HasNameModifier.java

package com.googlecode.gwt.test.internal;

import com.google.gwt.user.client.ui.HasName;
import com.googlecode.gwt.test.finder.GwtFinder;
import javassist.*;

public class HasNameModifier implements JavaClassModifier {

    private final CtClass hasNameCtClass;
    private final CtClass[] setArgs;

    HasNameModifier() {
        hasNameCtClass = GwtClassPool.getCtClass(HasName.class);
        setArgs = new CtClass[]{GwtClassPool.getCtClass(String.class)};
    }

    public void modify(CtClass classToModify) throws Exception {

        if (classToModify.isInterface()) {
            return;
        }

        if (classToModify.subtypeOf(hasNameCtClass)) {
            instrumentSetName(classToModify);
        }
    }

    private void addTextField(CtClass c) throws CannotCompileException {
        CtField oldTextField = CtField.make("private String instrument_oldName;", c);
        c.addField(oldTextField);
    }

    private void instrumentSetName(CtClass c) throws CannotCompileException {
        // add behavior to HasHTML.setHTML method
        try {
            CtMethod setName = c.getDeclaredMethod("setName", setArgs);
            addTextField(c);
            setName.insertBefore("this.instrument_oldName = this.getName();");
            setName.insertAfter(GwtFinder.class.getName()
                    + ".onSetName(this, $1, this.instrument_oldName);");
        } catch (NotFoundException e) {
            // don't instrument method if not existing
        }
    }
}