十一、持久层框架（MyBatis）

一、基于注解方式的CRUD

把xml方式的CRUD修改为注解方式

之前在xml中配置，是在<mapper></mapper>标签下写CRUD

<mapper namespace="com.demo.pojo">
    <select id="listProduct" parameterType="Product">
    select * from product_table
    </select>
    <insert id="addProduct" parameterType="Product">
        insert into product_table (name) values (#{name})
    </insert>
    <update id="updateProduct" parameterType="Product">
        update product_table set name=#{name} where id=#{id}
    </update>
    <delete id="deleteProduct" parameterType="Product">
        delete from product_table where id=#{id}
    </delete>
<mapper>

1、因此要增加Mapper接口方式实现

比如要把之前映射文件Product.xml配置方式变成注解方式的，新建一个ProductMapper接口，并在接口中声明的方法上，加上注解就可以（也就是把SQL语句从xml上移到了注解上来）

package com.demo.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import com.demo.pojo.Product;

public interface ProductMapper{
    @Insert(" inert into product_table (name) values (#{name}) ")
    public int add(Product product);
    @Delete(" delete from product_table where id=#{id} ")
    public void delete(int id);
    @Select(" select * from product_table where id=#{id} ")
    public Product select(int id);
    @Update(" update product_table set name=#{name} where id=#{id} ")
    public int update(Product product);
    @Select(" select * from product_table ")
    public List<Product> selectAll();
}

2、在mybatis-config.xml配置文件中，配置对ProductMapper接口的映射，至于原来的Product.xml映射文件是否保留都是随意

<?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>
      <package name="com.demo.pojo"/>
    </typeAliases>
    <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/demo?characterEncoding=UTF-8"/>
            <property name="username" value="root"/>
            <property name="password" value="admin"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
            <!--基于xml配置的映射文件-->
        <mapper resource="com/demo/pojo/Product.xml"/>
        <!--基于注解方式配置的映射-->
        <mapper class="com.demo.mapper.ProductMapper"/>
    </mappers>
</configuration>

3、TestMyBatis测试如下：

进行简单的CRUD测试。

package com.demo;
import java.io.IOException;
import java.io.InputSteam;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.io.Resouces;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.demo.pojo.Product;
import com.demo.mapper.ProductMapper;

public class TestMyBatis{
    public static void main(String[] args) throws IOException{
        String resouce="mybatis-config.xml";
        InputSteam inputStream=Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session=sqlSessionFactory.openSession();
        ProductMapper mapper=session.getMapper(ProductMapper.class);//加载基于注解方式配置的映射文件。

        select(mapper);
        insert(mapper);
        update(mapper);
        delete(mapper);
        selectAll(mapper);

        session.commit();
        session.close();

    }

    private static void select(ProductMapper mapper){
        Product p=mapper.get(1);//获取id=1的产品
        System.out.println(p);
    }

    private static void insert(ProductMapper mapper){
        Product p=new Product();
        p.setName("新增一个product");
        mapper.add(p);
        selectAll(mapper);
    }

    private static void update(ProductMapper mapper){
        Product p=new Product();
        p.setId(1);
        mapper.update(p);
        selectAll(mapper);
    }

    private static void delete(ProductMapper mapper){
        mapper.delete(1);
        selectAll(mapper);
    }

    private static void selectAll(ProductMapper mapper){
        List<Product> list=mapper.list();
        for(Product p:list){
            System.out.println(p);
        }
    }
}