Mybatis第二讲——熟悉使用XML配置SQL映射器

清疚 2022-03-25 03:28 254阅读 0赞

往期回顾：

[Mybatis第一讲][Mybatis]

**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：

![20190118131319839.png][]

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>
    <package name="com.java1234.model"></package>
    </typeAliases>
    
    	<environments default="development">
    		<environment id="development">
    			<transactionManager type="JDBC" />
    			<dataSource type="POOLED">  
    				<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>
    		
    		
    		<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：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lvbmdidXRpbmd4aWRl_size_16_color_FFFFFF_t_70][]

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]: https://blog.csdn.net/yongbutingxide/article/details/86498849
[20190118131319839.png]: /images/20220325/9ff8c85613664c789dfca581c9185f96.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lvbmdidXRpbmd4aWRl_size_16_color_FFFFFF_t_70]: /images/20220325/c658da6d9c2046fdb2bbe44c8418390a.png