99 lines
3.8 KiB
XML
99 lines
3.8 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<document>
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<properties>
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<title>Compatibility</title>
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<author email="dev@commons.apache.org">Commons Documentation Team</author>
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</properties>
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<body>
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<section name="Version compatibility of Commons Collections">
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<p>
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This page details the compatibility of different collections releases.
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</p>
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<p>
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There are two types of compatibility discussed here, source and binary.
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</p>
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<ul>
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<li>
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Two versions are source compatible when application code can be compiled
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against either version successfully. The compilation may result in deprecation warnings
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but that is perfectly acceptable.
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When code is source incompatible, it fails to compile, thus this type of incompatibility is easy to find.
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</li>
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<li>
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Two versions are binary compatible when application code compiled against
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one version will run using the other version without recompilation.
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This is much more difficult to test for, and follows quite complicated rules from the
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<a href="http://java.sun.com/docs/books/jls/second_edition/html/binaryComp.doc.html">Java language</a>.
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</li>
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</ul>
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<p>
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Releases of commons collections aim to be source and binary compatible within minor versions,
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and to avoid breakages as much as possible between major versions.
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</p>
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<p>
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Commons collections 3.0 is source compatible with version 2.1 and 2.0 with the exception
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of classes previously deprecated in 2.0/2.1 (which were removed in 3.0).
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</p>
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<p>
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Commons collections 3.0 is binary compatible with version 2.1 and 2.0
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<b>except for certain methods on one class</b>.
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As the release was a major version, this is permitted, however it was unintentional and an error.
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The problem is in the <b><code>IteratorUtils</code></b> class (see methods below).
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(Strictly speaking, there are some minor incompatibilities on other classes, but these
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changes were deliberate and have not caused any known issues.)
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</p>
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<p>
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It is not possible to make v2.1 and v3.0 compatible without futher binary incompatibility.
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The chosen solution is to provide a work around by releasing v2.1.1 and v3.1.
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The following deprecations must be resolved in v2.1.1 to allow compatibiilty with v3.1.
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</p>
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<ul>
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<li>Deprecated <code>IteratorUtils.arrayIterator(...)</code> -
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use <code>new ArrayIterator(...)</code> instead</li>
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<li>Deprecated <code>IteratorUtils.singletonIterator(...)</code> -
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use <code>new SingletonIterator(...)</code> instead</li>
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<li>Deprecated <code>IteratorUtils.emptyIterator()</code> -
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use <code>EmptyIterator.INSTANCE</code> instead</li>
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<li>Deprecated <code>IteratorUtils.emptyListIterator()</code> -
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use <code>EmptyListIterator.INSTANCE</code> instead</li>
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<li>Deprecated <code>IteratorUtils.EMPTY_ITERATOR</code> -
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use <code>EmptyIterator.INSTANCE</code> instead</li>
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<li>Deprecated <code>IteratorUtils.EMPTY_LIST_ITERATOR</code> -
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use <code>EmptyIterator.INSTANCE</code> instead</li>
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</ul>
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<p>
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For the future, a new tool <a href="http://clirr.sourceforge.net">clirr</a> is being developed
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to help spot binary incompatibility before release.
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</p>
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</section>
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</body>
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</document>
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