I've created FacesComponent which I want to initialize in constructor/postconstructor. The problem is that getAttributes() is empty in there. Below is the example.
#FacesComponent("articleComponent")
public class ArticleFacesComponent extends UINamingContainer {
private Article article;
public ArticleFacesComponent() {
Object idObj = getAttributes().get("articleId"); // I want to get article id to initialize object but getAttributes() is empty
...
article = em.find(Article.class, id);
}
}
You need to perform the job in the encodeAll() method. It's invoked during render response, when the component is about to be rendered.
#Override
public void encodeAll(FacesContext context) throws IOException {
// Here.
super.encodeAll(context);
}
Given that you're extending from UINamingContainer, you're most likely creating a backing component for a composite component. In that case, this article should provide you useful insights to get started: composite component with multiple input fields.
Unrelated to the concrete problem, accessing the DB in a component is a smell. Rather pass a fullworthy Article instance as component value instead of its ID. The component/renderer should only deal with front-end (HTTP/HTML) stuff based on the model, not with back-end (DB/SQL) stuff. You should provide the component exactly the model it needs to work with.
Like #BalusC said. But if you are using PrimeFaces you have to overwrite the encodeBegin() method. Else you may overwrite encodeAll().
Related
I'm trying to use the built-in laravel's Ioc container to inject a PageManager class inside a Page model and I'm a little lost.
What I'm trying to achieve is something like that:
class Pages extends Eloquent {
public function __construct(PagesManagerInterface $manager, array $attributes = array())
{
parent::__construct($attributes);
$this->manager = new $manager;
}
public function saveToDisk()
{
$this->manager->writeToFile();
}
But I obtain this error:
ErrorException: Argument 1 passed to Pages::__construct() must be an instance of PagesManagerInterface, none given.
I tried to add this in app/start/global.php:
App::bind('Pages',function(){
return new Pages(new PagesManager);
});
But is seems ignored by the framework, and also i don't know how to insert the $attribute array into this declaration.
I'm a little lost so any help is appreciated!
It's not a good idea to overload a model's constructor because new instances can be spawned behind the scenes through various methods, like Model::find().
When that happens, the dependencies you're asking for in your custom constructor aren't being passed in because the Model class isn't aware of them. So, you get that error message.
See the find() method here: http://laravel.com/api/source-class-Illuminate.Database.Eloquent.Model.html#380-397
See this post by Jason Lewis: http://forums.laravel.io/viewtopic.php?pid=47124#p47124
I think that what you need is:
App::bind('PagesManagerInterface',function(){
return new Pages(new PagesManager);
});
This tells Laravel to inject a new Page object everytime it needs an instance of your PagesManagerInterface wich wasn't passed while creating the model.
In Laravel you can use the IoC Container:
public function saveToDisk(){
$managerObject = app()->make('path\to\class\PagesManagerInterface');
$managerObject->writeToFile();
}
I want to use ManagedBean in my Converter. The ManagedBean is responsible for getting data from database. In Converter I want to convert string into object which must be get from database.
This is my Converter
#FacesConverter(forClass=Gallery.class, value="galleryConverter")
public class GalleryConverter implements Converter {
// of course this one is null
#ManagedProperty(value="#{galleryContainer}")
private GalleryContainer galleryContainer;
#Override
public Object getAsObject(FacesContext context, UIComponent component, String galleryId) {
return galleryContainer.findGallery(galleryId);
...
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object gallery) {
...
}
}
I know that galleryContainer will be null and if I want to inject ManagedBean into Converter I can mark it as ManagedBean too. The problem is that I want to do it in beautiful way, I don't want to look for some 'strange solution'. Maybe the problem is in my application? Maybe there is some other good solution to create object which must get data from database and used in converter? I want also to mention that I will prefer to use DependencyInjection instead of creating new object using new statement (it is easier to test and maintain). Any suggestions?
Instead of using #FacesConverter you should use #ManagedBean, because currently faces converter isn't a valid injection target. Nonetheless, you can choose your converter to be a managed bean, thus refer to it in your view as converter="#{yourConverter}" (by managed bean name) instead of converter="yourConverter" (by converter id).
Basic usage example:
#ManagedBean
#RequestScoped
public class YourConverter implements Converter {
#ManagedProperty...
...
//implementation of converter methods
}
Of course, reading BalusC's invaluable Communication in JSF 2.0 will shed some light on this question as well.
It is also worth mentioning that the scope of your converter bean may be changed to, for example, application or session, if it is not supposed to hold any state.
I have a search form that can search in different provider.
I started out by having a base controller
public SearchController : Controller
{
protected readonly ISearchService _searchService
public SearchController(ISearchService searchService)
{
_searchService= searchService;
}
public ActionResult Search(...)
{
// Use searchService to query and return a view.
}
}
And child controllers
TwitterController : SearchController
{
...
}
NewsController : SearchController
{
...
}
I use StructureMap to insert all my dependencies in the controller. With this setup, I was able to change the SearchService depending on the type of the controller being instanciated.
x.For<ISearchService>().ConditionallyUse(o =>
{
o.TheDefault.Is.OfConcreteType<NewsSearchService>();
o.If(c => c.ParentType == typeof(TwitterController))
.ThenIt.Is.OfConcreteType<TwitterSearchService>();
...
});
That even allowed me to set different Views for each controller, (just putting the corresponding folder (Twitter, News...) and the Parent controller is still handling all the Search, with a simple
return View(results)
which is displaying the correct view specific to twitter, news, or other
Now that was cool and looked great, I a single form and the different views are displayed in tabs on the same page. That's where it starts to get complicated with this approach. The form has to post to /Twitter to search in twitter, to /News to search in news... which means I should change the action parameter of the form depending on which tab I am and display the correct tab on when the form returns depending on.. the url? craziness follows.
If you have built something like this already or know what's the best approach to this, please advices are welcome.
Now I think I would have less pain using a parameter in the form and posting to a single controller. I am thinking of injecting the correct SearchService depending on this parameter. What would be the best approach? I thought of using a model binder,
So I would have my ActionMethod that look like this:
public ActionResult Search(ISearchService service, Query query)
{
var results = service.Find(query);
}
But I think would need to make a call like this in the ModelBinder
ObjectFactory.GetInstance(...);
Based on the querystring parameter that describe which provider to use, and that doesn't seem more elegant to me. I feel stuck, help :(.
Whenever you need to vary a dependency based on a run-time value, Abstract Factory is the general solution.
Instead of injecting ISearchService into your Controllers, inject an ISearchServiceFactory:
public SearchController : Controller
{
private readonly ISearchServiceFactory searchServiceFactory;
public SearchController(ISearchServiceFactory searchServiceFactory)
{
if (searchServiceFactory == null)
{
throw new ArgumentNullException("searchServiceFactory");
}
this.searchServiceFactory = searchServiceFactory;
}
public ActionResult Search(...)
{
// Use searchServiceFactory to create an ISearchService based on
// run-time values, and use it to query and return a view.
}
}
It is not entirely clear to me which run-time value you need to vary on, but assuming that it's the Query, ISearchServiceFactory might be defined like this:
public interface ISearchServiceFactory
{
ISearchService Create(Query query);
}
I was trying to figure out how to use the abstract factory pattern and still let structuremap resolve all the dependencies of my components.
I believe that is the way I am going to implement it, but I submit this here to get some feedback if someone would read this.
As explain in the previous answer, I do not want to build the whole object graph depending on which provider I need in the Abstract factory.
ie :
class StatServiceFactory : IStatServiceFactory
{
public IStatService Create(string provider)
{
switch(provider)
{
case "blog":
return new StatService(IFacetRepository,ISearchManager,IConfigManager,BooleanQueryBuilder);
//How to resolve the Config, the SearchManager, and BooleanQueryBuilder?
//Add more abstract factories? It starts to get messy in my opinion...
}
}
}
What I can do is have the abstract factory use my container to create an instance of my search managers depending on a parameter (coming from the querystring in my case)
Structuremap allows to create named instances this way :
x.For<ISearchManager>().Use<AbcSearchManager>().Named("Abc");
x.For<ISearchManager>().Use<DefSearchManager>().Named("Def");
I need a way to inject the container in my Abstract factory.
I would probably wrap the container in a wrapper defined like this. That would keep me from leaking Structuremap into my project. I dont need more that those 2 features within the abstract factory anyway, but it is not necessary:
public interface IContainerWrapper
{
object GetInstance<T>();
object GetNamedInstance<T>(string key);
}
and the implementation :
public class ContainerImpl : IContainerWrapper
{
private readonly Container _container
public ContainerImpl(Container container)
{
_container = container;
}
...
}
And setup StructureMap to resolve dependencies to my abstract factory like that :
x.For<IContainer>.Use(new ContainerImpl(this));
x.For<IFactory>.Use<Factory>()
My factory would be then much simpler and would create my instance like that :
public class SearchmanagerFactory
{
private readonly IContainerWrapper _container;
public SearchmanagerFactory(IContainerProvider containerProvider)
{
_container = containerProvider;
}
public ISearchManager Create(string provider)
{
//eed to handle the bad input for provider.
return (ISearchManager)
_container.Resolve<ISearchManager>(provider);
}
}
That seems pretty clean this way :).
Thoughts?
This is more an extensive comment than an answer to explain why an AbstractFactory seems complicated. Here is something that looks closer from the reality:
class StatServiceFactory : IStatServiceFactory
{
public IStatService Create(string provider)
{
switch(provider)
{
case "blog":
return new StatService(IFacetRepository,ISearchManager,IConfigManager,BooleanQueryBuilder);
//How to resolve the Config, the SearchManager, and BooleanQueryBuilder?
//Add more abstract factories? It starts to get messy in my opinion...
}
}
}
The FacetRepository is the same for any provider, but the SearchManager changes, the ConfigManager changes, and the BooleanQueryBuilder is an abstract class with different implementation for different provider (because every API doesnt use the same keyword for their queries) All those dependencies are currently resolved by structuremap, based on the type of the controller.
I would really like to keep the benefit of StructureMap here, rather than using factories all the way, for each different pieces.'
Please see my edit at the end of my question for another suggestion to my problem.
With my understading, the nature of a Action is that properties can be pushed w/ request parameter values. And, one wonderful feature is that Struts2 allows you to directly populate parameter values against Class type property ;)
Assuming there exists a Action and property class as below,
class Action extends ActionSupport {
User user;
#Action(value="hello" {#result=(.......)})
public void execute() {
........
}
.....
public void setUser(User user) {
this.user = user;
}
public User getUser() {
return this.user;
}
}
class User {
String name;
.....
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
}
you could populate User class property by doing like this.
http://...../hello.action?user.name=John or via jsp page
Then, I realize that there are actually people make an Action property as a Interface type. My question is what is the reason behind this. If there is a sample code demonstrating it will be great.
Thanks in advance!
Sorry, but your question does not make much sense.
To clarify:
"Properties": in Java a "property" of a class is something that is accesible via getter/setters method (setXXX() / getXXX() => property XXX), tipically (but not necessarily) corresponds to a private field.
In Struts2 you have an Action object and typically (not necessarily, not always) the properties are populated (set) from the request (via the "Parameters" interceptor), and later in the view stage read from the JSP (or whatever) page.
So, in your example, for the request http://...../hello.action?user.name=John , Struts2 would try to find in your action (...actually in your value stack) a property "user" which has a property "name", and try to set it (if the types are convertible). That is, he would try to call something like yourAction.getUser().setName("John") . Struts2 does not know -does not care- what type are the properties "User" or "Name", even if they are real fields or not. (They are expected to behaviour as "beans", though: i.e. they should have a default constructor).
Why and when you should code interfaces instead of concrete classes is something that is explained in any Java book, it's just a standard good practice and there are tons of pages about it. It has nothing to do with Struts2. In this context, for an Action, one is tipically only interested in doing so for some "service" fields, objects that are typically long-lived (perhaps singletons), are not instantiated by the action itself (nor by the request!). So, those interfaces are NOT the properties we are considering here, they ( usually ) are not exposed publically and usually are not populated nor read from the client.
Total Guice noob here, have read a few articles and seen the intro video, that's about it.
Here's my simplified old code that I'm trying to "guicifiy". Can't quite figure out how to, since (as far as I understand), I can only #inject-annotate one of the two constructors? How can a calling class create the one or the other instance? Or will I have to refactor this somehow?
public class MyDialog extends JDialog {
public MyDialog( JFrame parent, <other parameters...> ) {
super( parent );
}
public MyDialog( JDialog parent, <other parameters...>) {
super( parent );
}
}
You can only inject into the one ctor.
Depending on how this class is being used, you could:
Inject a factory into the client code with two "new" methods.
Roll all the arguments into one ctor and pass null when not required.
How can a calling class create the one or the other instance?
This suggests that the calling classes will want multiple instances of MyDialog? Then you need to use a hand-rolled factory (Assisted Inject can handle this for you if you only had one ctor). I don't know the details of what you are up to and I'm likely repeating what you already know but as a blanked statement I'd suggest also extracting an interface from MyDialog and have the factory return them. This way you can fake MyDialog in tests.
Constructor injection is very clean. mlk is right, saying that you can inject into one constructor only.
What you can do is use method injection:
public class Smt {
private int a;
private Cereal cereal;
private Personality personality;
private ignition;
public Smt() {
this.a = 5;
}
public Smt(int a) {
this.a = a;
}
#Inject
public void setup(#CiniMini Cereal cereal, #Rastafarian Personality personality,
Ignition ignition) {
this.cereal = cereal;
this.personality = personality;
this.ignition = ignition;
}
}
What Guice will do is call your class' setup class method and provide all the injections. Then you do the same thing as in the constructor--assign the objects to your class' attributes.
I agree with the previous comments.
Just an additional hint: constructor injection is supposed to provide all dependencies a class needs. As mlk says, one approach could be to annotate the constructor with most arguments and then refactor the other one to call the former by passing null values where needed.
Additionally, Guice 3.0 supports the so called Constructor Bindings which allow the programmer to specify which constructor to use. See here for more details.