设计模式之建造者模式

作用：1.实现对象的属性动态配置，即想赋值几个属性就赋值几个属性。
2.不允许外部创建实例，对象一旦被创建不允许改变对象属性值。
3.此模式在创建数据库连接池普遍使用。如spring对mongodb支持的包中MongoClientOptions类。
代码：

package designModel.builder;

import java.io.Serializable;

public class User implements Serializable{

	private static final long serialVersionUID = 1L;
	private String name;
	private int age;
	private String sex;
	private String address;
	private String mobile;
	
	private User(UserBuilder build) {
		this.name = build.name;
		this.age = build.age;
		this.sex = build.sex;
		this.address = build.address;
		this.mobile = build.mobile;
	}

	public String getName() {
		return name;
	}
	public int getAge() {
		return age;
	}
	public String getSex() {
		return sex;
	}
	public String getAddress() {
		return address;
	}
	public String getMobile() {
		return mobile;
	}
	public static UserBuilder getUserBuilder() {
		return new UserBuilder();
	}
	public static class UserBuilder{
		private String name;
		private int age;
		private String sex;
		private String address;
		private String mobile;
		public UserBuilder name(final String name) {
			this.name = name;
			return this;
		}
		public UserBuilder age(final int age) {
			this.age = age;
			return this;
		}
		public UserBuilder sex(final String sex) {
			this.sex = sex;
			return this;
		}
		public UserBuilder address(final String address) {
			this.address = address;
			return this;
		}
		public UserBuilder mobile(final String mobile) {
			this.mobile = mobile;
			return this;
		}
		public User build() {
			return new User(this);
		}
	}
	@Override
	public String toString() {
		return "User [name=" + name + ", age=" + age + ", sex=" + sex + ", address=" + address + ", mobile=" + mobile
				+ "]";
	}
	public static void main(String[] args) {
		User build = User.getUserBuilder().name("fdsafsda").age(12).address("fasdf").build();
		System.out.println(build);
	}
}

注意细节：1.私有的构造器，参数为作为builder的静态内部类。
2.对外提供static的getUserBuilder方法来创建builder。
3.只有get方法没有set方法，用以保证不能改变属性
4.builder的属性跟外部的属性一样，用来给属性赋值
5.builder提供build方法构建外部类对象