mybatis之注解式开发之关联查询

 package com.bjsxt.mapper;

 import org.apache.ibatis.annotations.Select;

 import com.bjsxt.pojo.Clazz;

 public interface ClazzMapper {

     @Select("select * from t_class where id=#{0}")
     Clazz selById(int id);
 }

 package com.bjsxt.mapper;

 import java.util.List;

 import org.apache.ibatis.annotations.One;
 import org.apache.ibatis.annotations.Result;
 import org.apache.ibatis.annotations.Results;
 import org.apache.ibatis.annotations.Select;

 import com.bjsxt.pojo.Student;

 public interface StudentMapper {

     @Select("select * from t_student")
     @Results(value = {
         @Result(column="id", property="id", id=true),
         @Result(column="name", property="name"),
         @Result(column="age", property="age"),
         @Result(column="gender", property="gender"),
         @Result(column="cid", property="cid"),
         @Result(property="clazz", one=@One(select="com.bjsxt.mapper.ClazzMapper.selById"), column="cid")
     })
     List<Student> sel();
 }

 package com.bjsxt.pojo;

 import java.io.Serializable;

 public class Clazz implements Serializable {

     private int id;
     private String name;
     private String room;

     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;
     }

     @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());
         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;
         return true;
     }

     @Override
     public String toString() {
         return "Clazz [id=" + id + ", name=" + name + ", room=" + room + "]";
     }
 }

 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;
     private Clazz clazz;

     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;
     }

     public Clazz getClazz() {
         return clazz;
     }

     public void setClazz(Clazz clazz) {
         this.clazz = clazz;
     }

     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + age;
         result = prime * result + cid;
         result = prime * result + ((clazz == null) ? 0 : clazz.hashCode());
         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 (clazz == null) {
             if (other.clazz != null)
                 return false;
         } else if (!clazz.equals(other.clazz))
             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
                 + ", clazz=" + clazz + "]";
     }
 }

 package com.bjsxt.test;

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;

 import com.bjsxt.mapper.StudentMapper;
 import com.bjsxt.pojo.Student;
 import com.bjsxt.util.MyBatisUtil;

 public class TestStu {

     public static void main(String[] args) {
         SqlSession session = MyBatisUtil.getSession();

         StudentMapper mapper = session.getMapper(StudentMapper.class);

         List<Student> sel = mapper.sel();
         for (Student student : sel) {
             System.out.println(student);
         }

         session.close();
     }

 }

 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

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE configuration
   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 <configuration>
     <!-- properties加载外部文件 -->
     <properties resource="db.properties" />
     <!-- settings标签 -->
     <settings>
         <!-- 设置MyBatis使用log4j日志支持 -->
         <setting name="logImpl" value="LOG4J"/>
     </settings>
     <!-- typeAliases给类型起别名 -->
     <typeAliases>
         <package name="com.bjsxt.pojo" />
     </typeAliases>
     <environments default="dev">
         <environment id="dev">
             <transactionManager type="JDBC" />
             <dataSource type="POOLED">
                 <property name="driver" value="${jdbc.driver}"/>
                 <property name="url" value="${jdbc.url}"/>
                 <property name="username" value="${jdbc.username}"/>
                 <property name="password" value="${jdbc.password}"/>
             </dataSource>
         </environment>
     </environments>
     <mappers>
         <package name="com.bjsxt.mapper" />
     </mappers>
 </configuration>