gistfile1.java

package org.shivas.core;

import junit.framework.TestCase;

import java.lang.annotation.*;
import java.lang.reflect.Field;
import java.util.*;

public class Test extends TestCase {

    @Retention(value = RetentionPolicy.RUNTIME)
    @Target(value = {ElementType.FIELD})
    static @interface Config {
        String key();
    }

    static class Configured {
        @Config(key="client.version")
        private static String CLIENT_VERSION;

        @Config(key="login.port")
        private static short LOGIN_PORT;
    }

    @Override
    protected void setUp() throws Exception {
        Configured.CLIENT_VERSION = null;
    }

    private List<Class<?>> getClasses(ClassLoader classLoader) throws ReflectiveOperationException {
        Class<?> clazz = classLoader.getClass();
        while (clazz != ClassLoader.class) {
            clazz = clazz.getSuperclass();
        }
        Field field = clazz.getDeclaredField("classes");
        field.setAccessible(true);

        return new ArrayList<Class<?>>((Collection<Class<?>>) field.get(classLoader));
    }

    private void injectConfigValues(Map<String, Object> configValues) throws ReflectiveOperationException {
        for (Class<?> clazz : getClasses(Thread.currentThread().getContextClassLoader())) {
            for (Field field : clazz.getDeclaredFields()) {
                Config annotation = field.getAnnotation(Config.class);
                if (annotation == null) continue;

                Object value = configValues.get(annotation.key());
                if (value == null) {
                    System.out.format("unknown config value \"%s\" in class %s\n", annotation.key(), clazz.getCanonicalName());
                } else {
                    if (!field.isAccessible()) {
                        field.setAccessible(true);
                    }
                    field.set(null, value);
                }
            }
        }
    }

    public void test1() {
        try {
            injectConfigValues(new HashMap<String, Object>() {{
                put("client.version", "1.29.1");
                put("login.port", (short) 5555);
            }});
        } catch (ReflectiveOperationException e) {
            e.printStackTrace();
        }

        assertEquals("1.29.1", Configured.CLIENT_VERSION);
        assertEquals(5555, Configured.LOGIN_PORT);
    }

}