八、持久层框架（MyBatis）

一、基于MyBatis的CRUD

1、首先是配置文件Category.xml修改

　　一次性修改配置文件Category.xml，提供CRUD对应的sql语句。

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE mapper
    PUBLIC "-//mybatis.rog//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

    <mapper namespace="com.demo.pojo">
        <insert id="addCategory" parameter Type="Category">
            insert into category_table  (name) values (#{name})
        </insert>
        <delete id="deleteCategory" parameter Type="Category">
            delete from category_table where id=#{id}
        </delete>
        <select id="getCategory" parameter Type="Category">
            select * from category_table where id=#{id}
        </select>
        <update id="updateCategory" parameter Type="Category">
            update category_table set name=#{name} where id=#{id}
        </update>
        <select id="listCategory" resultType="Category">
            select * from category_table
        </select>
    </mapper>

2、增加（insert）

通过session.insert()方法调用addCategory对应的SQL语句

<insert id="addCategory" parameter Type="Category">
    insert into category_table (name) values (#{name})
</insert>

Category c=new Category();
c.setName("插入一条Category数据");
session.insert("addCategory",c);

3、删除（delete）

通过session.delete()方法调用deleteCategory对应的SQL语句

<delete id="deleteCategory" parameterType="Category">
    delete from category_table where id=#{id}
</delete>

package com.demo.java;

import java.io.IOException;
import java.io.InputStream;
import java.uitl.List;

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.demo.pojo.Category;

public class TestMyBatis{
    public static void main(String[] args) throws IOException{
        String resource="mybatis-config.xml";
        InputStream inputStream=Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder();.build(inputStream);
        SqlSession session=sqlSessionFactory.openSession();

        Category c=new Category();
        c.setId(6);
        session.delete("deleteCategory",c);

        listAll(session);

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

    private static void listAll(SqlSession session){
        List<Category> list=session.selectList("listCategory");
        for(Category c:cs){
            System.out.println(c.getName());
        }
    }

}

4、修改（update）

通过session.update()方法调用updateCategory对应的SQL语句

<update id="updateCategory" parameterType="Category">
    update category_table set name=#{name} where id=#{id}
</update>

package com.demo.java;

import java.io.IOException;
import java.io.InputStream;
import java.uitl.List;

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.demo.pojo.Category;

public class TestMyBatis{
    public static void main(String[] args) throws IOException{
        String resource="mybatis-config.xml";
        InputStream inputStream=Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder();.build(inputStream);
        SqlSession session=sqlSessionFactory.openSession();

        Category c=session.selectOne("getCategory",3);
        c.setName("修改了Category名称");
        session.update("updateCategory",c);

        listAll(session);

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

    private static void listAll(SqlSession session){
        List<Category> list=session.selectList("listCategory");
        for(Category c:cs){
            System.out.println(c.getName());
        }
    }

}

5、模糊查询（like）

　　修改Category.xml，提供listCategoryByName查询语句

mysql的写法是如下：利用concat('%',#{0},'%')

<select id="listCategoryByName" parmaeterType="string" resultType="Category">
    select * from category_table where name like concat('%',#{0},'%')
</select>

oracle的写法如下：'%'||#{0}||'%'

select * from category_table where name like '%'||#{0}||'%'

<?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.how2java.pojo">
        <select id="listCategoryByName"  parameterType="string" resultType="Category">
            select * from   category_  where name like concat('%',#{0},'%')
        </select>
    </mapper>

测试代码如下：

package com.demo.java;

import java.io.IOException;
import java.io.InputStream;
import java.uitl.List;

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.demo.pojo.Category;

public class TestMyBatis{
    public static void main(String[] args) throws IOException{
        String resource="mybatis-config.xml";
        InputStream inputStream=Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder();.build(inputStream);
        SqlSession session=sqlSessionFactory.openSession();

        List<Category> cs=session.selectList("listCategoryByName","hello");
        for(Category c:cs){
            system.out.println(c.getName());
        }

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

}

6、多条件查询

同样还是修改Category.xml配置文件

<select id="listCategoryByIdAndName" parameterType="map" resultType="Category">
    select * from category_table where id>#{id} and name like concat('%',#{name},'%')
</select>

因为有多个参数，而selectList方法只能结构一个参数对象，所以需要把多个参数放在map里，然后把这个map对象作为参数传递进去

Map<String,Object> params=new HashMap<>():

params.put("id",3);
params.put("name","hello");
List<Category> cs=session.selectList("listCategoryByIdAndName",params);

package com.demo.java;

import java.io.IOException;
import java.io.InputStream;
import java.uitl.List;

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.demo.pojo.Category;

public class TestMyBatis{
    public static void main(String[] args) throws IOException{
        String resource="mybatis-config.xml";
        InputStream inputStream=Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder();.build(inputStream);
        SqlSession session=sqlSessionFactory.openSession();

        Map<String,Object> params=new HashMap<>();
        params.put("id",3);
        params.put("name","cat");
        List<Category> cs=session.selectList("listCategoryByIdAndName",params);
        for(Category c:cs){
            system.out.println(c.getName());
        }

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

}