mybatis 最简单实例

1. 配置文件

<?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>  
      
    <environments default="development">  
        <environment id="development">  
            <transactionManager type="JDBC"/>  
            <dataSource type="POOLED">  
                <property name="driver" value="com.mysql.jdbc.Driver"/>  
                <property name="url" value="jdbc:mysql://localhost:3306/orcl"/>  
                <property name="username" value="root"/>  
                <property name="password" value="xxxxxx"/>  
            </dataSource>  
        </environment>  
    </environments>  
      
      
    <mappers>
        <mapper resource="com/xiamen/domain/person.xml" />        
    </mappers>  
      
</configuration>  

 包括两个部分 1. 数据库连接 2. sql映射文件Mapper

 2. ORM对象

package com.xiamen.domain;import java.io.Serializable;

public class Person implements Serializable {

    private int personId;
    private String name;
    private String age;
    
    public int getPersonId() {
        return personId;
    }
    public void setPersonId(int personId) {
        this.personId = personId;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }

    
}

3. sql映射文件

<?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">

<mapper namespace="com.xiamen.mapper.PersonMapper">
 <select id="getPersonById" parameterType="int" resultType="com.xiamen.domain.Person">
       select * from person where personId=#{id}
 </select>
 <insert id="insertvalues" parameterType="com.xiamen.domain.Person">
     insert into person (personId,name,age) values (#{personId},#{name},#{age})
 </insert>
</mapper>

注意mapper的namespace的名字是mapper对象的完整路径名com.xiamen.mapper.PersonMapper(这样session就可以getMapper了)

因为mybatis的作用就是：使得接口绑定成为可能 

4. mapper接口

映射器是创建绑定映射语句的接口,所以mapper接口就是映射器

package com.xiamen.mapper;import com.xiamen.domain.Person;

public interface PersonMapper 
{
    Person getPersonById(int id);
}

5. 测试类

        String resource = "config/mybatis.xml";

Reader reader = Resources.getResourceAsReader(resource);
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = null;
        try {
            session = factory.openSession();
            Person person = (Person) session.selectOne(
            "com.xiamen.mapper.PersonMapper.getPersonById", 1);
            if(person == null)
                System.out.println("null");
            else
                System.out.println(person.toString());
            } 
        finally {
            session.close();
            }
        try {
            session = factory.openSession();
            PersonMapper mapper = session.getMapper(PersonMapper.class);
            Person person = mapper.getPersonById(1);
            if(person == null)
                System.out.println("null");
            else
                System.out.println(person.toString()); 
            } finally {
            session.close();
            }