Groovy example source code file (ReflectionUtils.java)

This example Groovy source code file (ReflectionUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

class, class, collection, collection, hashset, ignored_packages, magic_method, magic_method, method, method, reflection, reflectionutils, set, throwable, util

The Groovy ReflectionUtils.java source code

/*
 * Copyright 2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.reflection;

import java.lang.reflect.Method;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import java.util.Collections;

/**
 * This class contains utility methods to determine which class called the
 * current class to multiple levels of depth.  Calls used to handle the
 * groovy MOP are excluded from the level counting.
 */
public class ReflectionUtils {

    // these are packages in the call stack that are only part of the groovy MOP
    private static final Set<String> IGNORED_PACKAGES = new HashSet();

    static {
        //IGNORED_PACKAGES.add("java.lang.reflect");
        IGNORED_PACKAGES.add("groovy.lang");
        IGNORED_PACKAGES.add("org.codehaus.groovy.reflection");
        IGNORED_PACKAGES.add("org.codehaus.groovy.runtime.callsite");
        IGNORED_PACKAGES.add("org.codehaus.groovy.runtime.metaclass");
        IGNORED_PACKAGES.add("org.codehaus.groovy.runtime");
        IGNORED_PACKAGES.add("sun.reflect");
    }

    private static final Method MAGIC_METHOD;

    static {
        Method meth;
        try {
            Class srr = Class.forName("sun.reflect.Reflection");
            meth = srr.getMethod("getCallerClass", Integer.TYPE);
        } catch (Throwable t) {
            meth = null;
        }
        MAGIC_METHOD = meth;
    }

    /**
     * Determine whether or not the getCallingClass methods will return
     * any sensible results.  On JVMs that are not Sun derived i.e.
     * (gcj, Harmony) this will likely return false.  When not available
     * all getCallingClass methods will return null.
     *
     * @return true if getCallingClass can return anything but null, false if
     *         it will only return null.
     */
    public static boolean isCallingClassReflectionAvailable() {
        return MAGIC_METHOD != null;
    }

    /**
     * Get the immediate calling class, ignoring MOP frames.
     *
     * @return The Class of the caller
     */
    public static Class getCallingClass() {
        return getCallingClass(1);
    }

    /**
     * Get the called that is matchLevel stack frames before the call,
     * ignoring MOP frames.
     *
     * @param matchLevel how may call stacks down to look.
     *                   If it is less than 1 it is treated as though it was 1.
     * @return The Class of the matched caller, or null if there aren't
     *         enough stackframes to satisfy matchLevel
     */
    public static Class getCallingClass(int matchLevel) {
        return getCallingClass(matchLevel, Collections.EMPTY_SET);
    }

    /**
     * Get the called that is matchLevel stack frames before the call,
     * ignoring MOP frames and desired exclude packages.
     *
     * @param matchLevel           how may call stacks down to look.
     *                             If it is less than 1 it is treated as though it was 1.
     * @param extraIgnoredPackages A collection of string names of packages to exclude
     *                             in addition to the MOP packages when counting stack frames.
     * @return The Class of the matched caller, or null if there aren't
     *         enough stackframes to satisfy matchLevel
     */
    public static Class getCallingClass(int matchLevel, Collection<String> extraIgnoredPackages) {
        if (MAGIC_METHOD == null) {
            return null;
        }
        int depth = 0;
        try {
            Class c;
            // this super class stuff is for Java 1.4 support only
            // it isn't needed on a 5.0 VM
            Class sc;
            do {
                do {
                    c = (Class) MAGIC_METHOD.invoke(null, depth++);
                    if (c != null) {
                        sc = c.getSuperclass();
                    } else {
                        sc = null;
                    }
                } while (classShouldBeIgnored(c, extraIgnoredPackages)
                        || superClassShouldBeIgnored(sc));
            } while (c != null && matchLevel-- > 0);
            return c;
        } catch (Throwable t) {
            return null;
        }
    }

    private static boolean superClassShouldBeIgnored(Class sc) {
        return ((sc != null) && (sc.getPackage() != null) && "org.codehaus.groovy.runtime.callsite".equals(sc.getPackage().getName()));
    }

    private static boolean classShouldBeIgnored(Class c, Collection<String> extraIgnoredPackages) {
        return ((c != null)
                && (c.isSynthetic()
                    || (c.getPackage() != null
                        && (IGNORED_PACKAGES.contains(c.getPackage().getName())
                          || extraIgnoredPackages.contains(c.getPackage().getName())))));
    }
}