01 08Java中级之数据表与简单Java类映射转换

1 综合实战：数据表与简单Java类的映射转换

简单Java类是面向对象设计的主要分析基础。主要根据数据表的结构来实现简单Java类。

在数据库之中实际是提供有若干数据表的。在实际开发中，数据表与简单Java类之间的基本映射关系如下：

• 数据实体表的设计 = 类的定义；
• 表中的字段 = 类的成员属性；
• 表的外键关联 = 引用关联；
• 表的一行记录 = 类的一个实例化对象；
• 表的多行记录 = 对象数组。
  
  以上所对应数据表的关系之中可以发现有如下的关联存在：
• 一个部门有多个雇员；
• 一个雇员属于一个部门；
• 一个雇员有一个领导；
  下面将以上数据表转化为简单Java类的定义形式，在整个的程序代码之中要求可以获得如下信息：

1. 根据部门信息获得以下内容：
   （1）一个部门的完整信息；
   （2）一个部门之中所有雇员的完整信息；
   （3）一个雇员对应的领导的信息；
2. 根据雇员信息获得以下内容：
   （1）一个雇员所在部门信息；
   （2）一个雇员对应领导信息；

class Dept{
	private long code;
	private String name;
	private String location;
	private Emp emps[];

	public Dept(){}

	public Dept(long code, String name, String location){
		this.code = code;
		this.name = name;
		this.location = location;
	}

	public String getInfo(){
		return "部门编号： " + this.code + " 部门名称：" + this.name + " 部门地址：" + this.location;
	}

	public void setEmps(Emp[] emps){
		this.emps = emps;
	} 

	public Emp[] getEmps(){
		return this.emps;
	}

	public void setCode(long code){
		this.code = code;
	}

	public void setName(String name){
		this.name = name;
	}

	public void setLocation(String location){
		this.location = location;
	}

	public long getCode(){
		return this.code;
	}

	public String getName(){
		return this.name;
	}

	public String getLocation(){
		return this.location;
	}

}

class Emp{
	private long code;
	private String name;
	private String job;
	private double salary;
	private double commission;
	private Dept dept;
	private Emp manager;

	public Emp(){}

	public Emp(long code, String name, String job, double salary, double commission){
		this.code = code;
		this.name = name;
		this.job = job;
		this.salary = salary;
		this.commission = commission;
	}

	public String getInfo(){
		return "雇员编号：" + this.code + " 雇员姓名：" + this.name + " 雇员职位：" + this.job + " 雇员工资：" + this.salary + " 雇员佣金：" + this.commission;
	}

	public void setDept(Dept dept){
		this.dept = dept;
	}

	public Dept getDept(){
		return this.dept;
	}

	public void setManager(Emp manager){
		this.manager = manager;
	}

	public Emp getManager(){
		return this.manager;
	}

	public void setCode(long code){
		this.code = code;
	}

	public void setName(String name){
		this.name = name;
	}

	public void setJob(String job){
		this.job = job;
	}

	public void setSalary(double salary){
		this.salary = salary;
	}

	public void setCommission(double commission){
		this.commission = commission;
	}

	public long getCode(){
		return this.code;
	}

	public String getName(){
		return this.name;
	}

	public String getJob(){
		return this.job;
	}

	public double getSalary(){
		return this.salary;
	}

	public double getCommission(){
		return this.commission;
	}


}

public class JavaDemo{
	public static void main(String[] args){
		Dept dept = new Dept(10L, "软件开发部", "fujian, China");
		Emp empA = new Emp(1001L, "zsl", "java", 2000.0, 0.0);
		Emp empB = new Emp(1002L, "lks", "java", 3000.0, 0.0);
		Emp empC = new Emp(1003L, "hhy", "java", 4000.0, 0.0);
		dept.setEmps(new Emp[]{empA, empB, empC});
		empA.setDept(dept);
		empB.setDept(dept);
		empC.setDept(dept);
		empA.setManager(empB);
		empB.setManager(empC);
		System.out.println(dept.getInfo());
		for( int i = 0; i < dept.getEmps().length; i++ ){
			System.out.println("\t|- " + dept.getEmps()[i].getInfo());
			if(dept.getEmps()[i].getManager() != null){
				System.out.println("\t\t|- " + dept.getEmps()[i].getManager().getInfo());
			}
		}
		System.out.println(empA.getDept().getInfo());
		System.out.println(empA.getManager().getInfo());
	}
}

对于数据表与简单Java类之间的映射最好的解决步骤：
3. 先抛开所有的关联字段不看，写出类的基本组成，而后再通过引用配置关联字段的关系。
4. 配置关联字段。

在以后进行实际项目开发的过程之中一定是分两个步骤实现的：

• 第一步：根据表的结构关系进行对象的配置；
• 第二步：根据要求通过结构获取数据。

2 综合实战：一对多映射

按照表的要求将表的结构转换为类结构，同时可以获取如下信息：

• 获取一个分类的完整信息；
• 可以根据分类获取其对应的所有子分类信息。

class Divide{
	private long id;
	private String name;
	private DivideChild dividechild[];

	public Divide(){}

	public Divide(long id, String name){
		this.id = id;
		this.name = name;
	}

	public String getInfo(){
		return "分类ID：" + this.id + " 分类名称：" + this.name;
	}

	public void setDivideChild(DivideChild dividechild[]){
		this.dividechild = dividechild;
	}

	public DivideChild[] getDivideChild(){
		return this.dividechild;
	}

	public void setId(long id){
		this.id = id;
	}

	public void setName(String name){
		this.name = name;
	}

	public long getId(){
		return this.id;
	}

	public String getName(){
		return this.name;
	}
}

class DivideChild{
	private long id;
	private String name;
	private Divide divide;

	public DivideChild(){}

	public DivideChild(long id, String name){
		this.id = id;
		this.name = name;
	}

	public String getInfo(){
		return "子分类ID：" + this.id + " 子分类名称：" + this.name;
	}

	public void setDivide(Divide divide){
		this.divide = divide;
	}

	public void setId(long id){
		this.id = id;
	}

	public void setName(String name){
		this.name = name;
	}

	public long getId(){
		return this.id;
	}

	public String getName(){
		return this.name;
	}
}

public class JavaDemo{
	public static void main(String[] args){
		//first step: 进行对象关系配置
		Divide one = new Divide(1L, "book");
		DivideChild[] oneA = new DivideChild[]{
			new DivideChild(11L, "soft"),
			new DivideChild(12L, "hard")
		};
		one.setDivideChild(oneA);
		for( int i =0; i < oneA.length; i++ ){
			oneA[i].setDivide(one);
		}

		//second step：获取数据
		System.out.println(one.getInfo());
		for( int i =0; i < one.getDivideChild().length; i++ ){
			System.out.println("\t|- " + one.getDivideChild()[i].getInfo());
		}
	}
}

3 综合实战：多对多映射

按照表的要求将表的结构转换为类结构，同时可以获取如下信息：

• 获取一个用户访问的所有商品的详细信息；
• 获取一个商品被浏览过的全部的用户信息。

class Member {
	private long mid;
	private String name;
	private Product products[];

	public Member(){}

	public Member(long mid, String name){
		this.mid = mid;
		this.name = name;
	}

	public void setProducts(Product[] products){
		this.products = products;
	}

	public Product[] getProducts(){
		return this.products;
	}

	public String getInfo(){
		return "user' id: " + this.mid + "user's name: " + this.name; 
	}

	public void setMid(long mid){
		this.mid = mid;
	}

	public void setName(String name){
		this.name = name;
	}

	public long getMid(){
		return this.mid;
	}

	public String getName(){
		return this.name;
	}
}

class Product{
	private long pid;
	private String name;
	private Member members[];

	public Product(){}

	public Product(long pid, String name){
		this.pid = pid;
		this.name = name;
	}

	public void setMembers(Member[] members){
		this.members = members;
	}

	public Member[] getMembers(){
		return this.members;
	}

	public String getInfo(){
		return "Product's id: " + this.pid + "product's name: " + this.name; 
	}

	public void setPid(long pid){
		this.pid = pid;
	}

	public void setName(String name){
		this.name = name;
	}

	public long getPid(){
		return this.pid;
	}

	public String getName(){
		return this.name;
	}
}

public class JavaDemo{
	public static void main(String[] args){
		//first step: 进行对象关系配置
		Member memA = new Member(1001L, "lks");
		Member memB = new Member(1002L, "hhy");
		Product proA = new Product(1L, "zsl");
		Product proB = new Product(2L, "zslll");
		Product proC = new Product(3L, "zslllll");
		memA.setProducts(new Product[]{proA, proB, proC});
		memB.setProducts(new Product[]{proA, proC});
		proA.setMembers(new Member[]{memA, memB});
		proB.setMembers(new Member[]{memA});
		proC.setMembers(new Member[]{memA, memB});
		//second step：获取数据
		System.out.println("----------------显示用户访问商品信息--------------");
		System.out.println(memA.getInfo());
		for(int i = 0; i < memA.getProducts().length; i++){
			System.out.println(memA.getProducts()[i].getInfo());
		}
		System.out.println("----------------显示商品访问用户信息--------------");
		System.out.println(proA.getInfo());
		for(int i = 0; i < proA.getMembers().length; i++){
			System.out.println(proA.getMembers()[i].getInfo());
		}
	}
}

4 综合实战：复杂多对多映射

在进行实际项目开发过程中，对于用户的授权管理是一项重要的任务，下面给出了一个最为常见的用户权限管理的表结构设计，基本关系如下：

• 一个用户可以拥有多个角色，一个角色可能有多个用户；
• 一个角色可以拥有多个权限；
  
  要求实现如下查询功能：
• 可以根据一个用户找到该用户对应的所有角色，以及每一个角色对应的所有权限信息；
• 可以根据一个角色找到该角色下的所有权限，以及拥有此角色的全部用户信息；
• 可以根据一个权限找到具备有此权限的所有用户信息。

class Member {
	private String mid;
	private String name;
	private Role roles[];

	public Member(){}

	public Member(String mid, String name){
		this.mid = mid;
		this.name = name;
	}

	public void setRoles(Role[] roles){
		this.roles = roles;
	}

	public Role[]  getRoles(){
		return this.roles;
	}

	public String getInfo(){
		return "[Member] id: " + this.mid + "; name: " + this.name; 
	}

	public void setMid(String mid){
		this.mid = mid;
	}

	public void setName(String name){
		this.name = name;
	}

	public String getMid(){
		return this.mid;
	}

	public String getName(){
		return this.name;
	}
}

class Role {
	private String rid;
	private String name;
	private Member members[];
	private Privilege privileges[];

	public Role(){}

	public Role(String rid, String name){
		this.rid = rid;
		this.name = name;
	}

	public void setMembers(Member[] members){
		this.members = members;
	}

	public void setPrivileges(Privilege[] privileges){
		this.privileges = privileges;
	}

	public Member[] getMembers(){
		return this.members;
	}

	public Privilege[] getPrivileges(){
		return this.privileges;
	}

	public String getInfo(){
		return "[Role] id: " + this.rid + "; name: " + this.name; 
	}

	public void setRid(String rid){
		this.rid = rid;
	}

	public void setName(String name){
		this.name = name;
	}

	public String getRid(){
		return this.rid;
	}

	public String getName(){
		return this.name;
	}
}

class Privilege {
	private String pid;
	private String name;
	private Role role;

	public Privilege(){}

	public Privilege(String pid, String name){
		this.pid = pid;
		this.name = name;
	}

	public void setRole(Role role){
		this.role = role;
	}

	public Role getRole(){
		return this.role;
	}

	public String getInfo(){
		return "[Privilege] id: " + this.pid + "; name: " + this.name; 
	}

	public void setPid(String pid){
		this.pid = pid;
	}

	public void setName(String name){
		this.name = name;
	}

	public String getPid(){
		return this.pid;
	}

	public String getName(){
		return this.name;
	}
}

public class JavaDemo{
	public static void main(String[] args){
		//first step: 进行对象关系配置
		Member memA = new Member("1001", "lks");
		Member memB = new Member("1002", "hhy");
		Role roleA = new Role("5201", "system");
		Role roleB = new Role("5202", "people");
		Role roleC = new Role("5203", "data");
		Privilege privA=new Privilege("13141", "system shutdown");
		Privilege privB=new Privilege("13142", "system restart");
		Privilege privC=new Privilege("13143", "system initlize");
		Privilege privD=new Privilege("23141", "people add");
		Privilege privE=new Privilege("23142", "people delete");
		Privilege privF=new Privilege("23143", "people edit");
		Privilege privG=new Privilege("33141", "data copy");
		Privilege privH=new Privilege("33142", "data delete");
		Privilege privI=new Privilege("33143", "data cut");
		Privilege privJ=new Privilege("33144", "data clear");

		roleA.setPrivileges(new Privilege[]{privA, privB, privC});
		roleB.setPrivileges(new Privilege[]{privD, privE, privF});
		roleC.setPrivileges(new Privilege[]{privG, privH, privI, privJ});

		privA.setRole(roleA);
		privB.setRole(roleA);
		privC.setRole(roleA);
		privD.setRole(roleB);
		privE.setRole(roleB);
		privF.setRole(roleB);
		privG.setRole(roleC);
		privH.setRole(roleC);
		privI.setRole(roleC);
		privJ.setRole(roleC);

		memA.setRoles(new Role[]{roleA, roleB, roleC});
		memB.setRoles(new Role[]{roleA, roleC});

		roleA.setMembers(new Member[]{memA, memB});
		roleB.setMembers(new Member[]{memA});
		roleC.setMembers(new Member[]{memA, memB});
		//second step：获取数据
		System.out.println("-----------Member------------");
		System.out.println(memA.getInfo());
		for(int i = 0; i < memA.getRoles().length; i++){
			System.out.println("\t|- " + memA.getRoles()[i].getInfo());
			for(int j = 0; j < memA.getRoles()[i].getPrivileges().length; j++){
				System.out.println("\t\t|- " + memA.getRoles()[i].getPrivileges()[j].getInfo());
			}
		}
		System.out.println("-----------Role------------");
		System.out.println(roleA.getInfo());
		for(int i = 0; i < roleA.getPrivileges().length; i++){
			System.out.println("\t|- " + roleA.getPrivileges()[i].getInfo());
		}
		for(int i = 0; i < roleA.getMembers().length; i++){
			System.out.println("\t|- " + roleA.getMembers()[i].getInfo());
		}
		System.out.println("-----------Privilege------------");
		System.out.println(privA.getInfo());
		for(int i = 0; i < privA.getRole().getMembers().length; i++){
			System.out.println("\t|- " + privA.getRole().getMembers()[i].getInfo());
		}
	}
}