001    /*
002     * Created on Oct 10, 2007
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005     * in compliance with the License. You may obtain a copy of the License at
006     *
007     * http://www.apache.org/licenses/LICENSE-2.0
008     *
009     * Unless required by applicable law or agreed to in writing, software distributed under the License
010     * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011     * or implied. See the License for the specific language governing permissions and limitations under
012     * the License.
013     *
014     * Copyright @2007-2011 the original author or authors.
015     */
016    package org.fest.assertions;
017    
018    import static org.fest.util.Strings.*;
019    import static org.fest.util.ToString.toStringOf;
020    
021    /**
022     * Creates instances of JUnit's <code>ComparisonFailure</code>.
023     *
024     * @author Yvonne Wang
025     * @author Alex Ruiz
026     */
027    public final class ComparisonFailureFactory {
028    
029      private static final String EMPTY_MESSAGE = "";
030    
031      private static ConstructorInvoker constructorInvoker = new ConstructorInvoker();
032    
033      static void constructorInvoker(ConstructorInvoker newConstructorInvoker) {
034        constructorInvoker = newConstructorInvoker;
035      }
036    
037      /**
038       * Creates a new instance of JUnit's <code>ComparisonFailure</code> only if JUnit 4+ is in the classpath.
039       * @param message the identifying message or {@code null}.
040       * @param expected the expected value.
041       * @param actual the actual value.
042       * @return the created <code>ComparisonFailure</code>, or {@code null} if JUnit 4+ is not in the classpath.
043       */
044      public static AssertionError comparisonFailure(String message, Object expected, Object actual) {
045        try {
046          return newComparisonFailure(clean(message), expected, actual);
047        } catch (Exception e) {
048          return null;
049        }
050      }
051    
052      private static String clean(String message) {
053        return message == null ? "" : message;
054      }
055    
056      private static AssertionError newComparisonFailure(String message, Object expected, Object actual) throws Exception {
057        String className = "org.junit.ComparisonFailure";
058        Class<?>[] parameterTypes = new Class<?>[] { String.class, String.class, String.class };
059        Object[] parameterValues = new Object[] { format(message), asString(expected), asString(actual) };
060        Object o = constructorInvoker.newInstance(className, parameterTypes, parameterValues);
061        if (o instanceof AssertionError) return (AssertionError)o;
062        return null;
063      }
064    
065      private static String asString(Object o) {
066        if (o instanceof String) return quote((String)o);
067        if (o == null) return null;
068        return toStringOf(o);
069      }
070    
071      private static String format(String message) {
072        if (isEmpty(message)) return EMPTY_MESSAGE;
073        return String.format("[%s]", message);
074      }
075    
076      private ComparisonFailureFactory() {}
077    }