Re: Re: [Wicket-user] My take on Spring integration

Christian Essl Mon, 07 Nov 2005 14:18:40 -0800

Unfortunately I think this does not work.

Actually cglib creates at runtime a subclass where you can overridemethods and as with any java code you can not override final (or private)methods. So when a non overridable method is called on the proxy it is notpossible to delegate it and any state changes will only happen in theproxy and not in the proxied (real) page. On the other hand if the proxiedinstance calls one of its methods they will only effect its state and notthe state of the proxy.

Because of this and because the cglib proxy as a subclass also carrieseverything constructed in the cunstructor of the superclass I do not realylike cglib proxies.


But why not make it something like this (pseudo code - not tested):

public class AbstractSpringAwarePage extends WebPage
{
  public AbstractSpringAwarePage()
  {
    super();
    doInjection();
  }

private final void readObject(java.io.ObjectInputStream in) throwsIOException,

    ClassNotFoundException
  {
    in.defaultReadObject();
    //do for fields only now
    Class cl = this.getClass();
    while(cl != null && !AbstractSpringAwarePage.class.equals(cl)){
      Field[] fields = cl.getDeclaredFields();
        for(final Field field:fields){

//if field has spring annotation and it has a declaring class asinterface

                        
          //create a proxy
          InvocationHandler iH = new InvocationHandler(){
            private transient Object _target;

public Object invoke(Object proxy, Method method, Object[]args) throws Throwable

            {
               if(_target == null){
                  doInjection();
                  _target = field.get(AbstractSpringAwarePage.this);
               }
               return method.invoke(_target, args);
            }
          };
          Class proxyClass = field.getDeclaringClass();
          Object serviceProxy = Proxy.newProxyInstance(
                                    
Thread.currentThread().getContextClassLoader(),
                                    new Class[]{proxyClass}, iH);
          ///////////////
          //assign serviceProxy to field
        }
        cl = cl.getSuperclass();
     }
  }

  /**

* Override to load and assign custom beans. WARNING IS CALLED FROM THECONSTRUCTOR* DO NOT DEPEND ON STATE SET IN THE CONSTRUCTOR. DO NOT CALL METHODSWHICH DEPEND

   * ON INSTANCE STATE. DO NOT LET LEAK A REFERNCE TO THIS INSTANCE OUT.
   */
   protected void doInjection()
   {
     // Default implementation as Igor has.
   }
}

Sure this is not DI. It also does not provide AOP, livecylcle-managementetc as a container does. It is also not elegant with the constructorcalling the doInjection() method and it's magic.


However it is sugar for lookup. ie:

class MyPage(){
 @SpringBean("customerdao")
 protected CustomerDAO _customerDao; //no getter/setter

 public void someWhere(){
   _mydao.getCustomer("id");
 }
}

during testing:

MyPage page = new MyPage(){
  protected void doInjection(){
    _customerDao = new MockDAO();
  }
};

And you have the service ready in the constructor in case you want to giveit further to a component you construct in the constructor.

On Mon, 7 Nov 2005 12:27:12 -0800, Igor Vaynberg <[EMAIL PROTECTED]>wrote:

yes. but instead of doing the injection right away the proxy would do
injection-on-first-access.
that way you get lazy injection and strongly typed pages.

so you would annotate getter functions with the @SpringBean annot, andtheproxy would first call the getter ... if the getter returns null theproxy

would then look for the setter and invoke the setter with the dependency,
and then forward the call to the getter again.

sound like a good idea?

its not as elegant as being able to simply create the page and go, but it
does give us the benefit of lazy dependency lookups and solves
deserialization issues.

i guess of course if you want to use aop you can intercept new operatoron a

subclass of WebPage and do the wrapping automatically.

Or make the constructors of the page protected and create public static
factory methods. MyPage page=MyPage.construct(user, securitycontext);

-Igor


On 11/7/05, Christian Essl <[EMAIL PROTECTED]> wrote:


Do you mean when you construct the page you do something like

MyPage page = (MyPage) wrapInProxy(new MyPage(..));

and wrapInProxy does create the Proxy and does all the injection?

On Mon, 7 Nov 2005 11:56:23 -0800, Igor Vaynberg<[EMAIL PROTECTED]>

wrote:

> yeah, i was thinking cglib and extract at runtime
> never used cglib before though
>
> that way you just wrap the page with the proxy after you create it and
> there
> is no need to worry about serialization/deserialiation garbage
>
> -Igor
>
>
> On 11/7/05, Christian Essl <[EMAIL PROTECTED]> wrote:
>>

>> The interface of the setter parameter or of the field type. Ofcourse a

>> restriction. If you want more you could use cglib (or spring aop).
Don't
>> know.
>>
>>
>>
>> On Mon, 7 Nov 2005 11:27:28 -0800, Igor Vaynberg
>> <[EMAIL PROTECTED]>
>> wrote:
>>
>> > what interface would you use for the proxy though?
>> > -Igor
>> >
>> >
>> > On 11/7/05, Christian Essl <[EMAIL PROTECTED]> wrote:
>> >>
>> >> Thanks for the clarification and sorry for the confusion. So
>> >> readObject()
>> >> as you have it in your code is fine.
>> >>

>> >> > To get the bean context i simply make my applicationbeanimplement

>> >> > applicationcontextaware and then i use

>> >> > ((MyApplication)Application.get()).getBeanContext() staticlookup

>> >> which
>> >> > works because application object is always present.
>> >>

>> >> Still one question. The threadlocal used in Application.get() isset

>> at
>> >> the beginning of a request - on the request thread. I do not know
but
>> >> maybe the deserialization of the session could happen outside of a
>> >> request
>> >> - even in a totally different thread?
>> >>
>> >> Maybe in readObject() a dynamic proxy could be injected which
>> triggers
>> >> on
>> >> first access the onInject() method.
>> >>
>> >> Christian
>> >>
>> >> >
>> >> > -Igor
>> >> >
>> >> >
>> >> > On 11/7/05, Christian Essl <[EMAIL PROTECTED]> wrote:
>> >> >>
>> >> >> On Mon, 7 Nov 2005 15:25:29 +0100, Johan Compagner
>> >> >> <[EMAIL PROTECTED]>
>> >> >> wrote:
>> >> >>
>> >> >> > And there is also a thing like XML Serialization
>> >> >> > Which also doesn't use the java read/write object at all.
>> >> >> >
>> >> >>

>> >> >> Does this mean that the readObject is guaranteed to be calledon

>> Page

>> >> >> because it is serialized through the PageMap and is not adirect

>> >> session
>> >> >> attribute?
>> >> >>

>> >> >> I don't get realy clear with 'Serializable closure' in thespec:

>> >> >>
>> >> >> "Developers are not guaranteed that containers will call
>> readObject
>> >> and
>> >> >> writeObject methods on
>> >> >> session attributes if they implement them, but are guaranteed
that
>> >> the
>> >> >> Serializable closure of their attributes will be preserved."
>> >> >>

>> >> >> And if readObject() gets called on Pages can I than acesssomehow

>> the
>> >> >> ApplicationContext to get to the BeanContext?
>> >> >>
>> >> >> Please help.
>> >> >>
>> >> >> Thanks,
>> >> >> Christian
>> >> >>
>> >> >> >
>> >> >> > On 11/7/05, Christian Essl <[EMAIL PROTECTED]> wrote:
>> >> >> >>
>> >> >> >> Hi Igor,
>> >> >> >>
>> >> >> >> I looked through your code. Thanks for implementing it. I am
>> not
>> >> sure
>> >> >> >> wheter readObject() is the right place to do the
(re)injection.
>> >> >> >> According
>> >> >> >> to the servlet-spec in SVR 7.7.2 readObject() is not
guaranteed
>> to
>> >> be
>> >> >> >> called on session-attributes. (Instead session attributes
which
>> >> >> >> implement
>> >> >> >> HttpSessionActiviationListeners are informed on
>> deserialization).
>> >> >> Even
>> >> >> >> if
>> >> >> >> readObject is called I am not sure wheter there is an
>> >> >> ApplicationContext
>> >> >> >> to get to the BeanContext.
>> >> >> >>
>> >> >> >> I don't know wheter wicket has a mean to propogate these
>> >> >> >> HttpSessionEvents
>> >> >> >> on deserialization or a similar callback? If so I guess you
>> could
>> >> do
>> >> >> the
>> >> >> >> (re)injection there.
>> >> >> >>
>> >> >> >> Christian
>> >> >> >>
>> >> >> >> On Mon, 7 Nov 2005 01:13:31 -0800, Igor Vaynberg
>> >> >> >> <[EMAIL PROTECTED]>
>> >> >> >> wrote:
>> >> >> >>
>> >> >> >> > here is something i threw together that solves the
>> >> deserialization
>> >> >> and
>> >> >> >> > ability to use the new operator to create pages. atleast i
>> think
>> >> it

>> >> >> >> > does....its really late here and all i really know so faris

>> >> that
>> >> >> it
>> >> >> >> > compiles :)
>> >> >> >> >
>> >> >> >> > the idea is pretty simple, do the injection in the default
>> >> >> >> constructor,
>> >> >> >> > and
>> >> >> >> > then do it anytime the object is deserialized. you use a
>> >> >> @SpringBean
>> >> >> >> > annotation to denote the dependency. it can either be used
>> on a
>> >> >> field
>> >> >> >> or
>> >> >> >> > on
>> >> >> >> > a setter. If you specify the bean name it will be used to
>> find
>> >> the
>> >> >> >> bean,
>> >> >> >> > if

>> >> >> >> > you dont then the field's type or the setters argumenttype

>> will
>> >> be
>> >> >> >> used
>> >> >> >> > for
>> >> >> >> > the lookup.
>> >> >> >> >
>> >> >> >> > -Igor
>> >> >> >> >
>> >> >> >> >
>> >> >> >> > On 11/7/05, Igor Vaynberg <[EMAIL PROTECTED]> wrote:
>> >> >> >> >>
>> >> >> >> >> and you have to have the pages defined as beans in the
>> >> application
>> >> >> >> >> context? with their properties specified?
>> >> >> >> >>
>> >> >> >> >> -Igor
>> >> >> >> >>
>> >> >> >> >>

>> >> >> >> >> On 11/7/05, Igor Vaynberg <[EMAIL PROTECTED]>wrote:

>> >> >> >> >> >
>> >> >> >> >> > but how does the above handle deserealization of pages?
>> there
>> >> is
>> >> >> >> >> nothing
>> >> >> >> >> > to reinject the dependencies.
>> >> >> >> >> >
>> >> >> >> >> > -Igor
>> >> >> >> >> >
>> >> >> >> >> >
>> >> >> >> >> > On 11/7/05, [EMAIL PROTECTED] < [EMAIL PROTECTED]> wrote:
>> >> >> >> >> > >
>> >> >> >> >> > > IMHO pages are standing on the borderline between a
>> >> stateful
>> >> >> GUI
>> >> >> >> and
>> >> >> >> >> > > the rest of the application in form of stateless
>> services.
>> >> >> >> >> > > DI should be done by the IoC container, creating the
>> pages
>> >> can
>> >> >> >> >> better
>> >> >> >> >> > > be done the standard Wicket way (e.g. with
>> PageParameters).
>> >> >> >> >> > >
>> >> >> >> >> > > As described before I'm using a custom page factory
that
>> >> >> >> cooperates
>> >> >> >> >> > > with a wrapped page factory and the containing bean
>> >> factory:
>> >> >> >> >> > >
>> >> >> >> >> > > public class SpringInjectingPageFactory implements
>> >> >> IPageFactory,
>> >> >> >> >> > > BeanFactoryAware {
>> >> >> >> >> > >
>> >> >> >> >> > > private AutowireCapableBeanFactory beanFactory;
>> >> >> >> >> > > private IPageFactory pageFactory;
>> >> >> >> >> > >

>> >> >> >> >> > > public void setPageFactory(IPageFactory pageFactory){

>> >> >> >> >> > > this.pageFactory = pageFactory;
>> >> >> >> >> > > }
>> >> >> >> >> > >
>> >> >> >> >> > > public void setBeanFactory(BeanFactory beanFactory)
>> throws
>> >> >> >> >> > > BeansException {
>> >> >> >> >> > > this.beanFactory =
>> (AutowireCapableBeanFactory)beanFactory;
>> >> >> >> >> > > }
>> >> >> >> >> > >
>> >> >> >> >> > > public Page newPage(Class pageClass) {
>> >> >> >> >> > > Page page = this.pageFactory.newPage(pageClass);
>> >> >> >> >> > >
>> >> >> >> >> > > injectDependencies(page, pageClass.getName ());
>> >> >> >> >> > >
>> >> >> >> >> > > return page;
>> >> >> >> >> > > }
>> >> >> >> >> > >
>> >> >> >> >> > > public Page newPage(Class pageClass, PageParameters
>> >> >> parameters)
>> >> >> {
>> >> >> >> >> > > Page page = this.pageFactory.newPage(pageClass,
>> >> parameters);
>> >> >> >> >> > >
>> >> >> >> >> > > injectDependencies(page, pageClass.getName ());
>> >> >> >> >> > >
>> >> >> >> >> > > return page;
>> >> >> >> >> > > }
>> >> >> >> >> > >
>> >> >> >> >> > > private void injectDependencies(Page page, String
>> >> beanName) {
>> >> >> >> >> > > if (this.beanFactory.containsBean(beanName)) {
>> >> >> >> >> > > this.beanFactory.applyBeanPropertyValues(page,
>> beanName);
>> >> >> >> >> > > }
>> >> >> >> >> > > }
>> >> >> >> >> > > }
>> >> >> >> >> > >
>> >> >> >> >> > > Note that if you don't specify a name or id attribute
>> for
>> >> >> beans,
>> >> >> >> >> they
>> >> >> >> >> > > will be registered under their classname in Spring.
>> >> >> >> >> > > And NO, I don't use autowiring:
>> applyBeanPropertyValues()
>> >> does
>> >> >> >> not
>> >> >> >> >> > > autowire although it is located in
>> >> AutowireCapableBeanFactory.
>> >> >> >> >> > >
>> >> >> >> >> > > Sven
>> >> >> >> >> > >
>> >> >> >> >> > > >you are right, this is not ioc. but are
>> pages/components
>> >> >> managed
>> >> >> >> by
>> >> >> >> >> > > an ioc
>> >> >> >> >> > > >container?
>> >> >> >> >> > > >-Igor
>> >> >> >> >> > > >
>> >> >> >> >> > > >
>> >> >> >> >> > > >On 11/6/05, Alexandru Popescu <
>> >> >> >> >> [EMAIL PROTECTED]>
>> >> >> >> >> > > wrote:
>> >> >> >> >> > > >>
>> >> >> >> >> > > >> #: Igor Vaynberg changed the world a bit at a time
by
>> >> >> saying
>> >> >> >> on
>> >> >> >> >> > > 11/6/2005
>> >> >> >> >> > > >> 7:06 PM :#
>> >> >> >> >> > > >> > Or how about a simple solution:
>> >> >> >> >> > > >> >
>> >> >> >> >> > > >> > public MyApplication extends WebApplication {
>> >> >> >> >> > > >> > public Object lookup(String name) {
>> >> >> >> >> > > >> > Object=...do a lookup from somewhere like spring
>> >> context
>> >> >> or
>> >> >> >> app
>> >> >> >> >> > > >> object...;
>> >> >> >> >> > > >> > return object;
>> >> >> >> >> > > >> > }
>> >> >> >> >> > > >> > }
>> >> >> >> >> > > >> >
>> >> >> >> >> > > >> > public MyPage extends Page {
>> >> >> >> >> > > >> > public transient SomeService service;
>> >> >> >> >> > > >> >
>> >> >> >> >> > > >> > public SomeService getService() {
>> >> >> >> >> > > >> > if (service==null) {
>> >> >> >> >> > > >> >

>> >> >> >>service=getApplication().lookup(SomeService.class.getName());

>> >> >> >> >> > > >> > }
>> >> >> >> >> > > >> > return service;
>> >> >> >> >> > > >> > }
>> >> >> >> >> > > >> >

>> >> >> >> >> > > >> > I know its not quiete as elegant as ioc but ithas

>> >> none
>> >> >> of
>> >> >> >> the
>> >> >> >> >> > > >> performance
>> >> >> >> >> > > >> > hits an automatic injection would cause if it
would
>> be
>> >> >> done
>> >> >> >> on
>> >> >> >> >> > > >> > deserialization of every component. Also its a
lazy
>> >> >> lookup
>> >> >> >> so
>> >> >> >> >> you
>> >> >> >> >> > > dont
>> >> >> >> >> > > >> do it

>> >> >> >> >> > > >> > until its needed, and its only done once perpage

>> >> (until
>> >> >> it
>> >> >> >> >> gets
>> >> >> >> >> > > >> > deserialized).
>> >> >> >> >> > > >> >
>> >> >> >> >> > > >> > -Igor
>> >> >> >> >> > > >> >
>> >> >> >> >> > > >>

>> >> >> >> >> > > >> But this was exactly what I was suggesting toavoid

>> ;-).
>> >> >> >> Lookups
>> >> >> >> >> > > and
>> >> >> >> >> > > >> factories are not ioc/di.
>> >> >> >> >> > > >>
>> >> >> >> >> > > >> ./alex
>> >> >> >> >> > > >> --
>> >> >> >> >> > > >> .w( the_mindstorm )p.
>> >> >> >> >> > > >>
>> >> >> >> >> > > >>
>> >> >> >> >> > > >>
>> >> >> >> >> > > >>
>> -------------------------------------------------------
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>> >> >> your
>> >> >> >> very
>> >> >> >> >> > > own
>> >> >> >> >> > > >> Sony(tm)PSP. Click here to play:
>> >> >> >> >> > > http://sourceforge.net/geronimo.php
>> >> >> >> >> > > >> _______________________________________________
>> >> >> >> >> > > >> Wicket-user mailing list
>> >> >> >> >> > > >> [email protected]
>> >> >> >> >> > > >>
>> https://lists.sourceforge.net/lists/listinfo/wicket-user
>> >> >> >> >> > > >>
>> >> >> >> >> > >
>> >> >> >> >> > >

>> >> >> >> >> > >-------------------------------------------------------

>> >> >> >> >> > > SF.Net email is sponsored by:

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>> App
>> >> >> >> Server.
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>> >> >> >> >> > > it for free - -and be entered to win a 42" plasma tvor

>> >> your
>> >> >> very
>> >> >> >> >> own
>> >> >> >> >> > > Sony(tm)PSP. Click here to play:
>> >> >> >> http://sourceforge.net/geronimo.php
>> >> >> >> >> > > _______________________________________________
>> >> >> >> >> > > Wicket-user mailing list
>> >> >> >> >> > > [email protected]
>> >> >> >> >> > >
https://lists.sourceforge.net/lists/listinfo/wicket-user
>> >> >> >> >> > >
>> >> >> >> >> >
>> >> >> >> >> >
>> >> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> --
>> >> >> >> Christian Essl
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> ___________________________________________________________

>> >> >> >> Gesendet von Yahoo! Mail - Jetzt mit 1GB Speicher kostenlos-

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>> >> >> >> anmelden: http://mail.yahoo.de
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> -------------------------------------------------------
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>> >> own
>> >> >> >> Sony(tm)PSP. Click here to play:
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>> >> >> >> _______________________________________________
>> >> >> >> Wicket-user mailing list
>> >> >> >> [email protected]
>> >> >> >> https://lists.sourceforge.net/lists/listinfo/wicket-user
>> >> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >> --
>> >> >> Christian Essl
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >> ___________________________________________________________
>> >> >> Gesendet von Yahoo! Mail - Jetzt mit 1GB Speicher kostenlos -
Hier
>> >> >> anmelden: http://mail.yahoo.de
>> >> >>
>> >> >>
>> >> >>
>> >> >> -------------------------------------------------------
>> >> >> SF.Net email is sponsored by:
>> >> >> Tame your development challenges with Apache's Geronimo App
>> Server.
>> >> >> Download

>> >> >> it for free - -and be entered to win a 42" plasma tv or yourvery

>> own
>> >> >> Sony(tm)PSP. Click here to play:
>> http://sourceforge.net/geronimo.php
>> >> >> _______________________________________________
>> >> >> Wicket-user mailing list
>> >> >> [email protected]
>> >> >> https://lists.sourceforge.net/lists/listinfo/wicket-user
>> >> >>
>> >>
>> >>
>> >>
>> >> --
>> >> Christian Essl
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> ___________________________________________________________
>> >> Gesendet von Yahoo! Mail - Jetzt mit 1GB Speicher kostenlos - Hier
>> >> anmelden: http://mail.yahoo.de
>> >>
>> >>
>> >>
>> >> -------------------------------------------------------
>> >> SF.Net email is sponsored by:

>> >> Tame your development challenges with Apache's Geronimo AppServer.

>> >> Download
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own

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>> >> _______________________________________________
>> >> Wicket-user mailing list
>> >> [email protected]
>> >> https://lists.sourceforge.net/lists/listinfo/wicket-user
>> >>
>>
>>
>>
>> --
>> Christian Essl
>>
>>
>>
>>
>>
>> ___________________________________________________________
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>>
>>
>>
>> -------------------------------------------------------
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>> _______________________________________________
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>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/wicket-user
>>



--
Christian Essl





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Re: Re: [Wicket-user] My take on Spring integration

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