Model of responsibility chain in design mode

Model of responsibility chain in design mode

The responsibility chain pattern is an object's behavior pattern. In the chain of responsibility, many objects are linked together by each object's reference to its next generation. The request is passed on this chain until an object on the chain decides to process the request. The client making this request does not know which object on the chain is ultimately processing the request, which allows the system to reorganize and assign responsibilities dynamically without affecting the client. --Dr. Shanhong's "Java and Patterns"

Example: Simulation filter, the requested data for sensitive words, Chinese symbols, etc. to filter

First edition: processing of request requests via chained implementations

Filter interface

 Public Interface Filter {    string DoFilter (String msg);}

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Filter Chain

 Public class Filterchain {    privatenew arraylist<filter>();      Public Filterchain addfilter (Filter f) {        this. Filters.add (f);         return  This ;    }      Public List<filter> getfilters () {        return  filters;    }}

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Sensitive word Filter

 Public class Implements Filter {    @Override    public  string DoFilter (String msg) {        = Msg.replace ("Yellow", " Harmony ");         return result;}    }

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Symbol Filter

 Public class Implements Filter {    @Override    public  string DoFilter (String msg) {        = msg.replace (', ', ', ') ). replace ('. ', '. ');         return result;}    }

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Request message Processing

 Public classMessageprocessor {PrivateString message; PrivateFilterchain Filterchain;  Publicmessageprocessor (String message, Filterchain filterchain) { This. Message =message;  This. Filterchain =Filterchain; }     Publicstring Process () {string result=message;  for(Filter f:filterchain.getfilters ()) {result=f.dofilter (Result); }        returnresult; }}

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Test

 Public classTest { Public Static voidMain (string[] args) {String request= "Note, do not put the yellow joke."; Filterchain FC=NewFilterchain (); Fc.addfilter (NewSesitivefilter ()). addfilter (NewSymbolfilter ()); Messageprocessor Processor=Newmessageprocessor (Request, FC); String result=processor.process ();    SYSTEM.OUT.PRINTLN (result); }}

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OK, Requst chain processing is complete, but still insufficient: how to handle messages when multiple Filterchain are present? In fact, Filterchain is a large filter, so filterchain can implement the filter interface

Second Edition: Modify the Filterchain implementation filter interface

 Public classFilterchainImplementsFilter {Privatelist<filter> filters =NewArraylist<filter>();  PublicFilterchain addfilter (Filter f) { This. Filters.add (f); return  This; } @Override Publicstring DoFilter (String msg) {string result=msg;  for(Filter f:filters) {result=f.dofilter (Result); }        returnresult; }}

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Test

 Public classTest { Public Static voidMain (string[] args) {String request= "Be careful not to tell a dirty joke."; Filterchain FC=NewFilterchain (); Fc.addfilter (NewSesitivefilter ()); Filterchain FC2=NewFilterchain (); Fc2.addfilter (NewSymbolfilter ());        Fc.addfilter (FC2); String result=Fc.dofilter (Request);    SYSTEM.OUT.PRINTLN (result); }}

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OK, the request can now be handled perfectly, but when it is needed, the Filterchain can handle both the information sent by the client and the message returned by the server.

Third Edition: Increase the processing of response

Message Encapsulation

//Request Public classRequest {PrivateString msg;  PublicString getmsg () {returnmsg; }     Public voidsetmsg (String msg) { This. msg =msg; }}//Response Public classResponse {PrivateString msg;  PublicString getmsg () {returnmsg; }     Public voidsetmsg (String msg) { This. msg =msg; }}

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New Filter

 Public Interface Filter {    void  doFilter (Request request, Response Response);}

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Sensitive word Filter

 Public class Implements Filter {    @Override    publicvoid  doFilter (Request request, Response Response) {        request.setmsg (Request.getmsg (). replace ("yellow", "Harmony"));                Response.setmsg (Response.getmsg (). Replace ("Harmony", "yellow"));}    }

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Symbol Filter

 Public class Implements Filter {    @Override    publicvoid  doFilter (Request request, Response Response) {        request.setmsg (Request.getmsg (). Replace (', ', ', '). Replace ('. ', '. '));        Response.setmsg (Response.getmsg (). Replace (', ', ', '). Replace ('. ‘, ‘.‘ ));    }}

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Filter Chain

 Public classFilterchainImplementsFilter {Privatelist<filter> filters =NewArraylist<filter>();  PublicFilterchain addfilter (Filter f) { This. Filters.add (f); return  This; } @Override Public voidDoFilter (Request request, Response Response) { for(Filter f:filters) {f.dofilter (request, response); }    }}

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Test

 Public classTest { Public Static voidMain (string[] args) {Request Request=NewRequest (); Request.setmsg ("Be careful not to tell a dirty joke."); Filterchain FC=NewFilterchain (); Fc.addfilter (NewSesitivefilter ()); Filterchain FC2=NewFilterchain (); Fc2.addfilter (NewSymbolfilter ());                Fc.addfilter (FC2); Response Response=NewResponse (); Response.setmsg ("Harmonious society, good." ");        Fc.dofilter (request, response); System.out.println ("Request:" +request.getmsg ()); System.out.println ("Response:" +response.getmsg ()); }}

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OK, finally can handle reqeust and can deal with response, but! as if processing response order reversed

Fourth Edition: Fix the order of response processing

Modify Filter

 Public Interface Filter {    void  doFilter (Request request, Response Response, Filterchain chain);}

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Sensitive word Filter

 Public class Implements Filter {    @Override    publicvoid  doFilter (Request request, Response Response, Filterchain chain) {        request.setmsg (request.getmsg (). replace ("yellow", "harmony") + "->sesitivefilter");                Chain.dofilter (Request, response, chain);                Response.setmsg (Response.getmsg (). Replace ("Harmony", "yellow") + "->sesitivefilter");}    }

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Symbol Filter

 Public class Implements Filter {    @Override    publicvoid  doFilter (Request request, Response Response, Filterchain chain) {        request.setmsg (request.getmsg (). Replace (', ', ', '). Replace ('. ', '. ') + "->symbolfilter");        Chain.dofilter (Request, response, chain);                Response.setmsg (Response.getmsg (). Replace (', ', ', '). Replace ('. ‘, ‘.‘) + "->symbolfilter");}    }

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Filter Chain

 Public classFilterchainImplementsFilter {Privatelist<filter> filters =NewArraylist<filter>(); Private intindex = 0;//record the order of the filter executed         PublicFilterchain addfilter (Filter f) { This. Filters.add (f); return  This; } @Override Public voidDoFilter (Request request, Response Response, Filterchain chain) {if(Index = = filters.size ())return; Filter F=Filters.get (index); Index++;    F.dofilter (Request, response, chain); }}

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Test

 Public classTest { Public Static voidMain (string[] args) {Request Request=NewRequest (); Request.setmsg ("Be careful not to tell a dirty joke."); Filterchain FC=NewFilterchain (); Fc.addfilter (NewSesitivefilter ()); Filterchain FC2=NewFilterchain (); Fc2.addfilter (NewSymbolfilter ());                Fc.addfilter (FC2); Response Response=NewResponse (); Response.setmsg ("Harmonious society, good." ");        Fc.dofilter (Request, response, FC); System.out.println ("Request:" +request.getmsg ()); System.out.println ("Response:" +response.getmsg ()); }}

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OK, you are done! This is the processing logic of the filter in the web!

Model of responsibility chain in design mode