- /*
- * Copyright 2002-2004 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;
-
- import java.util.Collection;
- import java.util.Iterator;
- import java.util.Map;
-
- import org.apache.commons.collections.functors.ChainedClosure;
- import org.apache.commons.collections.functors.EqualPredicate;
- import org.apache.commons.collections.functors.ExceptionClosure;
- import org.apache.commons.collections.functors.ForClosure;
- import org.apache.commons.collections.functors.IfClosure;
- import org.apache.commons.collections.functors.InvokerTransformer;
- import org.apache.commons.collections.functors.NOPClosure;
- import org.apache.commons.collections.functors.SwitchClosure;
- import org.apache.commons.collections.functors.TransformerClosure;
- import org.apache.commons.collections.functors.WhileClosure;
-
- /**
- * <code>ClosureUtils</code> provides reference implementations and utilities
- * for the Closure functor interface. The supplied closures are:
- * <ul>
- * <li>Invoker - invokes a method on the input object
- * <li>For - repeatedly calls a closure for a fixed number of times
- * <li>While - repeatedly calls a closure while a predicate is true
- * <li>DoWhile - repeatedly calls a closure while a predicate is true
- * <li>Chained - chains two or more closures together
- * <li>Switch - calls one closure based on one or more predicates
- * <li>SwitchMap - calls one closure looked up from a Map
- * <li>Transformer - wraps a Transformer as a Closure
- * <li>NOP - does nothing
- * <li>Exception - always throws an exception
- * </ul>
- * All the supplied closures are Serializable.
- *
- * @since Commons Collections 3.0
- * @version $Revision: 1.9 $ $Date: 2004/05/26 21:50:52 $
- *
- * @author Stephen Colebourne
- */
- public class ClosureUtils {
-
- /**
- * This class is not normally instantiated.
- */
- public ClosureUtils() {
- super();
- }
-
- /**
- * Gets a Closure that always throws an exception.
- * This could be useful during testing as a placeholder.
- *
- * @see org.apache.commons.collections.functors.ExceptionClosure
- *
- * @return the closure
- */
- public static Closure exceptionClosure() {
- return ExceptionClosure.INSTANCE;
- }
-
- /**
- * Gets a Closure that will do nothing.
- * This could be useful during testing as a placeholder.
- *
- * @see org.apache.commons.collections.functors.NOPClosure
- *
- * @return the closure
- */
- public static Closure nopClosure() {
- return NOPClosure.INSTANCE;
- }
-
- /**
- * Creates a Closure that calls a Transformer each time it is called.
- * The transformer will be called using the closure's input object.
- * The transformer's result will be ignored.
- *
- * @see org.apache.commons.collections.functors.TransformerClosure
- *
- * @param transformer the transformer to run each time in the closure, null means nop
- * @return the closure
- */
- public static Closure asClosure(Transformer transformer) {
- return TransformerClosure.getInstance(transformer);
- }
-
- /**
- * Creates a Closure that will call the closure <code>count</code> times.
- * <p>
- * A null closure or zero count returns the <code>NOPClosure</code>.
- *
- * @see org.apache.commons.collections.functors.ForClosure
- *
- * @param count the number of times to loop
- * @param closure the closure to call repeatedly
- * @return the <code>for</code> closure
- */
- public static Closure forClosure(int count, Closure closure) {
- return ForClosure.getInstance(count, closure);
- }
-
- /**
- * Creates a Closure that will call the closure repeatedly until the
- * predicate returns false.
- *
- * @see org.apache.commons.collections.functors.WhileClosure
- *
- * @param predicate the predicate to use as an end of loop test, not null
- * @param closure the closure to call repeatedly, not null
- * @return the <code>while</code> closure
- * @throws IllegalArgumentException if either argument is null
- */
- public static Closure whileClosure(Predicate predicate, Closure closure) {
- return WhileClosure.getInstance(predicate, closure, false);
- }
-
- /**
- * Creates a Closure that will call the closure once and then repeatedly
- * until the predicate returns false.
- *
- * @see org.apache.commons.collections.functors.WhileClosure
- *
- * @param closure the closure to call repeatedly, not null
- * @param predicate the predicate to use as an end of loop test, not null
- * @return the <code>do-while</code> closure
- * @throws IllegalArgumentException if either argument is null
- */
- public static Closure doWhileClosure(Closure closure, Predicate predicate) {
- return WhileClosure.getInstance(predicate, closure, true);
- }
-
- /**
- * Creates a Closure that will invoke a specific method on the closure's
- * input object by reflection.
- *
- * @see org.apache.commons.collections.functors.InvokerTransformer
- * @see org.apache.commons.collections.functors.TransformerClosure
- *
- * @param methodName the name of the method
- * @return the <code>invoker</code> closure
- * @throws IllegalArgumentException if the method name is null
- */
- public static Closure invokerClosure(String methodName) {
- // reuse transformer as it has caching - this is lazy really, should have inner class here
- return asClosure(InvokerTransformer.getInstance(methodName));
- }
-
- /**
- * Creates a Closure that will invoke a specific method on the closure's
- * input object by reflection.
- *
- * @see org.apache.commons.collections.functors.InvokerTransformer
- * @see org.apache.commons.collections.functors.TransformerClosure
- *
- * @param methodName the name of the method
- * @param paramTypes the parameter types
- * @param args the arguments
- * @return the <code>invoker</code> closure
- * @throws IllegalArgumentException if the method name is null
- * @throws IllegalArgumentException if the paramTypes and args don't match
- */
- public static Closure invokerClosure(String methodName, Class[] paramTypes, Object[] args) {
- // reuse transformer as it has caching - this is lazy really, should have inner class here
- return asClosure(InvokerTransformer.getInstance(methodName, paramTypes, args));
- }
-
- /**
- * Create a new Closure that calls two Closures, passing the result of
- * the first into the second.
- *
- * @see org.apache.commons.collections.functors.ChainedClosure
- *
- * @param closure1 the first closure
- * @param closure2 the second closure
- * @return the <code>chained</code> closure
- * @throws IllegalArgumentException if either closure is null
- */
- public static Closure chainedClosure(Closure closure1, Closure closure2) {
- return ChainedClosure.getInstance(closure1, closure2);
- }
-
- /**
- * Create a new Closure that calls each closure in turn, passing the
- * result into the next closure.
- *
- * @see org.apache.commons.collections.functors.ChainedClosure
- *
- * @param closures an array of closures to chain
- * @return the <code>chained</code> closure
- * @throws IllegalArgumentException if the closures array is null
- * @throws IllegalArgumentException if any closure in the array is null
- */
- public static Closure chainedClosure(Closure[] closures) {
- return ChainedClosure.getInstance(closures);
- }
-
- /**
- * Create a new Closure that calls each closure in turn, passing the
- * result into the next closure. The ordering is that of the iterator()
- * method on the collection.
- *
- * @see org.apache.commons.collections.functors.ChainedClosure
- *
- * @param closures a collection of closures to chain
- * @return the <code>chained</code> closure
- * @throws IllegalArgumentException if the closures collection is null
- * @throws IllegalArgumentException if the closures collection is empty
- * @throws IllegalArgumentException if any closure in the collection is null
- */
- public static Closure chainedClosure(Collection closures) {
- return ChainedClosure.getInstance(closures);
- }
-
- /**
- * Create a new Closure that calls one of two closures depending
- * on the specified predicate.
- *
- * @see org.apache.commons.collections.functors.IfClosure
- *
- * @param predicate the predicate to switch on
- * @param trueClosure the closure called if the predicate is true
- * @param falseClosure the closure called if the predicate is false
- * @return the <code>switch</code> closure
- * @throws IllegalArgumentException if the predicate is null
- * @throws IllegalArgumentException if either closure is null
- */
- public static Closure ifClosure(Predicate predicate, Closure trueClosure, Closure falseClosure) {
- return IfClosure.getInstance(predicate, trueClosure, falseClosure);
- }
-
- /**
- * Create a new Closure that calls one of the closures depending
- * on the predicates.
- * <p>
- * The closure at array location 0 is called if the predicate at array
- * location 0 returned true. Each predicate is evaluated
- * until one returns true.
- *
- * @see org.apache.commons.collections.functors.SwitchClosure
- *
- * @param predicates an array of predicates to check, not null
- * @param closures an array of closures to call, not null
- * @return the <code>switch</code> closure
- * @throws IllegalArgumentException if the either array is null
- * @throws IllegalArgumentException if any element in the arrays is null
- * @throws IllegalArgumentException if the arrays are different sizes
- */
- public static Closure switchClosure(Predicate[] predicates, Closure[] closures) {
- return SwitchClosure.getInstance(predicates, closures, null);
- }
-
- /**
- * Create a new Closure that calls one of the closures depending
- * on the predicates.
- * <p>
- * The closure at array location 0 is called if the predicate at array
- * location 0 returned true. Each predicate is evaluated
- * until one returns true. If no predicates evaluate to true, the default
- * closure is called.
- *
- * @see org.apache.commons.collections.functors.SwitchClosure
- *
- * @param predicates an array of predicates to check, not null
- * @param closures an array of closures to call, not null
- * @param defaultClosure the default to call if no predicate matches
- * @return the <code>switch</code> closure
- * @throws IllegalArgumentException if the either array is null
- * @throws IllegalArgumentException if any element in the arrays is null
- * @throws IllegalArgumentException if the arrays are different sizes
- */
- public static Closure switchClosure(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
- return SwitchClosure.getInstance(predicates, closures, defaultClosure);
- }
-
- /**
- * Create a new Closure that calls one of the closures depending
- * on the predicates.
- * <p>
- * The Map consists of Predicate keys and Closure values. A closure
- * is called if its matching predicate returns true. Each predicate is evaluated
- * until one returns true. If no predicates evaluate to true, the default
- * closure is called. The default closure is set in the map with a
- * null key. The ordering is that of the iterator() method on the entryset
- * collection of the map.
- *
- * @see org.apache.commons.collections.functors.SwitchClosure
- *
- * @param predicatesAndClosures a map of predicates to closures
- * @return the <code>switch</code> closure
- * @throws IllegalArgumentException if the map is null
- * @throws IllegalArgumentException if the map is empty
- * @throws IllegalArgumentException if any closure in the map is null
- * @throws ClassCastException if the map elements are of the wrong type
- */
- public static Closure switchClosure(Map predicatesAndClosures) {
- return SwitchClosure.getInstance(predicatesAndClosures);
- }
-
- /**
- * Create a new Closure that uses the input object as a key to find the
- * closure to call.
- * <p>
- * The Map consists of object keys and Closure values. A closure
- * is called if the input object equals the key. If there is no match, the
- * default closure is called. The default closure is set in the map
- * using a null key.
- *
- * @see org.apache.commons.collections.functors.SwitchClosure
- *
- * @param objectsAndClosures a map of objects to closures
- * @return the closure
- * @throws IllegalArgumentException if the map is null
- * @throws IllegalArgumentException if the map is empty
- * @throws IllegalArgumentException if any closure in the map is null
- */
- public static Closure switchMapClosure(Map objectsAndClosures) {
- Closure[] trs = null;
- Predicate[] preds = null;
- if (objectsAndClosures == null) {
- throw new IllegalArgumentException("The object and closure map must not be null");
- }
- Closure def = (Closure) objectsAndClosures.remove(null);
- int size = objectsAndClosures.size();
- trs = new Closure[size];
- preds = new Predicate[size];
- int i = 0;
- for (Iterator it = objectsAndClosures.entrySet().iterator(); it.hasNext();) {
- Map.Entry entry = (Map.Entry) it.next();
- preds[i] = EqualPredicate.getInstance(entry.getKey());
- trs[i] = (Closure) entry.getValue();
- i++;
- }
- return switchClosure(preds, trs, def);
- }
-
- }