2

好的，这里有一些有趣的东西。请注意，这里的“元素”是 的一个实例PathElements，并且对于这些.resolve()，.relativize()已经过全面测试并且已知可以工作......指向相关方法实现的链接Path.resolve()，Path.relativize()

失败的测试方法的摘录：

/*
 * This test this part of the Path's .relativize() method:
 *
 * <p> For any two {@link #normalize normalized} paths <i>p</i> and
 * <i>q</i>, where <i>q</i> does not have a root component,
 * <blockquote>
 * <i>p</i><tt>.relativize(</tt><i>p</i><tt>.resolve(</tt><i>q</i><tt>))
 * .equals(</tt><i>q</i><tt>)</tt>
 * </blockquote>
 *
 * Unfortunately, that turns out NOT TO BE TRUE! Whether p is absolute or
 * relative, it is indeed the case that the path elements (root, names) are
 * the same but the filesystem DIFFERS.
 *
 * An as Path's .equals() requires that the two filesystems be equal in
 * order for two Paths to be equals, this contract can not be obeyed; or I
 * am doing something VERY wrong.
 */
@Test(enabled = false)
public void relativizeResolveRoundRobinWorks()
{
    /*
     * In order to set up the environment we define a mock
     * FileSystemProvider which both our mock filesystems will return when
     * .provider() is called.
     *
     * We also suppose that the same PathElementsFactory is used; while this
     * code is not written yet, there should be only one such factory per
     * FileSystemProvider anyway (which is fed into all generated FileSystem
     * instances -- at least that's the plan).
     *
     * Note that this test method assumes that .equals() and .hashCode() are
     * not implemented on GenericPath. As such we check that the FileSystem
     * is the same (this is required by Path's equals()) and that the path
     * elements are the same (this is this package's requirements).
     */
    final FileSystemProvider fsProvider = mock(FileSystemProvider.class);
    final PathElementsFactory elementsFactory
        = new UnixPathElementsFactory();
    final FileSystem fsForP = mock(FileSystem.class);
    final FileSystem fsForQ = mock(FileSystem.class);

    when(fsForP.provider()).thenReturn(fsProvider);
    when(fsForQ.provider()).thenReturn(fsProvider);

    /*
     * The path to be operated. As the contract says, it has no root
     * component.
     */
    final GenericPath q = new GenericPath(fsForQ, elementsFactory,
        new PathElements(null, new String[] { "q1", "q2" }));

    /*
     * The path against which both resolution and relativization are
     * performed. We take two versions of it: a non absolute one and an
     * absolute one.
     *
     * Note that since we use a UnixPathElementsFactory, we equate an
     * absolute path (or not) to a path which has a root component (or not).
     */
    GenericPath p;
    // "rr" as in "resolved, relativized"
    GenericPath rr;

    final CustomSoftAssertions soft = CustomSoftAssertions.create();

    /*
     * Try with the absolute version first...
     */
    p = new GenericPath(fsForP, elementsFactory,
        new PathElements("/", new String[] { "p1", "p2" }));
    rr = (GenericPath) p.relativize(p.resolve(q));

    soft.assertThat(rr.getFileSystem())
        .as("rr and q filesystems should be the same (p absolute)")
        .isSameAs(q.getFileSystem());
    soft.assertThat(rr.elements).hasSameContentsAs(q.elements);

    /*
     * Now with the non absolute version
     */
    p = new GenericPath(fsForP, elementsFactory,
        new PathElements(null, new String[] { "p1", "p2" }));
    rr = (GenericPath) p.relativize(p.resolve(q));

    soft.assertThat(rr.getFileSystem())
        .as("rr and q filesystems should be the same (p not absolute)")
        .isSameAs(q.getFileSystem());
    soft.assertThat(rr.elements).hasSameContentsAs(q.elements);

    soft.assertAll();
}

此测试失败：

org.assertj.core.api.SoftAssertionError: 
The following 2 assertions failed:
1) [rr and q filesystems should be the same (p absolute)] 
Expecting:
 <Mock for FileSystem, hashCode: 1125642929>
and actual:
 <Mock for FileSystem, hashCode: 1497261280>
to refer to the same object
2) [rr and q filesystems should be the same (p not absolute)] 
Expecting:
 <Mock for FileSystem, hashCode: 1125642929>
and actual:
 <Mock for FileSystem, hashCode: 1497261280>
to refer to the same object

显然如此！

  • r = p.resolve(q) 将给出一个与 p 共享相同文件系统的路径，而不是 q；
  • 因此，p.relativize(r) 也会给出一个与 p 具有相同文件系统的 Path；
  • 但是 Path 合约要求为了使两条路径相等，它们共享同一个文件系统。

在这种情况下，这总是错误的。

那么，这是文档中的一个公然错误还是我忽略了什么？

4

1 回答 1

0

答：文档没有提到来自其他文件系统的路径。

resolve 和 relativize 的文档在这里并不十分清楚。但是如果参数路径来自不同的文件系统，relativize 必须抛出 ProviderMismatchException。您的测试应该更早抛出。

路径上的约束可能因文件系统而异。考虑相对化的情况。可以从一个文件系统走到另一个不相交的文件系统的路径应该是什么样的？

注意：我测试了几个 FileSystem 实现并且都在这种情况下抛出。

于 2015-06-30T21:10:54.593 回答