If a SAX application needs to implement customized handling * for external entities, it must implement this interface and * register an instance with the SAX parser using the parser's * setEntityResolver method.
* *The parser will then allow the application to intercept any * external entities (including the external DTD subset and external * parameter entities, if any) before including them.
* *Many SAX applications will not need to implement this interface, * but it will be especially useful for applications that build * XML documents from databases or other specialised input sources, * or for applications that use URI types other than URLs.
* *The following resolver would provide the application * with a special character stream for the entity with the system * identifier "http://www.myhost.com/today":
* **#include* **#include * *class MyResolver : public EntityResolver { * public: * InputSource resolveEntity (const XMLCh* const publicId, * const XMLCh* const systemId); * ... * }; * * MyResolver::resolveEntity { * if (XMLString::compareString(systemId, "http://www.myhost.com/today")) { * MyReader* reader = new MyReader(); * return new InputSource(reader); * } else { * return null; * } * } * *
The application can also use this interface to redirect system * identifiers to local URIs or to look up replacements in a catalog * (possibly by using the public identifier).
* *The HandlerBase class implements the default behaviour for * this interface, which is simply always to return null (to request * that the parser use the default system identifier).
* * @see Parser#setEntityResolver * @see InputSource#InputSource * @see HandlerBase#HandlerBase */ class SAX_EXPORT EntityResolver { public: /** @name Constructors and Destructor */ //@{ /** Default Constructor */ EntityResolver() { } /** Destructor */ virtual ~EntityResolver() { } //@} /** @name The EntityResolver interface */ //@{ /** * Allow the application to resolve external entities. * *The Parser will call this method before opening any external * entity except the top-level document entity (including the * external DTD subset, external entities referenced within the * DTD, and external entities referenced within the document * element): the application may request that the parser resolve * the entity itself, that it use an alternative URI, or that it * use an entirely different input source.
* *Application writers can use this method to redirect external * system identifiers to secure and/or local URIs, to look up * public identifiers in a catalogue, or to read an entity from a * database or other input source (including, for example, a dialog * box).
* *If the system identifier is a URL, the SAX parser must * resolve it fully before reporting it to the application.
* * @param publicId The public identifier of the external entity * being referenced, or null if none was supplied. * @param systemId The system identifier of the external entity * being referenced. * @return An InputSource object describing the new input source, * or null to request that the parser open a regular * URI connection to the system identifier. * The returned InputSource is owned by the parser which is * responsible to clean up the memory. * @exception SAXException Any SAX exception, possibly * wrapping another exception. * @exception IOException An IO exception, * possibly the result of creating a new InputStream * or Reader for the InputSource. * @see InputSource#InputSource */ virtual InputSource* resolveEntity ( const XMLCh* const publicId , const XMLCh* const systemId ) = 0; //@} private : /* Unimplemented constructors and operators */ /* Copy constructor */ EntityResolver(const EntityResolver&); /* Assignment operator */ void operator=(const EntityResolver&); }; XERCES_CPP_NAMESPACE_END #endif