Java创建型模式之建造者模式详解

Fawn ·
更新时间:2024-11-10
· 1582 次阅读

目录

一.介绍

二.UML类图

三.具体代码

四.lombok的@Builder注解(拓展)

五.在Spring中的应用

一.介绍

建造者模式(Builder Pattern)属于创建型模式。如果一个对象具有复杂的内部结构或者内部属性本身相互依赖(有顺序要求),甚至对象中的某些属性的创建也有一个很复杂的过程,就可以使用建造者模式

二.UML类图

三.具体代码

业务代码

public class Product { private String part1; private String part2; public Product(String part1, String part2) { this.part1 = part1; this.part2 = part2; } @Override public String toString() { return "Product{" + "part1='" + part1 + '\'' + ", part2='" + part2 + '\'' + '}'; } } //控制每个部件的具体创建 interface Builder { void buildPart1(String part1); void buildPart2(String part2); Product build(); } class ChinaBuilder implements Builder{ private String part1; private String part2; @Override public void buildPart1(String part1) { this.part1 = "国产" + part1; } @Override public void buildPart2(String part2) { this.part2 = "国产" + part2; } @Override public Product build() { return new Product(part1, part2); } } //控制组装部件的顺序 class Director{ private Builder builder; public Director(Builder builder) { this.builder = builder; } public Product construct(String part1, String part2){ builder.buildPart1(part1); builder.buildPart2(part2); return builder.build(); } }

测试代码

public class BuilderTest { public static void main(String[] args) { Director director = new Director(new ChinaBuilder()); Product product = director.construct("传感器", "芯片"); System.out.println(product); //Product{part1='国产传感器', part2='国产芯片'} } } 四.lombok的@Builder注解(拓展)

我们先以静态内部类的方式实现简单场景下的建造者模式(以优雅的链式调用代替set)

业务代码

public class Product { private String part1; private String part2; public Product(String part1, String part2) { this.part1 = part1; this.part2 = part2; } @Override public String toString() { return "Product{" + "part1='" + part1 + '\'' + ", part2='" + part2 + '\'' + '}'; } static class Builder { private String part1; private String part2; public Builder part1(String part1) { this.part1 = part1; return this; } public Builder part2(String part2) { this.part2 = part2; return this; } public Product build(){ return new Product(part1, part2); } } }

测试类

public class ProductTest { public static void main(String[] args) { Product product = new Product.Builder().part1("传感器").part2("芯片").build(); System.out.println(product); //Product{part1='传感器', part2='芯片'} } }

下面看看lombok的@Builder注解的实现

业务代码

@Builder public class Product { private String part1; private String part2; }

在IDEA中打开Product.class文件,可以看出实际就是使用的简单场景的建造者模式

// // Source code recreated from a .class file by IntelliJ IDEA // (powered by FernFlower decompiler) // package com.designpattern.create.builder.lombok; public class Product { private String part1; private String part2; Product(String part1, String part2) { this.part1 = part1; this.part2 = part2; } public static Product.ProductBuilder builder() { return new Product.ProductBuilder(); } public static class ProductBuilder { private String part1; private String part2; ProductBuilder() { } public Product.ProductBuilder part1(String part1) { this.part1 = part1; return this; } public Product.ProductBuilder part2(String part2) { this.part2 = part2; return this; } public Product build() { return new Product(this.part1, this.part2); } public String toString() { return "Product.ProductBuilder(part1=" + this.part1 + ", part2=" + this.part2 + ")"; } } } 五.在Spring中的应用

org.springframework.web.servlet.mvc.method.RequestMappingInfo.DefaultBuilder

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