MorphCGI: Advanced Usage

Version 1.1, March 20 1997
MorphCGI Advanced Usage

Here are some sample applications that could be easily implemented using the MorphCGI class library. You need to have the library installed to understand some of the concepts presented here. If you have any new ideas or have used the MorphCGI class library to implement some of your applications, please Email me so that I may add your information to this list!

Please note that within the code samples, all external function calls or class names start with the prefix EXT.

Hierarchical database querying (using on-the-fly content generation)
Hierarchical database querying (using polymorphism)
Multipart FORMS processing

Hierarchical database querying using on-the-fly content generation

The logical design of this front-end is to start with a login/welcome screen:

File: welcome.html ------------------ <html> <title>Welcome to our Database</title> <body> <form method=get action=Login.cgi> <p>Login: <input name=login size=12> <p>Password: <input type=password name=passwd size=12> <p><input type=submit value="Login into the Database"> </form> </html>

File: Login.C (C++ source code) Target: Login.cgi (Login.o + MorphCGI.o) ---------------------------------------- .... #include "MorphCGI.h" .... #define ACCESS_ERROR 0 #define ACCESS_ADMIN 1 #define ACCESS_MANAGER 2 #define ACCESS_EMPLOYEE 3 main () { CGI *myCGI = new CGI (UNIX); char *host; int accessLevel; ... // open an output HTML with some basic formatting cout << "Content-type: text/html\n\n"; cout << "<html><title>Login Result</title><body>"; // drop values in the CGI object (void) myCgi->ObtainValues (); // check to see if remote host belongs to our domain (security feature) (void) myCgi->GetInfoValue (CGI_REMOTE_HOST, host); if (! EXTcheckDomain (host)) { cout << "<h2><blink>ERROR:<blink> Access Denied - unknown host</h2>"; exit (1); } // host is OK, now check password and assign user to an access level char *login, *pass; myCgi->GetDataValue ("login", login); myCgi->GetDataValue ("passwd", pass); if ((accessLevel = EXTgetAccess (login, pass)) == ACCESS_ERROR) { cout << "<h2><blink>ERROR:<blink> Access Denied - unknown user or wrong password</h2>"; exit (1); } // now based on the access level show a new form that will have selections to // query the database. Also, note that based on the access level the 'action' // taken on that form (the next level CGI program built using MorphCGI, that // will do the actual querying of the database) will be different. This in // essence is 'on-the-fly content generation', which could be extended to // any depth within the application domain. switch (accessLevel) { case ACCESS_ADMIN: // this will generate HTML tags for a FORM that will have querying // selections (predicates) for an admin // ie. it would have <form method=get action="ProcessAdminQuery.cgi"> EXTgenerateAdminQueryForm (); break; case ACCESS_MANAGER: // this will generate HTML tags for a FORM that will have querying // selections (predicates) for a manager // ie. it would have <form method=get action="ProcessManagerQuery.cgi"> EXTgenerateManagerQueryForm (); break; case ACCESS_EMPLOYEE: // this will generate HTML tags for a FORM that will have querying // selections (predicates) for an employee // ie. it would have <form method=get action="ProcessEmployeeQuery.cgi"> EXTgenerateEmployeeQueryForm (); break; default: cout << "<h2><blink>PROGRAM ERROR:<blink> Unknown Access Level</h2>"; exit (1); break; } .... // delete CGI object delete (myCGI); // end this HTML cout << "</body></html>"; .... }

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Hierarchical database querying using polymorphism

File: QueryHandler.h (C++ header code) ---------------------------------------- .... #include "MorphCGI.h" .... #define ACCESS_ERROR 0 #define ACCESS_ADMIN 1 #define ACCESS_MANAGER 2 #define ACCESS_EMPLOYEE 3 // high-level class that does the query handling using an appropriate flavor // all primary access method definitions default to ::CGI class QueryHandler : public CGI { public: QueryHandler (SYSTEM_TYPE sys); ~QueryHandler () { delete (user); }; QueryHandler *currentUser () { return user; }; protected: private: QueryHandler *user; }; // flavor of QueryHandler: encapsulates handling an admin query class ProcessAdminQuery : public QueryHandler { public: ProcessAdminQuery (QueryHandler *owner) : parent (owner) { htmlBuffer = new ofstream (stdout, ios::out); }; virtual ~ProcessAdminQuery (); // override if needed, to do other initialization stuff virtual BOOLEAN ObtainValues () { EXTsomethingElse::InitAdmin (); .... }; // override to obtain CGI values AND do other things like checking validity, // checking ranges and/or returning default values, etc. Note, that this // encapsulation now gives us the freedom to handle this GetDataValue () // call based on the context, viz. admin access virtual BOOLEAN GetDataValue (char *arg, char * &value) const { parent->GetDataValue (....); .... }; .... protected: // this method could generate the HTML content created by this object // viz. the HTML form tags for querying at the admin level void GenQuery () { htmlBuffer << outContent; htmlBuffer.flush (); }; .... private: ProcessAdminQuery (); // this contains the output buffer ofstream *htmlBuffer; // this contains the HTML content generated so far char *outContent; // parent pointer QueryHandler *parent; .... }; // flavor of QueryHandler: encapsulates handling an manager query class ProcessManagerQuery : public QueryHandler { public: ProcessManagerQuery (QueryHandler *owner) : parent (owner) { htmlBuffer = new ostream (stdout); }; // override if needed, to do other initialization stuff virtual BOOLEAN ObtainValues () { EXTsomethingElse::InitManager (); .... }; virtual ~ProcessManagerQuery (); // override to obtain CGI values AND do other things like checking validity, // checking ranges and/or returning default values, etc. Note, that this // encapsulation now gives us the freedom to handle this GetDataValue () // call based on the context, viz. manager access virtual BOOLEAN GetDataValue (char *arg, char * &value) const; { parent->GetDataValue (....); .... }; .... protected: // this method could generate the HTML content created by this object // viz. the HTML form tags for querying at the manager level void GenQuery () { htmlBuffer << outContent; htmlBuffer.flush (); }; .... private: ProcessManagerQuery (); // this contains the output buffer ofstream *htmlBuffer; // this contains the HTML content generated so far char *outContent; // parent pointer QueryHandler *parent; .... }; // flavor of QueryHandler: encapsulates handling an employee query class ProcessEmployeeQuery : public QueryHandler { public: ProcessEmployeeQuery (QueryHandler *owner) : parent (owner) { htmlBuffer = new ostream (stdout); }; // override if needed, to do other initialization stuff virtual BOOLEAN ObtainValues () { EXTsomethingElse::InitEmployee (); .... }; virtual ~ProcessEmployeeQuery (); // override to obtain CGI values AND do other things like checking validity, // checking ranges and/or returning default values, etc. Note, that this // encapsulation now gives us the freedom to handle this GetDataValue () // call based on the context, viz. employee access virtual BOOLEAN GetDataValue (char *arg, char * &value) const; { parent->GetDataValue (....); .... }; .... protected: // this method could generate the HTML content created by this object // viz. the HTML form tags for querying at the employee level void GenQuery () { htmlBuffer << outContent; htmlBuffer.flush (); }; .... private: ProcessEmployeeQuery (); // this contains the output buffer ofstream *htmlBuffer; // this contains the HTML content generated so far char *outContent; // parent pointer QueryHandler *parent; .... }; File: QueryHandler.C (C++ source code) Target: QueryHandler.o ---------------------------------------- .... #include "QueryHandler.h" .... QueryHandler::QueryHandler (SYSTEM_TYPE sys) { // drop values in the CGI object (void) this->CGI::ObtainValues (); // check to see if remote host belongs to our domain (security feature) (void) this->CGI::GetInfoValue (CGI_REMOTE_HOST, host); if (! EXTcheckDomain (host)) { cout << "<h2><blink>ERROR:<blink> Access Denied - unknown host</h2>"; exit (1); } // host is OK, now check password and assign user to an access level char *login, *pass; myCgi->GetDataValue ("login", login); myCgi->GetDataValue ("passwd", pass); if ((accessLevel = EXTgetAccess (login, pass)) == ACCESS_ERROR) { cout << "<h2><blink>ERROR:<blink> Access Denied - unknown user or wrong password</h2>"; exit (1); } // now select appropriate user-context object switch (accessLevel) { case ACCESS_ADMIN: user = new ProcessAdminQuery (this); break; case ACCESS_MANAGER: user = new ProcessManagerQuery (this); break; case ACCESS_EMPLOYEE: user = new ProcessEmployeeQuery (this); break; default: cout << "<h2><blink>PROGRAM ERROR:<blink> Unknown Access Level</h2>"; exit (1); break; } }

File: Login.C (C++ source code) Target: Login.cgi (Login.o + QueryHandler.o + MorphCGI.o) --------------------------------------------------------- .... #include "QueryHandler.h" .... main () { CGI *myCGI = new QueryHandler (UNIX); .... // open an output HTML with some basic formatting cout << "Content-type: text/html\n\n"; cout << "<html><title>Login Result</title><body>"; .... // generate appropriate query form content for next level myCGI->currentUser ()->GenQuery (); .... // delete CGI object delete (myCGI); // end this HTML cout << "</body></html>"; .... }

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Multipart FORMS processing

In such a case, using a little ingenuity and the MorphCGI class library, we can handle this easily with one common CGI program:

File: welcome.html ------------------ <html> <title>Set Your Database Preferences</title> <body> <hr> <h2>Administrator Preferences</h2> <form method=get action=Pref.cgi> <input type=hidden name=whichform value=adminform> <--- NOTE the unique label <p>Zone preferred: <input name=zone size=12> <p>Number of cached results: <input name=cachesize size=12> <p><input type=submit value="Set Database Preference"> </form> <hr> <h2>Manager Preferences</h2> <form method=get action=Pref.cgi> <input type=hidden name=whichform value=managerform>  <p>Type of coffee preferred: <input name=coffee size=12> <p>Number of guests: <input name=guests size=12> <p><input type=submit value="Set Database Preference"> </form> <hr> <h2>User Preferences</h2> <form method=get action=Pref.cgi> <input type=hidden name=whichform value=userform>  <p>Type of donut preferred: <input name=donut size=12> <p>Number of guests: <input name=guests size=12>  <p><input type=submit value="Set Database Preference"> </form> </body> </html>

File: Pref.C (C++ source code) Target: Pref.cgi (Pref.o + MorphCGI.o) ---------------------------------------- .... #include "MorphCGI.h" .... main () { CGI *myCGI = new CGI (UNIX); char *whichform; ... // drop values in the CGI object (void) myCgi->ObtainValues (); // check to see which form was really submitted and handle accordingly myCgi->GetDataValue ("whichform", whichform); if (! (strcmp (whichform, "adminform"))) { char *zone, *cachesize; myCgi->GetDataValue ("zone", zone); myCgi->GetDataValue ("cachesize", cachesize); // use the values to set the preferences EXTsetPrefAdmin (zone, atoi (cachesize)); .... } else if (! (strcmp (whichform, "managerform"))) { char *coffee, *guests; myCgi->GetDataValue ("coffee", coffee); myCgi->GetDataValue ("guests", guests); // use the values to set the preferences EXTsetPrefManger (coffee, atoi (guests)); .... } else // userform { char *donut, *guests; myCgi->GetDataValue ("donut", coffee); myCgi->GetDataValue ("guests", guests); // use the values to set the preferences // Note : FORM variable 'guests' is unique to this FORM // (same way as 'guests' is unique to the 'managerform' above) // For the sake of clarity we could use unique prefixes to identify // these variables i.e. managerguests, userguests. EXTsetPrefUser (donut, atoi (guests)); .... } .... // delete CGI object delete (myCGI); }

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The MorphCGI class library development product is owned and licensed exclusively by M0RPH.C0M. Copyright (C) 1996-97. All rights reserved. M0RPH.C0M allows users to download and use the provided software on an "As Is" basis. M0RPH.C0M reserves the right to modify any part of the software as and when it deems necessary, without notifying the end-user.