今儿直白的用盖房子为例，给你讲讲Java建造者模式

Posted 2022-03-05 华为云开发者社区

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本文分享自华为云社区《【Java设计模式】用盖房子案例讲解建造者模式(生成器模式)》，作者：我是一棵卷心菜。

现在我们需要建房子，过程为打桩、砌墙、封顶。房子有各种各样的，比如普通房，高楼，别墅，各种房子的过程虽然一样，但是要求不要相同的。请编写程序，完成需求

一、传统方式

1、类图分析

2、代码分析

先创建一个抽象类AbstractHouse，具有打地基、砌墙、封装屋顶以及建房子的功能

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">AbstractHouse</span> <span style="color:#cccccc"></span>
    <span style="color:#999999">//打地基</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildBasic</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#999999">//砌墙</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildWalls</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#999999">//封装屋顶</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">roofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#999999">//开始建房子</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">build</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f08d49">buildBasic</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        <span style="color:#f08d49">buildWalls</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        <span style="color:#f08d49">roofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

然后选择自己想建造的房子，我选择的是普通的房子，对应类CommonHouse

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">CommonHouse</span> <span style="color:#cc99cd">extends</span> <span style="color:#f8c555">AbstractHouse</span> <span style="color:#cccccc"></span>
    <span style="color:#cccccc">@Override</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildBasic</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">System</span><span style="color:#cccccc">.</span>out<span style="color:#cccccc">.</span><span style="color:#f08d49">println</span><span style="color:#cccccc">(</span><span style="color:#7ec699">"普通房子开始打地基"</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cccccc">@Override</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildWalls</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">System</span><span style="color:#cccccc">.</span>out<span style="color:#cccccc">.</span><span style="color:#f08d49">println</span><span style="color:#cccccc">(</span><span style="color:#7ec699">"普通房子开始建墙了"</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cccccc">@Override</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">roofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">System</span><span style="color:#cccccc">.</span>out<span style="color:#cccccc">.</span><span style="color:#f08d49">println</span><span style="color:#cccccc">(</span><span style="color:#7ec699">"普通房子准备封顶喽"</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

最后写一个类Client用来检测结果

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">Client</span> <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">static</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">main</span><span style="color:#cccccc">(</span><span style="color:#f8c555">String</span><span style="color:#cccccc">[</span><span style="color:#cccccc">]</span> args<span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">CommonHouse</span> commonHouse <span style="color:#67cdcc">=</span> <span style="color:#cc99cd">new</span> <span style="color:#f8c555">CommonHouse</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        commonHouse<span style="color:#cccccc">.</span><span style="color:#f08d49">build</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

3、代码结果

4、问题分析

优点是比较好理解，简单易操作。

缺点是设计的程序结构过于简单，没有设计缓存层对象，程序的扩展和维护不好。也就是说，这种设计方案，把产品(即房子)和创建产品的过程(即建房子流程) 封装在一起，耦合性增强了。

二、建造者模式

1、基本介绍

建造者模式（Builder Pattern）又叫生成器模式，是一种对象构建模式。它可以将复杂对象的建造过程抽象出来（抽象类别），使这个抽象过程的不同实现方法可以构造出不同表现（属性）的对象。

建造者模式是一步一步创建一个复杂的对象，它允许用户只通过指定复杂对象的类型和内容就可以构建它们，用户不需要知道内部的具体构建细节。

2、四个角色

Product（产品角色）：一个具体的产品对象。
Builder（抽象建造者）：创建一个Product对象的各个部件指定的接口/抽象类。
ConcreteBuilder（具体建造者）：实现接口，构建和装配各个部件。
Director（指挥者）：构建一个使用Builder接口的对象。它主要是用于创建一个复杂的对象。它主要有两个作用，一是：隔离了客户与对象的生产过程，二是：负责控制产品对象的生产过程

3、类图分析

4、代码分析

先创建一个房子类House，具有打地基、砌墙和封装屋顶的功能

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">House</span> <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">private</span> <span style="color:#f8c555">String</span> baise<span style="color:#cccccc">;</span>
    <span style="color:#cc99cd">private</span> <span style="color:#f8c555">String</span> wall<span style="color:#cccccc">;</span>
    <span style="color:#cc99cd">private</span> <span style="color:#f8c555">String</span> roofed<span style="color:#cccccc">;</span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">String</span> <span style="color:#f08d49">getBaise</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">return</span> baise<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">setBaise</span><span style="color:#cccccc">(</span><span style="color:#f8c555">String</span> baise<span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">this</span><span style="color:#cccccc">.</span>baise <span style="color:#67cdcc">=</span> baise<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">String</span> <span style="color:#f08d49">getWall</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">return</span> wall<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">setWall</span><span style="color:#cccccc">(</span><span style="color:#f8c555">String</span> wall<span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">this</span><span style="color:#cccccc">.</span>wall <span style="color:#67cdcc">=</span> wall<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">String</span> <span style="color:#f08d49">getRoofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">return</span> roofed<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">setRoofed</span><span style="color:#cccccc">(</span><span style="color:#f8c555">String</span> roofed<span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">this</span><span style="color:#cccccc">.</span>roofed <span style="color:#67cdcc">=</span> roofed<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

接着创建抽象的建造者HouseBuilder

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">HouseBuilder</span> <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">House</span> house <span style="color:#67cdcc">=</span> <span style="color:#cc99cd">new</span> <span style="color:#f8c555">House</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#999999">//将建造的流程写好，抽象的方法</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildBasic</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildWalls</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">abstract</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">roofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#999999">//建造房子好后，将产品(房子)返回</span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">House</span> <span style="color:#f08d49">buildHouse</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">return</span> house<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

然后创建指挥者HouseDirector，动态的指定制作流程，返回产品

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">HouseDirector</span> <span style="color:#cccccc"></span>
    <span style="color:#f8c555">HouseBuilder</span> houseBuilder <span style="color:#67cdcc">=</span> <span style="color:#cc99cd">null</span><span style="color:#cccccc">;</span>
    <span style="color:#999999">//空参构造器</span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">HouseDirector</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
    <span style="color:#cccccc"></span>
    <span style="color:#999999">//通过setter传入houseBuilder</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">setHouseBuilder</span><span style="color:#cccccc">(</span><span style="color:#f8c555">HouseBuilder</span> houseBuilder<span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#cc99cd">this</span><span style="color:#cccccc">.</span>houseBuilder <span style="color:#67cdcc">=</span> houseBuilder<span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#999999">//如何处理建造房子的流程，交给指挥者</span>
    <span style="color:#cc99cd">public</span> <span style="color:#f8c555">House</span> <span style="color:#f08d49">constructorHouse</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        houseBuilder<span style="color:#cccccc">.</span><span style="color:#f08d49">buildBasic</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        houseBuilder<span style="color:#cccccc">.</span><span style="color:#f08d49">buildWalls</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        houseBuilder<span style="color:#cccccc">.</span><span style="color:#f08d49">roofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        <span style="color:#cc99cd">return</span> houseBuilder<span style="color:#cccccc">.</span><span style="color:#f08d49">buildHouse</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

刚才建造的是普通的房子，现在我想要建造一个高楼类HighBuilding

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">HighBuilding</span> <span style="color:#cc99cd">extends</span> <span style="color:#f8c555">HouseBuilder</span> <span style="color:#cccccc"></span>
    <span style="color:#cccccc">@Override</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildBasic</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">System</span><span style="color:#cccccc">.</span>out<span style="color:#cccccc">.</span><span style="color:#f08d49">println</span><span style="color:#cccccc">(</span><span style="color:#7ec699">"高楼房子开始打地基"</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cccccc">@Override</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">buildWalls</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">System</span><span style="color:#cccccc">.</span>out<span style="color:#cccccc">.</span><span style="color:#f08d49">println</span><span style="color:#cccccc">(</span><span style="color:#7ec699">"高楼房子开始建墙了"</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
    <span style="color:#cccccc">@Override</span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">roofed</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#f8c555">System</span><span style="color:#cccccc">.</span>out<span style="color:#cccccc">.</span><span style="color:#f08d49">println</span><span style="color:#cccccc">(</span><span style="color:#7ec699">"高楼房子准备封顶喽"</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

最后写一个类用来测试

<span style="background-color:#2d2d2d"><span style="color:#cccccc"><code class="language-java"><span style="color:#cc99cd">public</span> <span style="color:#cc99cd">class</span> <span style="color:#f8c555">Client</span> <span style="color:#cccccc"></span>
    <span style="color:#cc99cd">public</span> <span style="color:#cc99cd">static</span> <span style="color:#cc99cd">void</span> <span style="color:#f08d49">main</span><span style="color:#cccccc">(</span><span style="color:#f8c555">String</span><span style="color:#cccccc">[</span><span style="color:#cccccc">]</span> args<span style="color:#cccccc">)</span> <span style="color:#cccccc"></span>
        <span style="color:#999999">//准备创建房子的指挥者</span>
        <span style="color:#f8c555">HouseDirector</span> houseDirector <span style="color:#67cdcc">=</span> <span style="color:#cc99cd">new</span> <span style="color:#f8c555">HouseDirector</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        <span style="color:#999999">//盖高楼</span>
        <span style="color:#f8c555">HighBuilding</span> highBuilding <span style="color:#67cdcc">=</span> <span style="color:#cc99cd">new</span> <span style="color:#f8c555">HighBuilding</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        <span style="color:#999999">//重置建造者</span>
houseDirector<span style="color:#cccccc">.</span><span style="color:#f08d49">setHouseBuilder</span><span style="color:#cccccc">(</span>highBuilding<span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
        <span style="color:#999999">//完成盖房子，返回产品(高楼)</span>
        houseDirector<span style="color:#cccccc">.</span><span style="color:#f08d49">constructorHouse</span><span style="color:#cccccc">(</span><span style="color:#cccccc">)</span><span style="color:#cccccc">;</span>
    <span style="color:#cccccc"></span>
<span style="color:#cccccc"></span>
</code></span></span>

5、代码结果

6、注意事项

每一个具体建造者都相对独立，而与其他的具体建造者无关，因此可以很方便地替换具体建造者或增加新的具体建造者，用户使用不同的具体建造者即可得到不同的产品对象
可以更加精细地控制产品的创建过程。将复杂产品的创建步骤分解在不同的方法中，使得创建过程更加清晰，也更方便使用程序来控制创建过程
增加新的具体建造者无须修改原有类库的代码，指挥者类针对抽象建造者类编程，系统扩展方便，符合 “开闭原则”
建造者模式所创建的产品一般具有较多的共同点，其组成部分相似，如果产品之间的差异性很大，则不适合使用建造者模式，因此其使用范围受到一定的限制。
如果产品的内部变化复杂，可能会导致需要定义很多具体建造者类来实现这种变化，导致系统变得很庞大，因此在这种情况下，要考虑是否选择建造者模式.

三、总结

那么抽象工厂模式与建造者模式有什么不同点呢？

抽象工厂模式实现对产品家族的创建，一个产品家族是这样的一系列产品：具有不同分类维度的产品组合，采用抽象工厂模式不需要关心构建过程，只关心什么产品，由什么工厂生产即可。而建造者模式则是要求按照指定的蓝图建造产品，它的主要目的是通过组装零配件而产生一个新产品。

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