How to get annotation's parameters from a class in jar file

Question

I want to get a class's (packaged in jar file) annotation parameters by java reflect.

My annotation like this

@Documented
@Retention(RUNTIME)
@Target(TYPE)    
public @interface TestPlugin {
    public String moduleName();
    public String plugVersion();
    public String minLeapVersion();    
}

My class like this

@TestPlugin(moduleName="xxx", plugVersion="1.0.0", minLeapVersion="1.3.0")

public class Plugin {

  ......

}

My access code like this

Class<?> clazz = this.loadClass(mainClassName);  // myself classloader

Annotation[] annos = clazz.getAnnotations();

for (Annotation anno : annos) {
    Class<? extends Annotation> annoClass = anno.annotationType();

    /* Question is here
    This code can get right annotationType: @TestPlugin. 
    Debug windows show anno is $Proxy33. 
    But I can't find any method to get annotation membervalues even though I can find them in debug windows.
    How can I get annotation's parameters?
    */
}

Debug windows info

Debug windows can be found in attached picture

Robbie
– Robbie

2017-01-16 12:29:55 +00:00
Commented Jan 16, 2017 at 12:29 — Robbie
– Robbie, Commented Jan 16, 2017 at 12:29

Community · Accepted Answer · 2017-05-23 11:45:49Z

1

The "real" annotation classes used by the Java VM are Dynamic Proxies for some technical reasons. This shouldn't bother you. They still "implement" your annotation class. Just use

TestPlugin plugin = clazz.getAnnotation(TestPlugin.class);

plugin.getClass() == TestPlugin.class; // false - is Dynamic proxy
TestPlugin.class.isAssignableFrom(plugin.getClass()); // true - Dynamic proxy implements TestPlugin interface

EDIT: Just found in another answer, that you could also ask your anno object in your loop, but do not use getClass(). Use .annotationType().

edited May 23, 2017 at 11:45

CommunityBot

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answered Jan 16, 2017 at 12:39

Florian Albrecht

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