ibatis关联对象的使用04

 

 

1、两个相互关联的对象

public class Classes {
	private int id;
	private String cname;
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getCname() {
		return cname;
	}
	public void setCname(String cname) {
		this.cname = cname;
	}
}
public class Student {
	private int id;
	private String name;
	private String sex;
	private Classes classes;
	
	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 getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Classes getClasses() {
		return classes;
	}
	public void setClasses(Classes classes) {
		this.classes = classes;
	}
}

 

 

 

 

从student 中关联到class 对象

 

Student s = (Student)sqlMapper.queryForObject("findStudent", 1);
		System.out.println(s.getName()+"属于班级："+s.getClasses().getCname());

 

使用别名映射

	<select id="findStudent" parameterClass="int" resultClass="Student">
		select
			s.name,
			s.sex,
			s.cid as "classes.id",
			c.cname as "classes.cname"
		from t_student s,t_classes c
		where s.cid = c.id and s.id = #id#
	</select>

 

 

a插入的用点导航 

 

	<insert id="saveStudent" parameterClass="Student">
		insert into t_student values (null,#name#,#sex#,#classes.id#)
	</insert>
	

 b写两条sql使用resultMap映射

 

<resultMap class="Student" id="findStudent-result">
		<result property="id" column="id"/>
		<result property="name" column="name"/>
		<result property="sex" column="sex"/>
		<result property="classes" column="cid" select="findClassesById"/>
	</resultMap>
	<select id="findStudent" parameterClass="int" resultMap="findStudent-result">
		select
			*
		from t_student
		where id = #id#
	</select>

 

	<select id="findClassesById" parameterClass="int" resultClass="Classes">
		select * from t_classes where id = #cid#
	</select>

 

 

2、

 

 

 

    select 
        s.name, 
        s.sex, 
        s.cid as "classes.id", 
        c.cname as "classes.cname" 
    from t_student s,t_classes c 
    where s.cid = c.id and s.id = #id#

as 后面加引号是什么意思 解释一下 而且resultClass是 stutent 但这里要要查Class类的name 这样行不行

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