Changes between Initial Version and Version 1 of ApertureDataAccessor

Timestamp:

10/12/05 14:12:48 (19 years ago)

Author:

dburkhar

Comment:

--

ApertureDataAccessor

@@ +1 @@
+= DataAccessors =
+
+== Java Interface ==
+
+{{{
+ /**
+  * A DataAccessor provides access to physical resources by creating DataObjects
+  * representing the resource, based on a url and optionally data about a previous access
+  * and other parameters.
+  */
+public interface DataAccessor {
+
+        /**
+         * Get a DataObject for the specified url. The resulting DataObject's ID may differ
+         * from the specified url due to normalization schemes, following of redirected URLs, etc. 
+         *
+         * An AccessData instance can optionally be specified with which the DataAccessor can store
+         * and retrieve information about previous accesses to resources. This is mostly useful
+         * for DataCrawlers who want to be able to incrementally scan a DataSource.
+         * When an AccessData instance is specified, the resulting DataObject can be null,
+         * indicating that the binary resource has not been modified since the last access.
+         * 
+         * A DataAccessor is always required to store something in the AccessData when a
+         * url is accessed, so that afterwards AccessData.isKnownId will return true.
+         * 
+         * Specific DataAccessor implementations may accept additional parameters through the params Map.
+         * 
+         * @param url         The url used to address the resource.
+         * @param dataSource  The source that will be registered as the source of the DataObject.
+         * @param accessData  Optional database containing information about previous accesses.
+         * @param params      Optional additional parameters needed to access the physical resource.
+         * @return A DataObject for the specified URI, or null when an AccessData instance has been
+         * specified and the binary resource has not been modified since the last access.
+         * @throws UrlNotFoundException when the binary resource could not be found
+         * @throws IOException When any other kind of I/O error occurs.
+         */
+        public DataObject get(String url, DataSource source,
+            AccessData accessData, Map<?,?> params) throws UrlNotFoundException, IOException;
+}
+}}}