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+/*
+ * MixinedClass.oj
+ *
+ * An OpenJava example for incorporating mixin mechanism.
+ *
+ * @author   Michiaki Tatsubori
+ * @version  %VERSION% %DATE%
+ * @see      java.lang.Object
+ *
+ * COPYRIGHT 1999 by Michiaki Tatsubori, ALL RIGHTS RESERVED.
+ */
+package examples.mixin;
+
+
+import java.lang.Object;
+import openjava.mop.*;
+import openjava.ptree.*;
+import openjava.syntax.*;
+
+
+/**
+ * The metaclass <code>MixinedClass</code> supports classes
+ * using mixin.
+ * <p>
+ * For example, the class <code>MixinedClass</code>:
+ * <pre>
+ * public class TextboxWithUndo instantiates MixinedClass
+ *    extends Textbox mixs Undo
+ * {
+ * }
+ * </pre>
+ * would be automatically implemented.
+ * <p>
+ *
+ * @author   Michiaki Tatsubori
+ * @version  1.0
+ * @since    %SOFTWARE% 1.0
+ * @see java.lang.Object
+ */
+public class MixinedClass instantiates Metaclass extends OJClass
+{
+
+    public static final String KEY_MIXES = "mixes";
+
+    /* overrides for translation */
+    public void translateDefinition() throws MOPException {
+    OJClass[] mixinClasses = getMixins();
+
+    for (int i = 0; i < mixinClasses.length; ++i) {
+        incorporateMixin(mixinClasses[i]);
+    }
+    }
+
+    public void incorporateMixin(OJClass mixinClazz) throws MOPException {
+        /* implicit forwarding to the same signature's */
+    addInterface(mixinClazz);
+        OJMethod[] mixeds = mixinClazz.getMethods();
+        for (int i = 0; i < mixeds.length; ++i) {
+            /* generate a forwarding method with forwarded's name */
+            addMethod(makeEmptyMethod(mixeds[i]));
+        }
+    }
+
+    /**
+     * Generates a empty method with specified name.
+     *
+     * @param  name  generating method's name.
+     * @param forwarded  method to which the generated method forwards.
+     * @return  a generated empty method.
+     */
+    private OJMethod makeEmptyMethod(OJMethod implementee)
+        throws MOPException
+    {
+    /* generates a return statement */
+        StatementList body = new StatementList();
+        if (implementee.getReturnType() == OJSystem.VOID) {
+            body.add(new ReturnStatement());
+        } else {
+            body.add(new ReturnStatement(Literal.constantNull()));
+        }
+
+        /* generates a new method without body */
+    return new OJMethod( this,
+        implementee.getModifiers().remove(OJModifier.ABSTRACT),
+        implementee.getReturnType(), implementee.getName(),
+        implementee.getParameterTypes(), implementee.getExceptionTypes(),
+        body );
+    }
+
+    /* extended information */
+
+    private OJClass[] getMixins() throws MOPException {
+        ObjectList suffix = (ObjectList) getSuffix(KEY_MIXES);
+    OJClass[] result = new OJClass[suffix.size()];
+    for (int i = 0; i < result.length; ++i) {
+        result[i] = OJClass.forName(suffix.get(i).toString());
+    }
+    return result;
+    }
+
+    /* override to extend syntax */
+    public static boolean isRegisteredKeyword( String keyword ) {
+        return keyword.equals( KEY_MIXES );
+    }
+
+    /* override to extend syntax */
+    public static SyntaxRule getDeclSuffixRule( String keyword ) {
+    if (keyword.equals( KEY_MIXES )) {
+        return new DefaultListRule(new TypeNameRule(), TokenID.COMMA);
+    }
+    return null;
+    }
+
+}
+