Mybatis應用

時間 2020-05-20

原文原文鏈接

工具類MyBatisUtils

在上一篇博客中經過sqlsession 中寫了一個就簡單的查詢方法並輸出測試咱們發現幾乎全部的增刪該查都會調用 sqlsession 這樣獲得代碼十分的冗餘全部在這裏咱們將這些公共的代碼都提到了一個公共的靜態類既方便理解也方便後期的維護java

 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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下面我寫一個簡單的案例來書寫一下這個MyBatisUtils的使用（接口和小配置的XML文件這裏就不展現了只是展現一下MyBatisUtils的使用）sql

1  @Test //使用工具類 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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這裏咱們僅僅用了三行代碼就實現了這個查詢仍是比較便於開發的apache

getMapper()

getMapper的做用，獲取到接口，直接經過點的方式調用方法，以避免直接手打的方式寫錯方法名，（強類型的方式）數組

public  void FirstList(){ SqlSession sqlSession = MybatisUtil.getSqlSession(); IUserDao mapper = sqlSession.getMapper(IUserDao.class); Map<String ,Object> map=new HashMap<String ,Object>() ; //Key千萬必定要和實體類對應
        map.put("uname","1"); map.put("upwd","1"); List<User> users = mapper.conditionFirst(map); System.out.println(users.size()); }

在mybatis中有一些智能標籤

他分爲 where ,if ,choose ,foreach的array方式 ,foreach的list方式 ,foreach的list自定義類型方式session

下面我書寫兩個例子mybatis

 1   <!--智能標籤forearch 數組-->
 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     <!--智能標籤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     <!--智能標籤forearch 自定義集合-->
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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測試類app

 1   @Test //智能標籤 forearch 數組
 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 //智能標籤 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 //智能標籤 forearch 集合自定義
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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這些智能標籤大大增長了咱們的開發速度，從而也減小咱們的代碼數量ide

多表關聯查詢（有一點難理解整整弄了半天）工具

先看一下實體類吧測試

 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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一共兩個實體類這是第二個

 1 package cn.wh.entity;  2 
 3 public class User {  4 
 5     // 用戶id
 6     private int uid;  7     // 用戶名
 8     private String uname;  9     //密碼
10     private String upwd; 11     //手機
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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測試類

 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     //查詢單一條 有條件 (一對多)
 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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第二種方式

 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 <!--多對一-->
22     <select id="findeUser" resultMap="Users">
23     SELECT * from user,usertype where user.typeid=usertype.typeid and user.uid=#{uid} 24     </select>
25     <!--多對多-->
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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測試類

 1     //多對一
 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     //多對多
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     }