1. 1对多，部门--员工 为例， 多的一方建外键。

domain,建立bean对象

public class Department {	private String id;	private String name;	private Set
    
      employees = new HashSet
     
      ();		public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public Set
      
        getEmployees() {		return employees;	}	public void setEmployees(Set
       
         employees) {		this.employees = employees;	}
       
      
     
    

public class Employee {	private String id;	private String name;	private double salary;	private Department department;	public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public double getSalary() {		return salary;	}	public void setSalary(double salary) {		this.salary = salary;	}	public Department getDepartment() {		return department;	}	public void setDepartment(Department department) {		this.department = department;	}	}

dao层实现增查功能

/* create table department( 	id varchar(40) primary key, 	name varchar(40) );  create table employee( 	id varchar(40) primary key, 	name varchar(40), 	salary double, 	department_id varchar(40), 	constraint department_id_FK foreign key(department_id) references department(id) );  * */public class DepartmentDao {		public void add(Department department) throws SQLException {		QueryRunner qr = new QueryRunner(JdbcUtils_C3P0.getDataSource());		// 1.取出department对象的基本信息存在 department表		String sql = "insert into department(id,name) values(?,?)";		Object[] params = {department.getId(), department.getName()};		qr.update(sql, params);						// 2. 取出department对象中所有的员工信息，存在员工表		sql = "insert into employee(id,name,salary,department_id) values(?,?,?,?)";		Set
    
      set = department.getEmployees();		Object[][] params2 = new Object[set.size()][];		int index = 0;		for(Employee e : set)		{			params2[index++] = new Object[]{e.getId(), e.getName(), e.getSalary(), department.getId()};		}		qr.batch(sql, params2);		// 3.更新员工表的外键列，说明员工所属部门	}		public Department find(String id) throws SQLException{		QueryRunner qr = new QueryRunner(JdbcUtils_C3P0.getDataSource());				//1.查出部门表的信息，存在department对象中		String sql = "select * from department where id=?";		Department d = (Department) qr.query(sql, id, new BeanHandler(Department.class));						//2.查出部门下的所有员工信息，存在department对象维护的员工对象中		// 不要直接轻易取出所有数据， 数据太多一定要分页		sql = "select id,name,salary from employee where department_id=?";		List list = (List) qr.query(sql, id, new BeanListHandler(Employee.class));				d.getEmployees().addAll(list);				return d;	}}
    

Service层实现调用， 这里仅用junit做测试

public class BusinessService {		DepartmentDao ddao = new DepartmentDao();	TeacherDao tdao = new TeacherDao();	PersonDao pdao = new PersonDao();		@Test	public void addDepartment() throws SQLException	{		Department d = new Department();		d.setId("1");		d.setName("开发部");				Employee e1 = new Employee();		e1.setId("1");		e1.setName("aaa");		e1.setSalary(300);				Employee e2 = new Employee();		e2.setId("2");		e2.setName("bbb");		e2.setSalary(300);				d.getEmployees().add(e1);		d.getEmployees().add(e2);		ddao.add(d);	}		@Test	public void findDepartment() throws SQLException	{		Department d = ddao.find("1");		System.out.println("department name: " + d.getName());		for( Employee e : d.getEmployees() )		{			System.out.println("Employee name: " + e.getName());		}	}		@Test	public void addTeacher() throws SQLException	{		Teacher t = new Teacher();		t.setId("1");		t.setName("张三");		t.setSalary(999999);				Student s1 = new Student();		s1.setId("1");		s1.setName("aaa");				Student s2 = new Student();		s2.setId("2");		s2.setName("bbb");				t.getStudents().add(s1);		t.getStudents().add(s2);				tdao.add(t);	}		@Test	public void findTeacher() throws SQLException	{		Teacher t = tdao.find("1");		System.out.println("teacher Name: " + t.getName());		for(Student s : t.getStudents())		{			System.out.println("Student name: " + s.getName());		}	}		@Test	public void addPerson() throws SQLException	{		Person p = new Person();		p.setId("id7788");		p.setName("kevin");				Idcard card = new Idcard();		card.setId(p.getId());		card.setAddress("广东中山");				p.setIdcard(card);		pdao.add(p);	}	}

2. 多对多，老师--学生为例， 建立中间表

domain,建立bean对象

public class Teacher {	private String id;	private String name;	private double salary;	private Set
    
      students = new HashSet
     
      ();		public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public double getSalary() {		return salary;	}	public void setSalary(double salary) {		this.salary = salary;	}	public Set
      
        getStudents() {		return students;	}	public void setStudents(Set
       
         students) {		this.students = students;	}		}
       
      
     
    

public class Student {	private String id;	private String name;	private Set
    
      teachers = new HashSet
     
      ();		public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public Set
      
        getTeachers() {		return teachers;	}	public void setTeachers(Set
       
         teachers) {		this.teachers = teachers;	}	}
       
      
     
    

Dao层实现 增查功能

/* create table teacher( 	id varchar(40) primary key, 	name varchar(40), 	salary double );  create table student( 	id varchar(40) primary key, 	name varchar(40) );   create table teacher_student( 	teacher_id varchar(40), 	student_id varchar(40), 	primary key(teacher_id, student_id), 	constraint teacher_id_FK foreign key(teacher_id) references teacher(id), 	constraint student_id_FK foreign key(student_id) references student(id)  );   * */public class TeacherDao {		public void add(Teacher t) throws SQLException	{		QueryRunner qr = new QueryRunner(JdbcUtils_C3P0.getDataSource());				//1.取出老师的基本信息，存在老师表		String sql = "insert into teacher(id, name, salary) values(?,?,?)";		Object[] params = {t.getId(), t.getName(), t.getSalary()};		qr.update(sql, params);		// 2.取出老师下面所有的学生，存在学生表		Set
    
      set = t.getStudents();		for(Student s : set)		{			sql = "insert into student(id, name) values(?,?)";			params = new Object[]{s.getId(), s.getName()};			qr.update(sql, params);						// 3.在中间表中说明老师和学生的关系			sql = "insert into teacher_student(teacher_id, student_id) values(?,?)";			params = new Object[]{t.getId(), s.getId()};			qr.update(sql, params);		}		}		public Teacher find(String id) throws SQLException	{		QueryRunner qr = new QueryRunner(JdbcUtils_C3P0.getDataSource());		// 1.从老师表中找出老师的基本信息		String sql = "select * from teacher where id=?";		Teacher t =  (Teacher) qr.query(sql, id, new BeanHandler(Teacher.class));						// 2.从中间表和学生表中得到老师所有的学生(尽量不取，取则 数据多要分页)		sql = "select s.id,s.name from teacher_student ts,student s where teacher_id=? and ts.student_id=s.id";		List
     
       list = (List
      
       ) qr.query(sql, id, new BeanListHandler(Student.class));		t.getStudents().addAll(list);		return t;	}}
      
     
    

service 层代码 如上 例一。

 

3. 1对1， 人--身份证为例， 建立主从关系

domain,建立bean对象

public class Person {		private String id;	private String name;	private Idcard idcard;		public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public Idcard getIdcard() {		return idcard;	}	public void setIdcard(Idcard idcard) {		this.idcard = idcard;	}	}

public class Idcard {		private String id;	private String address;	private Person person;		public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getAddress() {		return address;	}	public void setAddress(String address) {		this.address = address;	}	public Person getPerson() {		return person;	}	public void setPerson(Person person) {		this.person = person;	}		}

Dao层 实现增功能

/* create table person( 	id varchar(40) primary key, 	name varchar(40) );  create table idcard( 	id varchar(40) primary key, 	address varchar(100), 	constraint id_FK foreign key(id) references person(id) ); * */public class PersonDao {		public void add(Person p) throws SQLException {		QueryRunner qr = new QueryRunner(JdbcUtils_C3P0.getDataSource());		// 取出person的信息存在person表		String sql = "insert into person(id,name) values(?,?)";		Object params[] = { p.getId(), p.getName() };		qr.update(sql, params);		// 取出身份证的信息存在身份证表		sql = "insert into idcard(id,address) values(?,?)";		params = new Object[] { p.getId(), p.getIdcard().getAddress() };		qr.update(sql, params);	}