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Java基础-SSM之mybatis多对多关联

　　　　　　　　　　　　Java基础-SSM之mybatis多对多关联

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　作者：尹正杰

一.准备测试环境（创建数据库表）

1>.创建teas，stus，links表

use yinzhengjie;

create table teas(id int primary key auto_increment , tname varchar(20)) ;

create table stus(id int primary key auto_increment , sname varchar(20)) ;
        
create table links(tid int , sid int) ;

alter table links add constraint fk_tid foreign key (tid) references teas(id) ;
    
alter table links add constraint fk_sid foreign key (sid) references stus(id) ;

2>.添加Maven依赖

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <project xmlns="http://maven.apache.org/POM/4.0.0"
 3          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 5     <modelVersion>4.0.0</modelVersion>
 6     <groupId>cn.org.yinzhengjie</groupId>
 7     <artifactId>Mybatis</artifactId>
 8     <version>1.0-SNAPSHOT</version>
 9     <dependencies>
10         <dependency>
11             <groupId>junit</groupId>
12             <artifactId>junit</artifactId>
13             <version>4.11</version>
14         </dependency>
15         <dependency>
16             <groupId>mysql</groupId>
17             <artifactId>mysql-connector-java</artifactId>
18             <version>5.1.17</version>
19         </dependency>
20         <dependency>
21             <groupId>org.mybatis</groupId>
22             <artifactId>mybatis</artifactId>
23             <version>3.2.1</version>
24         </dependency>
25     </dependencies>
26 </project>

3>.目录结构如下：

二.编写自定义类

1>.Stu.java 文件内容

 1 /*
 2 @author :yinzhengjie
 3 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 4 EMAIL:y1053419035@qq.com
 5 */
 6 package cn.org.yinzhengjie.mybatis.domain.one2many;
 7 
 8 import java.util.ArrayList;
 9 import java.util.List;
10 
11 /**
12  *    客户
13  */
14 public class Customer {
15     private Integer id ;
16     private String name ;
17     private int age ;
18 
19     //建立从Customer到Order之间一对多关系,因为一个客户可能会有多个订单。我们将多个订单放在一个list中。
20     private List<Order> orders = new ArrayList<Order>() ;
21 
22     public List<Order> getOrders() {
23         return orders;
24     }
25 
26     public void setOrders(List<Order> orders) {
27         this.orders = orders;
28     }
29 
30     public Integer getId() {
31         return id;
32     }
33 
34     public void setId(Integer id) {
35         this.id = id;
36     }
37 
38     public String getName() {
39         return name;
40     }
41 
42     public void setName(String name) {
43         this.name = name;
44     }
45 
46     public int getAge() {
47         return age;
48     }
49 
50     public void setAge(int age) {
51         this.age = age;
52     }
53 }

2>.Tea.java 文件内容

 1 /*
 2 @author :yinzhengjie
 3 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 4 EMAIL:y1053419035@qq.com
 5 */
 6 package cn.org.yinzhengjie.mybatis.domain.many2many;
 7 
 8 import java.util.ArrayList;
 9 import java.util.List;
10 
11 public class Tea {
12     private Integer id ;
13     private String tname ;
14 
15     public Tea(String tname){
16         this.tname = tname ;
17     }
18     public Tea(){
19     }
20     private List<Stu> stus = new ArrayList<Stu>() ;
21 
22     public Integer getId() {
23         return id;
24     }
25 
26     public void setId(Integer id) {
27         this.id = id;
28     }
29 
30     public String getTname() {
31         return tname;
32     }
33 
34     public void setTname(String tname) {
35         this.tname = tname;
36     }
37 
38     public List<Stu> getStus() {
39         return stus;
40     }
41 
42     public void setStus(List<Stu> stus) {
43         this.stus = stus;
44     }
45 
46     public void addStus(Stu...stus){
47         for(Stu ss : stus){
48             this.getStus().add(ss) ;
49             ss.getTeas().add(this) ;
50         }
51     }
52 }

三.编写配置文件

1>.mybatis-config.xml 文件内容（需要开启批处理模式）

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 
 3 <!DOCTYPE configuration
 4         PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 5         "http://mybatis.org/dtd/mybatis-3-config.dtd">
 6 <configuration>
 7     <properties>
 8         <property name="driver" value="com.mysql.jdbc.Driver"/>
 9         <!--注意 : “?characterEncoding=utf-8&amp;autoReconnect=true&amp;failOverReadOnly=false&amp;allowMultiQueries=true” 表示开启批处理模式-->
10         <property name="url" value="jdbc:mysql://localhost:5200/yinzhengjie?characterEncoding=utf-8&amp;autoReconnect=true&amp;failOverReadOnly=false&amp;allowMultiQueries=true"/>
11         <property name="username" value="root"/>
12         <property name="password" value="yinzhengjie"/>
13     </properties>
14 
15     <!-- 我们使用typeAliases标签给我们自定义类起个别名。-->
16     <typeAliases>
17         <typeAlias type="cn.org.yinzhengjie.mybatis.domain.many2many.Tea" alias="_Tea" />
18         <typeAlias type="cn.org.yinzhengjie.mybatis.domain.many2many.Stu" alias="_Stu" />
19     </typeAliases>
20 
21     <environments default="development">
22         <environment id="development">
23             <transactionManager type="JDBC"/>
24             <dataSource type="POOLED">
25                 <property name="driver" value="${driver}"/>
26                 <property name="url" value="${url}"/>
27                 <property name="username" value="${username}"/>
28                 <property name="password" value="${password}"/>
29             </dataSource>
30         </environment>
31     </environments>
32     <mappers>
33         <!-- 我们使用mapper标签指定映射文件，使用resource指定具体的路径，如果没有写绝对路径，默认的根路径就在resources目录中-->
34         <mapper resource="TeaMapper.xml"/>
35         <mapper resource="StuMapper.xml"/>
36     </mappers>
37 </configuration>

2>.StuMapper.xml 文件内容

1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4 <!-- 定义名字空间 -->
5 <mapper namespace="stus">
6     <insert id="insert" useGeneratedKeys="true" keyProperty="id">
7         insert into stus(sname) values(#{sname}) ;
8     </insert>
9 </mapper>

3>.TeaMapper.xml 文件内容

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 3         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4 <!-- 定义名字空间 -->
 5 <mapper namespace="teas">
 6     <insert id="insert" useGeneratedKeys="true" keyProperty="id">
 7         insert into teas(tname) values(#{tname}) ;
 8     </insert>
 9     
10     <update id="updateLinks">
11       <foreach collection="stus" item="s">
12         insert into links(tid,sid) values(#{id}, #{s.id}) ;
13       </foreach>
14     </update>
15 
16     <delete id="deleteOne">
17       delete from links where tid = #{id} ;
18       delete from teas where id = #{id}
19     </delete>
20 
21 
22 
23     <update id="update">
24         <!--先删除关系(主键约束)-->
25       delete from links where tid = #{id} ;
26         <!--更新teas表信息-->
27       update teas set tname = #{tname} where id = #{id} ;
28         <!--循环插入每个学生信息-->
29         <foreach collection="stus" item="s">
30             insert into links(tid,sid) values(#{id} , #{s.id}) ;
31         </foreach>
32     </update>
33 
34     <select id="selectOne" resultMap="rm_Tea">
35         select
36           t.id tid,
37           t.tname ttname ,
38           s.id sid ,
39           s.sname ssname
40         from
41           teas t
42           left outer join links l on l.tid = t.id
43           left outer join stus s on s.id = l.sid
44         where
45           t.id = #{id}
46     </select>
47     
48     <resultMap id="rm_Tea" type="_Tea">
49         <id column="tid" property="id"/>
50         <result column="ttname"  property="tname"/>
51         <collection property="stus" column="tid" ofType="_Stu">
52             <id column="sid" property="id"/>
53             <result column="ssname" property="sname"/>
54         </collection>
55     </resultMap>
56 </mapper>

四.编写测试代码

1>.测试多对多代码如下：

 1 /*
 2 @author :yinzhengjie
 3 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 4 EMAIL:y1053419035@qq.com
 5 */
 6 package cn.org.yinzhengjie.mybatis.test;
 7 
 8 import cn.org.yinzhengjie.mybatis.domain.many2many.Stu;
 9 import cn.org.yinzhengjie.mybatis.domain.many2many.Tea;
10 import org.apache.ibatis.io.Resources;
11 import org.apache.ibatis.session.SqlSession;
12 import org.apache.ibatis.session.SqlSessionFactory;
13 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
14 import org.junit.Test;
15 
16 import java.io.InputStream;
17 
18 /**
19  * 测试多对多
20  */
21 public class TestMany2Many {
22     @Test
23     public void testInsertCustomer() throws Exception {
24         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
25         SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
26         SqlSession sess = sf.openSession();
27         Tea t1 = new Tea("t1");
28         Tea t2 = new Tea("t2");
29 
30         Stu s1 = new Stu("s1");
31         Stu s2 = new Stu("s2");
32         Stu s3 = new Stu("s3");
33         Stu s4 = new Stu("s4");
34 
35         t1.addStus(s1 , s2 , s3);
36         t2.addStus(s2 , s3 , s4);
37 
38         sess.insert("teas.insert" , t1);
39         sess.insert("teas.insert" , t2);
40 
41         sess.insert("stus.insert" , s1);
42         sess.insert("stus.insert" , s2);
43         sess.insert("stus.insert" , s3);
44         sess.insert("stus.insert" , s4);
45 
46         sess.update("teas.updateLinks" , t1);
47         sess.update("teas.updateLinks" , t2);
48 
49         sess.commit();
50         sess.close();
51     }
52 
53     @Test
54     public void testDeleteTea() throws Exception {
55         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
56         SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
57         SqlSession sess = sf.openSession();
58         sess.delete("teas.deleteOne" , 7) ;
59         sess.commit();
60         sess.close();
61     }
62 
63     /**
64      * 更新
65      */
66     @Test
67     public void testUpdate() throws Exception {
68         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
69         SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
70         SqlSession sess = sf.openSession();
71         Tea t1 = new Tea("tttt") ;
72         t1.setId(8);
73 
74         Stu s1 = new Stu();
75         s1.setId(13);
76 
77         Stu s2 = new Stu();
78         s2.setId(14);
79 
80         t1.addStus(s1,s2);
81 
82         sess.update("teas.update" , t1) ;
83         sess.commit();
84         sess.close();
85     }
86 
87     @Test
88     public void testSelectOne() throws Exception {
89         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
90         SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
91         SqlSession sess = sf.openSession();
92         Tea obj = (Tea)sess.selectOne("teas.selectOne", 7);
93 
94         System.out.println(obj.getTname());
95         sess.commit();
96         sess.close();
97     }
98 }

2>.统计函数和分页查询

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 
 3 <!DOCTYPE configuration
 4         PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 5         "http://mybatis.org/dtd/mybatis-3-config.dtd">
 6 <configuration>
 7     <properties>
 8         <property name="driver" value="com.mysql.jdbc.Driver"/>
 9         <!--注意 : “?characterEncoding=utf-8&amp;autoReconnect=true&amp;failOverReadOnly=false&amp;allowMultiQueries=true” 表示开启批处理模式-->
10         <property name="url" value="jdbc:mysql://localhost:5200/yinzhengjie?characterEncoding=utf-8&amp;autoReconnect=true&amp;failOverReadOnly=false&amp;allowMultiQueries=true"/>
11         <property name="username" value="root"/>
12         <property name="password" value="yinzhengjie"/>
13     </properties>
14 
15     <!-- 我们使用typeAliases标签给我们自定义类起个别名。-->
16     <typeAliases>
17         <typeAlias type="cn.org.yinzhengjie.mybatis.domain.many2many.Stu"     alias="_Stu" />
18         <typeAlias type="cn.org.yinzhengjie.mybatis.domain.many2many.Tea"        alias="_Tea" />
19     </typeAliases>
20 
21     <environments default="development">
22         <environment id="development">
23             <transactionManager type="JDBC"/>
24             <dataSource type="POOLED">
25                 <property name="driver" value="${driver}"/>
26                 <property name="url" value="${url}"/>
27                 <property name="username" value="${username}"/>
28                 <property name="password" value="${password}"/>
29             </dataSource>
30         </environment>
31     </environments>
32     <mappers>
33         <!-- 我们使用mapper标签指定映射文件，使用resource指定具体的路径，如果没有写绝对路径，默认的根路径就在resources目录中-->
34         <mapper resource="StatMapper.xml"/>
35     </mappers>
36 </configuration>

mybatis-config.xml 文件内容

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 3         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4 <!-- 定义名字空间 -->
 5 <mapper namespace="stats">
 6     <select id="countStus" resultType="int">
 7         select count(*) from stus
 8     </select>
 9 
10 
11     <select id="selectAllTeas" resultType="map">
12       select
13         t.id tid ,
14         t.tname ttname ,
15         s.id sid ,
16         s.sname ssname
17       from
18         teas t
19           left outer join links l on l.tid = t.id
20           left outer join stus s on s.id = l.sid
21     </select>
22 
23     <select id="selectStusPage" resultType="_Stu">
24         select * from stus where id > #{id} limit #{offset} , #{limit}
25     </select>
26 </mapper>

StatMapper.xml 文件内容

 1 /*
 2 @author :yinzhengjie
 3 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 4 EMAIL:y1053419035@qq.com
 5 */
 6 package cn.org.yinzhengjie.mybatis.test;
 7 
 8 import org.apache.ibatis.io.Resources;
 9 import org.apache.ibatis.session.SqlSession;
10 import org.apache.ibatis.session.SqlSessionFactory;
11 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
12 import org.junit.Test;
13 
14 import java.io.InputStream;
15 import java.util.HashMap;
16 import java.util.List;
17 import java.util.Map;
18 
19 /**
20  * 测试统计
21  */
22 public class TestStat {
23     @Test
24     public void testInsert() throws Exception {
25         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
26         SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
27         SqlSession sess = sf.openSession();
28         int count = sess.selectOne("stats.countStus");
29         List<Map<String,Object>> list = sess.selectList("stats.selectAllTeas");
30         for(Map<String, Object> map : list){
31             for(Map.Entry<String, Object> e : map.entrySet()){
32                 System.out.println(e.getKey() + "	" + e.getValue());
33             }
34             System.out.println("========================");
35         }
36         System.out.println(count);
37         sess.commit();
38         sess.close();
39     }
40 
41     @Test
42     public void testPage() throws Exception {
43         InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
44         SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);
45         SqlSession sess = sf.openSession();
46         Map<String , Object> map = new HashMap<String,Object>() ;
47         map.put("id" , 19) ;
48         map.put("offset" , 0) ;
49         map.put("limit" , 2) ;
50 //        map.put("id" , 19) ;
51 //        map.put("page" , new RowBounds(2, 2)) ;
52         List<Object> objects = sess.selectList("stats.selectStusPage", map);
53         System.out.println(objects);
54         sess.commit();
55         sess.close();
56 
57     }
58 }

　　测试的目录结构如下：

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原文地址：https://www.cnblogs.com/yinzhengjie/p/9287317.html