Loader


1   /***
2    * Julia: France Telecom's implementation of the Fractal API
3    * Copyright (C) 2001-2002 France Telecom R&D
4    *
5    * This library is free software; you can redistribute it and/or
6    * modify it under the terms of the GNU Lesser General Public
7    * License as published by the Free Software Foundation; either
8    * version 2 of the License, or (at your option) any later version.
9    *
10   * This library is distributed in the hope that it will be useful,
11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   * Lesser General Public License for more details.
14   *
15   * You should have received a copy of the GNU Lesser General Public
16   * License along with this library; if not, write to the Free Software
17   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18   *
19   * Contact: Eric.Bruneton@rd.francetelecom.com
20   *
21   * Author: Eric Bruneton
22   */
23  
24  package org.objectweb.fractal.julia.loader;
25  
26  import java.util.Map  ;
27  
28  /**
29   * An interface to load classes or to generate them on the fly.
30   */
31  
32  public interface Loader {
33  
34    /**
35     * Initializes this loader.
36     * 
37     * @param context the initialization arguments.
38     * @throws Exception if the initialization fails. 
39     */
40    
41    void init (Map   context) throws Exception  ;
42    
43    /**
44     * Loads the tree whose name is given.
45     *
46     * @param name a tree name.
47     * @return the tree whose name is given.
48     * @throws Exception if the tree is not found or cannot be loaded.
49     */
50    
51    Tree loadTree (String   name) throws Exception  ;
52  
53    /**
54     * Evaluates the given tree in the given context. Each leaf node of the given
55     * tree whose name begins with ' is replaced by the evaluation of the tree
56     * associated to this name in the given context (except if the result of this
57     * evaluation is "QUOTE"). For example the evaluation of "('x d)" in a context
58     * where x is associated to "(a 'y)", y is associated to "(b 'z)", and z is
59     * associated to "QUOTE" gives "((a (b 'z)) d)".
60     *
61     * @param tree the tree to be evaluated.
62     * @param context a map associating names to trees.
63     * @return the evaluated tree.
64     * @throws Exception if a name is not found in the given context. The
65     *      exception's detail is equal to this name.
66     */
67  
68    Tree evalTree (Tree tree, Map   context) throws Exception  ;
69  
70    /**
71     * Creates and returns the object whose description is given.
72     *
73     * @param objectDescriptor the descriptor of the object to be created. This
74     *      descriptor must be either of the form "className", or of the form
75     *      "(classDescriptor arg1 ... argN)". In the first case, "className"
76     *      must be the fully qualified name of a class. In the second case,
77     *      "classDescriptor" must be a valid class descriptor (see {@link
78     *      #loadClass(Tree) loadClass}). "arg1" ... "argN" can be arbitrary
79     *      trees.
80     * @param loader an optional class loader to load auxiliary classes.
81     * @return an object created according to the given description. If this
82     *      description is of the form "className", this method returns a new
83     *      instance of the "className" class (which must have a default public
84     *      constructor). If the description is of the form "(classDescriptor
85     *      arg1 ... argN)", the class described by "classDescriptor" is loaded or
86     *      generated with the {@link #loadClass loadClass} method, and a new
87     *      instance of this class is created (this class must have a default
88     *      public constructor). Then, if the arguments "arg1 ... argN" are not
89     *      empty, the {@link Initializable#initialize initialize} method is used
90     *      to initialize the previous instance (in this case, the
91     *      "classDescriptor" class must implement the {@link Initializable}
92     *      interface; the {@link Initializable#initialize initialize} method is
93     *      called with <tt>(arg1 ... argN)</tt> as parameter). Finally the
94     *      previously created object is returned.
95     * @throws Exception if the specified object cannot be created.
96     */
97  
98    Object   newObject (Tree objectDescriptor, Object   loader) throws Exception  ;
99  
100   /**
101    * Loads the class whose name is given.
102    *
103    * @param className the fully qualified name of the class to be returned.
104    * @param loader an optional class loader to load auxiliary classes.
105    * @return the class whose name is given.
106    * @throws ClassNotFoundException if the specified class is not found.
107    */
108 
109   Class   loadClass (String   className, Object   loader) throws ClassNotFoundException  ;
110 
111   /**
112    * Loads or generates the class whose descriptor is given.
113    *
114    * @param classDescriptor the descriptor of the class to be loaded or
115    *      dynamically generated. This descriptor must be either of the form
116    *      "className", or of the form "(objectDescriptor arg1 ... argN)". In the
117    *      first case, "className" must be the fully qualified name of a class.
118    *      In the second case, "objectDescriptor" must be a valid object
119    *      descriptor (see {@link #newObject newObject}), describing an object
120    *      that implements the {@link
121    *      org.objectweb.fractal.julia.asm.ClassGenerator} interface.
122    *      "arg1" ... "argN" can be arbitrary trees.
123    * @param loader an optional class loader to load auxiliary classes.
124    * @return the class whose description is given. If this description is of the
125    *      form "className", this method returns the "className" class. If the
126    *      description is of the form "(objectDescriptor arg1 ... argN)", the
127    *      class generator described by "objectDescriptor" is instantiated with
128    *      the {@link #newObject newObject} method, and its {@link
129    *      org.objectweb.fractal.julia.asm.ClassGenerator#generateClass
130    *      generateClass} method is used to generate a class (this method is
131    *      called with <tt>classDescriptor</tt> as second argument), which is
132    *      finally returned.
133    * @throws ClassNotFoundException is the specified class cannot be loaded or
134    *      dynamically generated.
135    */
136 
137   Class   loadClass (Tree classDescriptor, Object   loader) throws ClassNotFoundException  ;
138 }
139
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