数据库_jdbc_dbutils的使用+存储复杂对象

概述

day17java工程搭建步骤:
1,src下新建lib目录,导入第3方jar包
	commons-dbcp-1.2.2.jar
	commons-dbutils-1.2.jar
	commons-pool.jar
	mysql-connector-java-5.0.8-bin.jar
2,src下导入dbcpconfig.properties,并改库名day17
3,表的设计(一对多)
	一对多的关系演示,表的设计,多的一方设置外键列!
	mysql -uroot -proot
	set character_set_client=gb2312;
	set character_set_results=gb2312;
	use day17;
	  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)
	  );
	  //删除drop 外键列foreign key 约束名是department_id_FK
	  alter table employee drop foreign key department_id_FK;	  
	  alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete set null;
	  
	  alter table employee drop foreign key department_id_FK;
	  alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete cascade;
4,表的设计(多对多)
	//多对多的表设计,中间表,联合主键+两个外键列
	mysql -uroot -proot
	set character_set_client=gb2312;
	set character_set_results=gb2312;
	create database day17 character set utf8 collate utf8_general_ci;
	use day17;
	create table teacher
	(
		id varchar(40) primary key,
		name varchar(40),
		salary double
	) ;
	create table student
	(
		id varchar(40) primary key,
		name varchar(40)
	);
	//多对多的表设计,中间表,联合主键+两个外键列
	 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)
	 );
	 
	 alter table teacher_student drop foreign key teacher_id_FK;
	 alter table teacher_student add constraint teacher_id_FK foreign key(teacher_id) references teacher(id) on delete cascade; 
	 
	 alter table teacher_student drop foreign key student_id_FK;
	 alter table teacher_student add constraint student_id_FK foreign key(student_id) references student(id) on delete cascade;
5,建立包
	domain包,
		Department类,(成员String id,String name,Set employees)
		Employee类,(成员String id,String name,Department d)
		Teacher类,(成员String id,String name,double salary,set students)生成getter setter方法
		Student类,(成员String id,String name)生成getter setter方法
	utils包,
		JdbcUtils
	dao包,(重点)
		TeacherDao专门负责Teacher对象的CRUD
	service包,
		Tservice,薄薄的,new个Teacher对象,赋值,调用TeacherDao进行CRUD
		Dservice,薄薄的,new个Department对象,赋值,调用DepartmentDao进行CRUD

User位于domain包

package cn.itcast.domain;

import java.util.Date;
//改类对应Demo1_Dbutils,演示Dbutils的使用,完成CRUD
public class User {
	private int id;
	private String name;
	private String password;
	private String email;
	private Date birthday;
	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 getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getEmail() {
		return email;
	}
	public void setEmail(String email) {
		this.email = email;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
}

Demo1_Dbutils位于demo包

package cn.itcast.demo;

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

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

import cn.itcast.domain.User;
import cn.itcast.utils.JdbcUtils;

//演示Dbutils的使用,完成CRUD
//Dbutils是Hibernate的备选,是对JDBC的简单封装,核心是QueryRunner和ResultSetHandler
//导入commons-dbutils-1.2.jar
/*
 创建库和表:
	mysql -uroot -proot
	set character_set_client=gb2312;
	set character_set_results=gb2312;
 	use day17;
	 create table users(
		id int primary key,
		name varchar(40),
		password varchar(40),
		email varchar(60),
		birthday date
	);
 */
public class Demo1_Dbutils {
	//方法1,使用Dbutils完成user表的插入
	@Test
	public void insert() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="insert into users(id,name,password,email,birthday) values(?,?,?,?,?)";
//		Object[] params={1,"林黛玉","12345","[email protected]",new Date()};
		Object[] params={2,"薛宝钗","12354","[email protected]",new Date()};
		qr.update(sql, params);
	}
	//方法2,使用Dbutils完成user表的更新
	@Test
	public void update() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="update users set password=? where id=?";
		Object[] params={"0123456",1};
		qr.update(sql, params);
	}
	//方法3,使用Dbutils完成user表的删除
	@Test
	public void delete() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="delete from users where id=?";
		//由于只有一个参数,故可不能参数数组
		qr.update(sql,1);
	}
	//方法4,使用Dbutils完成user表的查询,将第一条记录封装到User类里面
	@Test
	public void query_1() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users where id=?";
		//由于只有一个参数,故可不能参数数组
		User u1=(User) qr.query(sql, 1, new BeanHandler(User.class));
		System.out.println(u1.getName());
		System.out.println(u1.getBirthday());
	}
	//方法5,使用Dbutils完成user表的查询,将所有记录逐一封装到User类里面,
	//再将所有User逐一添加到list,返回list
	@Test
	public void query_2() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		List list=(List) qr.query(sql, new BeanListHandler(User.class));
		System.out.println(list.size());
		//上面这儿停个断点,然后Debug As Junit Test
	}
	//方法6,使用Dbutils完成user表的批量插入(关键是二维数组使用)
	@Test
	public void batch() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="insert into users(id,name,password,email,birthday) values(?,?,?,?,?)";
		//(关键是二维数组使用)插入3条记录,每条记录需要5个参数
		Object[][] params=new Object[3][5];
		for (int i = 0; i < params.length; i++) {
			params[i]=new Object[]{3+i,"路人"+(i+1),"123","[email protected]",new Date()};
		}
		qr.batch(sql, params);
	}
}

Demo2_Dbutils位于demo包

package cn.itcast.demo;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Map;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.ArrayHandler;
import org.apache.commons.dbutils.handlers.ArrayListHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.KeyedHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import org.junit.Test;

import cn.itcast.domain.User;
import cn.itcast.utils.JdbcUtils;
//演示Dbutils的各个结果集处理器的使用
//Dbutils是Hibernate的备选,是对JDBC的简单封装,核心是QueryRunner和ResultSetHandler
//导入commons-dbutils-1.2.jar
/*
 创建库和表:
	mysql -uroot -proot
	set character_set_client=gb2312;
	set character_set_results=gb2312;
 	use day17;
	 create table users(
		id int primary key,
		name varchar(40),
		password varchar(40),
		email varchar(60),
		birthday date
	);
	
Class Summary
AbstractListHandler	Abstract class that simplify development of ResultSetHandler classes that convert ResultSet into List.
ArrayHandler	作用是:  converts a ResultSet into an Object[].
ArrayListHandler	作用是: converts the ResultSet into a List of Object[]s.
BeanHandler	作用是: converts the first ResultSet row into a JavaBean.
BeanListHandler	作用是: converts a ResultSet into a List of beans.
ColumnListHandler	作用是: converts one ResultSet column into a List of Objects.
KeyedHandler	作用是: returns a Map of Maps.
MapHandler	作用是: converts the first ResultSet row into a Map.
MapListHandler	作用是: converts a ResultSet into a List of Maps.
ScalarHandler	作用是: converts one ResultSet column into an Object.
	
 */
public class Demo2_Dbutils {
	/*Dbutils的结果集处理器_ArrayHandler的使用
	ArrayHandler(不需要参数)	作用是:  只将结果集的第一行记录的值保存到数组里!
	converts a ResultSet into an Object[].*/
	@Test
	public void ArrayHandler() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		Object[] arr=(Object[]) qr.query(sql, new ArrayHandler());
		for (Object obj : arr) {
			System.out.println(obj);
		}
		/*
		 1
		林黛玉
		12345
		[email protected]
		2013-12-29*/
	}
	/*Dbutils的结果集处理器_ArrayListHandler的使用
	ArrayListHandler(不需要参数)	作用是:  将结果集的每行记录的值保存到数组里
	再将这些数组,保存到一个集合里面!
	converts the ResultSet into a List of Object[]s*/
	@Test
	public void ArrayListHandler() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		List list=(List) qr.query(sql, new ArrayListHandler());
		for (Object arr : list) {
			Object[] a=new Object[]{};
			a=(Object[]) arr;
			for (Object value : a) {
				System.out.println(value);
				/*
				1
				林黛玉
				12345
				[email protected]
				2013-12-29
				2
				薛宝钗
				12354
				[email protected]
				2013-12-29*/

			}
		}
	}
	/*Dbutils的结果集处理器_ColumnListHandler的使用
	ColumnListHandler(需要参数:列名)	作用是:  只将指定列名的数据存入list(如取出所有名字)
	converts one ResultSet column into a List of Objects.*/
	@Test
	public void ColumnListHandler() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		List list=(List) qr.query(sql, new ColumnListHandler_my("name"));//需指定列名
		for (Object obj : list) {
			System.out.println(obj);//打印的是姓名列的所有值
			//林黛玉
			//薛宝钗

		}
	}
	//自己实现将指定列的数据存入list
	//自己写一个ColumnListHandler
	class ColumnListHandler_my implements ResultSetHandler{
		private String columnName;
		public ColumnListHandler_my(String columnName) {
			super();
			this.columnName = columnName;
		}
		public Object handle(ResultSet rs) throws SQLException {
			// 覆盖接口的方法
			//取出构造时指定的列名下所有的值,加到list,并返回list
			List list=new ArrayList();
			while(rs.next()){
				Object obj=rs.getObject(columnName);
				list.add(obj);
			}
			return list;
		}
		
	}
	
	
	
	
	
	
	
	
	
	/*ResultSetHandler 接口的实现类	KeyedHandler(keyName)：
	 * 将结果集中的每一行数据都封装到一个Map里(键为列名,值为列上值)，
	 * 再把这些map再存到一个map里，其key为指定的参数keyName。
	*/
	/*Dbutils的结果集处理器_KeyedHandler的使用(难点是泛型!)
	KeyedHandler(需要参数:列名作为key)	作用是:  将结果集的每一行都封装到
	一个小map(键为字段名,值为该字段的值),再将这些map存到另一个大map里面,
	(键为构造时的参数,即指定的列名为大map的键,值为小map)
	returns a Map of Maps*/
	@Test
	public void KeyedHandler() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		//表在设计时id是int类型,泛型是对象,所以键为Integer,
		//值是一个MAP(键是字段名,所以是String,值是字段上的值,所以是Object)
		Map<Integer, Map<String, Object>> map=(Map) qr.query(sql, new KeyedHandler("id"));
		for (Map.Entry<Integer, Map<String, Object>> en : map.entrySet()) {
			int id=en.getKey();
			Map<String, Object> map_0=en.getValue();
			for (Map.Entry<String, Object> entry : map_0.entrySet()) {
				String columnName=entry.getKey();
				Object columnValue=entry.getValue();
				System.out.println(columnName+" : "+columnValue);
				/*
				password : 12354
				email : [email protected]
				name : 薛宝钗
				id : 2
				birthday : 2013-12-29
				password : 12345
				email : [email protected]
				name : 林黛玉
				id : 1
				birthday : 2013-12-29*/

			}
		}
	}
	/*Dbutils的结果集处理器_MapHandler的使用
	MapHandler(不需要参数)	作用是:  只将结果集的第一行都封装到Map
	(键为字段名,值为该字段的值)
	converts the first ResultSet row into a Map.*/
	@Test
	public void MapHandler() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		Map<String, Object> map=(Map<String, Object>) qr.query(sql, new MapHandler());
		for (Map.Entry<String, Object> entry : map.entrySet()) {
			String columnName=entry.getKey();
			Object columnValue=entry.getValue();
			System.out.println(columnName+" : "+columnValue);
			/*
			password : 12345
			email : [email protected]
			name : 林黛玉
			id : 1
			birthday : 2013-12-29*/
		}
	}
	/*Dbutils的结果集处理器_MapListHandler的使用
	MapListHandler(不需要参数)	作用是:  只将结果集的每一行都封装到Map
	(键为字段名,值为该字段的值),再将这些Map逐个添加到集合list
	converts a ResultSet into a List of Maps.*/
	@Test
	public void MapListHandler() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		List<Map<String, Object>> list=(List<Map<String, Object>>) qr.query(sql, new MapListHandler());
		for (Map<String, Object> map : list) {
			for (Map.Entry<String, Object> entry : map.entrySet()) {
				String columnName=entry.getKey();
				Object columnValue=entry.getValue();
				System.out.println(columnName+" : "+columnValue);
				/*
				password : 12345
				email : [email protected]
				name : 林黛玉
				id : 1
				birthday : 2013-12-29
				password : 12354
				email : [email protected]
				name : 薛宝钗
				id : 2
				birthday : 2013-12-29*/

			}
		}
	}
	/*Dbutils的结果集处理器_ScalarHandler的使用
	ScalarHandler(需要参数:列名或列索引)	作用是:  将指定列的值封装成一个Object对象返回
	适合统计count(*)  count(user.id) 注意千万不能有空格!
	 converts one ResultSet column into an Object.
	 //ScalarHandler(参数int第几列,String列名) 将指定的列值存入到一个Object
	 */
	@Test
	public void ScalarHandler_1() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select count(*) from users";
		Object obj=qr.query(sql, new ScalarHandler(1));
		//System.out.println(obj); 2
		//注意obj直接转成Integer会出现类转换异常!?
		Long totalRecord=(Long) obj;
		Integer i= totalRecord.intValue();
		System.out.println(i);//2
	}
	@Test
	public void ScalarHandler_2() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select count(*) from users";
		//ScalarHandler(参数int第几列,String列名) 将指定的列值存入到一个Object
		Object obj=qr.query(sql, new ScalarHandler(1));
		Integer i=((Long)obj).intValue();
		System.out.println(i);
	}
	@Test
	public void totalRecord_3() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select count(*) from users";
		Object[] obj=(Object[]) qr.query(sql, new ArrayHandler());
		//因为ArrayHandler()返回的对象数组中的数字全是Long类型!不能强转成Integer
		//对象数组的第1个成员中保存的就是总记录数
		Integer i=((Long)obj[0]).intValue();
		System.out.println(i);
	}
	@Test
	public void totalRecord_4() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select count(*) from users";
		//ScalarHandler(参数int第几列,String列名) 将指定的列值存入到一个Object
		Integer i=((Long) qr.query(sql, new ScalarHandler(1))).intValue();
		System.out.println(i);
	}
	//方法4,使用Dbutils完成user表的查询,将第一条记录封装到User类里面
	@Test
	public void query_1() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users where id=?";
		//由于只有一个参数,故可不能参数数组
		User u1=(User) qr.query(sql, 1, new BeanHandler(User.class));
		System.out.println(u1.getName());
		System.out.println(u1.getBirthday());
	}
	//方法5,使用Dbutils完成user表的查询,将所有记录逐一封装到User类里面,
	//再将所有User逐一添加到list,返回list
	@Test
	public void query_2() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="select * from users";
		List list=(List) qr.query(sql, new BeanListHandler(User.class));
		System.out.println(list.size());
		//上面这儿停个断点,然后Debug As Junit Test
	}
	//方法6,使用Dbutils完成user表的批量插入(关键是二维数组使用)
	@Test
	public void batch() throws SQLException{
		//要使用Dbutils,不管三七二十一,先new个QueryRunner
		QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
		String sql="insert into users(id,name,password,email,birthday) values(?,?,?,?,?)";
		//(关键是二维数组使用)插入3条记录,每条记录需要5个参数
		Object[][] params=new Object[3][5];
		for (int i = 0; i < params.length; i++) {
			params[i]=new Object[]{3+i,"路人"+(i+1),"123","[email protected]",new Date()};
		}
		qr.batch(sql, params);
	}
}

JdbcUtils位于utils包

package cn.itcast.utils;
import java.io.InputStream;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
/**演示开源数据库连接池DBCP的使用
DBCP内部增强Connection的close方法使用的是装饰模式!
1,导入两个jar包到工程下的lib目录,变成奶瓶
commons-dbcp-1.2.2.jar
commons-pool.jar
2,设置src下的dbcpconfig.properties配置文件信息如库名!
3,新建一个工具类如:JdbcUtils_DBCP
4,定义成员记住DBCP创建出来的数据源(即连接池)
5,静态代码块中用BasicDataSourceFactory创建数据源(即连接池)
6,定义获取连接的方法
7,定义释放连接的方法
*/
public class JdbcUtils {
	private static DataSource ds;
	static{
	      try {
	         String pro_name="dbcpconfig.properties";
	          InputStream in=JdbcUtils.class.getClassLoader().getResourceAsStream(pro_name);
	          Properties pro = new Properties();
	          pro.load(in);
	        //DBCP连接池--固定代码:由工厂创建数据源(即连接池)
	          BasicDataSourceFactory factory=new BasicDataSourceFactory();
	          //用类成员记住根据配置文件创建出来的连接池!
	          ds=factory.createDataSource(pro);
	      } catch (Exception e) {
	         throw new ExceptionInInitializerError(e);
	      }
	}
	public static DataSource getDataSource(){
		//Dbutils工具构造函数需要一个连接池
		return ds;
	}
}

Department位于domain包

package cn.itcast.domain;

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

public class Department {
   private String id;
   private String name;
   //能不设计,就不设计!尽量不要记住多的一方
   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;
   }
}

Employee位于domain包

package cn.itcast.domain;
public class Employee {
   private String id;
   private String name;
   private double salary;
   private String department_id;
   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 String getDepartment_id() {
      return department_id;
   }
   public void setDepartment_id(String department_id) {
      this.department_id = department_id;
   }
}

DepartmentDao位于dao包

package cn.itcast.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 cn.itcast.domain.Department;
import cn.itcast.domain.Employee;
import cn.itcast.utils.JdbcUtils;
//1对多的关系演示CRUD
public class DepartmentDao {
   /*一对多的关系演示,表的设计,多的一方设置外键列!
     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)
     );
     //删除drop 外键列foreign key 约束名是department_id_FK
     alter table employee drop foreign key department_id_FK;     
     alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete set null;
     
     alter table employee drop foreign key department_id_FK;
     alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete cascade;
    */
   //这时候就是将1对多的复杂对象添加到数据库中!(涉及到多表操作!)
   public void add(Department d) throws SQLException{
      //为了简化开发,不管三七二十一,先new个QueryRunner
      QueryRunner qr=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()};
      qr.update(sql, params);
      //2.把department对象中维护的所有员工插入到员工表
      //3.更新员工表的外键列，说明员工的部门
      Set<Employee> set=d.getEmployees();
      for (Employee e : set) {
         sql="insert into employee(id,name,salary,department_id) values(?,?,?,?)";
         params=new Object[]{e.getId(),e.getName(),e.getSalary(),d.getId()};
         qr.update(sql, params);
      }      
   }
   //实际开发中,涉及到查找时,看需求,尽量不要查找出将多的一方!内存溢出!
   //实在要查(如订单:订单项),就用分页查询,limit X,Y
   //避免使用1对多,而要用多对1
   public Department find(String id) throws SQLException {
      QueryRunner qr=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) qr.query(sql, id, new BeanHandler(Department.class));
      //2.找员工表，找出部门下面所有员工(实际开发中慎用,内存溢出!)
      sql="select * from employee where department_id=?";
      List<Employee> list=(List<Employee>) qr.query(sql, id, new BeanListHandler(Employee.class));
      //List.add(list)是将list集合作为一个成员加入到List
      //List.addAll(list)是将list中的每一个成员逐一添加到List,所以这儿要用addAll
      d.getEmployees().addAll(list);
      return d;
   }

   public void delete_tranditional(String id) throws SQLException {
      // 传统方式删除1对多的Department对象
      //传统方法:先解除关系,即在多的一方将外键列置空,然后删除部门表
      QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
      String sql="update employee set department_id=null where department_id=?";
      qr.update(sql, id);
      sql="delete from department where id=?";
      qr.update(sql, id);
   }
   public void delete_cascade(String id) throws SQLException{
      //简单方法:创建员工表的时候设置级联(参数MYSQL文档)!
      QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
      //先删除掉employee表中原来的外键约束
      String sql="alter table employee drop foreign key department_id_FK";
      qr.update(sql);
      //然后添加一个带级联的外键约束
      sql="alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete set null";
      qr.update(sql);      
      //最后执行删除动作
      sql= "delete from department where id=?";
      qr.update(sql, id);
      /*
      //设置级联置空(on delete set null)
        //删除drop 外键列foreign key 约束名是department_id_FK
        alter table employee drop foreign key department_id_FK;     
        alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete set null;
        //设置级联删除(on delete cascade),部门解散的,员工全开除!
        alter table employee drop foreign key department_id_FK;
        alter table employee add constraint department_id_FK foreign key(department_id) references department(id) on delete cascade;
      
      reference_definition:
       REFERENCES tbl_name [(index_col_name,...)]
                  [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
                  [ON DELETE reference_option]
                  [ON UPDATE reference_option]
      reference_option:
          RESTRICT | CASCADE(级联删除) | SET NULL(级联置空) | NO ACTION
      */
   }
}

Dservice位于service包

package cn.itcast.service;
import java.sql.SQLException;
import org.junit.Test;
import cn.itcast.dao.DepartmentDao;
import cn.itcast.domain.Department;
import cn.itcast.domain.Employee;
public class Dservice {
	//薄薄的业务层,调用DAO添加一个部门对象到数据库
	@Test
	public void addDepartment() throws SQLException{
		Department d=new Department();
      d.setId("1");
      d.setName("工程部");
      Employee e1=new Employee();
      e1.setId("1");
      e1.setName("唐部长");
      e1.setSalary(1000);
      e1.setDepartment_id(d.getId());
      Employee e2=new Employee();
      e2.setId("2");
      e2.setName("桥梁技术员甲");
      e2.setSalary(100);
      e2.setDepartment_id(d.getId());
      Employee e3=new Employee();
      e3.setId("3");
      e3.setName("道路技术员乙");
      e3.setSalary(100);
      e3.setDepartment_id(d.getId());
      d.getEmployees().add(e1);
      d.getEmployees().add(e2);
      d.getEmployees().add(e3);
      //现在要将1对多的关系中的复杂对象Department存入数据库!
      DepartmentDao dao=new DepartmentDao();
      dao.add(d);
   }
   //薄薄的业务层,调用DAO根据id,查找出一个部门对象
   @Test
   public void find() throws SQLException{
      //现在要将1对多的关系中的复杂对象Department查找出来!
      DepartmentDao dao=new DepartmentDao();
      Department d=dao.find("1");
      System.out.println(d);
   }
   @Test
   public void delete1() throws SQLException{
      //现在要将1对多的关系中的复杂对象Department删除!
      DepartmentDao dao=new DepartmentDao();
      dao.delete_tranditional("1");
   }
   @Test
   public void delete2() throws SQLException{
      //现在要将1对多的关系中的复杂对象Department级联删除!
      DepartmentDao dao=new DepartmentDao();
      dao.delete_cascade("1");
   }
}

Teacher位于domain包

package cn.itcast.domain;
import java.util.HashSet;
import java.util.Set;
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;
   }
}

Student位于domain包

package cn.itcast.domain;
public class Student {
   private String id;
   private String name;
   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;
   }   
}

TeacherDao位于dao包

package cn.itcast.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 cn.itcast.domain.Student;
import cn.itcast.domain.Teacher;
import cn.itcast.utils.JdbcUtils;
//多对多的关系演示CRUD
/*多对多的表设计,中间表,联合主键+两个外键列
mysql -uroot -proot
set character_set_client=gb2312;
set character_set_results=gb2312;
create database day17 character set utf8 collate utf8_general_ci;
use day17;
create table teacher
(
   id varchar(40) primary key,
   name varchar(40),
   salary double
) ;
create table student
(
   id varchar(40) primary key,
   name varchar(40)
);
//多对多的表设计,中间表,联合主键+两个外键列
 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)
 );
 先删除外键约束
 alter table teacher_student drop foreign key teacher_id_FK;
 再添加一个外键约束(级联删除,即teacher表删除的时候,中间表的记录会被删除)
 alter table teacher_student add constraint teacher_id_FK foreign key(teacher_id) references teacher(id) on delete cascade; 
 先删除外键约束
 alter table teacher_student drop foreign key student_id_FK;
 再添加一个外键约束(级联删除,即student表删除的时候,中间表的记录会被删除)
 alter table teacher_student add constraint student_id_FK foreign key(student_id) references student(id) on delete cascade;
*/
public class TeacherDao {
   //多对多关系的方法1:添加一个Teacher对象到数据库
   //应该放到一个事务里面执行将多对多的关系中的Teacher存入数据库
   public void add(Teacher t) throws SQLException {
      //为了简化开发,不管三七二十一,先new个QueryRunner
      QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
      //1.取出Teacher基本信息,存Teacher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Teacher所有学生的数据，存学生表
      Set<Student> set=t.getStudents();
      for (Student s : set) {
         sql="insert into student(id,name) values(?,?)";
         //数组的静态初始化只能执行一次!
         params=new Object[]{s.getId(),s.getName()};
         qr.update(sql, params);
         //3.更新中间表，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);
      }
      
   }
   //多对多关系的方法2:查找并返回一个Teacher对象(涉及多表查询)
   public Teacher find(String id) throws SQLException{
      //为了简化开发,不管三七二十一,先new个QueryRunner
      QueryRunner qr=new QueryRunner(JdbcUtils.getDataSource());
      //1.找Teacher表，找出Teacher的基本信息
      String sql="select * from teacher where id=?";
      Teacher t=(Teacher) qr.query(sql, id, new BeanHandler(Teacher.class));
      //多表查询(重点)
      //2.找出老师的所有学生(实际开发中尽量不用,内存溢出)
      //sql="select * from teacher_student ts,student s where ts.teacher_id=? and ts.student_id=s.id";
      //s.*代表只取出所有学生的信息
      sql="select s.* from teacher_student ts,student s where ts.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;
   }
   //多对多关系的方法3:从数据库删除出一个对象(创建表的时候可以使用级联)
   public void delete(String id) throws SQLException{
      //为了简化开发,不管三七二十一,先new个QueryRunner
      QueryRunner qr = new QueryRunner(JdbcUtils.getDataSource());
      String sql = "delete from teacher where id=?";
      qr.update(sql, id);
   }
}

Tservice位于service包

package cn.itcast.service;
import java.sql.SQLException;
import org.junit.Test;
import cn.itcast.dao.TeacherDao;
import cn.itcast.domain.Student;
import cn.itcast.domain.Teacher;
public class Tservice {
	public static void main(String[] args) throws SQLException {
		TeacherDao dao=new TeacherDao();
		Teacher t=dao.find("1");
		System.out.println(t);
	}
	@Test
	public void addTeacher() throws SQLException{
		Teacher t=new Teacher();
      t.setId("1");
      t.setName("贾代儒");
      t.setSalary(1000);
      Student st1=new Student();
      st1.setId("1");
      st1.setName("宝玉");
      Student st2=new Student();
      st2.setId("2");
      st2.setName("秦钟");
      t.getStudents().add(st1);
      t.getStudents().add(st2);
      //现在要将多对多的关系中的复杂对象Teacher存入数据库!
      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);
   }
}

dbcpconfig.properties位于src目录

#连接设置
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/day17
#url=jdbc:mysql://localhost:3306/day16
#url=jdbc:mysql://localhost:3306/day14_customer
username=root
password=root
#<!-- 初始化连接 -->
initialSize=10
#最大连接数量
maxActive=50
#<!-- 最大空闲连接 -->
maxIdle=20
#<!-- 最小空闲连接 -->
minIdle=5
#<!-- 超时等待时间以毫秒为单位 6000毫秒/1000等于60秒 即等1分钟后仍没连接,这时才告诉人家,呆会再来,暂无连接! -->
maxWait=60000
#JDBC驱动建立连接时附带的连接属性属性的格式必须为这样：[属性名=property;] 
#注意："user" 与 "password" 两个属性会被明确地传递，因此这里不需要包含他们。
connectionProperties=useUnicode=true;characterEncoding=utf8
#指定由连接池所创建的连接的自动提交（auto-commit）状态。
defaultAutoCommit=true
#driver default 指定由连接池所创建的连接的只读（read-only）状态。
#如果没有设置该值，则“setReadOnly”方法将不被调用。（某些驱动并不支持只读模式，如：Informix）
defaultReadOnly=
#driver default 指定由连接池所创建的连接的事务级别（TransactionIsolation）。
#可用值为下列之一：（详情可见javadoc。）NONE,READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ, SERIALIZABLE
defaultTransactionIsolation=READ_COMMITTED

用到的第3方jar包

mysql-connector-java-5.0.8-bin.jar
commons-dbcp-1.2.2.jar
commons-pool.jar
commons-dbutils-1.2.jar