Java构造函数(反模式)超类字符串

Question

以下设计的目的是允许String值(实际上)子类化以启用许多将构建冲突的构造函数方法(例如,即使参数名称不同,方法签名也是相同的) .

请考虑以下(非功能性)设计:

Id接口(空标记接口)

public interface Id {}

类接口(空标记接口)

public interface Classes {}

标题界面(空标记界面)

public interface Title {}

工具类

public Tool(Id id) throws Exception
{
    this.span = new Span();

    this.span.addAttribute(new Attribute(Attribute.ID, (String)((Object) id)));
}

public Tool(Classes classes) throws Exception
{
    this.span = new Span();
    this.span.addAttribute(new Attribute(Attribute.CLASS, (String)((Object) classes)));
}

public Tool(Title title) throws Exception
{
    this.span = new Span();
    this.span.addAttribute(new Attribute(Attribute.TITLE, (String)((Object) title)));
}

public Tool(Id id, Classes classes, Title title) throws Exception
{
    this.span = new Span();
    this.span.addAttribute(new Attribute(Attribute.ID, (String)((Object) id)));
    this.span.addAttribute(new Attribute(Attribute.CLASS, (String)((Object) classes)));
    this.span.addAttribute(new Attribute(Attribute.TITLE, (String)((Object) title)));
}

public void Test() throws Exception
{
    Tool hammer = new Tool((Id)((Object)"hammer"));
    Tool poweredTool = new Tool((Classes)((Object)"tool powered"));
    Tool tool = new Tool((Id)((Object)"invention"), (Classes)((Object)"tool powered"), (Title)((Object)"define a new tool"));
}

该方法需要每个参数"type"的接口和从特定接口"type"到Object然后到String的向下转换/向上转换...

我对这种方法感到不舒服,我希望有一种设计模式可以减轻我对子类String的期望(仅用于构造方法区分的目的)......

我有一个可变方法,它采用任意的名称值对集合来提供固定参数构造函数的替代方法,但上面显示的构造函数是最常见的组合,因此为方便程序员,他们目前正在考虑提供...

谢谢!

Answer 1

考虑一下构造函数的外观,我建议你去掉它们并使用Builder模式:

class Tool {

    private Tool() { // Preventing direct instantiation with private constructor
        this.span = new Span();
    }

    ... // Tool class code

    public static Builder builder() {
        return new Builder();
    }

    public static class Builder {
        private final Tool tool = new Tool();

        public Builder withId(String id) { 
            tool.span.addAttribute(new Attribute(Attribute.ID, id));
            return this;
        }   

        ... // other methods in the same manner

        public Tool build() {
            // Add some validation if necessary
            return tool;
        }
    }
}

用法:

Tool tool = Tool.builder()
                .withId("id")
                .withClasses("classA, classB")
                .build();