[Mulgara-svn] r817 - branches/mgr-61-sparql/src/jar/query/java/org/mulgara/query/filter/value

[pag at mulgara.org]

Author: pag
Date: 2008-04-22 20:37:25 -0700 (Tue, 22 Apr 2008)
New Revision: 817

Added:
   branches/mgr-61-sparql/src/jar/query/java/org/mulgara/query/filter/value/ExternalFn.java
Log:
A placeholder for a future callout to Xalan functions.

Added: branches/mgr-61-sparql/src/jar/query/java/org/mulgara/query/filter/value/ExternalFn.java
===================================================================
--- branches/mgr-61-sparql/src/jar/query/java/org/mulgara/query/filter/value/ExternalFn.java	                        (rev 0)
+++ branches/mgr-61-sparql/src/jar/query/java/org/mulgara/query/filter/value/ExternalFn.java	2008-04-23 03:37:25 UTC (rev 817)
@@ -0,0 +1,120 @@
+/**
+ * The contents of this file are subject to the Open Software License
+ * Version 3.0 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.opensource.org/licenses/osl-3.0.txt
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ */
+package org.mulgara.query.filter.value;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.log4j.Logger;
+import org.mulgara.query.QueryException;
+import org.mulgara.query.filter.RDFTerm;
+
+/**
+ * Executes a function that isn't defined in these packages.
+ *
+ * @created Apr 22, 2008
+ * @author Paul Gearon
+ * @copyright &copy; 2008 <a href="http://www.topazproject.org/">The Topaz Project</a>
+ * @licence <a href="{@docRoot}/../../LICENCE.txt">Open Software License v3.0</a>
+ */
+public class ExternalFn extends AbstractAccessorFn {
+
+  /** The logger */
+  private final static Logger logger = Logger.getLogger(ExternalFn.class.getName());
+
+  /** The function to be run. This will be mapped to a functor or reflection code. */
+  private IRI fn;
+
+  /** The arguments of the function. */
+  private RDFTerm[] operands; 
+
+  /**
+   * Create a new function instance.
+   * @param fn The function to run.
+   * @param operands The arguments of the function.
+   */
+  public ExternalFn(IRI fn, RDFTerm... operands) {
+    super(operands);
+  }
+
+  // The ValueLiteral interface
+
+  /**
+   * @see org.mulgara.query.filter.value.ValueLiteral#getLexical()
+   * @throws QueryException if this function does not resolve to a literal.
+   */
+  public String getLexical() throws QueryException {
+    RDFTerm result = resolve();
+    if (result.isLiteral()) return ((ValueLiteral)result).getLexical();
+    throw new QueryException("Not valid to ask the lexical form of a: " + result.getClass().getSimpleName());
+  }
+
+  /**
+   * @see org.mulgara.query.filter.value.ValueLiteral#getLang()
+   * @throws QueryException if this function does not resolve to a literal.
+   */
+  public SimpleLiteral getLang() throws QueryException {
+    RDFTerm result = resolve();
+    if (result.isLiteral()) return ((ValueLiteral)result).getLang();
+    throw new QueryException("Not valid to ask the language of a: " + result.getClass().getSimpleName());
+  }
+
+  /**
+   * @see org.mulgara.query.filter.value.ValueLiteral#getType()
+   * @throws QueryException if this function does not resolve to a literal.
+   */
+  public IRI getType() throws QueryException {
+    RDFTerm result = resolve();
+    if (result.isLiteral()) return ((ValueLiteral)result).getType();
+    throw new QueryException("Not valid to ask the type of a: " + result.getClass().getSimpleName());
+  }
+
+  /** @see org.mulgara.query.filter.AbstractFilterValue#isSimple() */
+  public boolean isSimple() throws QueryException {
+    RDFTerm result = resolve();
+    if (result.isLiteral()) return ((ValueLiteral)result).isSimple();
+    throw new QueryException("Not valid to check if a non-literal is a simple literal: " + result.getClass().getSimpleName());
+  }
+
+  // The RDFTerm interface
+
+  /** @see org.mulgara.query.filter.RDFTerm#isBlank() */
+  public boolean isBlank() throws QueryException { return resolve().isBlank(); }
+
+  /** @see org.mulgara.query.filter.RDFTerm#isIRI() */
+  public boolean isIRI() throws QueryException { return resolve().isIRI(); }
+
+  /** @see org.mulgara.query.filter.RDFTerm#isLiteral() */
+  public boolean isLiteral() throws QueryException { return resolve().isLiteral(); }
+
+  /**
+   * Resolve the value of the function.
+   * @return The resolution of the function
+   * @throws QueryException if the function does not resolve
+   * TODO: call the appropriate function. This just returns the boolean TRUE for the moment.
+   */
+  protected RDFTerm resolve() throws QueryException {
+    logger.warn("Attempting to execute an unsupported function: " + fn + "(" + resolveArgs() + ")");
+    return Bool.TRUE;
+  }
+
+  /**
+   * A utility function to create a list of arguments to be passed to the external function.
+   * @return A {@link List} of arbitrary objects to be passed as arguments to the external function.
+   * @throws QueryException If any of the arguments could not be resolved.
+   */
+  private List<Object> resolveArgs() throws QueryException {
+    List<Object> result = new ArrayList<Object>(operands.length);
+    for (int i = 0; i < operands.length; i++) result.add(operands[i].getValue());
+    return result;
+  }
+}