Java -- 数据库 多表操作，1对多，多对多，1对1。 基于dbutils框架

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<Employee> employees = new HashSet<Employee>();

	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<Employee> getEmployees() {
		return employees;
	}
	public void setEmployees(Set<Employee> 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<Employee> 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<Student> students = new HashSet<Student>();

	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<Student> getStudents() {
		return students;
	}
	public void setStudents(Set<Student> students) {
		this.students = students;
	}
}

public class Student {
	private String id;
	private String name;
	private Set<Teacher> teachers = new HashSet<Teacher>();

	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<Teacher> getTeachers() {
		return teachers;
	}
	public void setTeachers(Set<Teacher> 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<Student> 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<Student> list = (List<Student>) 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);
	}