mybatis

持久层框架
MyBatis是支持普通 SQL查询，存储过程和高级映射的优秀持久层框架
MyBatis消除了几乎所有的 JDBC 代码和参数的手工设置以及结果集的检索
MyBatis使用简单的 XML或注解用于配置和原始映射，将接口和 Java 的POJOs
（Plan Old Java Objects，普通的 Java对象）映射成数据库中的记录。

 跟hibernate相比,我们还需要写sql,它介于hibernate和jdbc之间的框架

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总配置文件

在src根目录中  MyBatis配置文件mybatis.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>


    <!-- 配置的别名,在下面的xml中书写简单 -->
    <typeAliases>
        <typeAlias type="com.kaishengit.pojo.Admin" alias="Admin"/>
        <typeAlias type="com.kaishengit.pojo.Post" alias="Post"/>
    </typeAliases>
    <!-- environments中可以有多个environment,每个environment设置一个id,分别表示开发,测试,上线等等
        要使用哪个environment就default="xxx" -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <!-- 它自己提供数据源,不需要dbcp啊c3p0啊什么的 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///book"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    
    
    
    <!-- 声明写的其他的配置文件 -->
    <mappers>
        <mapper resource="com/kaishengit/mapper/AdminMapper.xml"/>
        <mapper resource="com/kaishengit/mapper/PostMapper.xml"/>
    </mappers>
    

</configuration>

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写AdminMapper.xml配置文件 写的这个配置文件要在主配置文件中声明一下

<?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">
<!-- 当前写的xml的完全限定名 以类的形式表示,这个xml文件类似与以前的dao -->
<mapper namespace="com.kaishengit.mapper.AdminMapper">
    <!--insert方法 id表示方法名  -->
    <insert id="save" parameterType="Admin">
        insert into admin(name,password) values("tom","123")
    </insert>
    
    
    
    
    <!-- 参数类型(传进来的id)parameterType="int"  返回类型resultType="com.kaishengit.pojo.Admin" -->
    <select id="findById" parameterType="int" resultType="com.kaishengit.pojo.Admin">
        select * from admin where id = #{id}
    </select>
    
    <!-- resultType：迒回值类型，如果是自己定义的Entity，需要在mybatis.xml中中配置别名。 -->
    <typeAliases>
        <typeAlias type="com.kaishengit.mybatis.entity.User" alias="User"/>
    </typeAliases>
    
    <!-- 这样就可以写resultType="Admin" -->
    

</mapper>

举例

import java.io.Reader;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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 Test {

    public static void main(String[] args) throws Exception {
        
        /* 1. 构建SqlSessionFactory对象 提供一个reader供读取xml文件*/
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
    
        
        /* 2.创建SqlSession对象 */
        /* SqlSession session = sessionFactory.openSession();*/
        // 自动提交,下面就不用写session.commit(); 
        SqlSession session = sessionFactory.openSession(true);
        
        /*******************************************************/
        
        //数据库操作都写在这里 
        
        //添加 
        session.insert("com.kaishengit.mapper.AdminMapper.save");
        // id查询
        Admin admin = (Admin) session.selectOne("com.kaishengit.mapper.AdminMapper.findById", 1);
        
        /******************************************************/
         //记得要提交和关闭
        // session.commit(); 
        session.close();
    }
}

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形式2：接口的形式

总配置文件

在src根目录中  MyBatis配置文件mybatis.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>


    <!-- 配置的别名,在下面的xml中书写简单 -->
    <typeAliases>
        <typeAlias type="com.kaishengit.pojo.Admin" alias="Admin"/>
        <typeAlias type="com.kaishengit.pojo.Post" alias="Post"/>
    </typeAliases>
    <!-- environments中可以有多个environment,每个environment设置一个id,分别表示开发,测试,上线等等
        要使用哪个environment就default="xxx" -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <!-- 它自己提供数据源,不需要dbcp啊c3p0啊什么的 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///book"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    
    
    
    <!-- 声明写的其他的配置文件 -->
    <mappers>
        <mapper resource="com/kaishengit/mapper/AdminMapper.xml"/>
        <mapper resource="com/kaishengit/mapper/PostMapper.xml"/>
    </mappers>
    

</configuration>

写AdminMapper.xml配置文件 写的这个配置文件要在主配置文件中声明一下

<?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">
<!-- 当前写的AdminMapper接口的完全限定名 -->
<mapper namespace="com.kaishengit.mapper.AdminMapper">


    <!--insert方法 id表示方法名  -->
    <insert id="save" parameterType="Admin">
        insert into admin(name,password) values(#{name},#{password})
    </insert>
    
    
        
    <update id="update" parameterType="Admin">
        update admin set name = #{name},password=#{password} where id = #{id}
    </update>
        
    <delete id="delete" parameterType="int">
        delete from admin where id = #{id}
    </delete>
    
        
    <!-- 参数类型(传进来的id)parameterType="int"  返回类型resultType="com.kaishengit.pojo.Admin" -->
    <select id="findById" parameterType="int" resultType="com.kaishengit.pojo.Admin">
        select * from admin where id = #{id}
    </select>
    
    
    
        
    <!-- 设置resultType="list"表示返回的是一个list数组,但是在程序中接收的时候
        list<Admin>是不知道返回的list里面是admin的是Oblect对象,所以需要设置resultMap="adminMap"
            然后设置一个节点resultMap-->
    <select id="findAll" resultType="list" resultMap="adminMap">
        select * from admin
    </select>
    
    
    <!-- 设置这个封装成Admin.相当于以前的rowMapper,都是进行封装 -->
    <resultMap type="Admin" id="adminMap">
        <!--  property属性名 column列名-->
        <id property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="password" column="password"/>
    </resultMap>
    
    
    <select id="findByName" parameterType="String" resultType="Admin">
        select * from admin where name = #{name}
    </select>
    <!-- parameterType="map"多个查询的时候,参数必须封装成对象后者map -->
    <select id="findByNameAndPassword" parameterType="map" resultType="Admin">
        select * from admin where name = #{name} and password = #{password}
    </select>
    
    
    <!-- 如果是多表查询,例如
    public class Admin {

        private Integer id;
        private String name;
        private String password;
        private List<Post> posts;
    }
    public class Post {

        private Integer id;
        private String title;
        private Admin admin;
    }-->
    <!-- 那么对于mybatis是不会像hibernate那样自动去查的,sql必须重写 -->
        <!-- 因为是一对多,一个admin会对应多个post,resultMap="adminPostMap" -->
     <select id="findById" parameterType="int" resultType="Admin" resultMap="adminPostMap">
         SELECT admin.id,NAME,PASSWORD,post.id AS pid,title,aid FROM admin
        INNER JOIN post
        ON admin.id = post.aid
        WHERE admin.id = #{id}
     </select>
    
    <!-- 设置这个封装成Admin.相当于以前的rowMapper,都是进行封装 -->
     <resultMap type="Admin" id="adminPostMap">
         <id property="id" column="id"/>
         <result property="name" column="name"/>
         <result property="password" column="password"/>
        <!-- admin中属性名property="posts" posts集合中都是post 类名ofType="Post" -->
         <collection property="posts" ofType="Post">
            <!-- 对于post里面的id不能和admin的id重复,改成pid,那么在sql语句中要设置别名 -->
             <id property="id" column="pid"/>
             <result property="title" column="title"/>
         </collection>
     </resultMap>
    


</mapper>

举例

写一个接口AdminMapper要和AdminMapper.xml相对应

import java.util.List;
import java.util.Map;

import com.kaishengit.pojo.Admin;

public interface AdminMapper {
// save()方法,要和xml中的save相对应 
    public void save(Admin admin);
    public Admin findById(int id);
    public void update(Admin admin);
    public void delete(int id);
    public List<Admin> findAll();
    public Admin findByName(String name);
    public Admin findByNameAndPassword(Map<String, Object> param);
    
}

import java.io.Reader;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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 Test {

    public static void main(String[] args) throws Exception {
        
        /* 1. 构建SqlSessionFactory对象 提供一个reader供读取xml文件*/
        Reader reader = Resources.getResourceAsReader("mybatis.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
    
        
        //2.创建SqlSession对象 
        /* SqlSession session = sessionFactory.openSession(); */
        // 自动提交,下面就不用写session.commit();
        SqlSession session = sessionFactory.openSession(true);
        
        /******************************************************/
        
        // 数据库操作都写在这里
        
        
        // 创建实现接口的对象 
        AdminMapper mapper = session.getMapper(AdminMapper.class);
        // 添加
        Admin admin = new Admin();
        admin.setName("iBatis");
        admin.setPassword("888888");
        
        mapper.save(admin);
        
        
        // 修改 
        Admin admin = mapper.findById(3);
        admin.setName("tom");
        mapper.update(admin);
        //删除 
        mapper.delete(4);
        
        // 查询 
        Admin admin = mapper.findById(1);     
        System.out.println(admin.getName());
        System.out.println(admin.getPassword());
        
        // 查询所有 
        List<Admin> adminList = mapper.findAll();
        System.out.println(adminList.size());
        for(Admin a : adminList) {
            System.out.println(a.getName());
        }
        //根据名字查 
        
        
        Admin admin = apper.findByName("tom");
        System.out.println(admin.getName());
        System.out.println(admin.getPassword());
        
        /*根据多个属性查询 
            因为在xml中只能接受一个参数类型,所以传过去多个参数的时候,只能封装成对象或者map
                */
        Map<String, Object> param = new HashMap<String, Object>();
        param.put("name", "tom");
        param.put("password", "000000");
        Admin admin =mapper.findByNameAndPassword(param);
        System.out.println(admin.getName());
        System.out.println(admin.getPassword());
        
        
        // 多表查询 查询admin  admin中有多个post
        Admin admin = mapper.findById(1);
        System.out.println(admin.getName());
        System.out.println(admin.getPassword());
        
        List<Post> postList = admin.getPosts();
        
        for(Post p : postList) {
            System.out.println(p.getTitle());
        }
        
        
        //多表查询 查询post,post对应一个admin
        
    /* 那就要新建一个postMapper.xml 
    <select id="findById" parameterType="int" resultType="Post" resultMap="postMap">
        SELECT admin.id,NAME,PASSWORD,post.id AS pid,title,aid FROM admin
        INNER JOIN post
        ON admin.id = post.aid
        WHERE post.id = #{id}
    </select>
    
    <resultMap type="Post" id="postMap">
        <id property="id" column="pid"/>
        <result property="title" column="title"/>
        <association property="admin" column="aid" javaType="Admin">
            <id property="id" column="id"/>
             <result property="name" column="name"/>
             <result property="password" column="password"/>
        </association>
    </resultMap>
    
    
    接口
    public interface PostMapper {

        public Post findById(int id);
    }
    
    
    
    程序中
    PostMapper mapper = session.getMapper(PostMapper.class);
    Post post = mapper.findById(1);
    System.out.println(post.getTitle());
    System.out.println(post.getAdmin().getName());
    */
        
        
        
        
        
        
        
        /******************************************************/
       //记得要提交和关闭
        //session.commit();
        session.close();
    }
}