多表关联查询_resultMap_集合对象

时间：2022-04-18 07:18:40

多表关联查询_resultMap_集合对象_N+1方式实现

 package com.bjsxt.mapper;

 import java.util.List;

 import com.bjsxt.pojo.Clazz;

 public interface ClazzMapper {

     List<Clazz> selAll();

 }
 package com.bjsxt.mapper;

 import java.util.List;

 import com.bjsxt.pojo.Student;

 public interface StudentMapper {

     List<Student> selByCid(int cid);

 }
 <?xml version="1.0" encoding="UTF-8"?>

 <!DOCTYPE mapper

   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

 <mapper namespace="com.bjsxt.mapper.ClazzMapper">

     <resultMap type="clazz" id="cmap">

         <id property="id" column="id" />

         <collection property="stus" select="com.bjsxt.mapper.StudentMapper.selByCid" column="id"></collection>

     </resultMap>

     <select id="selAll" resultMap="cmap">

         select * from t_class

     </select>

 </mapper>
 <?xml version="1.0" encoding="UTF-8"?>

 <!DOCTYPE mapper

   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

 <mapper namespace="com.bjsxt.mapper.StudentMapper">

     <select id="selByCid" resultType="student" parameterType="int">

         select * from t_student where cid=#{0}

     </select>

 </mapper>
 package com.bjsxt.pojo;

 import java.io.Serializable;

 import java.util.List;

 public class Clazz implements Serializable {

     private int id;

     private String name;

     private String room;

     private List<Student> stus;

     public Clazz() {

         super();

     }

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getRoom() {

         return room;

     }

     public void setRoom(String room) {

         this.room = room;

     }

     public List<Student> getStus() {

         return stus;

     }

     public void setStus(List<Student> stus) {

         this.stus = stus;

     }

     @Override

     public int hashCode() {

         final int prime = 31;

         int result = 1;

         result = prime * result + id;

         result = prime * result + ((name == null) ? 0 : name.hashCode());

         result = prime * result + ((room == null) ? 0 : room.hashCode());

         result = prime * result + ((stus == null) ? 0 : stus.hashCode());

         return result;

     }

     @Override

     public boolean equals(Object obj) {

         if (this == obj)

             return true;

         if (obj == null)

             return false;

         if (getClass() != obj.getClass())

             return false;

         Clazz other = (Clazz) obj;

         if (id != other.id)

             return false;

         if (name == null) {

             if (other.name != null)

                 return false;

         } else if (!name.equals(other.name))

             return false;

         if (room == null) {

             if (other.room != null)

                 return false;

         } else if (!room.equals(other.room))

             return false;

         if (stus == null) {

             if (other.stus != null)

                 return false;

         } else if (!stus.equals(other.stus))

             return false;

         return true;

     }

     @Override

     public String toString() {

         return "Clazz [id=" + id + ", name=" + name + ", room=" + room + ", stus=" + stus + "]";

     }

 }
 package com.bjsxt.pojo;

 import java.io.Serializable;

 public class Student implements Serializable {

     private int id;

     private String name;

     private int age;

     private String gender;

     private int cid;

     public Student() {

         super();

     }

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public int getAge() {

         return age;

     }

     public void setAge(int age) {

         this.age = age;

     }

     public String getGender() {

         return gender;

     }

     public void setGender(String gender) {

         this.gender = gender;

     }

     public int getCid() {

         return cid;

     }

     public void setCid(int cid) {

         this.cid = cid;

     }

     @Override

     public int hashCode() {

         final int prime = 31;

         int result = 1;

         result = prime * result + age;

         result = prime * result + cid;

         result = prime * result + ((gender == null) ? 0 : gender.hashCode());

         result = prime * result + id;

         result = prime * result + ((name == null) ? 0 : name.hashCode());

         return result;

     }

     @Override

     public boolean equals(Object obj) {

         if (this == obj)

             return true;

         if (obj == null)

             return false;

         if (getClass() != obj.getClass())

             return false;

         Student other = (Student) obj;

         if (age != other.age)

             return false;

         if (cid != other.cid)

             return false;

         if (gender == null) {

             if (other.gender != null)

                 return false;

         } else if (!gender.equals(other.gender))

             return false;

         if (id != other.id)

             return false;

         if (name == null) {

             if (other.name != null)

                 return false;

         } else if (!name.equals(other.name))

             return false;

         return true;

     }

     @Override

     public String toString() {

         return "Student [id=" + id + ", name=" + name + ", age=" + age + ", gender=" + gender + ", cid=" + cid + "]";

     }

 }
 package com.bjsxt.service;

 import java.util.List;

 import com.bjsxt.pojo.Clazz;

 public interface ClazzService {

     List<Clazz> selAll();

 }
 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;

     }

 }
 package com.bjsxt.test;

 import java.util.List;

 import com.bjsxt.pojo.Clazz;

 import com.bjsxt.service.ClazzService;

 import com.bjsxt.service.impl.ClazzServiceImpl;

 public class TestQuery {

     public static void main(String[] args) {

         ClazzService cs = new ClazzServiceImpl();

         List<Clazz> list = cs.selAll();

         for (Clazz clazz : list) {

             System.out.println(clazz);

         }

     }

 }
 package com.bjsxt.util;

 import java.io.IOException;

 import java.io.InputStream;

 import org.apache.ibatis.io.Resources;

 import org.apache.ibatis.session.SqlSession;

 import org.apache.ibatis.session.SqlSessionFactory;

 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 public class MyBatisUtil {

     private static SqlSessionFactory factory = null;

     static {

         try {

             InputStream is = Resources.getResourceAsStream("mybatis-cfg.xml");

             factory = new SqlSessionFactoryBuilder().build(is);

         } catch (IOException e) {

             e.printStackTrace();

         }

     }

     public static SqlSession getSession() {

         SqlSession session = null;

         if (factory != null) {

             // true表示开启自动提交

             // session = factory.openSession(true);

             session = factory.openSession();

         }

         return session;

     }

 }
 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

多表关联查询_resultMap_集合对象_关联方式实现

 package com.bjsxt.mapper;

 import java.util.List;

 import com.bjsxt.pojo.Clazz;

 public interface ClazzMapper {

     List<Clazz> selAll();

 }
 <?xml version="1.0" encoding="UTF-8"?>

 <!DOCTYPE mapper

   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

 <mapper namespace="com.bjsxt.mapper.ClazzMapper">

     <resultMap type="clazz" id="cmap">

         <id property="id" column="cid" />

         <result property="name" column="cname" />

         <result property="room" column="room" />

         <collection property="stus" javaType="list" ofType="student">

             <id property="id" column="sid" />

             <result property="name" column="sname" />

             <result property="age" column="age" />

             <result property="gender" column="gender" />

             <result property="cid" column="cid" />

         </collection>

     </resultMap>

     <select id="selAll" resultMap="cmap">

         select c.id cid, c.name cname, c.room, s.id sid, s.name sname, s.age, s.gender

         from t_student s

         right join t_class c

         on s.cid=c.id

     </select>

 </mapper>
 package com.bjsxt.pojo;

 import java.io.Serializable;

 import java.util.List;

 public class Clazz implements Serializable {

     private int id;

     private String name;

     private String room;

     private List<Student> stus;

     public Clazz() {

         super();

     }

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getRoom() {

         return room;

     }

     public void setRoom(String room) {

         this.room = room;

     }

     public List<Student> getStus() {

         return stus;

     }

     public void setStus(List<Student> stus) {

         this.stus = stus;

     }

     @Override

     public int hashCode() {

         final int prime = 31;

         int result = 1;

         result = prime * result + id;

         result = prime * result + ((name == null) ? 0 : name.hashCode());

         result = prime * result + ((room == null) ? 0 : room.hashCode());

         result = prime * result + ((stus == null) ? 0 : stus.hashCode());

         return result;

     }

     @Override

     public boolean equals(Object obj) {

         if (this == obj)

             return true;

         if (obj == null)

             return false;

         if (getClass() != obj.getClass())

             return false;

         Clazz other = (Clazz) obj;

         if (id != other.id)

             return false;

         if (name == null) {

             if (other.name != null)

                 return false;

         } else if (!name.equals(other.name))

             return false;

         if (room == null) {

             if (other.room != null)

                 return false;

         } else if (!room.equals(other.room))

             return false;

         if (stus == null) {

             if (other.stus != null)

                 return false;

         } else if (!stus.equals(other.stus))

             return false;

         return true;

     }

     @Override

     public String toString() {

         return "Clazz [id=" + id + ", name=" + name + ", room=" + room + ", stus=" + stus + "]";

     }

 }
 package com.bjsxt.pojo;

 import java.io.Serializable;

 public class Student implements Serializable {

     private int id;

     private String name;

     private int age;

     private String gender;

     private int cid;

     public Student() {

         super();

     }

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public int getAge() {

         return age;

     }

     public void setAge(int age) {

         this.age = age;

     }

     public String getGender() {

         return gender;

     }

     public void setGender(String gender) {

         this.gender = gender;

     }

     public int getCid() {

         return cid;

     }

     public void setCid(int cid) {

         this.cid = cid;

     }

     @Override

     public int hashCode() {

         final int prime = 31;

         int result = 1;

         result = prime * result + age;

         result = prime * result + cid;

         result = prime * result + ((gender == null) ? 0 : gender.hashCode());

         result = prime * result + id;

         result = prime * result + ((name == null) ? 0 : name.hashCode());

         return result;

     }

     @Override

     public boolean equals(Object obj) {

         if (this == obj)

             return true;

         if (obj == null)

             return false;

         if (getClass() != obj.getClass())

             return false;

         Student other = (Student) obj;

         if (age != other.age)

             return false;

         if (cid != other.cid)

             return false;

         if (gender == null) {

             if (other.gender != null)

                 return false;

         } else if (!gender.equals(other.gender))

             return false;

         if (id != other.id)

             return false;

         if (name == null) {

             if (other.name != null)

                 return false;

         } else if (!name.equals(other.name))

             return false;

         return true;

     }

     @Override

     public String toString() {

         return "Student [id=" + id + ", name=" + name + ", age=" + age + ", gender=" + gender + ", cid=" + cid + "]";

     }

 }
 package com.bjsxt.service;

 import java.util.List;

 import com.bjsxt.pojo.Clazz;

 public interface ClazzService {

     List<Clazz> selAll();

 }
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;

    }

}
 package com.bjsxt.test;

 import java.util.List;

 import com.bjsxt.pojo.Clazz;

 import com.bjsxt.service.ClazzService;

 import com.bjsxt.service.impl.ClazzServiceImpl;

 public class TestQuery {

     public static void main(String[] args) {

         ClazzService cs = new ClazzServiceImpl();

         List<Clazz> list = cs.selAll();

         for (Clazz clazz : list) {

             System.out.println(clazz);

         }

     }

 }
 package com.bjsxt.util;

 import java.io.IOException;

 import java.io.InputStream;

 import org.apache.ibatis.io.Resources;

 import org.apache.ibatis.session.SqlSession;

 import org.apache.ibatis.session.SqlSessionFactory;

 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 public class MyBatisUtil {

     private static SqlSessionFactory factory = null;

     static {

         try {

             InputStream is = Resources.getResourceAsStream("mybatis-cfg.xml");

             factory = new SqlSessionFactoryBuilder().build(is);

         } catch (IOException e) {

             e.printStackTrace();

         }

     }

     public static SqlSession getSession() {

         SqlSession session = null;

         if (factory != null) {

             // true表示开启自动提交

             // session = factory.openSession(true);

             session = factory.openSession();

         }

         return session;

     }

 }
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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