Collection主要處理“一對多”型別對映關係，例如，查詢部門中有多個員工，就需要使用的到集合：List<employee> emp,這樣，就會使用collection進行對映關聯查詢。

1.employee.java

package com.casv.model;

public class employee {

	private int uid;
	private String name;
	private String pwd;
	private department dept;

	public int getUid() {
		return uid;
	}

	public void setUid(int uid) {
		this.uid = uid;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPwd() {
		return pwd;
	}

	public void setPwd(String pwd) {
		this.pwd = pwd;
	}

	public department getDept() {
		return dept;
	}

	public void setDept(department dept) {
		this.dept = dept;
	}

}
 

package com.casv.model;

import java.util.List;

public class department {
   
	private int pid;
	private String pname;
	//使用List集合儲存員工資訊，並關聯employee實體類
    private List<employee> emplist;
	public int getPid() {
		return pid;
	}
	public void setPid(int pid) {
		this.pid = pid;
	}
	public String getPname() {
		return pname;
	}
	public void setPname(String pname) {
		this.pname = pname;
	}
	public List<employee> getEmplist() {
		return emplist;
	}
	public void setEmplist(List<employee> emplist) {
		this.emplist = emplist;
	}
	
}
 

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper SYSTEM "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.casv.dao.deptMapper">
    <resultMap id="departResulMap" type="depts" >
       <id column="p_id" property="pid"/>
       <result column="p_name" property="pname"/>
       <!-- 使用collection將employee實體類中欄位屬性巢狀進來 -->
       <collection column="p_id" property="emplist" ofType="emps" >
           <id column="u_id" property="uid"></id>
		   <result column="u_name" property="name"></result>
		    <result column="u_pwd" property="pwd"></result>
       </collection>
    </resultMap>
    <select id="selectDeptFetchEmp" parameterType="int" resultMap="departResulMap">
        <!-- 查詢根據部門id查詢有那些員工在其部門 -->
        select * from t_dept d inner join t_user u where d.p_id=u.p_id and d.p_id=#{id}
    </select>
</mapper>
 

ofType屬性可以區分是JavaBean（或欄位）屬性，還是集合包含屬性，讀作：“在emps物件型別中ArrayList中的emplist集合”。

4.config.xml中註冊deptMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration SYSTEM "http://mybatis.org/dtd/mybatis-3-config.dtd" >
<configuration>
	<!-- 配置實體類，起別名 -->
	<typeAliases>
		<typeAlias type="com.casv.model.employee" alias="emps" />
		<typeAlias type="com.casv.model.department" alias="depts"/>
		<!-- 掃描實體類包，後續可以直接使用類名
		<package name="com.casv.model.User"/>
		-->
	</typeAliases>
	<!-- 配置資料來源 -->
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC"></transactionManager>
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql://localhost:3306/userdatabase" />
				<property name="username" value="root" />
				<property name="password" value="123456" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<!-- 註冊deptMapper.xml -->
		<mapper resource="com/casv/dao/deptMapper.xml"></mapper>
	</mappers>
</configuration>

@Test 
public void test2(){
    session=MyBatisUtil.getSessionFactory().openSession();
    department dept=session.selectOne("com.casv.dao.deptMapper.selectDeptFetchEmp", 1);
    for(employee emp : dept.getEmplist()){
	System.out.println(emp.getName()+" "+dept.getPname());
    }
    session.close();
}