Mybatis应用

工具类MyBatisUtils

在上一篇博客中 通过sqlsession 中 写了一个就简单的查询方法 并输出测试  我们发现 几乎所有的增删该查 都会调用 sqlsession 这样得到代码十分的冗余 所有在这里我们将这些公共的代码 都提到了一个公共的静态类既方便理解也方便后期的维护

package cn.wh.util;

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

import java.io.IOException;
import java.io.InputStream;
public class MybatisUtil {
        static String path="mybatis-config.xml";
        static InputStream is;
        static SqlSessionFactory factory;
    static {
        try {
            is = org.apache.ibatis.io.Resources.getResourceAsStream(path);
            factory=new  SqlSessionFactoryBuilder().build(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession() {
        return factory.openSession();
    }
}

下面我写一个简单的案例 来书写一下这个MyBatisUtils的使用（接口和小配置的XML文件这里就不展示了 只是展示一下MyBatisUtils的使用）

 @Test //使用工具类 MybatisUtil
    public void  MybatisUtil(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        User user= sqlSession.selectOne("SelectUser");
        System.out.println(user.getUname()+"=");
    }

这里我们仅仅用了三行代码就实现了这个查询 还是比较便于开发的

getMapper()

getMapper的作用，获取到接口，直接通过点的方式调用方法，以免直接手打的方式写错方法名，（强类型的方式）

   public  void  FirstList(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUserDao mapper = sqlSession.getMapper(IUserDao.class);
        Map<String ,Object> map=new HashMap<String ,Object>() ;
        //Key千万一定要和实体类对应
        map.put("uname","1");
        map.put("upwd","1");
        List<User> users = mapper.conditionFirst(map);
        System.out.println(users.size());
    }

在mybatis中 有一些智能标签 

他分为 where ,if ,choose ,foreach的array方式 ,foreach的list方式 ,foreach的list自定义类型方式

下面我书写两个例子

  <!--智能标签forearch 数组-->
    <select id="conditionByforearch" resultMap="MessageResult">
     SELECT * from user 
     <where>
         uid in
         <foreach collection="array" item="myid" open="(" close=")" separator=",">
          #{myid}
         </foreach>
     </where>
    </select>
    <!--智能标签forearch 集合-->
    <select id="conditionByforearchList" resultMap="MessageResult">
        SELECT * from user
        <where>
            uid in
            <foreach collection="list" item="myid" open="(" close=")" separator=",">
                #{myid}
            </foreach>
        </where>
    </select>
    <!--智能标签forearch 自定义集合-->
    <select id="conditionByforearchListSecond" resultMap="MessageResult">
        SELECT * from user
        <where>
            uid in
            <foreach collection="list" item="user" open="(" close=")" separator=",">
                #{user.uid}
            </foreach>
        </where>
    </select>

测试类

  @Test //智能标签 forearch 数组
    public  void  conditionByforearch(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUserDao mapper = sqlSession.getMapper(IUserDao.class);
        int [] bookid={1,2};
        List<User> condition = mapper.conditionByforearch(bookid);
        for (User item:condition
             ) {
            System.out.println(item.getUname());
        }
    }
    @Test //智能标签 forearch 集合
    public  void  conditionByforearchList(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUserDao mapper = sqlSession.getMapper(IUserDao.class);
     List<Integer> list=new ArrayList<>();
            list.add(1);
        List<User> condition = mapper.conditionByforearchList(list);
        for (User item:condition
                ) {
            System.out.println(item.getUname());
        }
    }
    @Test //智能标签 forearch 集合自定义
    public  void  SecondconditionByforearchList(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUserDao mapper = sqlSession.getMapper(IUserDao.class);
        List<User> list=new ArrayList<User>();
        User user=new User();
        user.setUid(1);
        list.add(user);
        User user1=new User();
        user1.setUid(2);
        list.add(user1);
        List<User> condition = mapper.conditionByforearchListSecond(list);
        for (User item:condition
             ) {
            System.out.println(item.getUname());
        }

    }

这些智能标签大大增加了我们的开发速度，从而也减少我们的代码数量

多表关联查询（有一点难理解 整整弄了半天  ）

先看一下实体类吧

package cn.wh.entity;

import java.util.ArrayList;
import java.util.List;

public class UserType {
    private Integer typeid;
    private  String typeName;
    private  Integer uid;

    private List<User> users=new ArrayList<User>();

    public List<User> getUsers() {
        return users;
    }

    public void setUsers(List<User> users) {
        this.users = users;
    }

    public Integer getTypeid() {
        return typeid;
    }

    public void setTypeid(Integer typeid) {
        this.typeid = typeid;
    }

    public String getTypeName() {
        return typeName;
    }

    public void setTypeName(String typeName) {
        this.typeName = typeName;
    }

    public Integer getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }
}

一共两个实体类这是第二个

package cn.wh.entity;

public class User {

    // 用户id
    private int uid;
    // 用户名
    private String uname;
    //密码
    private  String upwd;
    //手机
    private  String phone;

    private  UserType  userType;

    public UserType getUserType() {
        return userType;
    }

    public void setUserType(UserType userType) {
        this.userType = userType;
    }

    public String getUpwd() {
        return upwd;
    }

    public void setUpwd(String upwd) {
        this.upwd = upwd;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }


    public int getUid() {
        return uid;
    }
    public void setUid(int uid) {
        this.uid = uid;
    }
    public String getUname() {
        return uname;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
}

第一套方式

<?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="cn.wh.dao.IUserType">
    <resultMap type="cn.wh.entity.UserType" id="UserType">
        <id column="typeid" jdbcType="INTEGER" property="typeid"/>
        <result column="typeName" jdbcType="VARCHAR" property="typeName" />


        <collection property="users" ofType="cn.wh.entity.User">
            <id column="uid" jdbcType="INTEGER" property="uid"/>
            <result column="uname" jdbcType="VARCHAR" property="uname" />
        </collection>
    </resultMap>

    <resultMap type="cn.wh.entity.UserType" id="UserType1">
        <id column="typeid" jdbcType="INTEGER" property="typeid"/>
        <result column="typeName" jdbcType="VARCHAR" property="typeName" />
        <collection property="users" ofType="cn.wh.entity.User" select="ss" column="typeid">
        </collection>
    </resultMap>
<select id="listType" resultMap="UserType">
select user.uid from usertype,user
where user.typeid=usertype.typeid
and user.uid='1'


</select>
    <select id="UserTypecondition" resultMap="UserType1">
         SELECT typeid from  usertype
        where typeid='1'
    </select>
    <select id="ss" resultType="cn.wh.entity.User">
        SELECT * from user
        where typeid='1'
  </select>
</mapper>

测试类

    @Test
 public  void  userTypeList(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUserType mapper = sqlSession.getMapper(IUserType.class);
        UserType userType = mapper.listType();
        System.out.println(userType.getUsers().size());
    }
    //查询单一条 有条件 (一对多)
    @Test
    public  void  userTypeListcondition(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUserType mapper = sqlSession.getMapper(IUserType.class);
        UserType userType = mapper.UserTypecondition(1);
        List<User> users = userType.getUsers();
        System.out.println(users);
        for (User item:users
             ) {
            System.out.println(item.getUpwd());
        }
}

第二种方式

<?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="cn.wh.dao.IUser">

    <resultMap id="Users" type="cn.wh.entity.User">
        <id column="uid" jdbcType="INTEGER" property="uid"/>
        <result column="uname" jdbcType="VARCHAR" property="uname" />
        <association property="userType" javaType="cn.wh.entity.UserType">
            <id column="typeid" jdbcType="INTEGER" property="typeid"/>
            <result column="typeName" jdbcType="VARCHAR" property="typeName" />
        </association>
    </resultMap>
    <resultMap id="manyUsers" type="cn.wh.entity.User">
        <id column="uid" jdbcType="INTEGER" property="uid"/>
        <result column="uname" jdbcType="VARCHAR" property="uname" />
        <association property="userType" javaType="cn.wh.entity.UserType" column="uid" select="ss">
        </association>
    </resultMap>
<!--多对一-->
    <select id="findeUser" resultMap="Users">
    SELECT * from user,usertype where user.typeid=usertype.typeid and user.uid=#{uid}
    </select>
    <!--多对多-->
    <select id="findempmany" resultMap="manyUsers">
          SELECT uid from user
        where typeid='1'
    </select>
    <select id="ss" resultType="cn.wh.entity.UserType">
         SELECT * from  usertype
        where typeid='1'
    </select>

</mapper>

测试类

    //多对一
   @Test
    public  void manyTOne(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUser mapper = sqlSession.getMapper(IUser.class);
        User user = mapper.findeUser(2);

        System.out.println(user.getUname()+"=");
    }
    //多对多
    @Test
    public  void manyTomany(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        IUser mapper = sqlSession.getMapper(IUser.class);
        User user = mapper.findempmany(1);
        System.out.println(user.getUserType().getUid());
    }