/interpreter/tags/at2-build270707/src/edu/vub/at/objects/symbiosis/JavaClass.java

  1/**
  2 * AmbientTalk/2 Project
  3 * JavaClass.java created on 3-nov-2006 at 10:54:38
  4 * (c) Programming Technology Lab, 2006 - 2007
  5 * Authors: Tom Van Cutsem & Stijn Mostinckx
  6 * 
  7 * Permission is hereby granted, free of charge, to any person
  8 * obtaining a copy of this software and associated documentation
  9 * files (the "Software"), to deal in the Software without
 10 * restriction, including without limitation the rights to use,
 11 * copy, modify, merge, publish, distribute, sublicense, and/or
 12 * sell copies of the Software, and to permit persons to whom the
 13 * Software is furnished to do so, subject to the following
 14 * conditions:
 15 *
 16 * The above copyright notice and this permission notice shall be
 17 * included in all copies or substantial portions of the Software.
 18 *
 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 26 * OTHER DEALINGS IN THE SOFTWARE.
 27 */
 28package edu.vub.at.objects.symbiosis;
 29
 30import edu.vub.at.exceptions.InterpreterException;
 31import edu.vub.at.exceptions.XArityMismatch;
 32import edu.vub.at.exceptions.XDuplicateSlot;
 33import edu.vub.at.exceptions.XTypeMismatch;
 34import edu.vub.at.exceptions.XUnassignableField;
 35import edu.vub.at.exceptions.XUndefinedSlot;
 36import edu.vub.at.objects.ATBoolean;
 37import edu.vub.at.objects.ATContext;
 38import edu.vub.at.objects.ATField;
 39import edu.vub.at.objects.ATMethod;
 40import edu.vub.at.objects.ATNil;
 41import edu.vub.at.objects.ATObject;
 42import edu.vub.at.objects.ATTable;
 43import edu.vub.at.objects.ATTypeTag;
 44import edu.vub.at.objects.coercion.NativeTypeTags;
 45import edu.vub.at.objects.grammar.ATSymbol;
 46import edu.vub.at.objects.mirrors.PrimitiveMethod;
 47import edu.vub.at.objects.mirrors.Reflection;
 48import edu.vub.at.objects.natives.NATBoolean;
 49import edu.vub.at.objects.natives.NATNumber;
 50import edu.vub.at.objects.natives.NATObject;
 51import edu.vub.at.objects.natives.NATTable;
 52import edu.vub.at.objects.natives.NATText;
 53import edu.vub.at.objects.natives.grammar.AGSymbol;
 54import edu.vub.at.util.logging.Logging;
 55import edu.vub.util.IdentityHashMap;
 56
 57import java.io.IOException;
 58import java.lang.ref.SoftReference;
 59
 60/**
 61 * A JavaClass instance represents a Java Class under symbiosis.
 62 * 
 63 * Java classes are treated as AmbientTalk 'singleton' objects:
 64 * 
 65 *  - cloning a Java class results in the same Java class instance
 66 *  - sending 'new' to a Java class invokes the constructor and returns a new instance of the class under symbiosis
 67 *  - all static fields and methods of the Java class are reflected under symbiosis as fields and methods of the AT object
 68 *  
 69 * A Java Class object that represents an interface can furthermore be used
 70 * as an AmbientTalk type. The type's name corresponds to the interface's full name.
 71 *  
 72 * JavaClass instances are pooled (on a per-actor basis): there should exist only one JavaClass instance
 73 * for each Java class loaded into the JVM. Because the JVM ensures that a Java class
 74 * can only be loaded once, we can use the Java class wrapped by the JavaClass instance
 75 * as a unique key to identify its corresponding JavaClass instance.
 76 *  
 77 * @author tvcutsem
 78 */
 79public final class JavaClass extends NATObject implements ATTypeTag {
 80	
 81	/**
 82	 * A thread-local hashmap pooling all of the JavaClass wrappers for
 83	 * the current actor, referring to them using SOFT references, such
 84	 * that unused wrappers can be GC-ed when running low on memory.
 85	 */
 86	private static final ThreadLocal _JAVACLASS_POOL_ = new ThreadLocal() {
 87        protected synchronized Object initialValue() {
 88            return new IdentityHashMap();
 89        }
 90	};
 91	
 92	/**
 93	 * Allocate a unique symbiont object for the given Java class.
 94	 */
 95	public static final JavaClass wrapperFor(Class c) {
 96		IdentityHashMap map = (IdentityHashMap) _JAVACLASS_POOL_.get();
 97		if (map.containsKey(c)) {
 98			SoftReference ref = (SoftReference) map.get(c);
 99			JavaClass cls = (JavaClass) ref.get();
100			if (cls != null) {
101				return cls;
102			} else {
103				map.remove(c);
104				cls = new JavaClass(c);
105				map.put(c, new SoftReference(cls));
106				return cls;
107			}
108		} else {
109			JavaClass jc = new JavaClass(c);
110			map.put(c, new SoftReference(jc));
111			return jc;
112		}
113	}
114	
115	// primitive fields and method of a JavaClass wrapper
116	
117	private static final AGSymbol _PTS_NAME_ = AGSymbol.jAlloc("parentTypes");
118	private static final AGSymbol _TNM_NAME_ = AGSymbol.jAlloc("typeName");
119	
120	/** def isSubtypeOf(type) { nil } */
121	private static final PrimitiveMethod _PRIM_STP_ = new PrimitiveMethod(
122			AGSymbol.jAlloc("isSubtypeOf"), NATTable.atValue(new ATObject[] { AGSymbol.jAlloc("type")})) {
123      
124	    private static final long serialVersionUID = -6864350539143194204L;
125
126		public ATObject base_apply(ATTable arguments, ATContext ctx) throws InterpreterException {
127			if (!arguments.base_length().equals(NATNumber.ONE)) {
128				throw new XArityMismatch("isSubtypeOf", 1, arguments.base_length().asNativeNumber().javaValue);
129			}
130			return ctx.base_lexicalScope().asJavaClassUnderSymbiosis().base_isSubtypeOf(arguments.base_at(NATNumber.ONE).asTypeTag());
131		}
132	};
133	
134	private final Class wrappedClass_;
135	
136	/**
137	 * A JavaClass wrapping a class c is an object that has the lexical scope as its lexical parent
138	 * and has NIL as its dynamic parent.
139	 * 
140	 * If the JavaClass wraps a Java interface type, JavaClass instances are
141	 * also types.
142	 */
143	private JavaClass(Class wrappedClass) {
144		super(wrappedClass.isInterface() ?
145			  new ATTypeTag[] { NativeTypeTags._TYPETAG_, NativeTypeTags._ISOLATE_ } :
146			  NATObject._NO_TYPETAGS_);
147		wrappedClass_ = wrappedClass;
148		
149		// add the two fields and one method needed for an ATTypeTag
150		if (wrappedClass.isInterface()) {
151			Class[] extendedInterfaces = wrappedClass_.getInterfaces();
152			ATObject[] types = new ATObject[extendedInterfaces.length];
153			for (int i = 0; i < extendedInterfaces.length; i++) {
154				types[i] = JavaClass.wrapperFor(extendedInterfaces[i]);
155			}
156			
157			try {
158				super.meta_defineField(_PTS_NAME_, NATTable.atValue(types));
159				super.meta_defineField(_TNM_NAME_, AGSymbol.jAlloc(wrappedClass_.getName()));
160				super.meta_addMethod(_PRIM_STP_);
161			} catch (InterpreterException e) {
162				Logging.Actor_LOG.fatal("Error while initializing Java Class as type tag: " + wrappedClass.getName(), e);
163			}
164		}
165	}
166	
167	/** return the class object denoted by this AmbientTalk symbiont */
168	public Class getWrappedClass() { return wrappedClass_; }
169	
170	public JavaClass asJavaClassUnderSymbiosis() throws XTypeMismatch { return this; }
171	
172    public ATBoolean base__opeql__opeql_(ATObject comparand) throws InterpreterException {
173        return NATBoolean.atValue(this.equals(comparand));
174    }
175	
176	public boolean equals(Object other) {
177		return ((other instanceof JavaClass) &&
178				(wrappedClass_.equals(((JavaClass) other).wrappedClass_)));
179	}
180        
181    /**
182     * Fields can be defined within a symbiotic Java class object. They are added
183     * to its AmbientTalk symbiont, but only if they do not clash with already
184     * existing field names.
185     */
186    public ATNil meta_defineField(ATSymbol name, ATObject value) throws InterpreterException {
187        if (Symbiosis.hasField(wrappedClass_, Reflection.upSelector(name), true)) {
188    	    throw new XDuplicateSlot(name);
189        } else {
190    	    return super.meta_defineField(name, value);
191        }
192    }
193    
194	/**
195	 * Symbiotic Java class objects are singletons.
196	 */
197	public ATObject meta_clone() throws InterpreterException { return this; }
198	
199	/**
200	 * aJavaClass.new(@args) == invoke a Java constructor
201	 * AmbientTalk objects can add a custom new method to the class in order to intercept
202	 * instance creation. The original instance can then be performed by invoking the old new(@args).
203	 * 
204	 * For example, imagine we want to extend the class java.lang.Point with a 3D coordinate, e.g. a 'z' field:
205	 * <tt>
206	 * def Point := jlobby.java.awt.Point;
207	 * def oldnew := Point.new;
208	 * def Point.new(x,y,z) { // 'override' the new method
209	 *   def point := oldnew(x,y); // invokes the Java constructor
210	 *   def point.z := z; // adds a field dynamically to the new JavaObject wrapper
211	 *   point; // important! new should return the newly created instance
212	 * }
213	 * def mypoint := Point.new(1,2,3);
214	 * </tt>
215	 */
216    public ATObject meta_newInstance(ATTable initargs) throws InterpreterException {
217    	return Symbiosis.symbioticInstanceCreation(wrappedClass_, initargs.asNativeTable().elements_);
218    }
219    
220    /**
221     * Methods can be added to a symbiotic Java class object provided they do not already
222     * exist in the Java class.
223     */
224    public ATNil meta_addMethod(ATMethod method) throws InterpreterException {
225        ATSymbol name = method.base_name();
226        if (Symbiosis.hasMethod(wrappedClass_, Reflection.upSelector(name), true)) {
227    	    throw new XDuplicateSlot(name);
228        } else {
229    	    return super.meta_addMethod(method);
230        }
231    }
232
233    /**
234     * Fields can be grabbed from a symbiotic Java class object. Fields that correspond
235     * to static fields in the Java class are returned as JavaField instances.
236     */
237    public ATField meta_grabField(ATSymbol fieldName) throws InterpreterException {
238        try {
239        	return new JavaField(null,
240        			             Symbiosis.getField(wrappedClass_, Reflection.upSelector(fieldName), true));
241        } catch(XUndefinedSlot e) {
242        	return super.meta_grabField(fieldName);
243        }
244    }
245
246    /**
247     * Methods can be grabbed from a symbiotic Java class object. Methods that correspond
248     * to static methods in the Java class are returned as JavaMethod instances.
249     */
250    public ATMethod meta_grabMethod(ATSymbol methodName) throws InterpreterException {
251        JavaMethod choices = Symbiosis.getMethods(wrappedClass_, Reflection.upSelector(methodName), true);
252        if (choices != null) {
253        	return choices;
254        } else {
255        	return super.meta_grabMethod(methodName);
256        }
257    }
258
259    /**
260     * Querying a symbiotic Java class object for its fields results in a table containing
261     * both 'native' static Java fields and the fields of its AT symbiont
262     */
263    public ATTable meta_listFields() throws InterpreterException {
264		// instance fields of the wrapped object's class
265		JavaField[] jFields = Symbiosis.getAllFields(null, wrappedClass_);
266        // fields of the AT symbiont
267    	ATObject[] symbiontFields = super.meta_listFields().asNativeTable().elements_;
268    	return NATTable.atValue(NATTable.collate(jFields, symbiontFields));
269    }
270
271    /**
272     * Querying a symbiotic Java class object for its methods results in a table containing
273     * both 'native' static Java methods and the methods of its AT symbiont
274     */
275    public ATTable meta_listMethods() throws InterpreterException {
276		// instance methods of the wrapped object's class
277		JavaMethod[] jMethods = Symbiosis.getAllMethods(wrappedClass_, true);
278        // methods of the AT symbiont
279		ATObject[] symbiontMethods = super.meta_listMethods().asNativeTable().elements_;
280		return NATTable.atValue(NATTable.collate(jMethods, symbiontMethods));
281    }
282
283	public ATBoolean meta_isCloneOf(ATObject original) throws InterpreterException {
284		return NATBoolean.atValue(this == original);
285	}
286	
287	public NATText meta_print() throws InterpreterException {
288		return NATText.atValue("<java:"+wrappedClass_.toString()+">");
289	}
290
291	/**
292     * A Java Class object remains unique within an actor.
293     */
294    public ATObject meta_resolve() throws InterpreterException {
295    	return wrapperFor(wrappedClass_);
296    }
297    
298    /* ========================
299     * == ATTypeTag Interface ==
300     * ======================== */
301    
302    /**
303     * If this class represents an interface type, parentTypes
304     * are wrappers for all interfaces extended by this Java interface type
305     */
306	public ATTable base_superTypes() throws InterpreterException {
307		return super.impl_invokeAccessor(this, _PTS_NAME_, NATTable.EMPTY).asTable();
308	}
309
310	public ATSymbol base_typeName() throws InterpreterException {
311		return super.impl_invokeAccessor(this, _TNM_NAME_, NATTable.EMPTY).asSymbol();
312	}
313
314	/**
315	 * A Java interface type used as a type can only be a subtype of another
316	 * Java interface type used as a type, and only if this type is assignable
317	 * to the other type.
318	 */
319	public ATBoolean base_isSubtypeOf(ATTypeTag other) throws InterpreterException {
320		if (other instanceof JavaClass) {
321			JavaClass otherClass = (JavaClass) other;
322			// wrappedClass <: otherClass <=> otherClass >= wrappedClass
323			return NATBoolean.atValue(otherClass.wrappedClass_.isAssignableFrom(wrappedClass_));
324		} else {
325			return NATBoolean._FALSE_;
326		}
327	}
328	
329	// IMPLEMENTATION INTERFACE
330	
331    /**
332     * A symbiotic Java class object has all of the public static fields
333     * of its Java class plus all of the fields defined in the AT symbiont.
334     */
335	protected boolean hasLocalField(ATSymbol atSelector) throws InterpreterException {
336		return Symbiosis.hasField(wrappedClass_, Reflection.upSelector(atSelector), true) ||
337			   super.hasLocalField(atSelector);
338	}
339
340	/**
341     * A symbiotic Java class object has all of the public static methods
342     * of its Java class plus all of the methods defined in the AT symbiont.
343     */
344	protected boolean hasLocalMethod(ATSymbol atSelector) throws InterpreterException {
345		return Symbiosis.hasMethod(wrappedClass_, Reflection.upSelector(atSelector), true) ||
346		       super.hasLocalMethod(atSelector);
347	}
348	
349	protected ATObject getLocalField(ATSymbol selector) throws InterpreterException {
350		try {
351			return Symbiosis.readField(null, wrappedClass_, Reflection.upSelector(selector));
352		} catch(XUndefinedSlot e) {
353			return super.getLocalField(selector);
354		}
355	}
356	
357	protected ATMethod getLocalMethod(ATSymbol methodName) throws InterpreterException {
358        JavaMethod choices = Symbiosis.getMethods(wrappedClass_, Reflection.upSelector(methodName), true);
359        if (choices != null) {
360        	return choices;
361        } else {
362        	return super.getLocalMethod(methodName);
363        }
364	}
365	
366	protected void setLocalField(ATSymbol selector, ATObject value) throws InterpreterException {
367		try {
368			Symbiosis.writeField(null, wrappedClass_, Reflection.upSelector(selector), value);
369		} catch(XUndefinedSlot e) {
370			super.setLocalField(selector, value);
371		} catch(XUnassignableField e) {
372			// field may have been final, in which case there 'is no such field'
373			super.setLocalField(selector, value);
374		}
375	}
376	
377}