行为模式之职责链模式（在线文档帮助系统）

不念不忘少年蓝@ 2022-08-17 14:16 174阅读 0赞

题目：某公司欲开发一个软件系统的在线文档帮助系统，用户可以在任何一个查询环境中输入查询关键字，如果当前查询环境下没有相关内容，则系统会将查询按照一定的顺序转发给其他查询环境。设查询环境如下：JavaSearchContext、SQLSearchContext、UMLSearchContext。

类图

![20151126000308748][]

package 职责链模式实例之在线文档帮助系统;
    
    public class Client {
    	public static void main(String[] args) {
    		SearchContext objJava,objSQL,objUML;
    		
    		objJava = new JavaSearchContext();
    		objSQL = new SQLSearchContext();
    		objUML = new UMLSearchContext();
    		
    		objJava.setSuccessor(objSQL);
    		objSQL.setSuccessor(objUML);
    		
    		SearchKey key1 = new SearchKey("java");
    		objJava.handleRequest(key1);
    		
    		SearchKey key2 = new SearchKey("sql");
    		objSQL.handleRequest(key2);
    		
    		SearchKey key3 = new SearchKey("uml");
    		objUML.handleRequest(key3);	
    	}
    }

package 职责链模式实例之在线文档帮助系统;
    
    public abstract class SearchContext {
    	protected SearchContext successor;
    	public void setSuccessor(SearchContext successor) {
    		this.successor = successor;
    	}
    	public abstract void handleRequest(SearchKey key);
    }

package 职责链模式实例之在线文档帮助系统;
    
    public class JavaSearchContext extends SearchContext{
    	public void handleRequest(SearchKey key) {
    		String key1 = "java";
    		if(key1.equals(key.getKey()))
    			System.out.println("在JavaSearchContext中找到了");
    		else
    			if(this.successor != null) this.successor.handleRequest(key);
    	}
    }

package 职责链模式实例之在线文档帮助系统;
    
    public class SQLSearchContext extends SearchContext{
    	public void handleRequest(SearchKey key) {
    		String key1 = "sql";
    		if(key1.equals(key.getKey()))
    			System.out.println("在SQLSearchContext中找到了");
    		else
    			if(this.successor != null) this.successor.handleRequest(key);
    	}
    }

package 职责链模式实例之在线文档帮助系统;
    
    public class UMLSearchContext extends SearchContext{
    	public void handleRequest(SearchKey key) {
    		String key1 = "uml";
    		if(key1.equals(key.getKey()))
    			System.out.println("在UMLSearchContext中找到了");
    		else
    			if(this.successor != null) this.successor.handleRequest(key);
    	}
    }

Eclipse运行效果图

![20151126000721376][]

[20151126000308748]: /images/20220731/4a80adbadf374c08a5225410ca4bc22b.png
[20151126000721376]: /images/20220731/f22c470d23dd4cd995eb1510dd515971.png