过滤器、过滤器链的实现

写了一小段关于过滤器、过滤器链的 Toy Codejava

1、过滤器接口web

public interface Filter {

	public void doFilter(Invocation invocation, FilterChain chain);

}

public class FirstFilter implements Filter {
	
	public void doFilter(Invocation invocation, FilterChain chain) {
		System.out.println("before: args size=" + invocation.getArgs().length);
		chain.doFilter(invocation);
		System.out.println("after: args size=" + invocation.getArgs().length); //注释掉?

	}
	
}

public class SecondFilter implements Filter {

	public void doFilter(Invocation invocation, FilterChain chain) {
		System.out.println("before: arg=" + Arrays.asList(invocation.getArgs()));
		chain.doFilter(invocation);
		System.out.println("after: arg=" + Arrays.asList(invocation.getArgs()));// 注释掉?
	}

}

public interface FilterChain {

	public FilterChain addFilter(Filter filter);

	public void doFilter(Invocation invocation);

}

public class DefaultFilterChain implements FilterChain {

	private List<Filter> filters = new ArrayList<Filter>();

	private int index = 0;

	public FilterChain addFilter(Filter filter) {
		filters.add(filter);
		return this;
	}

	public void doFilter(Invocation invocation) {
		if (filters.isEmpty())
			return;
		if (index == filters.size()) {
			// 一次过滤器链调用结束,复位index.不复位会怎样?
			index = 0;
			return;
		}
		filters.get(index++).doFilter(invocation, this);
	}

}

public class Service {

	public void say(String name) {
		System.out.println("hello " + name);
	}
}

public class Invocation {

	private Object target;

	private Method method;

	private Object[] args;

	public Invocation(Object target, Method method, Object[] args) {
		super();
		this.target = target;
		this.method = method;
		this.args = args;
	}

	public Object invoke() throws Exception {
		return method.invoke(target, args);
	}

	//... getter & setter

}

public class Context {

	private FilterChain chain;

	private Invocation invocation;

	public Context(FilterChain chain, Invocation invocation) {
		super();
		this.chain = chain;
		this.invocation = invocation;
	}

	public Object invoke() throws Exception {
		chain.doFilter(invocation);
		return invocation.invoke();
	}

	public static void main(String[] args) throws Exception {
		FilterChain chain = new DefaultFilterChain().addFilter(new FirstFilter()).addFilter(new SecondFilter());
		Invocation invocation = new Invocation(new Service(), Service.class.getMethod("say", String.class),
				new Object[] { "jack" });
		Context context = new Context(chain, invocation);
		context.invoke(); //循环调用invoke会怎样？
	}

}

before: args size=1
before: arg=[jack]
after: arg=[jack]
after: args size=1
hello jack

6、UML类图this

Web工程里面web.xml配置的Filter实现是否是也是这个道理？code

是的！xml