Apache Tapestry PageActivationContext tutorial


The idea behind this annotation is nice and very simple. It's all about telling tapestry how to hypothetically convert a string to an object of your choice. This string is actually a key used to look up a desired object.


Now to do that you need to provide tapestry with your value encoder implementation then go ahead and use the @PageActivationContext annotation.


First create a value encoder service :

package com.skycomm.cth.services.encoders;
import org.apache.tapestry5.ValueEncoder;
import org.apache.tapestry5.services.ValueEncoderFactory;
import com.jarmy.beans.UserInfo;
import com.jarmy.services.dao.UserDAO;
public class UserInfoEncoder implements ValueEncoder, ValueEncoderFactory {
    private final UserDAO userDao;
    public UserInfoEncoder(UserDAO userDao) {
        this.userDao = userDao;
    }
    @Override
    public ValueEncoder create(Class paramClass) {
        return this;
    }
    @Override
    public String toClient(UserInfo paramV) {
        return paramV.getId();
    }
    @Override
    public UserInfo toValue(String paramString) {
        return userDao.getById(paramString);
    }
}

Then within your page java class:

@PageActivationContext
private UserInfo user;
Remeber, you should not create an onActivate() method (not sure about the onPassivate() method, I think you can't create that one too), as Tapestry will attempt to create it but will throw an exception if it find it already implemented !


Now go ahead and use your object presented to you on a silver platter :D


Is this framework UNBELIEVABLE or what ?!


Please, if you have any improvement to my post, questions, recommendations...fire away :)

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