责任链模式

最新推荐文章于 2025-07-13 15:53:06 发布

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本文介绍了一种使用Java实现的过滤器模式，通过具体的例子展示了如何创建请求和响应对象，以及如何利用过滤器链来处理这些请求。具体包括了HtmlFilter、XMLFilter和JavascriptFilter三个过滤器的具体实现。

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1、ServletResponse

package com.sunrex.design.pattern;

public class ServletResponse {

	public String responseStr() {
		return " response " + (ServletRequest.i--);
	}
}

2、ServletRequest

package com.sunrex.design.pattern;

public class ServletRequest {
	public static int i = 0;
	public String getAttribute(String str) {
		i++;
		return str + " + " + i;
	} 
}

3、Filter接口

package com.sunrex.design.pattern;

public interface Filter {
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain);
}

4、FilterChain类

package com.sunrex.design.pattern;

import java.util.ArrayList;
import java.util.List;

public class FilterChain implements Filter {

	private List<Filter> filters = new ArrayList<Filter>();
	int index = 0;
	
	public FilterChain addFilter(Filter filter) {
		this.filters.add(filter);
		return this;
	}
	
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) {
		if(index >= filters.size()) return;
		Filter f = filters.get(index);
		index ++;
		f.doFilter(request, response, chain);
	}
	
}

5、HtmlFilter类

package com.sunrex.design.pattern;

public class HtmlFilter implements Filter {

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) {
		System.out.println("--HtmlFilter.start--"+ request.getAttribute("test"));
		chain.doFilter(request, response, chain);
		System.out.println("--HtmlFilter.end--" + response.responseStr());
	}

}

6、XMLFilter类

package com.sunrex.design.pattern;

public class XMLFilter implements Filter {

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) {
		System.out.println("  --XMLFilter.start--"+ request.getAttribute("test"));
		chain.doFilter(request, response, chain);
		System.out.println("  --XMLFilter.end--" + response.responseStr());
	}
}

7、JavascriptFilter类

package com.sunrex.design.pattern;

public class JavascriptFilter implements Filter {

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) {
		System.out.println("    --JavascriptFilter.start-- " + request.getAttribute("test"));
		chain.doFilter(request, response, chain);
		System.out.println("    --JavascriptFilter.end--" + response.responseStr());
	}

}

8、测试类-FilterTest类

package com.sunrex.design.pattern;

public class FilterTest {

	public static void main(String[] args) {
		FilterChain fc = new FilterChain();
		fc.addFilter(new HtmlFilter()).addFilter(new XMLFilter()).addFilter(new JavascriptFilter());
		ServletRequest request = new ServletRequest();
		ServletResponse response = new ServletResponse();
		
		fc.doFilter(request, response, fc);
	}

}

9、程序执行结果

--HtmlFilter.start--test + 1
  --XMLFilter.start--test + 2
    --JavascriptFilter.start-- test + 3
    --JavascriptFilter.end-- response 3
  --XMLFilter.end-- response 2
--HtmlFilter.end-- response 1