casting problem
I am having trouble casting the return value of a function call to the correct type of a field. FieldSetEditor.edit calls ClassRewriter.setField
which returns an Object. I would like the return value to be cast to the correct type. I tried defining setField with generics,
public <T> T setField(Clazz<T> ....) {
...
return (T)object;
}
but as generics are not supported, that does not help...
Also what would happen if someone entered a " in the string that
I pass in the field?
package com.sun.labs.rdf;
import com.sun.labs.rdf.annotations.RDF;
import javassist.*;
import javassist.expr.ExprEditor;
import javassist.expr.FieldAccess;
/**
* @author Henry Story
*/
public class ClassRewriter {
public static String reverse(String value) {
int length = value.length();
StringBuffer buff = new StringBuffer(length);
for (int i = length - 1; i >= 0; i--) {
buff.append(value.charAt(i));
}
System.out.println("TranslateEditor.reverse returning " + buff);
return buff.toString();
}
public static Object setField(Object o,String url, Object value) {
System.out.println("setting o="+o+" R="+url+" v="+value);
return value;
}
public static void main(String[] args) {
if (args.length != 0) {
try {
// set up class loader with translator
EditorTranslator xtor = new EditorTranslator(new FieldSetEditor());
ClassPool pool = ClassPool.getDefault();
Loader loader = new Loader();
loader.addTranslator(pool, xtor);
// invoke the "main" method of the application class
loader.run(args);
} catch (Throwable ex) {
ex.printStackTrace();
}
} else {
System.out.println("Usage: ClassRewriter main-class args...");
}
}
}
class EditorTranslator implements Translator {
private ExprEditor m_editor;
EditorTranslator(ExprEditor editor) {
m_editor = editor;
}
public void start(ClassPool pool) {
System.out.println("start pool");
}
public void onLoad(ClassPool pool, String cname)
throws NotFoundException, CannotCompileException {
System.out.println("cname(in Onload)=" + cname);
CtClass clas = pool.get(cname);
clas.instrument(m_editor);
}
}
class FieldSetEditor extends ExprEditor {
FieldSetEditor() {
}
public void edit(FieldAccess arg) throws CannotCompileException {
System.out.println("in edit- field=" + arg.getFieldName());
try {
String field;
if ((field=containsRDF(arg.getField().getAnnotations()))!=null) {
if (arg.isWriter()) {
StringBuffer code = new StringBuffer();
code.append("$0.");
code.append(arg.getFieldName());
// code.append("=com.sun.labs.rdf.sommer.ClassRewriter.reverse($1);");
code.append("=($r)com.sun.labs.rdf.sommer.ClassRewriter.setField($0,\""+field+"\",$1);");
System.out.println("code="+code.toString());
arg.replace(code.toString());
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace(); //todo: decide what exception to throw
} catch (NotFoundException e) {
e.printStackTrace(); //todo: decide what exception to throw
}
}
private String containsRDF(Object[] annotations) {
for (Object o: annotations) {
if (o instanceof RDF) return ((RDF)o).value();
}
return null;
}
}