/*
* Copyright 2006 the original author or authors.
*
* 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 jdave.contract;
import jdave.ExpectationFailedException;
import jdave.IContract;
/**
* A contract to ensure that equals method is correctly implemented
* and is consistent with hashCode method.
*
* Example:
* <blockquote>
* <pre>
* public void isConsistentWithEqualsAndHashCode() {
* object = new SampleDomainObject(1);
* specify(object, satisfies(new EqualsHashCodeContract<SampleDomainObject>() {
* protected SampleDomainObject equal() {
* return new SampleDomainObject(1);
* }
* protected SampleDomainObject nonEqual() {
* return new SampleDomainObject(2);
* }
* protected SampleDomainObject subType() {
* return new SampleDomainObject(1) {};
* }
* }));
* }
* </pre>
* </blockquote>
*
* @see java.lang.Object#equals(Object)
* @see java.lang.Object#hashCode()
*
* @author Joni Freeman
*/
public abstract class EqualsHashCodeContract<T> implements IContract {
public void isSatisfied(Object obj) throws ExpectationFailedException {
if (obj.equals(null)) {
throw new ExpectationFailedException(obj + " equals null");
}
try {
obj.equals("");
} catch (ClassCastException e) {
throw new ExpectationFailedException(obj.getClass().getSimpleName() + ".equals(Object) does not check for ClassCastException");
}
if (!obj.equals(equal())) {
throw new ExpectationFailedException(obj + " does not equal " + equal());
}
if (obj.equals(nonEqual())) {
throw new ExpectationFailedException(obj + " does equal " + nonEqual());
}
if (subType() != null) {
if (obj.equals(subType())) {
throw new ExpectationFailedException(obj + " does equal " + subType());
}
}
int hash1 = obj.hashCode();
int hash2 = equal().hashCode();
if (hash1 != hash2) {
throw new ExpectationFailedException("hashCodes must equal for equal objects, " +
hash1 + " != " + hash2);
}
}
/**
* @return an Object which is equal to the Object whose contract is enforced
*/
protected abstract T equal();
/**
* @return an Object which is not equal to the Object whose contract is enforced
*/
protected abstract T nonEqual();
/**
* Generally sub-types should not equal with super types.
* This check can be skipped by returning null.
*
* @return an Object which is a sub-type of the Object whose contract is enforced or null
*/
protected abstract T subType();
}