Class reflection to get class member:field, method, constructor - Java Reflection

Java examples for Reflection:Class

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Description

Class reflection to get class member:field, method, constructor

Demo Code

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Member;
import static java.lang.System.out;

enum ClassMember {
    CONSTRUCTOR, FIELD, METHOD, CLASS, ALL
}

public class ClassSpy {
    public static void main(String... args) {
        try {//from   w w w  .j a  v  a  2  s.com
            Class<?> c = Class.forName(args[0]);
            out.format("Class:%n  %s%n%n", c.getCanonicalName());

            Package p = c.getPackage();
            out.format("Package:%n  %s%n%n", (p != null ? p.getName()
                    : "-- No Package --"));

            for (int i = 1; i < args.length; i++) {
                switch (ClassMember.valueOf(args[i])) {
                case CONSTRUCTOR:
                    printMembers(c.getConstructors(), "Constructor");
                    break;
                case FIELD:
                    printMembers(c.getFields(), "Fields");
                    break;
                case METHOD:
                    printMembers(c.getMethods(), "Methods");
                    break;
                case CLASS:
                    printClasses(c);
                    break;
                case ALL:
                    printMembers(c.getConstructors(), "Constuctors");
                    printMembers(c.getFields(), "Fields");
                    printMembers(c.getMethods(), "Methods");
                    printClasses(c);
                    break;
                default:
                    assert false;
                }
            }

            // production code should handle these exceptions more gracefully
        } catch (ClassNotFoundException x) {
            x.printStackTrace();
        }
    }

    private static void printMembers(Member[] mbrs, String s) {
        out.format("%s:%n", s);
        for (Member mbr : mbrs) {
            if (mbr instanceof Field)
                out.format("  %s%n", ((Field) mbr).toGenericString());
            else if (mbr instanceof Constructor)
                out.format("  %s%n", ((Constructor) mbr).toGenericString());
            else if (mbr instanceof Method)
                out.format("  %s%n", ((Method) mbr).toGenericString());
        }
        if (mbrs.length == 0)
            out.format("  -- No %s --%n", s);
        out.format("%n");
    }

    private static void printClasses(Class<?> c) {
        out.format("Classes:%n");
        Class<?>[] clss = c.getClasses();
        for (Class<?> cls : clss)
            out.format("  %s%n", cls.getCanonicalName());
        if (clss.length == 0)
            out.format("  -- No member interfaces, classes, or enums --%n");
        out.format("%n");
    }
}

/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

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