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package sample.vector;
import java.io.IOException;
import javassist.*;
import javassist.preproc.Assistant;
/**
* This is a Javassist program which produce a new class representing
* vectors of a given type. For example,
*
* <ul>import java.util.Vector by sample.vector.VectorAssistant(int)</ul>
*
* <p>requests the Javassist preprocessor to substitute the following
* lines for the original import declaration:
*
* <ul><pre>
* import java.util.Vector;
* import sample.vector.intVector;
* </pre></ul>
*
* <p>The Javassist preprocessor calls <code>VectorAssistant.assist()</code>
* and produces class <code>intVector</code> equivalent to:
*
* <ul><pre>
* package sample.vector;
*
* public class intVector extends Vector {
* pubilc void add(int value) {
* addElement(new Integer(value));
* }
*
* public int at(int index) {
* return elementAt(index).intValue();
* }
* }
* </pre></ul>
*
* <p><code>VectorAssistant.assist()</code> uses
* <code>sample.vector.Sample</code> and <code>sample.vector.Sample2</code>
* as a template to produce the methods <code>add()</code> and
* <code>at()</code>.
*/
public class VectorAssistant implements Assistant {
public final String packageName = "sample.vector.";
/**
* Calls <code>makeSubclass()</code> and produces a new vector class.
* This method is called by a <code>javassist.preproc.Compiler</code>.
*
* @see javassist.preproc.Compiler
*/
public CtClass[] assist(ClassPool pool, String vec, String[] args)
throws CannotCompileException
{
if (args.length != 1)
throw new CannotCompileException(
"VectorAssistant receives a single argument.");
try {
CtClass subclass;
CtClass elementType = pool.get(args[0]);
if (elementType.isPrimitive())
subclass = makeSubclass2(pool, elementType);
else
subclass = makeSubclass(pool, elementType);
CtClass[] results = { subclass, pool.get(vec) };
return results;
}
catch (NotFoundException e) {
throw new CannotCompileException(e);
}
catch (IOException e) {
throw new CannotCompileException(e);
}
}
/**
* Produces a new vector class. This method does not work if
* the element type is a primitive type.
*
* @param type the type of elements
*/
public CtClass makeSubclass(ClassPool pool, CtClass type)
throws CannotCompileException, NotFoundException, IOException
{
CtClass vec = pool.makeClass(makeClassName(type));
vec.setSuperclass(pool.get("java.util.Vector"));
CtClass c = pool.get("sample.vector.Sample");
CtMethod addmethod = c.getDeclaredMethod("add");
CtMethod atmethod = c.getDeclaredMethod("at");
ClassMap map = new ClassMap();
map.put("sample.vector.X", type.getName());
vec.addMethod(CtNewMethod.copy(addmethod, "add", vec, map));
vec.addMethod(CtNewMethod.copy(atmethod, "at", vec, map));
pool.writeFile(vec.getName());
return vec;
}
/**
* Produces a new vector class. This uses wrapped methods so that
* the element type can be a primitive type.
*
* @param type the type of elements
*/
public CtClass makeSubclass2(ClassPool pool, CtClass type)
throws CannotCompileException, NotFoundException, IOException
{
CtClass vec = pool.makeClass(makeClassName(type));
vec.setSuperclass(pool.get("java.util.Vector"));
CtClass c = pool.get("sample.vector.Sample2");
CtMethod addmethod = c.getDeclaredMethod("add");
CtMethod atmethod = c.getDeclaredMethod("at");
CtClass[] args1 = { type };
CtClass[] args2 = { CtClass.intType };
CtMethod m
= CtNewMethod.wrapped(CtClass.voidType, "add", args1,
null, addmethod, null, vec);
vec.addMethod(m);
m = CtNewMethod.wrapped(type, "at", args2,
null, atmethod, null, vec);
vec.addMethod(m);
pool.writeFile(vec.getName());
return vec;
}
private String makeClassName(CtClass type) {
return packageName + type.getSimpleName() + "Vector";
}
}
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