Mybatis配置一对多的关联关系（五）

　　问题：是查询一个部门中的员工？

一、web项目构架

　　　　　　

二、lib文件的jar

　　　　

三、配置大小配置和该工具类

　　1大配置mybatis-config.xml

<?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>

     <!-- 别名的定制 -->
     <typeAliases>
        <!-- 按类型名定制别名  -->
        <!--   <typeAlias type="cn.happy.entity.Student" alias="Student"/> -->

        <!-- 拿当前指定包下的简单类名作为别名  -->
        <package name="cn.happy.entity"/>
     </typeAliases>

    <environments default="development">
    <environment id="development">

      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
        <property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>
        <property name="username" value="T2"/>
        <property name="password" value="T2"/>
      </dataSource>
    </environment>
  </environments>
    <mappers>
        <mapper resource="cn/happy/dao/DeptDAO.xml" />
    </mappers>
</configuration>

2小配置

<?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="cn.happy.dao.IDeptDAO">

  <resultMap type="Dept" id="deptMapper">
     <id property="deptno" column="deptno"/>
     <result property="deptname" column="deptname"/>
     <collection property="emps" ofType="Emp">
        <id property="empno" column="empno"/>
        <result property="empname" column="empname"/>
     </collection>
  </resultMap>

 <!-- one2many -->

  <select id="getDeptById" resultMap="deptMapper">
     select dept.deptno,deptname,empno,empname from dept,emp
     where dept.deptno=emp.deptno and dept.deptno=#{deptno}
  </select>

</mapper>

3工具类

package cn.happy.util;

import java.io.IOException;
import java.io.Reader;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * 工具类
 * @author Happy
 *
 */
public class MybatisUtil {
    private static String config="mybatis-config.xml";
    static Reader reader;
    static{
        try {
            reader= Resources.getResourceAsReader(config);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    private static SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader);
    //提供一个可以获取到session的方法
    public static SqlSession getSession() throws IOException{

        System.out.println("22222"+factory);
        //弊病，就是工厂是
           // 1.1 openSession到底做了什么
           SqlSession session = factory.openSession();
           System.out.println("3333");
            return session;
    }
}

四、配置实体类

1Emp

package cn.happy.entity;
/**
 * 员工
 * @author Administrator
 *
 */
public class Emp {
    private Integer empno;
    private String empname;
    private Integer empage;
    public Integer getEmpno() {
        return empno;
    }
    public void setEmpno(Integer empno) {
        this.empno = empno;
    }
    public String getEmpname() {
        return empname;
    }
    public void setEmpname(String empname) {
        this.empname = empname;
    }
    public Integer getEmpage() {
        return empage;
    }
    public void setEmpage(Integer empage) {
        this.empage = empage;
    }

}

2Dept

package cn.happy.entity;

import java.util.HashSet;
import java.util.Set;

/**
 * 部门
 * @author Administrator
 *
 */
public class Dept {
    private Integer deptno;
    private String deptname;
    //配置一对多的关系
    private Set<Emp> emps=new HashSet<Emp>();

    public Set<Emp> getEmps() {
        return emps;
    }
    public void setEmps(Set<Emp> emps) {
        this.emps = emps;
    }
    public Integer getDeptno() {
        return deptno;
    }
    public void setDeptno(Integer deptno) {
        this.deptno = deptno;
    }
    public String getDeptname() {
        return deptname;
    }
    public void setDeptname(String deptname) {
        this.deptname = deptname;
    }

}

五接口

package cn.happy.dao;

import cn.happy.entity.Dept;

public interface IDeptDAO {

    //根据部门编号查询该部门
        public Dept getDeptById(Integer id);
}

六测试

package cn.happy.test;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.junit.Before;
import org.junit.Test;

import cn.happy.dao.IDeptDAO;
import cn.happy.entity.Dept;

import cn.happy.util.MybatisUtil;

public class MyTest {
    IDeptDAO dao;
    @Before
    public void initData() throws IOException{
        SqlSession session = MybatisUtil.getSession();
         dao = session.getMapper(IDeptDAO.class);
    }

    @Test
    public void getDeptById() throws IOException{
        Dept dept = dao.getDeptById(2);
        System.out.println(dept);
    }

}