Builder模式

 先上uml图

应用场景一：解决多构造函数的问题

     如Person对象，在不同的场景需要使用到的参数不同，使用Set属性方式不优雅，如果属性值过多代码也会显得非常的冗余。

另一种实现方式是在构造函数中初始化属性，如果场景复杂，那么构造器也需要增加很多，使用起来非常不方便，使用Builder则会灵活很多。

public class Person {

	private String idNo;
	private String name;
	private String phone;
	private String cardNo;

	public Person(Builder builder) {
		this.idNo = builder.idNo;
		this.name = builder.name;
		this.phone = builder.phone;
		this.cardNo = builder.cardNo;
	}

	public static class Builder {
		private String idNo;
		private String name;
		private String phone;
		private String cardNo;

		public Builder idNo(String idNo) {
			this.idNo = idNo;
			return this;
		}

		public Builder name(String name) {
			this.name = name;
			return this;
		}

		public Builder phone(String phone) {
			this.phone = phone;
			return this;
		}

		public Builder cardNo(String cardNo) {
			this.cardNo = cardNo;
			return this;
		}

		public Person build() {
			return new Person(this);
		}
	}

	public String getIdNo() {
		return idNo;
	}

	public void setIdNo(String idNo) {
		this.idNo = idNo;
	}

	public String getName() {
		return name;
	}

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

	public String getPhone() {
		return phone;
	}

	public void setPhone(String phone) {
		this.phone = phone;
	}

	public String getCardNo() {
		return cardNo;
	}

	public void setCardNo(String cardNo) {
		this.cardNo = cardNo;
	}

	@Override
	public String toString() {
		return "Person [idNo=" + idNo + ", name=" + name + ", phone=" + phone + ", cardNo=" + cardNo + "]";
	}

}

Director代码如下

Person person = new Person.Builder()
				.name("张三三")
				.phone("155510311122")
				.idNo("10101010100100")
				.build();