如何为非法反射访问警告抛出异常？

Question

How can I throw an exception for an illegal reflective access warning? For example, consider the following code:

import org.apache.commons.lang3.builder.*;

class Test {
    public static void main(String[] args) {
        System.out.println(ReflectionToStringBuilder.toString(Boolean.TRUE));
    }
}

This code prints the following warning to System.err:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.commons.lang3.builder.ReflectionToStringBuilder (file:/Users/brianschack/eclipse-workspace/User%20Libraries/com
mons-lang3-3.7/commons-lang3-3.7.jar) to field java.lang.Boolean.value
WARNING: Please consider reporting this to the maintainers of org.apache.commons.lang3.builder.ReflectionToStringBuilder
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

Boolean.TRUE is such a simple value that I don't really need ReflectionToStringBuilder. But more complex types (such as HashMap) print the same warning. I chose Boolean.TRUE in order to simplify this example.

When I searched for this warning message, I found suggestions to report it to the package maintainer, avoid the warning, or disable it altogether ( JDK9: An illegal reflective access operation has occurred. org.python.core.PySystemState ).

I would like to throw an exception for the warning in order to get a stack trace of where the illegal access occurred. Then I could change the code to avoid the illegal access that caused the warning. I would also like to make a unit test that would check for the warning in the future.

I tried to test for printing to System.err according to the StackOverflow question, JUnit test for System.out.println() . This involves setting System.err to a ByteArrayOutputStream and then examining the contents. But unfortunately, according to How to hide warning “Illegal reflective access” in java 9 without JVM argument? , the IllegalAccessLogger gets a reference to System.err during JVM bootstrap before I can change it.

I also tried closing System.err, but it seems that printing to a closed stream silently fails instead of throwing an exception. Notice that the output for the following code does not contain the string "err-2":

Code:

class Test {
    public static void main(String[] args) {
        System.out.println("Start");
        System.err.println("err-1");
        System.err.close();
        System.err.println("err-2");
        System.out.println("End");
    }
}

Output:

Start
err-1
End

Answer 1

1. Open the Eclipse development environment.
2. Choose Run menu –> Run Configurations... –> Java Application –> (your configuration) –> Arguments.
3. In the VM arguments text box, type "--illegal-access=deny" [0].
4. Click the Apply button.
5. Click the Run button.
6. Illegal access will throw the java.lang.reflect.InaccessibleObjectException [1].

[0] http://mail.openjdk.java.net/pipermail/jigsaw-dev/2017-May/012673.html

[1] http://docs.oracle.com/javase/9/docs/api/java/lang/reflect/InaccessibleObjectException.html