具有特权的JVM中的Java文件setWritable

Question

我使用带有图像 java:8u111-jdk 的 Gitlab CI 从源代码构建 Apache Flink，发现文件权限测试失败，因为文件权限未得到遵守。

其中一个单元测试如下:

    @Test
    public void testDeleteDirectory() throws Exception {

        // deleting a non-existent file should not cause an error

        File doesNotExist = new File(tmp.newFolder(), "abc");
        FileUtils.deleteDirectory(doesNotExist);

        // deleting a write protected file should throw an error

        File cannotDeleteParent = tmp.newFolder();
        File cannotDeleteChild = new File(cannotDeleteParent, "child");

        try {
            assumeTrue(cannotDeleteChild.createNewFile());
            assumeTrue(cannotDeleteParent.setWritable(false));
            assumeTrue(cannotDeleteChild.setWritable(false));

            FileUtils.deleteDirectory(cannotDeleteParent);
            fail("this should fail with an exception");
        }
        catch (AccessDeniedException ignored) {
            // this is expected
        }
        finally {
            //noinspection ResultOfMethodCallIgnored
            cannotDeleteParent.setWritable(true);
            //noinspection ResultOfMethodCallIgnored
            cannotDeleteChild.setWritable(true);
        }
    }

测试结果为:

testDeleteDirectory(org.apache.flink.util.FileUtilsTest)  Time elapsed: 0.022 sec  <<< FAILURE!
java.lang.AssertionError: this should fail with an exception
    at org.junit.Assert.fail(Assert.java:88)
    at org.apache.flink.util.FileUtilsTest.testDeleteDirectory(FileUtilsTest.java:129)

当我深入研究代码时，我在 java.io.File 中发现了以下语句:

On some platforms it may be possible to start the Java virtual machine with special privileges that allow it to modify files that disallow write operations.

所以我怀疑是CI环境出了问题。我怎样才能进一步调试问题？谢谢!

环境:

• docker镜像:java:8u111-jdk
• 操作系统内核:Linux 4.9.0-8-amd64 x86_64
• 发行版:Debian 8
• JDK版本:openjdk 1.8.0_111

Answer 1

问题是我们以 root 用户身份运行此代码，因此我们能够删除写保护的文件。