/interpreter/tags/at2dist041108/src/edu/vub/at/objects/symbiosis/JavaPackage.java

  1/**
  2 * AmbientTalk/2 Project
  3 * JavaPackage.java created on 19-nov-2006 at 12:31:39
  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.XClassNotFound;
 32import edu.vub.at.objects.ATClosure;
 33import edu.vub.at.objects.ATContext;
 34import edu.vub.at.objects.ATObject;
 35import edu.vub.at.objects.ATTypeTag;
 36import edu.vub.at.objects.ATTable;
 37import edu.vub.at.objects.coercion.NativeTypeTags;
 38import edu.vub.at.objects.grammar.ATSymbol;
 39import edu.vub.at.objects.mirrors.NativeClosure;
 40import edu.vub.at.objects.mirrors.PrimitiveMethod;
 41import edu.vub.at.objects.mirrors.Reflection;
 42import edu.vub.at.objects.natives.FieldMap;
 43import edu.vub.at.objects.natives.MethodDictionary;
 44import edu.vub.at.objects.natives.NATNumber;
 45import edu.vub.at.objects.natives.NATObject;
 46import edu.vub.at.objects.natives.NATTable;
 47import edu.vub.at.objects.natives.NATText;
 48import edu.vub.at.objects.natives.grammar.AGSymbol;
 49
 50import java.util.LinkedList;
 51import java.util.Vector;
 52
 53/**
 54 * A JavaPackage represents (part of) a Java package name and serves the same purpose
 55 * as AmbientTalk Namespace objects, but for loading Java classes rather than AT objects.
 56 * 
 57 * The behaviour of a JavaPackage object relies on Java naming conventions for automatic
 58 * loading of classes. If some Java code does not follow the naming conventions, then explicit
 59 * loading of packages or classes must be done via a JavaPackage's provided base-level methods.
 60 * 
 61 * Selecting a field f from a JavaPackage encapsulating the path p has the following semantics:
 62 *  - if f starts with an uppercase symbol, the field access is interpreted as a class reference:
 63 *    The JavaPackage tries to load the class p.f.
 64 *    If the class does not exist, an XSelectorNotFound exception is thrown.
 65 *  - if f starts with a lowercase symbol, the field access is interpreted as a subpackage reference:
 66 *    The JavaPackage creates a new field referring to a JavaPackage whose path equals 'p.f.'
 67 *    
 68 * JavaPackage instances are isolates, hence, they are pass-by-copy.
 69 * 
 70 * @author tvcutsem
 71 */
 72public final class JavaPackage extends NATObject {
 73
 74	private static final String _PKG_SEP_ = ".";
 75
 76	/** def class(name) { nil } */
 77	private static final PrimitiveMethod _PRIM_CLS_ = new PrimitiveMethod(
 78			AGSymbol.jAlloc("class"), NATTable.atValue(new ATObject[] { AGSymbol.jAlloc("name")})) {
 79		public ATObject base_apply(ATTable arguments, ATContext ctx) throws InterpreterException {
 80			return ((JavaPackage)ctx.base_lexicalScope()).base_class(arguments.base_at(NATNumber.ONE).asSymbol());
 81		}
 82	};
 83	/** def package(name) { nil } */
 84	private static final PrimitiveMethod _PRIM_PKG_ = new PrimitiveMethod(
 85			AGSymbol.jAlloc("package"), NATTable.atValue(new ATObject[] { AGSymbol.jAlloc("name")})) {
 86		public ATObject base_apply(ATTable arguments, ATContext ctx) throws InterpreterException {
 87			return ((JavaPackage)ctx.base_lexicalScope()).base_package(arguments.base_at(NATNumber.ONE).asSymbol());
 88		}
 89	};
 90	
 91	private final String path_;
 92	
 93	/**
 94	 * A JavaPackage object encapsulates a package path.
 95	 * A package path is a '.'-separated string, always ending with a '.'
 96	 * The jlobby root package has an empty package path
 97	 * 
 98	 * A JavaPackage is initialized as an AT/2 isolate object.
 99	 * 
100	 * @param path the pathname of this JavaPackage, e.g. 'java.' or 'java.lang.'
101	 */
102	public JavaPackage(String path) {
103		super(new ATTypeTag[] { NativeTypeTags._ISOLATE_ });
104		path_ = path;
105		try {
106			super.meta_addMethod(_PRIM_CLS_);
107			super.meta_addMethod(_PRIM_PKG_);
108		} catch (InterpreterException e) {
109			throw new RuntimeException("Failed to initialize a JavaPackage: " + e.getMessage());
110		}
111	}
112	
113	/**
114	 * Private constructor used only for cloning
115	 */
116	private JavaPackage(FieldMap map,
117			  		   Vector state,
118			  		   LinkedList customFields,
119			  		   MethodDictionary methodDict,
120			  		   ATObject dynamicParent,
121			  		   ATObject lexicalParent,
122			  		   byte flags,
123			  		   ATTypeTag[] types,
124			  		   String path) throws InterpreterException {
125		super(map, state, customFields, methodDict, dynamicParent, lexicalParent, flags, types);
126		path_ = path;
127	}
128	
129	/**
130	 * For a JavaPackage object, doesNotUnderstand triggers the querying of the Java classpath
131	 * to load classes corresponding to the missing selector. Depending on the case of the
132	 * selector's first letter, the access is interpreted as a class or a package reference.
133	 */
134	public ATClosure meta_doesNotUnderstand(final ATSymbol selector) throws InterpreterException {
135		// first, convert the AmbientTalk name to a Java selector.
136		String s = selector.base_text().asNativeText().javaValue;
137		if (Character.isUpperCase(s.charAt(0))) {
138			// the field access is interpreted as a class reference
139			return new NativeClosure.Accessor(selector, this) {
140				protected ATObject access() throws InterpreterException {
141					return base_class(selector);
142				}
143			};
144		} else {
145			// the field access is interpreted as a package reference
146			return new NativeClosure.Accessor(selector, this) {
147				protected ATObject access() throws InterpreterException {
148					return base_package(selector);
149				}
150			};
151		}
152	}
153
154	public NATText meta_print() throws InterpreterException {
155		return NATText.atValue("<jpackage:"+path_+">");
156	}
157	
158	protected NATObject createClone(FieldMap map,
159			  					Vector state,
160			  					LinkedList customFields,
161			  					MethodDictionary methodDict,
162			  					ATObject dynamicParent,
163			  					ATObject lexicalParent,
164			  					byte flags, ATTypeTag[] types) throws InterpreterException {
165		return new JavaPackage(map,
166    		  				      state,
167    		  				      customFields,
168    		  				      methodDict,
169    		  				      dynamicParent,
170    		  				      lexicalParent,
171    		  				      flags,
172    		  				      types,
173    		  				      path_);
174	}
175	
176	/**
177	 * Allows the AT programmer to explicitly load a class. This might be necessary if the
178	 * class starts with a lowercase letter.
179	 */
180	public ATObject base_class(ATSymbol selector) throws InterpreterException {
181		// try to see if a class corresponding to the selector prefixed with
182		// this package's pathname exists
183		String qualifiedClassname = path_ + Reflection.upSelector(selector);
184		try {
185			Class c = Class.forName(qualifiedClassname);
186		    JavaClass jc = JavaClass.wrapperFor(c);
187			// bind the new class to the selector within this JavaPackage
188			this.meta_defineField(selector, jc);
189			return jc;
190		} catch (ClassNotFoundException e) {
191			throw new XClassNotFound(qualifiedClassname, e);
192		}
193	}
194	
195	/**
196	 * Allows the AT programmer to explicitly load a package. This might be necessary if the
197	 * package starts with an uppercase letter.
198	 */
199	public ATObject base_package(ATSymbol selector) throws InterpreterException {
200         // define a new Java package with a trailing '.'
201		JavaPackage jpkg = new JavaPackage(path_ + Reflection.upSelector(selector) + _PKG_SEP_);
202		this.meta_defineField(selector, jpkg);
203		return jpkg;
204	}
205	
206}