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

 1 package cn.wh.util;
 2 
 3 import org.apache.ibatis.session.SqlSession;
 4 import org.apache.ibatis.session.SqlSessionFactory;
 5 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 6 
 7 import java.io.IOException;
 8 import java.io.InputStream;
 9 public class MybatisUtil {
10         static String path="mybatis-config.xml";
11         static InputStream is;
12         static SqlSessionFactory factory;
13     static {
14         try {
15             is = org.apache.ibatis.io.Resources.getResourceAsStream(path);
16             factory=new  SqlSessionFactoryBuilder().build(is);
17         } catch (IOException e) {
18             e.printStackTrace();
19         }
20     }
21     public static SqlSession getSqlSession() {
22         return factory.openSession();
23     }
24 }

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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）

1  @Test //使用工具类 MybatisUtil
2     public void  MybatisUtil(){
3         SqlSession sqlSession = MybatisUtil.getSqlSession();
4         User user= sqlSession.selectOne("SelectUser");
5         System.out.println(user.getUname()+"=");
6     }

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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

 1   <!--智能标签forearch 数组-->
 2     <select id="conditionByforearch" resultMap="MessageResult">
 3      SELECT * from user 
 4      <where>
 5          uid in
 6          <foreach collection="array" item="myid" open="(" close=")" separator=",">
 7           #{myid}
 8          </foreach>
 9      </where>
10     </select>
11     <!--智能标签forearch 集合-->
12     <select id="conditionByforearchList" resultMap="MessageResult">
13         SELECT * from user
14         <where>
15             uid in
16             <foreach collection="list" item="myid" open="(" close=")" separator=",">
17                 #{myid}
18             </foreach>
19         </where>
20     </select>
21     <!--智能标签forearch 自定义集合-->
22     <select id="conditionByforearchListSecond" resultMap="MessageResult">
23         SELECT * from user
24         <where>
25             uid in
26             <foreach collection="list" item="user" open="(" close=")" separator=",">
27                 #{user.uid}
28             </foreach>
29         </where>
30     </select>

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测试类

 1   @Test //智能标签 forearch 数组
 2     public  void  conditionByforearch(){
 3         SqlSession sqlSession = MybatisUtil.getSqlSession();
 4         IUserDao mapper = sqlSession.getMapper(IUserDao.class);
 5         int [] bookid={1,2};
 6         List<User> condition = mapper.conditionByforearch(bookid);
 7         for (User item:condition
 8              ) {
 9             System.out.println(item.getUname());
10         }
11     }
12     @Test //智能标签 forearch 集合
13     public  void  conditionByforearchList(){
14         SqlSession sqlSession = MybatisUtil.getSqlSession();
15         IUserDao mapper = sqlSession.getMapper(IUserDao.class);
16      List<Integer> list=new ArrayList<>();
17             list.add(1);
18         List<User> condition = mapper.conditionByforearchList(list);
19         for (User item:condition
20                 ) {
21             System.out.println(item.getUname());
22         }
23     }
24     @Test //智能标签 forearch 集合自定义
25     public  void  SecondconditionByforearchList(){
26         SqlSession sqlSession = MybatisUtil.getSqlSession();
27         IUserDao mapper = sqlSession.getMapper(IUserDao.class);
28         List<User> list=new ArrayList<User>();
29         User user=new User();
30         user.setUid(1);
31         list.add(user);
32         User user1=new User();
33         user1.setUid(2);
34         list.add(user1);
35         List<User> condition = mapper.conditionByforearchListSecond(list);
36         for (User item:condition
37              ) {
38             System.out.println(item.getUname());
39         }
40 
41     }

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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

 1 package cn.wh.entity;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 public class UserType {
 7     private Integer typeid;
 8     private  String typeName;
 9     private  Integer uid;
10 
11     private List<User> users=new ArrayList<User>();
12 
13     public List<User> getUsers() {
14         return users;
15     }
16 
17     public void setUsers(List<User> users) {
18         this.users = users;
19     }
20 
21     public Integer getTypeid() {
22         return typeid;
23     }
24 
25     public void setTypeid(Integer typeid) {
26         this.typeid = typeid;
27     }
28 
29     public String getTypeName() {
30         return typeName;
31     }
32 
33     public void setTypeName(String typeName) {
34         this.typeName = typeName;
35     }
36 
37     public Integer getUid() {
38         return uid;
39     }
40 
41     public void setUid(Integer uid) {
42         this.uid = uid;
43     }
44 }

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一共两个实体类这是第二个

 1 package cn.wh.entity;
 2 
 3 public class User {
 4 
 5     // 用户id
 6     private int uid;
 7     // 用户名
 8     private String uname;
 9     //密码
10     private  String upwd;
11     //手机
12     private  String phone;
13 
14     private  UserType  userType;
15 
16     public UserType getUserType() {
17         return userType;
18     }
19 
20     public void setUserType(UserType userType) {
21         this.userType = userType;
22     }
23 
24     public String getUpwd() {
25         return upwd;
26     }
27 
28     public void setUpwd(String upwd) {
29         this.upwd = upwd;
30     }
31 
32     public String getPhone() {
33         return phone;
34     }
35 
36     public void setPhone(String phone) {
37         this.phone = phone;
38     }
39 
40 
41     public int getUid() {
42         return uid;
43     }
44     public void setUid(int uid) {
45         this.uid = uid;
46     }
47     public String getUname() {
48         return uname;
49     }
50     public void setUname(String uname) {
51         this.uname = uname;
52     }
53 }

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第一套方式

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE mapper
 3         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="cn.wh.dao.IUserType">
 6     <resultMap type="cn.wh.entity.UserType" id="UserType">
 7         <id column="typeid" jdbcType="INTEGER" property="typeid"/>
 8         <result column="typeName" jdbcType="VARCHAR" property="typeName" />
 9 
10 
11         <collection property="users" ofType="cn.wh.entity.User">
12             <id column="uid" jdbcType="INTEGER" property="uid"/>
13             <result column="uname" jdbcType="VARCHAR" property="uname" />
14         </collection>
15     </resultMap>
16 
17     <resultMap type="cn.wh.entity.UserType" id="UserType1">
18         <id column="typeid" jdbcType="INTEGER" property="typeid"/>
19         <result column="typeName" jdbcType="VARCHAR" property="typeName" />
20         <collection property="users" ofType="cn.wh.entity.User" select="ss" column="typeid">
21         </collection>
22     </resultMap>
23 <select id="listType" resultMap="UserType">
24 select user.uid from usertype,user
25 where user.typeid=usertype.typeid
26 and user.uid='1'
27 
28 
29 </select>
30     <select id="UserTypecondition" resultMap="UserType1">
31          SELECT typeid from  usertype
32         where typeid='1'
33     </select>
34     <select id="ss" resultType="cn.wh.entity.User">
35         SELECT * from user
36         where typeid='1'
37   </select>
38 </mapper>

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测试类

 1     @Test
 2  public  void  userTypeList(){
 3         SqlSession sqlSession = MybatisUtil.getSqlSession();
 4         IUserType mapper = sqlSession.getMapper(IUserType.class);
 5         UserType userType = mapper.listType();
 6         System.out.println(userType.getUsers().size());
 7     }
 8     //查询单一条 有条件 (一对多)
 9     @Test
10     public  void  userTypeListcondition(){
11         SqlSession sqlSession = MybatisUtil.getSqlSession();
12         IUserType mapper = sqlSession.getMapper(IUserType.class);
13         UserType userType = mapper.UserTypecondition(1);
14         List<User> users = userType.getUsers();
15         System.out.println(users);
16         for (User item:users
17              ) {
18             System.out.println(item.getUpwd());
19         }
20 }

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第二种方式

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE mapper
 3         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="cn.wh.dao.IUser">
 6 
 7     <resultMap id="Users" type="cn.wh.entity.User">
 8         <id column="uid" jdbcType="INTEGER" property="uid"/>
 9         <result column="uname" jdbcType="VARCHAR" property="uname" />
10         <association property="userType" javaType="cn.wh.entity.UserType">
11             <id column="typeid" jdbcType="INTEGER" property="typeid"/>
12             <result column="typeName" jdbcType="VARCHAR" property="typeName" />
13         </association>
14     </resultMap>
15     <resultMap id="manyUsers" type="cn.wh.entity.User">
16         <id column="uid" jdbcType="INTEGER" property="uid"/>
17         <result column="uname" jdbcType="VARCHAR" property="uname" />
18         <association property="userType" javaType="cn.wh.entity.UserType" column="uid" select="ss">
19         </association>
20     </resultMap>
21 <!--多对一-->
22     <select id="findeUser" resultMap="Users">
23     SELECT * from user,usertype where user.typeid=usertype.typeid and user.uid=#{uid}
24     </select>
25     <!--多对多-->
26     <select id="findempmany" resultMap="manyUsers">
27           SELECT uid from user
28         where typeid='1'
29     </select>
30     <select id="ss" resultType="cn.wh.entity.UserType">
31          SELECT * from  usertype
32         where typeid='1'
33     </select>
34 
35 </mapper>

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测试类

 1     //多对一
 2    @Test
 3     public  void manyTOne(){
 4         SqlSession sqlSession = MybatisUtil.getSqlSession();
 5         IUser mapper = sqlSession.getMapper(IUser.class);
 6         User user = mapper.findeUser(2);
 7 
 8         System.out.println(user.getUname()+"=");
 9     }
10     //多对多
11     @Test
12     public  void manyTomany(){
13         SqlSession sqlSession = MybatisUtil.getSqlSession();
14         IUser mapper = sqlSession.getMapper(IUser.class);
15         User user = mapper.findempmany(1);
16         System.out.println(user.getUserType().getUid());
17     }

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原文地址：https://www.cnblogs.com/wh1520577322/p/9266835.html

Mybatis应用

工具类MyBatisUtils

getMapper()

在mybatis中 有一些智能标签

在mybatis中有一些智能标签