多表关联查询_resultMap_集合对象

多表关联查询_resultMap_集合对象_N+1方式实现

 1 package com.bjsxt.mapper;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Clazz;
 6 
 7 public interface ClazzMapper {
 8 
 9     List<Clazz> selAll();
10 }

 1 package com.bjsxt.mapper;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Student;
 6 
 7 public interface StudentMapper {
 8 
 9     List<Student> selByCid(int cid);
10 }

 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="com.bjsxt.mapper.ClazzMapper">
 6     <resultMap type="clazz" id="cmap">
 7         <id property="id" column="id" />
 8         <collection property="stus" select="com.bjsxt.mapper.StudentMapper.selByCid" column="id"></collection>
 9     </resultMap>
10     <select id="selAll" resultMap="cmap">
11         select * from t_class
12     </select>
13 </mapper>

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="com.bjsxt.mapper.StudentMapper">
6     <select id="selByCid" resultType="student" parameterType="int">
7         select * from t_student where cid=#{0}
8     </select>
9 </mapper>

 1 package com.bjsxt.pojo;
 2 
 3 import java.io.Serializable;
 4 import java.util.List;
 5 
 6 public class Clazz implements Serializable {
 7 
 8     private int id;
 9     private String name;
10     private String room;
11     private List<Student> stus;
12 
13     public Clazz() {
14         super();
15     }
16 
17     public int getId() {
18         return id;
19     }
20 
21     public void setId(int id) {
22         this.id = id;
23     }
24 
25     public String getName() {
26         return name;
27     }
28 
29     public void setName(String name) {
30         this.name = name;
31     }
32 
33     public String getRoom() {
34         return room;
35     }
36 
37     public void setRoom(String room) {
38         this.room = room;
39     }
40 
41     public List<Student> getStus() {
42         return stus;
43     }
44 
45     public void setStus(List<Student> stus) {
46         this.stus = stus;
47     }
48 
49     @Override
50     public int hashCode() {
51         final int prime = 31;
52         int result = 1;
53         result = prime * result + id;
54         result = prime * result + ((name == null) ? 0 : name.hashCode());
55         result = prime * result + ((room == null) ? 0 : room.hashCode());
56         result = prime * result + ((stus == null) ? 0 : stus.hashCode());
57         return result;
58     }
59 
60     @Override
61     public boolean equals(Object obj) {
62         if (this == obj)
63             return true;
64         if (obj == null)
65             return false;
66         if (getClass() != obj.getClass())
67             return false;
68         Clazz other = (Clazz) obj;
69         if (id != other.id)
70             return false;
71         if (name == null) {
72             if (other.name != null)
73                 return false;
74         } else if (!name.equals(other.name))
75             return false;
76         if (room == null) {
77             if (other.room != null)
78                 return false;
79         } else if (!room.equals(other.room))
80             return false;
81         if (stus == null) {
82             if (other.stus != null)
83                 return false;
84         } else if (!stus.equals(other.stus))
85             return false;
86         return true;
87     }
88 
89     @Override
90     public String toString() {
91         return "Clazz [id=" + id + ", name=" + name + ", room=" + room + ", stus=" + stus + "]";
92     }
93 
94 }

  1 package com.bjsxt.pojo;
  2 
  3 import java.io.Serializable;
  4 
  5 public class Student implements Serializable {
  6 
  7     private int id;
  8     private String name;
  9     private int age;
 10     private String gender;
 11     private int cid;
 12 
 13     public Student() {
 14         super();
 15     }
 16 
 17     public int getId() {
 18         return id;
 19     }
 20 
 21     public void setId(int id) {
 22         this.id = id;
 23     }
 24 
 25     public String getName() {
 26         return name;
 27     }
 28 
 29     public void setName(String name) {
 30         this.name = name;
 31     }
 32 
 33     public int getAge() {
 34         return age;
 35     }
 36 
 37     public void setAge(int age) {
 38         this.age = age;
 39     }
 40 
 41     public String getGender() {
 42         return gender;
 43     }
 44 
 45     public void setGender(String gender) {
 46         this.gender = gender;
 47     }
 48 
 49     public int getCid() {
 50         return cid;
 51     }
 52 
 53     public void setCid(int cid) {
 54         this.cid = cid;
 55     }
 56 
 57     @Override
 58     public int hashCode() {
 59         final int prime = 31;
 60         int result = 1;
 61         result = prime * result + age;
 62         result = prime * result + cid;
 63         result = prime * result + ((gender == null) ? 0 : gender.hashCode());
 64         result = prime * result + id;
 65         result = prime * result + ((name == null) ? 0 : name.hashCode());
 66         return result;
 67     }
 68 
 69     @Override
 70     public boolean equals(Object obj) {
 71         if (this == obj)
 72             return true;
 73         if (obj == null)
 74             return false;
 75         if (getClass() != obj.getClass())
 76             return false;
 77         Student other = (Student) obj;
 78         if (age != other.age)
 79             return false;
 80         if (cid != other.cid)
 81             return false;
 82         if (gender == null) {
 83             if (other.gender != null)
 84                 return false;
 85         } else if (!gender.equals(other.gender))
 86             return false;
 87         if (id != other.id)
 88             return false;
 89         if (name == null) {
 90             if (other.name != null)
 91                 return false;
 92         } else if (!name.equals(other.name))
 93             return false;
 94         return true;
 95     }
 96 
 97     @Override
 98     public String toString() {
 99         return "Student [id=" + id + ", name=" + name + ", age=" + age + ", gender=" + gender + ", cid=" + cid + "]";
100     }
101 
102 }

 1 package com.bjsxt.service;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Clazz;
 6 
 7 public interface ClazzService {
 8 
 9     List<Clazz> selAll();
10 }

 1 package com.bjsxt.service.impl;
 2 
 3 import java.util.List;
 4 
 5 import org.apache.ibatis.session.SqlSession;
 6 
 7 import com.bjsxt.mapper.ClazzMapper;
 8 import com.bjsxt.pojo.Clazz;
 9 import com.bjsxt.service.ClazzService;
10 import com.bjsxt.util.MyBatisUtil;
11 
12 public class ClazzServiceImpl implements ClazzService {
13 
14     public List<Clazz> selAll() {
15         SqlSession session = MyBatisUtil.getSession();
16         
17         ClazzMapper mapper = session.getMapper(ClazzMapper.class);
18         List<Clazz> list = mapper.selAll();
19         
20         session.close();
21         return list;
22     }
23 
24 }

 1 package com.bjsxt.test;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Clazz;
 6 import com.bjsxt.service.ClazzService;
 7 import com.bjsxt.service.impl.ClazzServiceImpl;
 8 
 9 public class TestQuery {
10 
11     public static void main(String[] args) {
12         ClazzService cs = new ClazzServiceImpl();
13         List<Clazz> list = cs.selAll();
14         for (Clazz clazz : list) {
15             System.out.println(clazz);
16         }
17     }
18 
19 }

 1 package com.bjsxt.util;
 2 
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 
 6 import org.apache.ibatis.io.Resources;
 7 import org.apache.ibatis.session.SqlSession;
 8 import org.apache.ibatis.session.SqlSessionFactory;
 9 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
10 
11 public class MyBatisUtil {
12 
13     private static SqlSessionFactory factory = null;
14 
15     static {
16         try {
17             InputStream is = Resources.getResourceAsStream("mybatis-cfg.xml");
18             factory = new SqlSessionFactoryBuilder().build(is);
19         } catch (IOException e) {
20             e.printStackTrace();
21         }
22     }
23 
24     public static SqlSession getSession() {
25         SqlSession session = null;
26         if (factory != null) {
27             // true表示开启自动提交
28             // session = factory.openSession(true);
29             session = factory.openSession();
30         }
31         return session;
32     }
33 }

1 jdbc.driver=com.mysql.jdbc.Driver
2 jdbc.url=jdbc:mysql://localhost:3306/java505
3 jdbc.username=root
4 jdbc.password=root

 1 # Set root category priority to INFO and its only appender to CONSOLE.
 2 log4j.rootCategory=ERROR, CONSOLE
 3 # log4j.rootCategory=DEBUG, CONSOLE, LOGFILE
 4 
 5 # 单独设置SQL语句的输出级别为DEBUG级别
 6 log4j.logger.com.bjsxt.mapper=DEBUG
 7 
 8 # CONSOLE is set to be a ConsoleAppender using a PatternLayout.
 9 log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
10 log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
11 log4j.appender.CONSOLE.layout.ConversionPattern=- %m%n
12 
13 # LOGFILE is set to be a File appender using a PatternLayout.
14 log4j.appender.LOGFILE=org.apache.log4j.FileAppender
15 log4j.appender.LOGFILE.File=d:/test.log
16 log4j.appender.LOGFILE.Append=true
17 log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
18 log4j.appender.LOGFILE.layout.ConversionPattern=- %m %l%n

多表关联查询_resultMap_集合对象_关联方式实现

 1 package com.bjsxt.mapper;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Clazz;
 6 
 7 public interface ClazzMapper {
 8 
 9     List<Clazz> selAll();
10 }

 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="com.bjsxt.mapper.ClazzMapper">
 6     <resultMap type="clazz" id="cmap">
 7         <id property="id" column="cid" />
 8         <result property="name" column="cname" />
 9         <result property="room" column="room" />
10         <collection property="stus" javaType="list" ofType="student">
11             <id property="id" column="sid" />
12             <result property="name" column="sname" />
13             <result property="age" column="age" />
14             <result property="gender" column="gender" />
15             <result property="cid" column="cid" />
16         </collection>
17     </resultMap>
18     <select id="selAll" resultMap="cmap">
19         select c.id cid, c.name cname, c.room, s.id sid, s.name sname, s.age, s.gender
20         from t_student s
21         right join t_class c
22         on s.cid=c.id
23     </select>
24 </mapper>

 1 package com.bjsxt.pojo;
 2 
 3 import java.io.Serializable;
 4 import java.util.List;
 5 
 6 public class Clazz implements Serializable {
 7 
 8     private int id;
 9     private String name;
10     private String room;
11     private List<Student> stus;
12 
13     public Clazz() {
14         super();
15     }
16 
17     public int getId() {
18         return id;
19     }
20 
21     public void setId(int id) {
22         this.id = id;
23     }
24 
25     public String getName() {
26         return name;
27     }
28 
29     public void setName(String name) {
30         this.name = name;
31     }
32 
33     public String getRoom() {
34         return room;
35     }
36 
37     public void setRoom(String room) {
38         this.room = room;
39     }
40 
41     public List<Student> getStus() {
42         return stus;
43     }
44 
45     public void setStus(List<Student> stus) {
46         this.stus = stus;
47     }
48 
49     @Override
50     public int hashCode() {
51         final int prime = 31;
52         int result = 1;
53         result = prime * result + id;
54         result = prime * result + ((name == null) ? 0 : name.hashCode());
55         result = prime * result + ((room == null) ? 0 : room.hashCode());
56         result = prime * result + ((stus == null) ? 0 : stus.hashCode());
57         return result;
58     }
59 
60     @Override
61     public boolean equals(Object obj) {
62         if (this == obj)
63             return true;
64         if (obj == null)
65             return false;
66         if (getClass() != obj.getClass())
67             return false;
68         Clazz other = (Clazz) obj;
69         if (id != other.id)
70             return false;
71         if (name == null) {
72             if (other.name != null)
73                 return false;
74         } else if (!name.equals(other.name))
75             return false;
76         if (room == null) {
77             if (other.room != null)
78                 return false;
79         } else if (!room.equals(other.room))
80             return false;
81         if (stus == null) {
82             if (other.stus != null)
83                 return false;
84         } else if (!stus.equals(other.stus))
85             return false;
86         return true;
87     }
88 
89     @Override
90     public String toString() {
91         return "Clazz [id=" + id + ", name=" + name + ", room=" + room + ", stus=" + stus + "]";
92     }
93 
94 }

  1 package com.bjsxt.pojo;
  2 
  3 import java.io.Serializable;
  4 
  5 public class Student implements Serializable {
  6 
  7     private int id;
  8     private String name;
  9     private int age;
 10     private String gender;
 11     private int cid;
 12 
 13     public Student() {
 14         super();
 15     }
 16 
 17     public int getId() {
 18         return id;
 19     }
 20 
 21     public void setId(int id) {
 22         this.id = id;
 23     }
 24 
 25     public String getName() {
 26         return name;
 27     }
 28 
 29     public void setName(String name) {
 30         this.name = name;
 31     }
 32 
 33     public int getAge() {
 34         return age;
 35     }
 36 
 37     public void setAge(int age) {
 38         this.age = age;
 39     }
 40 
 41     public String getGender() {
 42         return gender;
 43     }
 44 
 45     public void setGender(String gender) {
 46         this.gender = gender;
 47     }
 48 
 49     public int getCid() {
 50         return cid;
 51     }
 52 
 53     public void setCid(int cid) {
 54         this.cid = cid;
 55     }
 56 
 57     @Override
 58     public int hashCode() {
 59         final int prime = 31;
 60         int result = 1;
 61         result = prime * result + age;
 62         result = prime * result + cid;
 63         result = prime * result + ((gender == null) ? 0 : gender.hashCode());
 64         result = prime * result + id;
 65         result = prime * result + ((name == null) ? 0 : name.hashCode());
 66         return result;
 67     }
 68 
 69     @Override
 70     public boolean equals(Object obj) {
 71         if (this == obj)
 72             return true;
 73         if (obj == null)
 74             return false;
 75         if (getClass() != obj.getClass())
 76             return false;
 77         Student other = (Student) obj;
 78         if (age != other.age)
 79             return false;
 80         if (cid != other.cid)
 81             return false;
 82         if (gender == null) {
 83             if (other.gender != null)
 84                 return false;
 85         } else if (!gender.equals(other.gender))
 86             return false;
 87         if (id != other.id)
 88             return false;
 89         if (name == null) {
 90             if (other.name != null)
 91                 return false;
 92         } else if (!name.equals(other.name))
 93             return false;
 94         return true;
 95     }
 96 
 97     @Override
 98     public String toString() {
 99         return "Student [id=" + id + ", name=" + name + ", age=" + age + ", gender=" + gender + ", cid=" + cid + "]";
100     }
101 
102 }

 1 package com.bjsxt.service;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Clazz;
 6 
 7 public interface ClazzService {
 8 
 9     List<Clazz> selAll();
10 }

package com.bjsxt.service.impl;

import java.util.List;

import org.apache.ibatis.session.SqlSession;

import com.bjsxt.mapper.ClazzMapper;
import com.bjsxt.pojo.Clazz;
import com.bjsxt.service.ClazzService;
import com.bjsxt.util.MyBatisUtil;

public class ClazzServiceImpl implements ClazzService {

    public List<Clazz> selAll() {
        SqlSession session = MyBatisUtil.getSession();
        
        ClazzMapper mapper = session.getMapper(ClazzMapper.class);
        List<Clazz> list = mapper.selAll();
        
        session.close();
        return list;
    }

}

 1 package com.bjsxt.test;
 2 
 3 import java.util.List;
 4 
 5 import com.bjsxt.pojo.Clazz;
 6 import com.bjsxt.service.ClazzService;
 7 import com.bjsxt.service.impl.ClazzServiceImpl;
 8 
 9 public class TestQuery {
10 
11     public static void main(String[] args) {
12         ClazzService cs = new ClazzServiceImpl();
13         List<Clazz> list = cs.selAll();
14         for (Clazz clazz : list) {
15             System.out.println(clazz);
16         }
17     }
18 
19 }

 1 package com.bjsxt.util;
 2 
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 
 6 import org.apache.ibatis.io.Resources;
 7 import org.apache.ibatis.session.SqlSession;
 8 import org.apache.ibatis.session.SqlSessionFactory;
 9 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
10 
11 public class MyBatisUtil {
12 
13     private static SqlSessionFactory factory = null;
14 
15     static {
16         try {
17             InputStream is = Resources.getResourceAsStream("mybatis-cfg.xml");
18             factory = new SqlSessionFactoryBuilder().build(is);
19         } catch (IOException e) {
20             e.printStackTrace();
21         }
22     }
23 
24     public static SqlSession getSession() {
25         SqlSession session = null;
26         if (factory != null) {
27             // true表示开启自动提交
28             // session = factory.openSession(true);
29             session = factory.openSession();
30         }
31         return session;
32     }
33 }

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/java505
jdbc.username=root
jdbc.password=root

# Set root category priority to INFO and its only appender to CONSOLE.
log4j.rootCategory=ERROR, CONSOLE
# log4j.rootCategory=DEBUG, CONSOLE, LOGFILE

# 单独设置SQL语句的输出级别为DEBUG级别
log4j.logger.com.bjsxt.mapper=DEBUG

# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=- %m%n

# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:/test.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=- %m %l%n

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原文地址：https://www.cnblogs.com/wq-9/p/10242278.html