MyBatis框架學習二

時間 2019-12-16

標籤 java mysql sql 數據庫 apache session mybatis app dom 測試欄目 MyBatis 简体版

原文原文鏈接

增刪改查操做

mapper接口本質就是原來的Dao接口，知識爲了方便咱們的書寫，一個mapper接口對應一個mapper映射文件java

將UserMapper改名爲UserDao，說明本質mysql

修改對應的mapper映射文件的namespace屬性，對應上接口。sql

編寫接口

 1 package com.like.dao;
 2 
 3 import com.like.pojo.User;
 4 
 5 import java.util.List;
 6 
 7 public interface UserDao{
 8     //獲取所有的用戶
 9     List<User>selectUser();
10     
11     //根據id查找用戶
12     User electUserById(int id);
13 
14     //添加一個用戶
15     int addUser(User user);
16 
17     //刪除用戶
18     int deleteUserByID(int id);
19 
20     //修改用戶
21     int updateUser(User user);        
22  }

對應的mapper語句編寫

 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標籤的namespace對應的Mapper接口的類，報名+類名-->
 6 <mapper namespace="com.like.dao.UserDao">
 7 <!--select標籤的id對應映射接口的方法名字    resultType:返回結果的類型   中間就編寫sql語句-->
 8 <select id="selectUser" resultType="com.like.pojo.User">
 9 select*from user
10 </select>
11 <select id="selectUserById" resultType="com.like.pojo.User">
12 select*from user where id =#{id}
13 </select>
14 
15 <!--咱們須要接受一個自定義的對象(引用隊形) 須要設置parameterTpye,爲參數類型
16       接收這個對象的值，直接使用#{對象字段名}
17 -->
18 <insert id="addUser" parameterType="com.like.pojo.User">
19 inset into user(id,name,pwd)values(#{id},#{name},#{pwd})
20 </insert>
21 
22 <delete id="deleteUserByID" parameterType="int">
23 delete from user where id =#{id}
24 </delete>
25 
26 <update id="updateUser" parameterType="com.like.pojo.User">
27 updata user set name=#{name},pwd=#{pwd}where id=#{id}
28 </update>
29 </mapper>

測試類

 1 package com.like.dao;
 2 
 3 import com.like.dao.UserDao;
 4 import com.like.pojo.User;
 5 import dom.like.utils.MyBatisUtils;
 6 import org.apache.ibatis.session.SqlSession;
 7 import org.apache.ibatis.session.SqlSessionFactory;
 8 import org.junit.Test;
 9 import java.util.List;
10 
11 public class UserMapperTest{
12 
13   @Test
14   public void selectUser(){
15    //1.拿到sqlSessionFactory對象
16   SqlSessionFactory sqlSessionFactory=MyBatisUtils.getSqlSessionFactory();
17   //2.經過sqlSessionFactory對象openSession()建立一個sqlSession.
18   SqlSession sqlSession =sqlSessionFactory.openSession();
19   //3.經過sqlSession得到mapper對象，參數爲映射文件對應的接口類的class隊形
20   UserDao mapper =sqlSession.getMapper(UserDao.class);
21   //4.經過mapper對象來執行操做；
22   List<User>users =mapper.selectUser();
23   //得到結果集
24   for (User user : users){
25   System.out.println(user);
26 }
27 sqlSession.close();//關閉sqlSession
28 
29 }      
30 @Test
31     public void addUser(){
32         User user = new User(4,"qinjiang","123456");
33 
34         SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
35         SqlSession sqlSession = sqlSessionFactory.openSession();
36         UserDao mapper = sqlSession.getMapper(UserDao.class);
37 
38         int i = mapper.addUser(user);
39 
40         //沒有插入成功的緣由：沒有提交事務；
41         sqlSession.commit(); //提交事務
42         sqlSession.close(); //關閉sqlSession
43 
44         if (i>0){
45             System.out.println("插入成功！");
46         }
47 
48     }
49 
50     @Test
51     public void deleteUserByID(){
52         SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession();
53         UserDao mapper = sqlSession.getMapper(UserDao.class);
54         int i = mapper.deleteUserByID(4);
55 
56         //記得提交事務，不然刪除不成功！
57         sqlSession.commit();//提交事務
58         sqlSession.close();//關閉
59 
60         if (i>0){
61             System.out.println(i);
62         }
63     }
64 
65     @Test
66     public void updateUser(){
67         SqlSession sqlSession = MyBatisUtils.getSqlSessionFactory().openSession();
68         UserDao mapper = sqlSession.getMapper(UserDao.class);
69         User user = new User(1,"李柯","like");
70         mapper.updateUser(user);
71 
72         sqlSession.commit();
73         sqlSession.close();
74 
75     }
76 }

注意點總結數據庫

增改刪須要提交事務！apache

若是出現亂碼，如今sql中進行測試，sql沒問題，就檢查配置文件session

jdbc:mysql://localhost:3306/mybatis?
useSSL=true&amp;useUnicode=true&amp;characterEncoding="utf-8"

參數問題mybatis

若是時基本數據類型，能夠省略，但建議寫上引用類型必須寫指定的包名+類名。app

配置文件的詳解

mybatis-config文件解析dom

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE configuration>
 3               PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4               "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 configuration  配置
 6     properties  配置文件
 7     settiongs    mybatis設置
 8     typeHandlers    爲java類起別名
 9     objectFactory    對象工廠
10     plugins    插件
11     environments    環境
12         transactionManager    :事務管理
13         dataSource :數據源
14     mappers     映射器

優化配置文件測試

建立一個database.properties

1 driver = com.mysql.jdbc.Driver
2 url = jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=utf-8
3 username = root
4 password = 123456

在mybatis核心配置文件中引入properties配置文件,並用${}表達式引入其中的值

 1 <configuration>
 2 
 3     <!--配置文件修改-->
 4     <properties resource="database.properties"/>
 5 
 6     <environments default="development">
 7         <environment id="development">
 8             <transactionManager type="JDBC"/>
 9             <dataSource type="POOLED">
10                 <property name="driver" value="${driver}"/>
11                 <property name="url" value="${url}"/>
12                 <property name="username" value="${username}"/>
13                 <property name="password" value="${password}"/>
14             </dataSource>
15         </environment>
16     </environments>
17 
18     <mappers>
19         <mapper resource="com/kuang/dao/userMapper.xml"/>
20     </mappers>
21 
22 </configuration>

優化別名

注意點,位置必須正確

 1 <!--配置別名-->
 2 <typeAliases>
 3 
 4     <!--配置指定類的別名-->
 5     <typeAlias type="com.like.pojo.User" alias="User"/>
 6 
 7     <!--
 8         能夠爲一個包的全部類指定別名，這個別名爲類名
 9         com.like.pojo.User    -  >  User
10         com.like.pojo.Student   -  >  Student
11 
12         -->
13     <package name="com.like.pojo"/>
14 
15 </typeAliases>

優化完畢後咱們在mapper映射文件中就能夠使用別名了

 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 
 6 <!--mapper標籤的namespace對應Mapper接口的類,包名+類名-->
 7 <mapper namespace="com.like.dao.UserDao">
 8 
 9     <!--select標籤的id對應映射接口的方法名字  resultType:返回結果的類型  中間就編寫sql語句-->
10     <select id="selectUser" resultType="User">
11     select * from user
12     </select>
13 
14     <select id="selectUserById" resultType="User">
15         select * from user where id = #{id}
16     </select>
17 
18     <!--
19     咱們須要接受一個自定義的對象（引用對象），須要設置parameterType，爲參數類型
20     接受這個對象的值，直接使用 #{對象字段名}
21     -->
22     <insert id="addUser" parameterType="User">
23         insert into user(id ,name, pwd) values (#{id},#{name},#{pwd})
24     </insert>
25 
26     <delete id="deleteUserByID" parameterType="int">
27         delete from user where id = #{id}
28     </delete>
29 
30     <update id="updateUser" parameterType="User">
31         update user set name =#{name},pwd = #{pwd} where id = #{id}
32     </update>
33 
34 </mapper>

環境配置

 1 <environments default="development">
 2     <environment id="development">
 3         <transactionManager type="JDBC"/>
 4         <dataSource type="POOLED">
 5             <property name="driver" value="${driver}"/>
 6             <property name="url" value="${url}"/>
 7             <property name="username" value="${username}"/>
 8             <property name="password" value="${password}"/>
 9         </dataSource>
10     </environment>
11 </environments>

映射器

1,resource(推薦)

2,url

3,class

4.package

<!-- 使用相對於類路徑的資源引用 -->
<mappers>
  <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
  <mapper resource="org/mybatis/builder/BlogMapper.xml"/>
  <mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>