diff options
Diffstat (limited to 'tutorial/Adapter.html')
| -rw-r--r-- | tutorial/Adapter.html | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/tutorial/Adapter.html b/tutorial/Adapter.html new file mode 100644 index 0000000..ae333a2 --- /dev/null +++ b/tutorial/Adapter.html @@ -0,0 +1,258 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<html> + + +<head> +<title>OpenJava : Tutorial</title> +<meta http-equiv="Keywords" content="java, openjava, reflection"> +</head> + + +<body bgcolor="white" + text="#000000" link="#007fff" vlink="#006fdf" alink="#ff0000"> + + +<!----------------------------------------------------------------------> + + +<center> + +<h1><font color="Blue">OpenJava Tutorial</font></h1> + +</center> + + +<!----------------------------------------------------------------------> +<hr width="100%"> +<!----------------------------------------------------------------------> + + +<h2>6. <font color="blue">Callee-side Translation</font></h2> + + +<p>In this section, an example of simple translation at <i>callee-side</i> +is described. + + +<h3>6.1. What the base-level program should look like</h3> + +<br><blockquote><pre><font color=darkblue> +import java.util.*; +public class <font color=black>VectorStack</font> <b>instantiates <font color=black>AdapterClass</font></b> + <b>adapts <font color=black>Vector</font> in v to <font color=black>Stack</font></b> +{ + <font color=black>Vector</font> v; + public <font color=black>VectorStack</font>( <font color=black>Vector</font> v ) { + this.v = v; + } + public <font color=black>void</font> push( <font color=black>Object</font> o ) { + v.addElement( o ); + } + public <font color=black>Object</font> pop() { + <font color=black>Object</font> result = peek(); + v.removeElementAt( v.size() - 1 ); + return result; + } + public <font color=black>Object</font> peek() { + return v.elementAt( v.size() - 1 ); + } +} +</font></pre></blockquote> + +<br><blockquote><pre><font color=darkblue> +public interface <font color=black>Stack</font> +{ + public <font color=black>int</font> size(); + public <font color=black>boolean</font> isEmpty(); + public <font color=black>Enumeration</font> elements(); + public <font color=black>Object[]</font> toArray(); + public <font color=black>int</font> hashCode(); + public <font color=black>void</font> push( <font color=black>Object</font> o ); + public <font color=black>Object</font> pop(); + public <font color=black>Object</font> peek(); +} +</font></pre></blockquote> + + +<h3>6.2. What the base-level program should be translated</h3> + +<p>Like following: +<br><blockquote><pre><font color=darkblue> +import java.util.*; +public class <font color=black>VectorStack</font> implements <font color=black>Stack</font> +{ + <font color=black>Vector</font> v; + public <font color=black>VectorStack</font>( <font color=black>Vector</font> v ) { + this.v = v; + } + public <font color=black>void</font> push( <font color=black>Object</font> o ) { + v.addElement( o ); + } + public <font color=black>Object</font> pop() { + <font color=black>Object</font> result = peek(); + v.removeElementAt( v.size() - 1 ); + return result; + } + public <font color=black>Object</font> peek() { + return v.elementAt( v.size() - 1 ); + } + <b>public <font color=black>Object[]</font> toArray() {</b> + <b>return v.toArray();</b> + <b>}</b> + <b>public <font color=black>int</font> size() {</b> + <b>return v.size();</b> + <b>}</b> + <b>public <font color=black>Enumeration</font> elements() {</b> + <b>return v.elements();</b> + <b>}</b> + <b>public <font color=black>boolean</font> isEmpty() {</b> + <b>return v.isEmpty();</b> + <b>}</b> + <b>public <font color=black>int</font> hashCode() {</b> + <b>return v.hashCode();</b> + <b>}</b> +} +</font></pre></blockquote> + + +<h3>6.3. Write a meta-level program</h3> + +<br><blockquote><pre><font color=darkblue> +import io.devnulllabs.openjava.mop.*; +import io.devnulllabs.openjava.ptree.*; +import io.devnulllabs.openjava.syntax.*; + +/** + * The metaclass <code>AdapterClass</code> supports classes + * implementing an adapter role of the Adapter pattern. + * The target's methods with same signatures as the adaptee's are + * automatically implemented into the adapter class. + */ +public class AdapterClass instantiates Metaclass extends OJClass +{ + + public static final String KEY_ADAPTS = "adapts"; + + /* overrides for translation */ + public void translateDefinition() throws MOPException { + OJClass target = getTarget(), adaptee = getAdaptee(); + if (target == null || adaptee == null) return; + + /* implicit forwarding to the same signature's */ + OJMethod[] adapteds = adaptee.getMethods( this ); + for (int i = 0; i < adapteds.length; ++i) { + /* picks up the method with same signature */ + OJMethod m; + try { + m = getTarget().getMethod( adapteds[i].getName(), + adapteds[i].getParameterTypes(), + this ); + } catch ( NoSuchMemberException e ) { /* not match */ continue; } + + /* generate a forwarding method with forwarded's name */ + addMethod( makeForwardingMethod( m.getName(), m ) ); + } + + addInterface( getTarget() ); + } + + /** + * Generates a forwarding method with specified name. + * + * @param name generating method's name. + * @param forwarded method to which the generated method forwards. + * @return a generated forwarding method. + */ + private OJMethod makeForwardingMethod( String name, OJMethod forwarded ) + throws MOPException + { + /* generates a new method without body */ + OJMethod result = new OJMethod( + this, + forwarded.getModifiers().remove( OJModifier.ABSTRACT ), + forwarded.getReturnType(), + name, + forwarded.getParameterTypes(), + forwarded.getExceptionTypes(), + null + ); + + /* generates a method call and return statement */ + ExpressionList params = result.getParameterVariables(); + Expression expr = new MethodCall( getContainer(), name, params ); + StatementList body = new StatementList(); + if (forwarded.getReturnType() == OJSystem.VOID) { + body.add( new ExpressionStatement( expr ) ); + body.add( new ReturnStatement() ); + } else { + body.add( new ReturnStatement( expr ) ); + } + + result.setBody( body ); + return result; + } + + /* extended information */ + + private OJClass getAdaptee() throws MOPException { + ObjectList suffix = (ObjectList) getSuffix( KEY_ADAPTS ); + return OJClass.forName( suffix.get( 0 ).toString() ); + } + + private Variable getContainer() throws MOPException { + ObjectList suffix = (ObjectList) getSuffix( KEY_ADAPTS ); + return new Variable( suffix.get( 1 ).toString() ); + } + + private OJClass getTarget() throws MOPException { + ObjectList suffix = (ObjectList) getSuffix( KEY_ADAPTS ); + return OJClass.forName( suffix.get( 2 ).toString() ); + } + + /* override to extend syntax */ + public static boolean isRegisteredKeyword( String keyword ) { + return keyword.equals( KEY_ADAPTS ); + } + + /* override to extend syntax */ + public static SyntaxRule getDeclSuffixRule( String keyword ) { + if (keyword.equals( KEY_ADAPTS )) { + return new CompositeRule( + new TypeNameRule(), + new PrepPhraseRule( "in", new NameRule() ), + new PrepPhraseRule( "to", new TypeNameRule() ) ); + } + return null; + } + +} + +</font></pre></blockquote> + + +<!----------------------------------------------------------------------> +<hr width="100%"> +<!----------------------------------------------------------------------> + + +<center> + +Please send any message to : +<address> +mich@acm.org +</address><BR> + +</center> + + +<font size=1>Copyright (C) 1999 by Michaki Tatsubori.</font><br> +<font size=1>Java(TM) is a trademark of Sun Microsystems, Inc.</font> + + +<!----------------------------------------------------------------------> + + +</body> + + +</html> |