![]() Public int ExampleMethods.varArgsMethod(.) Public boolean ExampleMethods.simpleMethod(,int) This command prints the following: Number of constructors: 1 Note: Remember to compile the example ExampleMethods with the -parameters compiler option: java MethodParameterSpy ExampleMethods The following command prints the formal parameter names of the constructors and methods of the classĮxampleMethods. The example also prints other information about each parameter. MethodParameterSpy example illustrates how to retrieve the names of the formal parameters of all constructors and methods of a given class. ![]() class file, and thus enable the Reflection API to retrieve formal parameter names, compile the source file with the -parameters option to the javac compiler. To store formal parameter names in a particular. In addition, some parameter names, such as secret or password, may expose information about security-sensitive methods. class files, and the Java Virtual Machine (JVM) would use more memory. In particular, these tools would have to handle larger. class files that contain parameter names. This is because many tools that produce and consume class files may not expect the larger static and dynamic footprint of. class files do not store formal parameter names by default. (The classesĮxecutable and therefore inherit the method Executable.getParameters.) However. (" -> PrivateInaccessible.You can obtain the names of the formal parameters of any method or constructor with the method Javac -source 1.8 -target 1.8 CallDefaultMethodThroughReflection.java It’s also available in this gist here.Ĭompile it with JDK 9 or 10 (because it also tries using JDK 9+ API: MethodHandles.privateLookupIn()), but compile it using this command, so you can also run the class on JDK 8: The following class tries all combinations. So far, I’ve just been trying to run different things on different JDKs. So, there’s a solution (hack) that works on Java 8 but not on 9 or 10, and there’s a solution that works on Java 9 and 10, but not on Java 8. ![]() Great, it works in Java 9 and 10, what about Java 8?Ĭaused by: : no private access for invokespecial: interface Duck, from ProxyDemoĪt $Lookup.findSpecial(MethodHandles.java:1002) One of the Jigsaw project’s goals is to precisely not allow such hacks to persist. If we run the program with the -illegal-access=deny flag:Įxception in thread "main" : Unable to make $Lookup() accessible: module java.base does not "opens " to unnamed module java.base/.checkCanSetAccessible(AccessibleObject.java:337)Īt java.base/.checkCanSetAccessible(AccessibleObject.java:281)Īt java.base/.checkCanSetAccessible(Constructor.java:192)Īt java.base/.setAccessible(Constructor.java:185) WARNING: All illegal access operations will be denied in a future release WARNING: Use -illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: Please consider reporting this to the maintainers of ProxyDemo WARNING: Illegal reflective access by ProxyDemo (file:/C:/Users/lukas/workspace/playground/target/classes/) to constructor $Lookup() WARNING: An illegal reflective access operation has occurred When googling further, we might find the following solution, which accesses MethodHandles.Lookup‘s internals through reflection: We get the following IllegalAccessException:Ĭaused by: : no private access for invokespecial: interface Duck, from Duck/packageĪt .makeAccessException(MemberName.java:850)Īt $Lookup.checkSpecialCaller(MethodHandles.java:1572)Īt $Lookup.unreflectSpecial(MethodHandles.java:1231)īummer. The almost same code snippet no longer works. So, the original Google search turned up results that indicate we need to use the MethodHandles API. You simply cannot do this):Įxception in thread "main" Ĭaused by: Īt 0(Native Method)Īt (NativeMethodAccessorImpl.java:62)Īt (DelegatingMethodAccessorImpl.java:43)Īt .invoke(Method.java:498)Ĭaused by: Thread.currentThread().getContextClassLoader(),īut this will just generate a long long stack trace of nested exceptions (this isn’t specific to the method being a default method. Duck duck = (Duck) Proxy.newProxyInstance(
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