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Java example source code file (VirtualConstructor.java)

This example Java source code file (VirtualConstructor.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, hashmap, instanceconstructor, iterator, map, string, typedatabase, util, virtualconstructor, vmobject, wrongtypeexception

The VirtualConstructor.java Java example source code

/*
 * Copyright (c) 2000, 2011, 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.
 *
 */

package sun.jvm.hotspot.runtime;

import java.util.*;
import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.types.*;

/** This class provides generalized "virtual constructor"
    functionality for VMObjects. In simple terms, it creates
    correctly-typed Java wrapper objects for underlying Addresses,
    using the "RTTI-like" functionality of TypeDataBase. For example,
    if the given Address really is a DefNewGeneration*, the Java object
    created for it will be of type
    sun.jvm.hotspot.memory.DefNewGeneration, assuming the mapping from
    type "DefNewGeneration" to class
    sun.jvm.hotspot.memory.DefNewGeneration has been set up. */

public class VirtualConstructor extends InstanceConstructor<VMObject> {
  private TypeDataBase db;
  private Map          map; // Map<String, Class>

  public VirtualConstructor(TypeDataBase db) {
    this.db = db;
    map     = new HashMap();
  }

  /** Adds a mapping from the given C++ type name to the given Java
      class. The latter must be a subclass of
      sun.jvm.hotspot.runtime.VMObject. Returns false if there was
      already a class for this type name in the map. */
  public boolean addMapping(String cTypeName, Class clazz) {
    if (map.get(cTypeName) != null) {
      return false;
    }

    map.put(cTypeName, clazz);
    return true;
  }

  /** Instantiate the most-precisely typed wrapper object available
      for the type of the given Address. If no type in the mapping
      matched the type of the Address, throws a WrongTypeException.
      Returns null for a null address (similar behavior to
      VMObjectFactory). */
  public VMObject instantiateWrapperFor(Address addr) throws WrongTypeException {
    if (addr == null) {
      return null;
    }

    for (Iterator iter = map.keySet().iterator(); iter.hasNext(); ) {
      String typeName = (String) iter.next();
      if (db.addressTypeIsEqualToType(addr, db.lookupType(typeName))) {
        return (VMObject) VMObjectFactory.newObject((Class) map.get(typeName), addr);
      }
    }

    throw newWrongTypeException(addr);
  }
}

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