mybatis从零基础到增删改查数据库

最新推荐文章于 2024-03-17 16:08:47 发布

YMY327

最新推荐文章于 2024-03-17 16:08:47 发布

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分类专栏： mybatis 文章标签： mybatis

本文链接：https://blog.youkuaiyun.com/u011714944/article/details/38172717

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本文详细介绍如何在Eclipse环境下使用MyBatis框架实现对MySQL数据库的基本操作，包括创建数据库、配置环境、编写DTO类及XML配置文件，并提供完整的测试代码示例。

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本文是mybatis框架一个初步的入门总结，最全的最好的资料应该参考这个：http://mybatis.github.io/mybatis-3/zh/index.html

本文在Eclipse下搭建一个小程序可以测试mybatis对mysql数据库进行增删改查这几个基本功能。

1.首先建立数据库，我建立的数据库叫test，编码是UTF-8，里面有两张表，它们是这样的：

两张表的数据我填的是这样的，当然可以随便填，不过最好在person中有1个以上name相同的，后面会用到：

2.在ECLIPISE下建立DYNAMIC WEB PROJECT，别忘了在BUILD PATH下加入mybatis和mysql的jar包。这个工程的布局是这样的：

文件和类的用途后面解释

Main里面有程序的static void main函数。Test类封装了测试mybatis框架功能的函数。xml都是框架的配置文件。Person与Student是DTO数据传输对象。两个Mapper类都是接口类，用途后面讲。

3.配置Configuration.xml。在src文件夹下先建立这个文件。

<?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>
    <typeAliases> 
        <typeAlias alias="Person" type="com.ymy.mybatis.model.Person"/> 
        <typeAlias alias="Student" type="com.ymy.mybatis.model.Student"/> 
        <!-- short name of java classes -->
    </typeAliases> 

    <environments default="development">
        <environment id="development">
        	<!--
        	choose any name for default and id
        	  -->
        <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver"/>
            <property name="url" value="jdbc:mysql://127.0.0.1:3306/test"/>
            <property name="username" value="root"/>
            <property name="password" value="31415926"/>
            <property name="driver.encoding" value="UTF8"/>
            <!--property name="PROPERTY NAME" value="${var name}"/-->
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <mapper resource="com/ymy/mybatis/model/Person.xml"/>
        <mapper resource="com/ymy/mybatis/model/Student.xml"/>
        <!-- xml of mapper class -->
    </mappers>
</configuration>

标签解释：

<typeAliases> 定义的是别名，全名是type里的一大串，起个别名减少了后面的书写量。

<environments>和<environment>配置了数据库的信息，一个environments下可以配多个environment来访问多个数据库，这超出了本文讨论范围。这个文章：http://zhangbo-peipei-163-com.iteye.com/blog/2052924讲了多数据源配置。

<property name>和value改成自己的数据库的就行了

<mappers>下定义多个<mapper>每个mapper对应一个DTO类型，以及它们对应的数据库操作。mapper resource后面是对应DTO的xml文件的实际位置。

3.建立DTO类Student和Person。

Student类:

package com.ymy.mybatis.model;

public class Student {
	private int id;
	private String name;
	private int score;

	public Student() {
	}

	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 getScore() {
		return score;
	}

	public void setScore(int score) {
		this.score = score;
	}
}

Person类：

package com.ymy.mybatis.model;

public class Person {
	private int id;
	private String name;
	private int age;
	private String address;

	public Person(String name, int age, String address) {
		this.name = name;
		this.age = age;
		this.address = address;
	}

	public Person(int id, String name, int age, String address) {
		this.id = id;
		this.name = name;
		this.age = age;
		this.address = address;
	}

	public Person() {
	}

	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 String getAddress() {
		return address;
	}

	public void setUserAddress(String userAddress) {
		this.address = userAddress;
	}
}

4.配置Student.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.ymy.mybatis.model.StudentMapper">
    <select id="selectStudentByID" parameterType="int" resultType="Student">
        select * from student where id = #{id}
    </select>
</mapper>

解释：<mapper namespace>那句，相当于在命名空间com.ymy.mybatis.model.StudentMapper下定义了一个叫selectStudentByID的语句，它接收的参数类型（parameterType）为int，返回类型为Student。到后面我们定义了接口类StudentMapper，mybatis就会把接口中的函数和xml中的定义绑定。<select>标签说明这是查询类型的操作。

接口类StudentMapper：

package com.ymy.mybatis.model;

public interface StudentMapper {
	public Student selectStudentByID(int id);
}

配置Person.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.ymy.mybatis.model.PersonMapper">
        <resultMap id="personResultMap" type="Person">
             <id property="id" column="id" />
             <result property="name" column="name"/>
             <result property="age" column="age"/>
             <result property="address" column="address"/>

        </resultMap>

        <select id="selectPersonByID" parameterType="int" resultType="Person">
             select * from person where id = #{id}
        </select>
    
        <select id="selectPersonByName" parameterType="String" resultMap="personResultMap">
             select * from person where name = #{name}
        </select>
    
        <select id="lastInsertId" resultType="int">
              select last_insert_id()
        </select>
    
        <insert id="addPerson" parameterType="Person">
                insert into person (id,name,age,address)
                values (NULL,#{name},#{age},#{address})
        </insert>

        <update id="updatePerson" parameterType="Person">
                update person set
                name = #{name},
                age = #{age},
    	        address= #{address}
                where id = #{id}
        </update>

        <delete id="deletePerson" parameterType="int">
             delete from person where id = #{id}
        </delete>
</mapper>

看sql语句就知道都是干啥的了，增删改查已经全了。重点是selectPersonByName。数据库里有重名的人，所以会查询到多个人。这时返回类型标签成了resultMap。值为personResultMap。文件最前面定义了personResultMap。result里面property是DTO里变量的名称。column和数据库里的名称对应。

接口类PersonMapper:

package com.ymy.mybatis.model;

import java.util.List;

public interface PersonMapper {
	public Person selectPersonByID(int id);
	public List<Person> selectPersonByName(String name);
	
	public void addPerson(Person person);
	public void deletePerson(int id);
	public void updatePerson(Person person);
	public int lastInsertId();
}

5.写测试代码：

Test类：

package com.ymy.mybatis.test;

import java.io.*;
import java.util.*;

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.ymy.mybatis.model.*;

public class Test {
	private static SqlSessionFactory sqlSessionFactory;
	// it should be static
	// every thread should have its own SqlSession instance
	private static Reader reader;
	static {
		try {
			reader = Resources.getResourceAsReader("Configuration.xml");
			sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
			// every database should have its own SqlSessionFactory
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public void getPersonList(String userName) {
		SqlSession session = sqlSessionFactory.openSession();
		try {
			PersonMapper mapper = session.getMapper(PersonMapper.class);
			List<Person> people = mapper.selectPersonByName(userName);
			for (Person person : people) {
				System.out.print("Name: " + person.getName() + "\t");
				System.out.print("Age: " + person.getAge() + "\t");
				System.out.println("Addr: " + person.getAddress());
			}
		} finally {
			session.close();
		}
	}

	public void addPerson() {
		@SuppressWarnings("resource")
		Scanner inputer = new Scanner(System.in);
		System.out.println("Input a person's name age and address");
		String name = inputer.next();
		int age = inputer.nextInt();
		String address = inputer.next();

		Person newPerson = new Person(name, age, address);
		SqlSession session = sqlSessionFactory.openSession();
		try {
			PersonMapper mapper = session.getMapper(PersonMapper.class);
			mapper.addPerson(newPerson);
			int last_id = mapper.lastInsertId();
			System.out.println("Insert id = " + last_id);
			session.commit();
		} finally {
			session.close();
		}
	}
	
	public void updatePerson() {
		@SuppressWarnings("resource")
		Scanner inputer = new Scanner(System.in);
		System.out.println("Input a person's id, name, age and address");
		int id = inputer.nextInt();
		String name = inputer.next();
		int age = inputer.nextInt();
		String address = inputer.next();

		Person person = new Person(id, name, age, address);
		SqlSession session = sqlSessionFactory.openSession();
		try {
			PersonMapper mapper = session.getMapper(PersonMapper.class);
			mapper.updatePerson(person);
			session.commit();
			System.out.println("OK!");
		} finally {
			session.close();
		}
	}

	public void deletePerson() {
		@SuppressWarnings("resource")
		Scanner inputer = new Scanner(System.in);
		System.out.println("Input an id to delete:");
		int id = inputer.nextInt();

		SqlSession session = sqlSessionFactory.openSession();
		try {
			PersonMapper mapper = session.getMapper(PersonMapper.class);
			mapper.deletePerson(id);
			session.commit();
		} finally {
			session.close();
		}
	}
	
	public void selectPersonById(){
		@SuppressWarnings("resource")
		Scanner inputer = new Scanner(System.in);
		System.out.println("Input an id to select:");
		int id = inputer.nextInt();
		
		SqlSession session = sqlSessionFactory.openSession();
		try {
			PersonMapper mapper = session.getMapper(PersonMapper.class);
			Person person = mapper.selectPersonByID(id);
			System.out.print("Name: " + person.getName() + "\t");
			System.out.print("Age: " + person.getAge() + "\t");
			System.out.println("Addr: " + person.getAddress());
		} finally {
			session.close();
		}
	}
	
	public void selectStudentById(){
		@SuppressWarnings("resource")
		Scanner inputer = new Scanner(System.in);
		System.out.println("Input an student id to select:");
		int id = inputer.nextInt();
		
		SqlSession session = sqlSessionFactory.openSession();
		try {
			StudentMapper mapper = session.getMapper(StudentMapper.class);
			Student student = mapper.selectStudentByID(id);
			System.out.print("Name: " + student.getName() + "\t");
			System.out.print("ID: " + student.getID() + "\t");
			System.out.println("Score: " + student.getScore());
		} finally {
			session.close();
		}
	}

}

解释：我们通过SqlSession类的对象获取映射（使用getMapper方法），通过映射调用Student和Person接口类里的函数。SqlSession参与数据库的管理事务。当执行了修改数据库内容的语句后调用commit()方法讲更改的内容写入数据库。完成后及时关闭SqlSession对象，调用close()方法。

最后写Main类，然后运行程序：

package com.ymy.mybatis.test;

public class Main {
	public static void main(String[] args) {
		Test t1 = new Test();
		t1.selectPersonById();
		t1.getPersonList("Bill");// find Bill
		t1.addPerson();
		t1.deletePerson();
		t1.updatePerson();
		
		t1.selectStudentById();
	}
}