表：一对多：（简单代码示例）

数据库表创建：create table department( id int primary key, name varchar(100));create table employee( id int primary key, name varchar(100), salary float(8,2), dept_id int, constraint dept_id_fk foreign key(dept_id) references department(id));

domain类：

Department：

public class Department {  private Integer id; private String name; private List<Employee> emps=new ArrayList<Employee>(); public  Integer getId() {   return id; } public void setId( Integer id) {   this.id = id; } public String getName() {   return name; } public void setName(String name) {   this.name = name; } public List<Employee> getEmps() {   return emps; } public void setEmps(List<Employee> emps) {   this.emps = emps; } @Override public String toString() {   return "Department [id=" + id + ", name=" + name + ", emps=" + emps    + "]"; } }

Employee：

public class Employee {  private  Integer id; private String name; private Float salary; public  Integer getId() {   return id; } public void setId( Integer id) {   this.id = id; } public String getName() {   return name; } public void setName(String name) {   this.name = name; } public Float getSalary() {   return salary; } public void setSalary(Float salary) {   this.salary = salary; }

 @Override

 public String toString() {   return "Employee [id=" + id + ", name=" + name + ", salary=" + salary    +"]"; }

 

}

dao实现：

public class DaoImpl {  private QueryRunner qr =new QueryRunner(DBCPUtil.getDataSource()); public void addDepartment(Department department) throws SQLException{   qr.update("insert into department(id,name) values(?,?)", department.getId(),department.getName());  List<Employee> emps=department.getEmps();  if(emps!=null&&emps.size()>0){    for(Employee emp:emps){     qr.update("insert into employee(id,name,salary,dept_id) values(?,?,?,?)",emp.getId(),emp.getName(),emp.getSalary(),department.getId());   }  } } public void findDepartmentById(){    }}

多对多：

数据库表创建：create table teacher( id int primary key, name varchar(100), money float(8,2));create table student( id int primary key, name varchar(100), grade varchar(100));create table teacher_student( t_id int, s_id int, primary key(t_id,s_id), constraint t_id_fk foreign key(t_id) references teacher(id), constraint s_id_fk foreign key(s_id) references student(id));domain类：student：public class Student {  private int id; private String name; private String grade; private List<Teacher> teachers = new ArrayList<Teacher>(); 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 getGrade() {   return grade; } public void setGrade(String grade) {   this.grade = grade; } public List<Teacher> getTeachers() {   return teachers; } public void setTeachers(List<Teacher> teachers) {   this.teachers = teachers; } @Override public String toString() {   return "Student [id=" + id + ", name=" + name + ", grade=" + grade    + "]"; } }teacher类：public class Teacher {  private int id;// Integer private String name; private float money; private List<Student> students = new ArrayList<Student>(); 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 float getMoney() {   return money; } public void setMoney(float money) {   this.money = money; } public List<Student> getStudents() {   return students; } public void setStudents(List<Student> students) {   this.students = students; } @Override public String toString() {   return "Teacher [id=" + id + ", name=" + name + ", money=" + money    + "]"; } }

dao实现类：

public class CustomerDaoImpl {  private QueryRunner qr = new QueryRunner(DBCPUtil.getDataSource());

 public void addCustomer(Customer c) {

  try {    // 保存客户的基本信息   qr.update("insert into customer values(?,?)", c.getId(),     c.getName());   // 看看客户有没有订单，有订单还要进行保存   List<Orders> os = c.getOrders();   if (os != null && os.size() > 0) {     for (Orders o : os) {      qr.update("insert into orders values(?,?,?,?)", o.getId(),       o.getNum(), o.getMoney(), c.getId());    }   }  } catch (SQLException e) {    throw new RuntimeException(e);  } }

 // 查询客户时要不要查询客户拥有的订单呢？ //看需求（Hibernate用的延迟加载）

 // 要查询出来

 public Customer findByCustomerId(int customerId) {   try {    Customer c = qr.query("select * from customer where id=?",     new BeanHandler<Customer>(Customer.class), customerId);   if(c!=null){     //有查询结果    //查询该客户的订单    List<Orders> os = qr.query("select * from orders where customer_id=?", new BeanListHandler<Orders>(Orders.class), c.getId());    c.setOrders(os);   }   return c;  } catch (SQLException e) {    throw new RuntimeException(e);  } }}

test类：

public class TeacherDaoImplTest {  private TeacherDaoImpl dao = new TeacherDaoImpl();   public void addTest(){   Teacher t1= new Teacher();  t1.setId(1);  t1.setName("QB");  t1.setMoney(10000);    Teacher t2= new Teacher();  t2.setId(2);  t2.setName("WZT");  t2.setMoney(10000);    Student s1 = new Student();  s1.setId(1);  s1.setName("HCH");  s1.setGrade("A");    Student s2 = new Student();  s2.setId(2);  s2.setName("HFZJ");  s2.setGrade("A");    //建立关系  t1.getStudents().add(s1);  t1.getStudents().add(s2);    t2.getStudents().add(s1);  t2.getStudents().add(s2);    dao.addTeacher(t1);  dao.addTeacher(t2);   }   public void testQuery(){   Teacher t = dao.findTeacherById(2);  System.out.println(t);  System.out.println("他教过的学员：");  for(Student s:t.getStudents())   System.out.println(s); }}