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);
}