Java 构造函数(反模式)父类(super class) String

Question

以下设计的目的是允许 String 值(实际上)被子类化，以建立许多冲突的构造函数方法(例如，即使参数名称不同，方法签名也将相同)有所不同)。

请考虑以下(非功能性)设计:

Id 接口(interface)(空标记接口(interface))

public interface Id {}

类接口(interface)(空标记接口(interface))

public interface Classes {}

标题界面(一个空的标记界面)

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“类型”有一个接口(interface)，以及从特定接口(interface)“类型”到对象然后到字符串的向下转换/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 String 进行子类化的愿望(仅用于构造函数方法区分的目的)...

我有一个可变参数方法，它采用名称值对的任意集合来提供固定参数构造函数的替代方案，但上面显示的构造函数是最常见的组合，因此为了方便程序员，目前正在考虑使用它们所提供的...

谢谢!

Answer 1

考虑到你的构造函数的外观，我建议你摆脱它们并使用 Builder pattern相反:

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();