
	</select>

	<resultMap type="Student" id="StudentResult">
		<id property="id" column="id"/>
		<result property="name" column="name"/>
		<result property="age" column="age"/>
	</resultMap> 
	
	<select id="getAllStudents" resultMap="StudentResult">
	select * from t_student 
	</select>
</mapper>

Student.java

package com.java1234.model;

public class Student {

	private Integer id;
	private String name;
	private Integer age;
	
	
	
	public Student() {
		super();
	}
	public Student(String name, Integer age) {
		super();
		this.name = name;
		this.age = age;
	}
	
	public Student(Integer id, String name, Integer age) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
	}
	
	
}

jdbc.properties

jdbc.driverClassName=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?useSSL=false&serverTimezone=GMT
jdbc.username=root
jdbc.password=000

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>
	<properties resource="jdbc.properties"/>
   <!-- 
<typeAliases>
	 <typeAlias alias="Student" type="com.java1234.model.Student"/>	
</typeAliases>
这是对数量不多的类进行配置的，不适用于大量的类
	-->
<typeAliases>
<package name="com.java1234.model"></package>
</typeAliases>

	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">  <!-- 数据库连接池 -->
				<property name="driver" value="${jdbc.driverClassName}" />
				<property name="url" value="${jdbc.url}" />
				<property name="username" value="${jdbc.username}" />
				<property name="password" value="${jdbc.password}" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<!--  <mapper resource="com/java1234/mappers/StudentMapper.xml" /> -->
		<!--  <mapper class="com.java1234.mappers.StudentMapper/> 这两种都是用于数量不多的配置-->
		<package name="com.java1234.mappers"/>
	</mappers>
</configuration>

新版eclipse自带junit，不需要自己手动导入jar包，

使用junit来测试：

Mybatis第二讲——熟悉使用XML配置SQL映射器

MybatisTest.java

package com.java1234.service;

import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import com.java1234.mappers.StudentMapper;
import com.java1234.model.Student;
import com.java1234.util.SqlSessionFactoryUtil;

class MybatisTest {

	private SqlSession sqlSession=null;
	private StudentMapper studentMapper=null;
	@BeforeEach
	void setUp() throws Exception {
		sqlSession=SqlSessionFactoryUtil.openSession();
	    studentMapper=sqlSession.getMapper(StudentMapper.class);
	}

	@AfterEach
	void tearDown() throws Exception {
		sqlSession.close();
	}

	/**
	 * 添加学生信息
	 */
	@Test
	void testAdd() {
		Student s=new Student("王二小",18);
		int result=studentMapper.add(s);

		sqlSession.commit();
		if(result>0) {
			System.out.println("添加成功");
		}else {
			System.out.println("添加失败");
		}
	}
	
	/**
	 * 删除学生
	 */
	@Test
	void testDelete() {
		int result=studentMapper.delete(15);
		sqlSession.commit();
		if(result>0) {
			System.out.println("删除成功");
		}else {
			System.out.println("删除失败");
		}
	}

	/**
	 * 更新学生信息
	 */
	@Test
	void testUPdate() {
		Student student=new Student(12,"王伟",33);
		int result=studentMapper.update(student);
		sqlSession.commit();
		if(result>0) {
			System.out.println("修改成功");
		}else {
			System.out.println("修改失败");
		}
	}
	
	/**
	 * 根据id来查找某个学生信息
	 */
	@Test
	void testGetStudentById() {
		Student stu=studentMapper.getStudentById(1);
		sqlSession.commit();
		System.out.println(stu);
	}
	
	/**
	 * 得到所有的学生信息
	 */
	@Test
	void testGetAllStudent() {
		List<Student> listStudent=studentMapper.getAllStudents();
		sqlSession.commit();
		for(Student s:listStudent) {
			System.out.println(s);
		}
	}
}

可以实现对数据库的增删改查。

Mybatis第二讲——熟悉使用XML配置SQL映射器

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