设计模式：Filter过滤器

原文地址：https://blog.csdn.net/u011697278/article/details/53729830

场景1： 

每种Filter进行某种处理，将各个Filter连在一起形成一个FilterChain。当需要往FilterChain中加入新的Filter，或者改变各个Filter的处理顺序时，可以方便的扩展。

1个接口：

public interface Filter {
    public String dofilter(String msg);
}

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3种实现类：

public class SensitiveWordFilter implements Filter{

    @Override
    public String dofilter(String msg) {
        return msg.replace("fuck", "f**k").replace("Fuck", "F**k");
    }

}

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public class StopWordFilter implements Filter{

    @Override
    public String dofilter(String msg) {
        return msg.replace("and", "").replace("to", "").replace("ing", "").replace("is", "");
    }

}

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public class FaceFilter implements Filter{

    @Override
    public String dofilter(String msg) {
        return msg.replace(":(", "^V^");
    }

}

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用1个FilterChain连接起来：

public class FilterChain implements Filter{

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

    @Override
    public String dofilter(String msg) {
        String r = msg;
        for(Filter f : filters)
            r = f.dofilter(r);
        return r;
    }

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

}

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main方法调用：

public class Main {

    public static void main(String[] args){

        String msg = "Today is raining. What a fucking day! :(";

        FilterChain fc = new FilterChain();
        fc.addFilter(new SensitiveWordFilter())
          .addFilter(new StopWordFilter())
          .addFilter(new FaceFilter());

        String result = fc.dofilter(msg);
        System.out.println(msg);
        System.out.println(result);

    }

}

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场景2： 
客户端==>服务端，参照javax.servlet 

2种对象：

public class Request {
    public String requestSTR;
}

public class Response {
    public String responseSTR;
}

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1个Filter接口：

public interface Filter {
    public void dofilter(Request request,Response response, FilterChain fc);
}

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3种实现类：

public class SensitiveWordFilter implements Filter{

    @Override
    public void dofilter(Request request, Response response, FilterChain fc) {
        request.requestSTR = request.requestSTR.replace("fuck", "f**k").replace("Fuck", "F**k");
        request.requestSTR += "--SensitiveWordFilter()";
        fc.dofilter(request, response, fc);
        response.responseSTR += "--SensitiveWordFilter()";
    }

}

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public class StopWordFilter implements Filter{


    @Override
    public void dofilter(Request request, Response response, FilterChain fc) {
        request.requestSTR = request.requestSTR.replace("and", "").replace("to", "").replace("ing", "").replace("is", "");
        request.requestSTR += "--StopWordFilter()";
        fc.dofilter(request, response, fc);
        response.responseSTR += "--StopWordFilter()";
    }

}

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public class FaceFilter implements Filter{

    @Override
    public void dofilter(Request request, Response response, FilterChain fc) {
        request.requestSTR = request.requestSTR.replace(":(", "^V^");
        request.requestSTR += "--FaceFilter()";
        fc.dofilter(request, response, fc);
        response.responseSTR += "--FaceFilter()";
    }

}

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FilterChain

public class FilterChain implements Filter{

    List<Filter> filters = new ArrayList<Filter>();
    int index = 0;

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


    @Override
    public void dofilter(Request request, Response response, FilterChain fc) {
        if(index == filters.size())
            return;
        Filter f = filters.get(index);
        index++;
        f.dofilter(request, response, this);
    }

}

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Main：

public class Main {

    public static void main(String[] args){

        Request request = new Request();
        request.requestSTR = "Today is raining. What a fucking day! :(";
        Response response = new Response();
        response.responseSTR = "";

        FilterChain fc = new FilterChain();
        fc.addFilter(new SensitiveWordFilter())
          .addFilter(new StopWordFilter())
          .addFilter(new FaceFilter());

        fc.dofilter(request,response,fc);
        System.out.println(request.requestSTR);
        System.out.println(response.responseSTR);

    }

}

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Reference：马士兵java视频，设计模式