module java.base does not read module java.desktop

Question

When I run this test (using jmockit and TestNG, not sure if that's relevant):

public class Test {
  @Test public void test(@Mocked ProcessBuilder pb) throws IOException {
    new Expectations() {{ pb.start(); result = null; }};
    assertNull(m());
  }

  public static Process m() throws IOException {
    return new ProcessBuilder("").start();
  }
}

I get this exception:

java.lang.IllegalAccessError: class java.lang.ProcessBuilder (in module java.base) cannot access class javax.print.PrintException (in module java.desktop) because module java.base does not read module java.desktop

at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java)
....

I am using build 177.

I can rerun the test using --add-reads java.base=java.desktop argument and it works fine but I don't really understand what is happening here.

Why am I getting that exception?

My guess would be some interaction with classes that are being loaded implicitly; `PrintException` does extend `IOException`, and this *feels* like the inexplicable `HeadlessException`s when using something not obviously Swing-related. I suggest filing a bug about a possible hidden class dependency. — chrylis -cautiouslyoptimistic-, Jul 10 '17 at 17:54
Are the classes/jars on the modulepath or the classpath? Are any modules defined for your code? — Michael Easter, Jul 10 '17 at 18:21
@MichaelEaster on the classpath - I haven't defined any module. It's a simple project with a pom.xml with a dependency on TestNG and jmockit and one file (the Test class in the question). The pom includes an argLine of `-Djdk.attach.allowAttachSelf` for surefire to allow jmockit to run. — assylias, Jul 10 '17 at 18:25

score 8 · Answer 1 · answered Jul 10 '17 at 19:36

8

The IllegalAccessError hints that JMockit has instrumented ProcessBuilder (in java.base) with a reference to an exception in the java.desktop module. I don't know why it choose this exception, that may be something for the JMockit mailing list. However it does explain why --add-reads fixes the issue.

answered Jul 10 '17 at 19:36

Alan Bateman

5,283
1
20
25

3

Thanks - I've raised the issue there: https://github.com/jmockit/jmockit1/issues/428 – assylias Jul 11 '17 at 08:11

score 2 · Accepted Answer · answered Jul 13 '17 at 02:17

The issue has been fixed for JMockit 1.34.

During startup, JMockit modifies a JRE class (adding a few fields) in order to provide support for the mocking of JRE classes. The actual class which gets modified is arbitrary, and javax.print.PrintException was used (as a secondary choice) just because it usually never gets loaded in a typical test run. On JDK 9, this class is not accessible from the "base" module, so it was now replaced by another one which is.

module java.base does not read module java.desktop

2 Answers2

Linked