Java example source code file (VerifyProtectedConstructor.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, classloader, exception, extra, fail, string, verifyerror, verifyprotectedconstructor

The VerifyProtectedConstructor.java Java example source code

/*
 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */


/**
 * @test

 * @bug 6490436
 * @summary Verify that protected constructor calls are not allowed for classfile version >= 50 (but that they are allowed for lesser versions).
 * @author Keith McGuigan
 */

public class VerifyProtectedConstructor extends ClassLoader {
  public static void main(String argv[]) throws Exception {
    VerifyProtectedConstructor t = new VerifyProtectedConstructor();

    t.loadSuperClass();

    try {
      t.checkClassVersion(49); // should not throw VerifyError
    }
    catch(VerifyError e) {
       throw new Exception("FAIL: should be no VerifyError for CF version 49");
    }

    try {
      t.checkClassVersion(50); // should throw VerifyError
      throw new Exception("FAIL: should be a VerifyError for CF version 50");
    }
    catch(VerifyError e) {
       System.out.println("PASS");
    }
  }

  private void loadSuperClass() {
    /* -- code for super class A.A --
       package A;
       public class A {
         protected A() {}
       }
    */
    long[] cls_data = {
      0xcafebabe00000032L, 0x000a0a0003000707L,
      0x0008070009010006L, 0x3c696e69743e0100L,
      0x0328295601000443L, 0x6f64650c00040005L,
      0x010003412f410100L, 0x106a6176612f6c61L,
      0x6e672f4f626a6563L, 0x7400210002000300L,
      0x0000000001000400L, 0x0400050001000600L,
      0x0000110001000100L, 0x0000052ab70001b1L,
      0x0000000000000000L // 2 bytes extra
    };
    final int EXTRA = 2;
    byte cf_bytes[] = toByteArray(cls_data);
    defineClass("A.A", cf_bytes, 0, cf_bytes.length - EXTRA);
  }

  private int num_calls;
  private static String classNames[] = { "B.B", "C.C" };

  private void checkClassVersion(int version) throws VerifyError {
    // This class is in violation of the spec since it accesses
    // a protected constructor of a superclass while not being in the
    // same package.
    /* -- code for test class --
        package B;
        public class B extends A.A {
          public static void f() { new A.A(); }
        }
    */
    long[] cls_data = {
      0xcafebabe00000032L, 0x000b0a0002000807L,
      0x000907000a010006L, 0x3c696e69743e0100L,
      0x0328295601000443L, 0x6f6465010001660cL,
      0x0004000501000341L, 0x2f41010003422f42L,
      0x0021000300020000L, 0x0000000200010004L,
      0x0005000100060000L, 0x0011000100010000L,
      0x00052ab70001b100L, 0x0000000009000700L,
      0x0500010006000000L, 0x1500020000000000L,
      0x09bb000259b70001L, 0x57b1000000000000L // no extra bytes
    };
    final int EXTRA = 0;

    byte cf_bytes[] = toByteArray(cls_data);

    // set version
    cf_bytes[7] = (byte)version;

    // Change B.B to C.C, D.D, ... for subsequent calls so we can call this
    // multiple times and define different classes.
    cf_bytes[61] += num_calls;
    cf_bytes[63] += num_calls;
    String name = classNames[num_calls];
    num_calls++;

    Class c = defineClass(name, cf_bytes, 0, cf_bytes.length - EXTRA);

    try { c.newInstance(); } // to force linking, thus verification
    catch(InstantiationException e) {}
    catch(IllegalAccessException e) {}
  }

  static private byte[] toByteArray(long arr[]) {
    // convert long array to byte array
    java.nio.ByteBuffer bbuf = java.nio.ByteBuffer.allocate(arr.length * 8);
    bbuf.asLongBuffer().put(java.nio.LongBuffer.wrap(arr));
    return bbuf.array();
  }
}