设计模式6--责任链模式（The chain of responsibility pattern）

最新推荐文章于 2025-06-04 00:23:46 发布

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最新推荐文章于 2025-06-04 00:23:46 发布

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本文通过一个具体的Java实现案例介绍了责任链设计模式的应用。该模式允许请求沿着处理者链传递，直到有一个处理者决定处理此请求。每个处理者包含对另一个处理者的引用，形成了一个链。文中展示了如何创建不同级别的帮助接口实现，并将它们串联起来处理特定类型的请求。

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如果一个处理不了，就传给链上的小一个来处理。
subject notification subject1

subject-->object1-->object2-->object3

interface HelpInterface
{
	public void getHelp(int helpConstant);
}

public class FrontEnd implements HelpInterface
{
	final int FRONT_END_HELP = 1;
	HelpInterface successor;
	
	public FrontEnd(HelpInterface s)
	{
		successor = s;
	}
	
	public void getHelp(int helpConstant)
	{
		if(helpConstant != FRONT_END_HELP) {
			successor.getHelp(helpConstant);
		} else {
			System.out.println("This is the front end.");
		}
	} 
}
public class IntermediateLayer implements HelpInterface
{
	final int INTERMEDIATE_LAYER_HELP = 2;
	HelpInterface successor;
	
	public FrontEnd(HelpInterface s)
	{
		successor = s;
	}
	
	public void getHelp(int helpConstant)
	{
		if(helpConstant != INTERMEDIATE_LAYER_HELP) {
			successor.getHelp(helpConstant);
		} else {
			System.out.println("This is the IntermediateLayer.");
		}
	} 
}

public class Application implements HelpInterface
{			
	public Application()
	{
	}
	
	public void getHelp(int helpConstant)
	{	
		System.out.println("This is the MegaGigaCo application.");		
	} 
}

public class TestHelp
{
	public static void main(String args[])
	{
		final int FRONT_END_HELP = 1;
		final int INTERMEDIATE_LAYER_HELP = 2;
		final int GENERAL_HELP = 3;
		
		Application app = new Application();
		
		IntermediateLayer intermediateLayer = new IntermediateLayer(app);
		
		FrontEnd frontEnd = new FrontEnd(intermediateLayer);
		
		frontEnd.getHelp(GENERAL_HELP);
	}
}