mybatis（二）接口编程 、动态sql 、批量删除 、动态更新、连表查询

原理等不在赘述，这里主要通过代码展现。

在mybatis（一）基础上，新建一个dao包，并在里面编写接口，然后再在xml文件中引入接口路径，其他不变，在运用阶段将比原始方法更节约时间，因为不用再去手动的

引用sql,我们只需调用dao层的方法，然后让dao层的方法去找配置文件，去找sql，sql查询数据并赋值给对象，或者设置对象参数值在经过sql更新到数据库，小伙伴们这就是

orm对象关系映射模型！（个人见解，不对之处请指正。）

新增后项目：

一、新建一个com.ckx.dao包，并new一个（interface）DeptDao.java。

DeptDao.java：

package com.ckx.dao;

import java.util.List;

import org.apache.ibatis.annotations.Param;

import com.ckx.entity.Dept;

public interface DeptDao {
    //通过ID查数据
    public Dept selectDeptById(int deptno);
    //查询一个结果集
    public List<Dept> selectDeptAll();
    //多条件动态 ，查询注意@Param的重要性，没有回报参数not find错误
    public List<Dept> selectDeptByMore(@Param("deptno") int deptno,@Param("dname") String dname);
    //根据ID动态修改
    public int updateDeptById(Dept d);
    //批量删除
    public int deleteDepts(List<Integer> list);
    //新增
    public int insertDept(Dept d);
    public int insertDept2(Dept d);
    //多表关联
    public Dept selectDeptEmps(int t);

}

二、配置Dept.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">
<!--接口编程-->
<mapper namespace="com.ckx.dao.DeptDao">

    <resultMap type="Dept" id="DeptList">
        <result column="deptno" property="deptno"/>
        <result column="dname" property="dname"/>
        <result column="loc" property="loc"/>
        <!--        代表集合数据  property：实体bean中的属性名称 ofType：数据类型 -->
        <collection property="emps" ofType="Emp">
            <result column="EMPNO" property="empno" />
            <result column="ENAME" property="ename" />
            <result column="JOB" property="job" />
            <result column="MGR" property="mgr" />
            <result column="HIREDATE" property="hiredate" />
            <result column="SAL" property="sal" />
            <result column="COMM" property="comm" />
            <result column="DEPNO" property="depno" />
        </collection>
    </resultMap>
<!--    通过ID查询-->
    <select id="selectDeptById" parameterType="int" resultType="Dept">
        select * from dept where deptno = #{deptno}
    </select>
<!--    查询整张表，注意返回参数是一个DeptList集合，这个需要在上面配置-->
    <select id="selectDeptAll"  resultMap="DeptList">
        select * from dept
    </select>
<!--    多参数动态查询-->
    <select id="selectDeptByMore"  resultMap="DeptList">
        select * from dept
        <where>
            <if test="deptno != 0">
                deptno = #{deptno}
            </if>
            <if test="dname != null">
                or dname like #{dname}
            </if>
        </where>
    </select>
<!--    动态更新数据-->
    <update id="updateDeptById"  parameterType="Dept">
        update
        dept
        <set>
            <if test="deptno != null">
                 dname = #{dname},
            </if>
            <if test="deptno != null">
                 loc = #{loc}
            </if>
        </set>
        where
        deptno = #{deptno}
    </update>
<!--    批量删除-->
    <delete id="deleteDepts" parameterType="list">
        delete from dept where deptno in
        <foreach item="item" index="index" collection="list" open="("
            separator=", " close=") ">
            #{item}
         </foreach>
    </delete>
<!--    新增数据-->
    <insert id="insertDept" parameterType="Dept" >
        insert into dept (deptno,dname,loc) values (#{deptno},#{dname},#{loc})
    </insert>
<!--    连表查询，注意1、到层返回值为对象类本身 2、查询返回值为list集合。-->
    <select id="selectDeptEmps" parameterType="int" resultMap="DeptList">
        SELECT d.DNAME,e.*  FROM dept d,emp e WHERE d.DEPTNO=e.DEPNO and d.DEPTNO = #{deptno}
    </select>

<!--    未完成-->
    <sql id='dept'>TEST_USER</sql>
     <!-- 注意这里需要先查询自增主键值 -->
     <insert id="insertDept2" parameterType="Dept">
         <selectKey keyProperty="deptno" resultType="int" order="BEFORE">
             SELECT LAST_INSERT_deptno()
         </selectKey>
         insert into <include refid="dept" /> (deptno,dname,loc)
             values ( #{deptno},#{dname},#{loc} )
     </insert>

</mapper>

三、测试

DeptTest.java：

package com.ckx.test;

import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

import javax.mail.Session;

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.ckx.dao.DeptDao;
import com.ckx.entity.Dept;
import com.ckx.entity.Emp;

public class DeptTest {
    static SqlSessionFactory sessionFactory;
    static Reader reader;
    static SqlSession sqlSession;

    static {
        try {
            reader = Resources.getResourceAsReader("config.xml");
            sessionFactory = new SqlSessionFactoryBuilder().build(reader);
            sqlSession = sessionFactory.openSession();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void select(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        Dept d =  dao.selectDeptById(10);
        System.out.println(d.getDname());
    }

    public void selectDeptAll(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        List<Dept> list = dao.selectDeptAll();

        for (Dept dept : list) {
            String s = dept.getDname();
            System.out.println(s);
        }

        Iterator<Dept> ite = list.iterator();
        while (ite.hasNext()) {
            Dept d = ite.next();
            String ss = d.getLoc();
            System.out.println(ss);
        }

        for (int i = 0; i < list.size(); i++) {
            Dept d = list.get(i);
            int t = d.getDeptno();
            System.out.println(t);
        }
    }

    public void selectDeptByMore(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        List<Dept> list = dao.selectDeptByMore(20,"A%");
        Iterator<Dept> it = list.iterator();
        while (it.hasNext()) {
            Dept dept = (Dept) it.next();
            String s = dept.getDname();
            System.out.println(s);
        }
    }

    public void updateDeptById(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        Dept d = new Dept();
        d.setDeptno(10);
        d.setDname("ASC");
        d.setLoc("desc");
        dao.updateDeptById(d);
        System.out.println(d.getDeptno()+d.getDname()+d.getLoc());
        sqlSession.commit();
    }

    public void deleteDepts(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        List<Integer> list = new ArrayList<Integer>();
        list.add(0);
        dao.deleteDepts(list);
    }

    public void insertDept(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        Dept d = new Dept();
        d.setDeptno(10);
        d.setDname("assc");
        d.setLoc("deff");
        dao.insertDept(d);
        sqlSession.commit();
    }
    //多表联查
    public void selectDeptEmps(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        Dept d = dao.selectDeptEmps(10);
        List<Emp> list = d.getEmps();
        for (Emp emp : list) {
            String s = emp.getEname();
            System.out.println(d.getDname()+"\t"+s);
        }

    }
    ;
    //主键自增为完成
     public void insertDept2(){
        DeptDao dao = sqlSession.getMapper(DeptDao.class);
        Dept d = new Dept();
        d.setDname("sss");
        d.setLoc("ddd");
        dao.insertDept(d);
        sqlSession.commit();
        System.out.println(d.getDeptno());
    }

    public static void main(String[] args) {
        DeptTest dt = new DeptTest();
        dt.selectDeptEmps();
    }
}

以上皆为测试过运行正常的方法，每一个方法的调用只需能改dt后的方法即可。

具体注意说明：