Add TransformedPredicate, which transforms before calling a predicate

bug 26946, from Alban Peignier


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@131603 13f79535-47bb-0310-9956-ffa450edef68

RELEASE-NOTES.html

@@ -25,6 +25,7 @@ No interface changes, or deprecations have occurred.
 
 <center><h3>NEW CLASSES</h3></center>
 <ul>
+<li>[26946] TransformedPredicate - A predicate where the input object is transformed</li>
 </ul>
 
 <center><h3>ENHANCEMENTS</h3></center>

project.xml

@@ -183,6 +183,9 @@
     <contributor>
       <name>Kasper Nielsen</name>
     </contributor>
+    <contributor>
+      <name>Alban Peignier</name>
+    </contributor>
     <contributor>
       <name>Steve Phelps</name>
     </contributor>

src/java/org/apache/commons/collections/PredicateUtils.java

@@ -34,6 +34,7 @@ import org.apache.commons.collections.functors.NullIsTruePredicate;
 import org.apache.commons.collections.functors.NullPredicate;
 import org.apache.commons.collections.functors.OnePredicate;
 import org.apache.commons.collections.functors.OrPredicate;
+import org.apache.commons.collections.functors.TransformedPredicate;
 import org.apache.commons.collections.functors.TransformerPredicate;
 import org.apache.commons.collections.functors.TruePredicate;
 import org.apache.commons.collections.functors.UniquePredicate;
@@ -63,7 +64,7 @@ import org.apache.commons.collections.functors.UniquePredicate;
  * All the supplied predicates are Serializable.
  *
  * @since Commons Collections 3.0
- * @version $Revision: 1.16 $ $Date: 2004/02/18 01:15:42 $
+ * @version $Revision: 1.17 $ $Date: 2004/03/13 16:34:46 $
  * 
  * @author Stephen Colebourne
  * @author Ola Berg
@@ -453,4 +454,20 @@ public class PredicateUtils {
         return NullIsTruePredicate.getInstance(predicate);
     }
 
+    // Transformed
+    //-----------------------------------------------------------------------
+    /**
+     * Creates a predicate that transforms the input object before passing it
+     * to the predicate.
+     * 
+     * @param transformer  the transformer to call first
+     * @param predicate  the predicate to call with the result of the transform
+     * @return the predicate
+     * @throws IllegalArgumentException if the transformer or the predicate is null
+	 * @since Commons Collections 3.1
+     */
+    public static Predicate transformedPredicate(Transformer transformer, Predicate predicate) {
+        return TransformedPredicate.getInstance(transformer, predicate);
+    }
+
 }

src/java/org/apache/commons/collections/functors/TransformedPredicate.java

@@ -0,0 +1,93 @@
+/*
+ *  Copyright 2001-2004 The Apache Software Foundation
+ *
+ *  Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.apache.commons.collections.functors;
+
+import java.io.Serializable;
+
+import org.apache.commons.collections.Predicate;
+import org.apache.commons.collections.Transformer;
+
+/**
+ * Predicate implementation that transforms the given object before invoking
+ * another <code>Predicate</code>.
+ * 
+ * @since Commons Collections 3.1
+ * @version $Revision: 1.1 $ $Date: 2004/03/13 16:34:46 $
+ * @author Alban Peignier
+ * @author Stephen Colebourne
+ */
+public final class TransformedPredicate implements Predicate, Serializable {
+
+    /** Serial version UID */
+    static final long serialVersionUID = -5596090919668315834L;
+    
+    /** The transformer to call */
+    private final Transformer transformer;
+    /** The predicate to call */
+    private final Predicate predicate;
+
+    /**
+     * Factory to create the predicate.
+     * 
+     * @param transformer  the transformer to call
+     * @param predicate  the predicate to call with the result of the transform
+     * @return the predicate
+     * @throws IllegalArgumentException if the transformer or the predicate is null
+     */
+    public static Predicate getInstance(Transformer transformer, Predicate predicate) {
+        if (transformer == null) {
+            throw new IllegalArgumentException("The transformer to call must not be null");
+        }
+        if (predicate == null) {
+            throw new IllegalArgumentException("The predicate to call must not be null");
+        }
+        return new TransformedPredicate(transformer, predicate);
+    }
+
+    /**
+     * Constructor that performs no validation.
+     * Use <code>getInstance</code> if you want that.
+     */
+    public TransformedPredicate(Transformer transformer, Predicate predicate) {
+        this.transformer = transformer;
+        this.predicate = predicate;
+    }
+    
+    /**
+     * Return the predicate result.
+     */
+    public boolean evaluate(Object object) {
+        Object result = transformer.transform(object);
+        return predicate.evaluate(result);
+    }
+
+    /**
+     * Gets the predicate in use.
+     * @return the predicate
+     */
+    public Predicate getPredicate() {
+        return predicate;
+    }
+
+    /**
+     * Gets the transformer in use.
+     * @return the transformer
+     */
+    public Transformer getTransformer() {
+        return transformer;
+    }
+
+}

src/test/org/apache/commons/collections/TestPredicateUtils.java

@@ -18,7 +18,9 @@ package org.apache.commons.collections;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 
 import junit.framework.Test;
@@ -29,7 +31,7 @@ import junit.textui.TestRunner;
  * Tests the org.apache.commons.collections.PredicateUtils class.
  * 
  * @since Commons Collections 3.0
- * @version $Revision: 1.7 $ $Date: 2004/02/18 01:20:35 $
+ * @version $Revision: 1.8 $ $Date: 2004/03/13 16:34:46 $
  *
  * @author Stephen Colebourne
  */
@@ -813,4 +815,24 @@ public class TestPredicateUtils extends junit.framework.TestCase {
         fail();
     }
     
+    // transformed
+    //------------------------------------------------------------------
+
+    public void testTransformedPredicate() {
+        assertEquals(true, PredicateUtils.transformedPredicate(
+                TransformerUtils.nopTransformer(),
+                PredicateUtils.truePredicate()).evaluate(new Object()));
+                
+        Map map = new HashMap();
+        map.put(Boolean.TRUE, "Hello");
+        Transformer t = TransformerUtils.mapTransformer(map);
+        Predicate p = PredicateUtils.equalPredicate("Hello");
+        assertEquals(false, PredicateUtils.transformedPredicate(t, p).evaluate(null));
+        assertEquals(true, PredicateUtils.transformedPredicate(t, p).evaluate(Boolean.TRUE));
+        try {
+            PredicateUtils.transformedPredicate(null, null);
+            fail();
+        } catch (IllegalArgumentException ex) {}
+    }
+
 }