Mybatis实现一对一，一对多级联查询

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什么是一对一，一对多

准备学生表和班级表

创建实体类

声明接口

xml配置文件

测试

注解的方式

测试

什么是一对一，一对多

一对一：代表一个对象对应一个对象，可以认为是一个人对应一张身份证，一张身份证对应一个人

一对多：代表一个对象对应多个对象，可以认为一个班级对应多个学生

准备学生表和班级表

学生student和班级class是一对一的关系

班级class和学生student是一对多的关系

创建实体类

班级class实体类

复制代码

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import java.util.List;

public class BanJi {
	private int classid;
	private String classname;
	private List<Student> slist;
	public BanJi() {
		super();
		// TODO Auto-generated constructor stub
	}
	public BanJi(int classid, String classname, List<Student> slist) {
		super();
		this.classid = classid;
		this.classname = classname;
		this.slist = slist;
	}
	@Override
	public String toString() {
		return "BaJi [classid=" + classid + ", classname=" + classname + ", slist=" + slist + "]";
	}
	public int getClassid() {
		return classid;
	}
	public void setClassid(int classid) {
		this.classid = classid;
	}
	public String getClassname() {
		return classname;
	}
	public void setClassname(String classname) {
		this.classname = classname;
	}
	public List<Student> getSlist() {
		return slist;
	}
	public void setSlist(List<Student> slist) {
		this.slist = slist;
	}

}

学生student实体类

复制代码

import java.util.Date;

public class Student {
	private int sid;
	private String sname;
	private Date birthday;
	private String ssex;
	private int classid;
	//外部属性
	private BanJi bj;
	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Student(int sid, String sname, Date birthday, String ssex, int classid, BanJi bj) {
		super();
		this.sid = sid;
		this.sname = sname;
		this.birthday = birthday;
		this.ssex = ssex;
		this.classid = classid;
		this.bj = bj;
	}
	@Override
	public String toString() {
		return "Student [sid=" + sid + ", sname=" + sname + ", birthday=" + birthday + ", ssex=" + ssex + ", classid="
				+ classid + ", bj=" + bj + "]";
	}
	public int getSid() {
		return sid;
	}
	public void setSid(int sid) {
		this.sid = sid;
	}
	public String getSname() {
		return sname;
	}
	public void setSname(String sname) {
		this.sname = sname;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public String getSsex() {
		return ssex;
	}
	public void setSsex(String ssex) {
		this.ssex = ssex;
	}
	public int getClassid() {
		return classid;
	}
	public void setClassid(int classid) {
		this.classid = classid;
	}
	public BanJi getBj() {
		return bj;
	}
	public void setBj(BanJi bj) {
		this.bj = bj;
	}
	
}

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import java.util.Date;

public class Student {
	private int sid;
	private String sname;
	private Date birthday;
	private String ssex;
	private int classid;
	//外部属性
	private BanJi bj;
	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Student(int sid, String sname, Date birthday, String ssex, int classid, BanJi bj) {
		super();
		this.sid = sid;
		this.sname = sname;
		this.birthday = birthday;
		this.ssex = ssex;
		this.classid = classid;
		this.bj = bj;
	}
	@Override
	public String toString() {
		return "Student [sid=" + sid + ", sname=" + sname + ", birthday=" + birthday + ", ssex=" + ssex + ", classid="
				+ classid + ", bj=" + bj + "]";
	}
	public int getSid() {
		return sid;
	}
	public void setSid(int sid) {
		this.sid = sid;
	}
	public String getSname() {
		return sname;
	}
	public void setSname(String sname) {
		this.sname = sname;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public String getSsex() {
		return ssex;
	}
	public void setSsex(String ssex) {
		this.ssex = ssex;
	}
	public int getClassid() {
		return classid;
	}
	public void setClassid(int classid) {
		this.classid = classid;
	}
	public BanJi getBj() {
		return bj;
	}
	public void setBj(BanJi bj) {
		this.bj = bj;
	}
	
}