273 Database URI TYPEs

Oracle supports the UriType family of types that can be used to store and query Uri-refs inside the database. The UriType itself is an abstract object type and the HTTPURITYPE, XDBURITYPE and DBURITYPE are subtypes of it.

You can create a UriType column and store instances of the DBURITYPE, XDBURITYPE or the HTTPURITYPE inside of it. You can also define your own subtypes of the UriType to handle different URL protocols.

Oracle also provides a UriFactory package that can be used as a factory method to automatically generate various instances of these UriTypes by scanning the prefix, such as http:// or /oradb. You can also register your subtype and provide the prefix that you support. For instance, if you have written a subtype to handle the gopher protocol, you can register the prefix gopher:// to be handled by your subtype. The UriFactory will then generate your subtype instance for any URL starting with that prefix.

This chapter contains the following topics:

Summary of URITYPE Supertype Subprograms

The UriType is the abstract super type. It provides a standard set of functions to get the value pointed to by the URI. The actual implementation of the protocol must be defined by the subtypes of this type.

Instances of this type cannot be created directly. However, you can create columns of this type and store subtype instances in it, and also select from columns without knowing the instance of the URL stored.

Table 273-1 URITYPE Type Subprograms

Method Description

GETBLOB

Returns the BLOB located at the address specified by the URL.

GETCLOB

Returns the CLOB located at the address specified by the URL.

GETCONTENTTYPE

Returns the URL, in escaped format, stored inside the UriType instance.

GETEXTERNALURL

Returns the URL, in escaped format, stored inside the UriType instance.

GETURL

Returns the URL, in non-escaped format, stored inside the UriType instance.

GETXML

Returns the XMLType located at the address specified by the URL.

GETBLOB

This function returns the BLOB located at the address specified by the URL. This function can be overridden in the subtype instances. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getBlob()

RETURN BLOB;

 This function returns the BLOB located at the address specified by the URL.
MEMBER FUNCTION getBlob(

   content OUT VARCHAR2)

RETURN BLOB;

 This function returns the BLOB located at the address specified by the URL and the content type.
FUNCTION getBlob(

   csid IN NUMBER)

RETURN BLOB;

 This function returns the BLOB located at the address specified by the URL in the specified character set.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.
csid (IN) Character set id of the document. Must be a valid Oracle id and greater than 0; otherwise returns an error

GETCLOB

This function returns the CLOB located at the address specified by the URL. This function can be overridden in the subtype instances. This function returns either a permanent CLOB or a temporary CLOB. If a temporary CLOB is returned, it must be freed. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getClob()

RETURN clob;

 This function returns the CLOB located at the address specified by the URL.
MEMBER FUNCTION getClob(

   content OUT VARCHAR2)

RETURN clob;

 This function returns the CLOB located at the address specified by the URL and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

GETCONTENTTYPE

This function returns the content type of the document pointed to by the URI. This function can be overridden in the subtype instances. This function returns the content type as VARCHAR2.

Syntax

MEMBER FUNCTION getContentType()
RETURN VARCHAR2;

GETEXTERNALURL

This function returns the URL, in escaped format, stored inside the UriType instance. The subtype instances override this member function to provide additional semantics. For instance, the HTTPURITYPE function does not store the prefix http:// in the URL itself. When generating the external URL, it appends the prefix and generates it. For this reason, use the getExternalUrl function or the getUrl function to get to the URL value instead of using the attribute present in the UriType instance.

Syntax

MEMBER FUNCTION getExternalUrl()
RETURN varchar2;

GETURL

This function returns the URL, in non-escaped format, stored inside the UriType instance. The subtype instances override this member function to provide additional semantics. For instance, the HTTPURITYPE function does not store the prefix http:// in the URL itself. When generating the external URL, it appends the prefix and generates it. For this reason, use the getExternalUrl function or the getUrl function to get to the URL value instead of using the attribute present in the UriType instance.

Syntax

MEMBER FUNCTION getUrl()
RETURN varchar2;

GETXML

This function returns the XMLType located at the address specified by the URL. This function can be overridden in the subtype instances. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getXML()

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL.
MEMBER FUNCTION getXML(

   content OUT VARCHAR2)

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

Summary of HTTPURITYPE Subtype Subprograms

The HTTPURITYPE is a subtype of the UriType that provides support for the HTTP protocol. This uses the UTL_HTTP package underneath to access the HTTP URLs. Proxy and secure wallets are not supported in this release.

Table 273-2 HTTPURITYPE Type Subprorgams

Method Description

CREATEURI

Creates an instance of HTTPURITYPE from the given URI.

GETBLOB

Returns the BLOB located at the address specified by the URL.

GETCLOB

Returns the CLOB located at the address specified by the URL.

GETCONTENTTYPE

Returns the content type of the document pointed to by the URI.

GETEXTERNALURL

Returns the URL, in escaped format, stored inside the UriType instance.

GETURL

Returns the URL, in non-escaped format, stored inside the UriType instance.

GETXML

Returns the XMLType located at the address specified by the URL

HTTPURITYPE

Creates an instance of HTTPURITYPE from the given URI.

CREATEURI

This static function constructs a HTTPURITYPE instance. The HTTPURITYPE instance does not contain the prefix http:// in the stored URL.

Syntax

STATIC FUNCTION createUri(
   url IN varchar2)
RETURN HTTPURITYPE;
Parameter IN / OUT Description
url (IN) The URL string containing a valid HTTP URL; escaped format.

GETBLOB

This function returns the BLOB located at the address specified by the HTTP URL.

Syntax Description
MEMBER FUNCTION getBlob()

RETURN blob;

 This function returns the BLOB located at the address specified by the HTTP URL.
MEMBER FUNCTION getBlob(

   content OUT VARCHAR2)

RETURN blob;

 This function returns the BLOB located at the address specified by the HTTP URL and the content type.
FUNCTION getBlob(

   csid IN NUMBER)

RETURN BLOB;

 This function returns the BLOB located at the address specified by the URL in the specified character set.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.
csid (IN) Character set id of the document. Must be a valid Oracle id and greater than 0; otherwise returns an error.

GETCLOB

This function returns the CLOB located by the HTTP URL address. If a temporary CLOB is returned, it must be freed.

Syntax Description
MEMBER FUNCTION getClob()

RETURN clob;

 Returns the CLOB located at the address specified by the HTTP URL.
MEMBER FUNCTION getClob(

   content OUT VARCHAR2)

RETURN clob;

 Returns the CLOB located at the address specified by the HTTP URL and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

GETCONTENTTYPE

Returns the content type of the document pointed to by the URI.

Syntax

MEMBER FUNCTION getContentType()
RETURN VARCHAR2;

GETEXTERNALURL

This function returns the URL, in escaped format, stored inside the HTTPURITYPE instance. The subtype instances override this member function. The HTTPURITYPE function does not store the prefix http://, but generates it for the external URL.

Syntax

MEMBER FUNCTION getExternalUrl()
RETURN varchar2;

GETURL

This function returns the URL, in non-escaped format, stored inside the HTTPURITYPE instance.

Syntax

MEMBER FUNCTION getUrl()
RETURN varchar2;

GETXML

This function returns the XMLType located at the address specified by the URL. An error is thrown if the address does not point to a valid XML document.

Syntax Description
MEMBER FUNCTION getXML()

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL.
MEMBER FUNCTION getXML(

   content OUT VARCHAR2)

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

HTTPURITYPE

This constructs a HTTPURITYPE instance. The HTTPURITYPE instance does not contain the prefix http:// in the stored URL.

Syntax

CONSTRUCTOR FUNCTION HTTPURITYPE(
   url IN varchar2);
Parameter IN / OUT Description
url (IN) The URL string containing a valid HTTP URL. The URL string is expected in escaped format. For example, non-url characters are represented as the hexadecimal value for the UTF-8 encoding of those characters.

Summary of DBURITYPE Subtype Subprogams

The DBURITYPE is a subtype of the UriType that provides support for DBUri-refs. A DBUri-ref is an intra-database URL that can be used to reference any row or row-column data in the database. The URL is specified as an XPath expression over a XML visualization of the database. The schemas become elements which contain tables and views. These tables and view further contain the rows and columns inside them.

Table 273-3 DBURITYPE Type Subprograms

Method Description

CREATEURI

Constructs a DBURITYPE instance.

DBURITYPE

Creates an instance of DBURITYPE from the given URI.

GETBLOB

Returns the BLOB located at the address specified by the DBURITYPE instance.

GETCLOB

Returns the CLOB located at the address specified by the DBURITYPE instance.

GETCONTENTTYPE

Returns the content type of the document pointed to by the URI.

GETEXTERNALURL

Returns the URL, in escaped format, stored inside the DBURITYPE instance.

GETURL

Returns the URL, in non-escaped format, stored inside the DBURITYPE instance.

GETXML

Returns the XMLType located at the address specified by the URL

CREATEURI

This static function constructs a DBURITYPE instance. Parses the URL given and creates a DBURITYPE instance.

Syntax

STATIC FUNCTION createUri(
   url IN varchar2)
RETURN DBURITYPE;
Parameter IN / OUT Description
url (IN) The URL string, in escaped format, containing a valid DBURITYPE.

DBURITYPE

This constructs a DBURITYPE instance.

Syntax

CONSTRUCTOR FUNCTION DBURITYPE(
   url IN varchar2);
Parameter IN / OUT Description
url (IN) The URL string containing a valid DBURITYPE. The URL string is expected in escaped format. For example, non-URL characters are represented as the hexadecimal value for the UTF-8 encoding of those characters.

GETBLOB

This function returns the BLOB located at the address specified by the URL. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getBlob()

RETURN blob;

 This function returns the BLOB located at the address specified by the URL.
MEMBER FUNCTION getBlob(

   content OUT VARCHAR2)

RETURN blob;

 This function returns the BLOB located at the address specified by the URL and the content type.
FUNCTION getBlob(

   csid IN NUMBER)

RETURN BLOB;

 This function returns the BLOB located at the address specified by the URL in the specified character set.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.
csid (IN) Character set id of the document. Must be a valid Oracle id and greater than 0; otherwise returns an error.

GETCLOB

This function returns the CLOB located at the address specified by the DBURITYPE instance. If a temporary CLOB is returned, it must be freed. The document returned may be an XML document or a text document. When the DBUri-ref identifies an element in the XPath, the result is a well-formed XML document. On the other hand, if it identifies a text node, then what is returned is only the text content of the column or attribute. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getClob()

RETURN clob;

 Returns the CLOB located at the address specified by the DBURITYPE instance.
MEMBER FUNCTION getClob(

   content OUT VARCHAR2)

RETURN clob;

 Returns the CLOB located at the address specified by the DBURITYPE instance and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

GETCONTENTTYPE

This function returns the content type of the document pointed to by the URI.

Syntax

MEMBER FUNCTION getContentType()
RETURN VARCHAR2;

GETEXTERNALURL

This function returns the URL, in escaped format, stored inside the DBURITYPE instance. The DBUri servlet URL that processes the DBURITYPE has to be appended before using the escaped URL in Web pages.

Syntax

MEMBER FUNCTION getExternalUrl()
RETURN varchar2;

GETURL

This function returns the URL, in non-escaped format, stored inside the DBURITYPE instance.

Syntax

MEMBER FUNCTION getUrl()
RETURN varchar2;

GETXML

This function returns the XMLType located at the address specified by the URL. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getXML()

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL.
MEMBER FUNCTION getXML(

   content OUT VARCHAR2)

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

Summary of XDBURITYPE Subtype Subprograms

XDBURITYPE is a new subtype of URIType. It provides a way to expose documents in the Oracle XML DB hierarchy as URIs that can be embedded in any URIType column in a table. The URL part of the URI is the hierarchical name of the XML document it refers to. The optional fragment part uses the XPath syntax, and is separated from the URL part by '#'. The more general XPointer syntax for specifying a fragment is not currently supported.

Table 273-4 XDBURITYPE Type Subprograms

Method Description

CREATEURI

Returns the UriType corresponding to the specified URL.

GETBLOB

Returns the BLOB corresponding to the contents of the document specified by the XDBURITYPE instance.

GETCLOB

Returns the CLOB corresponding to the contents of the document specified by the XDBURITYPE instance.

GETCONTENTTYPE

Returns the content type of the document pointed to by the URI.

GETEXTERNALURL

Returns the URL, in escaped format, stored inside the XDBURITYPE instance.

GETURL

Returns the URL, in non-escaped format, stored inside the XDBURITYPE instance.

GETXML

Returns the XMLType corresponding to the contents of the document specified by the URL.

XDBURITYPE

Creates an instance of XDBURITYPE from the given URI.

CREATEURI

This static function constructs a XDBURITYPE instance. Parses the URL given and creates a XDBURITYPE instance.

Syntax

STATIC FUNCTION createUri(
   url IN varchar2)
RETURN XDBURITYPE
Parameter IN / OUT Description
url (IN) The URL string, in escaped format, containing a valid XDBURITYPE.

GETBLOB

This function returns the BLOB located at the address specified by the XDBURITYPE instance. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getBlob()

RETURN blob;

 This function returns the BLOB located at the address specified by the URL.
MEMBER FUNCTION getBlob(

   content OUT VARCHAR2)

RETURN blob;

 This function returns the BLOB located at the address specified by the URL and the content type.
FUNCTION getBlob(

   csid IN NUMBER)

RETURN BLOB;

 This function returns the BLOB located at the address specified by the URL in the specified character set.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.
csid (IN) Character set id of the document. Must be a valid Oracle id and greater than 0; otherwise returns an error.

GETCLOB

This function returns the CLOB located at the address specified by the XDBURITYPE instance. If a temporary CLOB is returned, it must be freed. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getClob()

RETURN clob;

 Returns the CLOB located at the address specified by the XDBUriType instance.
MEMBER FUNCTION getClob(

   content OUT VARCHAR2)

RETURN clob;

 Returns the CLOB located at the address specified by the XDBUriType instance and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

GETCONTENTTYPE

This function returns the content type of the document pointed to by the URI. This function returns the content type as VARCHAR2.

Syntax

MEMBER FUNCTION getContentType()
RETURN VARCHAR2;

GETEXTERNALURL

This function returns the URL, in escaped format, stored inside the XDBURITYPE instance.

Syntax

MEMBER FUNCTION getExternalUrl()
RETURN varchar2;

GETURL

This function returns the URL, in non-escaped format, stored inside the XDBURITYPE instance.

Syntax

MEMBER FUNCTION getUrl()
RETURN varchar2;

GETXML

This function returns the XMLType located at the address specified by the URL. The options are described in the following table.

Syntax Description
MEMBER FUNCTION getXML()

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL.
MEMBER FUNCTION getXML(

   content OUT VARCHAR2)

RETURN XMLType;

 This function returns the XMLType located at the address specified by the URL and the content type.

Parameter IN / OUT Description
content (OUT) Content type of the document to which URI is pointing.

XDBURITYPE

This constructs a XDBURITYPE instance.

Syntax

CONSTRUCTOR FUNCTION XDBURITYPE(
   url     IN   VARCHAR2,
   flags   IN   RAW := NULL)
 RETURN self AS RESULT;
Parameter IN / OUT Description
url (IN) The URL string containing a valid XDBUriType. The URL string is expected in escaped format. For example, non-URL characters are represented as the hexadecimal value for the UTF-8 encoding of those characters.
flags (IN) Possible values are:

  • 1 - Expand all XInclude elements before returning the result contents. If any XInclude element cannot be successfully resolved according to the XInclude fallback semantics, then an error is raised.

  • 2 - Indicates that any errors during document retrieval should be suppressed

  • 3 - Both flag bits (1, 2) are enabled

Summary of URIFACTORY Package Subprograms

The UriFactory package contains factory methods that can be used to generate the appropriate instance of the URI types without having to hard code the implementation in the program.

The UriFactory package also provides the ability to register new subtypes of the UriType to handle various other protocols. For example, you can invent a new protocol ecom:// and define a subtype of the UriType to handle that protocol and register it with UriFactory. After that any factory method would generate the new subtype instance if it sees the ecom:// prefix.

Table 273-5 URIFACTORY Type Subprograms

Method Description

GETURI

Returns the correct URL handler for the given URL string.

ESCAPEURI

Returns a URL in escaped format.

UNESCAPEURI

Returns a URL in unescaped format.

REGISTERURLHANDLER

Registers a particular type name for handling a particular URL.

UNREGISTERURLHANDLER

Unregisters a URL handler.

GETURI

This factory method returns the correct URI handler for the given URI string. It returns a subtype instance of the UriType that can handle the protocol. By default, it always creates an XDBURITYPE instance, if it cannot resolve the URL. A URL handler can be registered for a particular prefix using the REGISTERURLHANDLER function. If the prefix matches, GETURI would then use that subtype.

Syntax

FUNCTION getUri(
   url IN Varchar2)
RETURN UriType;
Parameter IN / OUT Description
uri (IN) The URL string, in escaped format, containing a valid HTTP URL.

ESCAPEURI

This function returns a URL in escaped format. The subtype instances override this member function to provide additional semantics. For instance, the HTTPURITYPE does not store the prefix http:// in the URL itself. When generating the external URL, it appends the prefix and generates it. For this reason, use the GETEXTERNALURL function or the GETURI function to get to the URL value instead of using the attribute present in the UriType.

Syntax

MEMBER FUNCTION escapeUri()
RETURN varchar2;
Parameter IN / OUT Description
url (IN) The URL string to be returned in escaped format.

UNESCAPEURI

This function returns a URL in unescaped format. This function is the reverse of the ESCAPEURI function. This function scans the string and converts any non-URL hexadecimal characters into the equivalent UTF-8 characters. Since the return type is a VARCHAR2, the characters would be converted into the equivalent characters as defined by the database character set.

Syntax

FUNCTION unescapeUri()
RETURN varchar2;
Parameter IN / OUT Description
url (IN) The URL string to be returned in unescaped format.

REGISTERURLHANDLER

Registers a particular type name for handling a particular URL. The type specified must be valid and must be a subtype of the UriType or one of its subtypes. It must also implement the createUri static member function. This function is called by the GETURI function to generate an instance of the type. The stripprefix parameter indicates that the prefix must be stripped off before calling this function.

Syntax

PROCEDURE registerUrlHandler(
   prefix IN varchar2,
   schemaName IN varchar2,
   typename IN varchar2,
   ignoreCase IN boolean := true,
   stripprefix IN boolean := true);
Parameter IN / OUT Description
prefix (IN) The prefix to handle; for example, http://.
schemaName (IN) Name of the schema where the type resides; case sensitive.
typename (IN) The name of the type to handle the URL; case sensitive.
ignoreCase (IN) Ignore case when matching prefixes.
stripprefix (IN) Strip prefix before generating the instance of the type.

UNREGISTERURLHANDLER

This procedure unregisters a URL handler. This only unregisters user registered handler prefixes and not predefined system prefixes such as http://.

Syntax

PROCEDURE unregisterUrlHandler(
   prefix IN varchar2);
Parameter IN / OUT Description
prefix (IN) The prefix to be unregistered.