JDBC多表操作

一、一对多关系：部门管理系统

1、数据库

       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) on delete set null;
       );

constraint department_id_FK foreign key(department_id) references department(id) on delete set null; 设置级联 
当主表的记录删除后，从表的外键置为空

2、对象

Department.java：部门

 package com.domain;

 import java.util.HashSet;
 import java.util.Set;

 public class Department {

     private String id;
     private String name;

     //设置一个Set集合保存所有员工
     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;
     }
 }

在多对一的情况下，要注意“一”的一方是否需要维护多的一方数据的集合

Employee.java:员工

 package com.domain;

 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;
     }
 }

3、dao层

DepartmentDao.java

 package com.dao;
 import java.sql.SQLException;
 import java.util.List;
 import java.util.Set;

 import org.apache.commons.dbutils.QueryRunner;
 import org.apache.commons.dbutils.handlers.BeanHandler;
 import org.apache.commons.dbutils.handlers.BeanListHandler;

 import com.domain.Department;
 import com.domain.Employee;
 import com.utils.JdbcUtils;

 public class DepartmentDao {
     //插入操作
     public void insert(Department d) throws SQLException{
         QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());

         //1、把Department对象的数据插入到department表
         String sql = "insert into department(id,name) values(?,?)";
         Object params[] = {d.getId(),d.getName()};
         runner.update(sql, params);

         //2、把department维护的所有员工保存在employee表
         Set<Employee> set = d.getEmployees();
         for(Employee e : set){
             sql = "insert into employee(id,name,salary,department_id) values(?,?,?,?)";

             //3、更新员工的外键列，说明员工所在的部门
             params = new Object[]{e.getId(),e.getName(),e.getSalary(),d.getId()};
             runner.update(sql, params);
         }
     }

     //查找
     public Department find(String id) throws SQLException{

         QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());

         //1.找部门表，查出部门的基本信息
         String sql = "select * from department where id=?";
         Department d = (Department) runner.query(sql, id, new BeanHandler(Department.class));

         //2.找员工表，找出部门下面所有员工
         sql = "select * from employee where department_id=?";
         List list = (List) runner.query(sql, id, new BeanListHandler(Employee.class));

         d.getEmployees().addAll(list);

         return d;
     }

     //删除
     public void delete(String id) throws SQLException{
         QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
         String sql = "delete from department where id=?";
         runner.update(sql, id);
     }
 }

4、service层

 package com.service;

 import java.sql.SQLException;

 import org.junit.Test;

 import com.dao.DepartmentDao;
 import com.domain.Department;
 import com.domain.Employee;

 public class Bservice {
     @Test
     public void add() throws SQLException{
         Department d = new Department();
         d.setId("111");
         d.setName("开发部");

         Employee e1 = new Employee();
         e1.setId("1");
         e1.setName("aa");
         e1.setSalary(10000);

         Employee e2 = new Employee();
         e2.setId("2");
         e2.setName("bb");
         e2.setSalary(10000);

         d.getEmployees().add(e1);
         d.getEmployees().add(e2);

         DepartmentDao dao = new DepartmentDao();
         dao.insert(d);
     }

     @Test
     //查找
     public void find() throws SQLException{

         DepartmentDao dao = new DepartmentDao();
         Department d = dao.find("111");
         System.out.println(d.getName());

     }

     @Test
     //删除
     public void delete() throws SQLException{

         DepartmentDao dao = new DepartmentDao();
         dao.delete("111");
     }
 }

5、工具类

JdbcUtils.java

 package com.utils;

 import java.io.IOException;
 import java.io.InputStream;
 import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.Properties;

 import javax.sql.DataSource;

 import org.apache.commons.dbcp.BasicDataSourceFactory;

 public class JdbcUtils {
     private static DataSource ds;
     static{
         try {
             Properties prop = new Properties();
             InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");
             prop.load(in);

             //创建数据源
             BasicDataSourceFactory factory = new BasicDataSourceFactory();
             ds = factory.createDataSource(prop);
         } catch (Exception e) {
             throw new ExceptionInInitializerError(e);
         }
     }

     //提供数据源
     public static DataSource getDataSource(){
         return ds;
     }

     //获取连接
     public static Connection  getConnection() throws SQLException{
         return ds.getConnection();
     }
 }

二、多对多关系：老师-----学生

1、数据库

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)
);

2、实体类

Teacher.java

 import java.util.HashSet;
 import java.util.Set;

 public class Teacher {
     private String id;
     private String name;
     private double salary;
10     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;
     }

 }

Student.java

 import java.util.HashSet;
 import java.util.Set;

 public class Student {
     private String id;
     private String name;
 9     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;
     }

 }

3、dao层

TeacherDao.java

 import java.sql.SQLException;
 import java.util.List;
 import java.util.Set;

 import org.apache.commons.dbutils.QueryRunner;
 import org.apache.commons.dbutils.handlers.BeanHandler;
 import org.apache.commons.dbutils.handlers.BeanListHandler;

 import cn.itcast.domain.Student;
 import cn.itcast.domain.Teacher;
 import cn.itcast.utils.JdbcUtils;

 public class TeacherDao {

     public void add(Teacher t) throws SQLException {

         QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());

         //1`.取出老师存老师表
         String sql = "insert into teacher(id,name,salary) values(?,?,?)";
         Object params[] = {t.getId(),t.getName(),t.getSalary()};
         runner.update(sql, params);

25         //2.取出老师所有学生的数据，存学生表
26         Set<Student> set = t.getStudents();
27         for(Student s : set){
28             sql = "insert into student(id,name) values(?,?)";
29             params = new Object[]{s.getId(),s.getName()};
30             runner.update(sql, params);
31
32             //3.更新中间表，说明老师和学生的关系
33             sql = "insert into teacher_student(teacher_id,student_id) values(?,?)";
34             params = new Object[]{t.getId(),s.getId()};
35             runner.update(sql, params);
36         }
37     }

     public Teacher find(String id) throws SQLException{

         QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());

         //1.找老师表，找出老师的基本信息
         String sql = "select * from teacher where id=?";
         Teacher t = (Teacher) runner.query(sql, id, new BeanHandler(Teacher.class));

47         //2.找出老师的所有学生    多表查询
49         sql = "select s.* from teacher_student ts,student s where ts.teacher_id=? and ts.student_id=s.id";
50         List list = (List) runner.query(sql, id, new BeanListHandler(Student.class));

         t.getStudents().addAll(list);
         return t;
     }

     public void delete(String id){
         QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
         String sql = "delete from teacher where id=?";

     }
 }

4、测试

     @Test
     public void addTeacher() throws SQLException{

         Teacher t = new Teacher();
         t.setId("1");
         t.setName("老张");
         t.setSalary(100000);

         Student s1 = new Student();
         s1.setId("1");
         s1.setName("aa");

         Student s2 = new Student();
         s2.setId("2");
         s2.setName("bb");

         t.getStudents().add(s1);
         t.getStudents().add(s2);

         TeacherDao dao = new TeacherDao();
         dao.add(t);
     }

     @Test
     public void findTeacher() throws SQLException{
         TeacherDao dao = new TeacherDao();
         Teacher t = dao.find("1");
         System.out.println(t);
     }