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>