Is it possible to create a TextBox using GWT.create, not the constructor, and wrap an existing HTML element?
I tried:
TextBox text=GWT.create(TextBox.class)
text.setElement(DOM.createInput()) (2)
The above fails on line (2) with "cannot set element twice ..."
I need this in order to use GwtMockito and test a component that needs to create a TextBox.
Thank you!
UIObject have a package protected replaceElement Method which will do what you like to do.
Building a wrapper in the right package like this:
package com.google.gwt.user.client.ui;
import com.google.gwt.dom.client.Element;
public class ElementReplace
{
public static void replaceElement(UIObject obj, Element elem)
{
obj.replaceElement(elem);
}
}
and it is possible to access the method.
It seems you'd have to resort to using some sort of factory:
public interface TextBoxFactory {
TextBox wrap(Element element);
}
This will get injected into your view and you'll use the factory to wrap the existing element in a TextBox. The default implementation will, of course, just use TextBox#wrap(Element), as suggested by Baz. For the purposes of your tests, you'll use an implementation that returns a Mockito mock.
Not the prettiest solution, but given the circumstances, I can't think of a "cleaner" one.
Related
I am creating a custom widget, say "CustomWid" in UiBinder.
And in CustomWid.java file I am writing two constructors
one with zero args like
CustomWid(){....}
another with some args like
CustomWid(String a,String b){......}
So,Now I am using my custom widget in another .ui.xml file,in that .ui.xml file
it is working fine when we give
<my:CustomWid/> alone,
and also fine when we give like
<my:CustomWid a="srt1" b="str2"/> alone
But "MY PROBLEM" is whenever I am trying to give both the tags in the one .ui.xml as
<my:CustomWid/>
<my:CustomWid a="str1" b="str2"/>
Now it is throwing error when i am using both types of tags in a single .ui.xml
I mean How to use my custom widget tag like a prdefined tag?
I am using #uiConstructor, but it showing error
Please developers... I need answer as early as possible
UiBinder will only ever use a single constructor for a given widget: either its zero-arg constructor, or a #UiConstructor (I'm surprised that you say it works when using either one or the other call but not both: one should fail in every case, and one should succeed in every case; if you haven't annotated a constructor with #UiConstructor, then <my:CustomWid/> should always work and <my:CustomWid a="str1" b="str2"/> should always fail)
There are two solutions here:
use setters for the a and b attributes (void setA(String a) and void setB(String b))), and possibly check later (say, in onLoad or onAttach) that you have either none or both of A and B, but not one without the other (if that's your rule).
use #UiField(provided = true) when you need to use the other constructor (if you choose to have UiBinder use the zero-arg constructor –i.e. no #UiConstructor–, then that means you'll have to move the a="str1" b="str2" from the XML to the Java code: #UiField(provided = true) CustomWid myCustomWid = new CustomWid("str1", "str2")).
The first option has my preference.
It Will not show any errors...'
#UiConstructor
public Component(String displayText,String heading)
{
initWidget(uiBinder.createAndBindUi(this));
this.displayText.setText(displayText);
this.heading.setText(heading);
}`
now use another constructor with default parameters also it will work
public Component()
{
initWidget(uiBinder.createAndBindUi(this));
}
now if you add with xml parameters component and without parameters also works in the same page.
I have the following situation. There are two combos on my UI form, one shows the list of vegetables and another one shows a list of fruits.
In my supporting view class I'd like to declare such methods:
#UiFactory
SimpleComboBox<Vegetable> createVegetablesCombo() {
return vegetables;
}
#UiFactory
SimpleComboBox<Fruit> createFruitsCombo() {
return fruits;
}
But it seems that GWT does not recognize parameterized returned types... Every time I get an error:
ERROR: Duplicate factory in class VegetablesAndFruitsView for type SimpleComboBox.
Is it possible to handle this case? Is there a good example of multiple comboboxes on one UI form?
From the perspective of Java (not GWT, not UiBinder, but the Java language itself) at runtime there isn't a difference between SimpleComboBox<Vegetable> and SimpleComboBox<Fruit>. That said, this error is coming from UiBinder's code generation, which is looking for all #UiConstructor methods, and using them to build things.
So what does UiBinder have to work with? From the UiBinder XML, there is no generics. The only way UiBinder could get this right is if you happen to have included a #UiField entry in your class with the proper generics. This then would require #UiField annotations any time there might be ambiguity like this, something GWT doesn't presently do.
What are you trying to achieve in this? You are returning a field (either vegetables or fruits) - why isn't that field just tagged as #UiField(provided=true)? Then, whatever wiring you are doing to assign those fields can be used from UiBinder without the need for the #UiConstructor methods at all.
#UiField(provided=true)
SimpleComboBox<Fruit> fruits;
//...
public MyWidget() {
fruits = new SimpleComboBox<Fruit>(...);
binder.createAndBind(this);
}
...
<form:SimpleComboBox ui:field="fruits" />
If this is just an over-simplification, and you actually plan on creating new objects in those methods, then consider passing an argument in, something like String type, and returning a different SimpleComboBox<?> based on the value. From your UiBinder xml, you could create the right thing like this:
<field:SimpleComboBox type="fruit" />
I have a new project where I am using GWT-Views like Composite, etc.
I have injected the items in the main menu (like ProductList below) using GinInjector. This works fine!
Somewhere I want to have a reference from a small component to an item from my main menu in order to update it. I try to inject it this way:
public class ProductForm extends Composite {
...
#Inject
ProductList list;
....
}
But when I use the list I always get null. Whereby, ProductList is defined this way:
public class MyModule extends AbstractGinModule {
...
#Override
protected void configure() {
bind(ProductList.class).asEagerSingleton();
bind(ProductForm.class).asEagerSingleton();
}
...
}
Any idea what I am doing wrong?!
Solution:
I failed to mention that ProductForm is an element of the ProductList using the UIBinder's #UIField tag, So That injecting it will create a new object rather than the one created using UIBinder.
I had to restructure my code to include presenters and an event bus so that no direct references between views are needed (other than the #UIField attributes).
I was working through Gin documentation : I'll quote it here :
Gin "Magic"
Gin tries to make injection painless and remove as much boilerplate from your code as possible. To do that the generated code includes some magic behind the scenes which is explained here.
Deferred Binding
One way Gin optimizes code is by automating GWT deferred binding. So if you inject an interface or class1 bound through deferred binding (but not through a Guice/Gin binding), Gin will internally call GWT.create on it and inject the result. One example are GWT messages and constants (used for i18n purposes):
public interface MyConstants extends Constants {
String myWords();
}
public class MyWidget {
#Inject
public MyWidget(MyConstants myconstants) {
// The injected constants object will be fully initialized -
// GWT.create has been called on it and no further work is necessary.
}
}
Note: Gin will not bind the instances created through GWT.create in singleton scope. That should not cause unnecessary overhead though, since deferred binding generators usually implement singleton patterns in their generated code.
You can see for yourself in this URL : http://code.google.com/p/google-gin/wiki/GinTutorial
It fails to mention why a singleton cannot be autogenerated by deferred binding and injected.
You can fix this by handcreating, using GWT.create(YourFactoryInterface.class).getProductList() in the constructor.
This means for testing puposes, you will need to pull the GWT.create into a seperate method and override it in a subclass and use that for testing like :
YourFactoryInterface getFactory() {
return GWT.create(YourFactoryInterface.class)
}
and
getFactory().getProductList()
Gin's asEagerSingleton() binding was broken for quite a while, and was injecting null. Not sure when the fix went in, but I had problems with eager singletons on v1.0. See the issue or the explanation, if you're interested. I'd either switch to regular .in(Singleton.class) bindings, or make sure you're using Gin 1.5.
Is the Ginjector creating the ProductForm? I think maybe that is needed to make it populate the injected variable.
i'm trying to dynamically add the class attribute to the body tag, and i came across this class. but i can't seem to understand how to use this class. i have something like this in my page class (or panel class, as i tried with that too):
add(new BodyTagAttributeModifier("class", "homepage", this));
this doesn't even compile, saying there's something wrong with the 2nd parameter. but i think String is automatically considered a Model in wicket, like the Label class. am i missing something here?
What if you just add an wicket:id to the body attribute and use the AttributeAppender class? Or, if the body attribute already has an id, can't you just use this class?
http://wicket.sourceforge.net/apidocs/wicket/behavior/AttributeAppender.html
Some Wicket Components have this String-to-model-shortcut (like Label), but it's not a general feature. You have to convert your String into a Model manually:
add(new BodyTagAttributeModifier("class", Model.of("homepage"), this));
GWT.create() is the reflection equivalent in GWT,
But it take only class literals, not fully qualified String for the Class name.
How do i dynamically create classes with Strings using GWT.create()?
Its not possible according to many GWT forum posts but how is it being done in frameworks like Rocket-GWT (http://code.google.com/p/rocket-gwt/wiki/Ioc) and Gwittir (http://code.google.com/p/gwittir/wiki/Introspection)
It is possible, albeit tricky. Here are the gory details:
If you only think as GWT as a straight Java to JS, it would not work. However, if you consider Generators - Special classes with your GWT compiler Compiles and Executes during compilation, it is possible. Thus, you can generate java source while even compiling.
I had this need today - Our system deals with Dynamic resources off a Service, ending into a String and a need for a class. Here is the solutuion I've came up with - btw, it works under hosted, IE and Firefox.
Create a GWT Module declaring:
A source path
A Generator (which should be kept OUTSIDE the package of the GWT Module source path)
An interface replacement (it will inject the Generated class instead of the interface)
Inside that package, create a Marker interface (i call that Constructable). The Generator will lookup for that Marker
Create a base abstract class to hold that factory. I do this in order to ease on the generated source code
Declare that module inheriting on your Application.gwt.xml
Some notes:
Key to understanding is around the concept of generators;
In order to ease, the Abstract base class came in handy.
Also, understand that there is name mandling into the generated .js source and even the generated Java source
Remember the Generator outputs java files
GWT.create needs some reference to the .class file. Your generator output might do that, as long as it is referenced somehow from your application (check Application.gwt.xml inherits your module, which also replaces an interface with the generator your Application.gwt.xml declares)
Wrap the GWT.create call inside a factory method/singleton, and also under GWT.isClient()
It is a very good idea to also wrap your code-class-loading-calls around a GWT.runAsync, as it might need to trigger a module load. This is VERY important.
I hope to post the source code soon. Cross your fingers. :)
Brian,
The problem is GWT.create doen't know how to pick up the right implementation for your abstract class
I had the similar problem with the new GWT MVP coding style
( see GWT MVP documentation )
When I called:
ClientFactory clientFactory = GWT.create(ClientFactory.class);
I was getting the same error:
Deferred binding result type 'com.test.mywebapp.client.ClientFactory' should not be abstract
All I had to do was to go add the following lines to my MyWebapp.gwt.xml file:
<!-- Use ClientFactoryImpl by default -->
<replace-with class="com.test.mywebapp.client.ClientFactoryImpl">
<when-type-is class="com.test.mywebapp.client.ClientFactory"/>
</replace-with>
Then it works like a charm
I ran into this today and figured out a solution. The questioner is essentially wanting to write a method such as:
public <T extends MyInterface> T create(Class<T> clz) {
return (T)GWT.create(clz);
}
Here MyInterface is simply a marker interface to define the range of classes I want to be able to dynamically generate. If you try to code the above, you will get an error. The trick is to define an "instantiator" such as:
public interface Instantiator {
public <T extends MyInterface> T create(Class<T> clz);
}
Now define a GWT deferred binding generator that returns an instance of the above. In the generator, query the TypeOracle to get all types of MyInterface and generate implementations for them just as you would for any other type:
e.g:
public class InstantiatorGenerator extends Generator {
public String generate(...) {
TypeOracle typeOracle = context.getTypeOracle();
JClassType myTYpe= typeOracle.findType(MyInterface.class.getName());
JClassType[] types = typeOracle.getTypes();
List<JClassType> myInterfaceTypes = Collections.createArrayList();
// Collect all my interface types.
for (JClassType type : types) {
if (type.isInterface() != null && type.isAssignableTo(myType)
&& type.equals(myType) == false) {
myInterfaceTypes.add(type);
}
for (JClassType nestedType : type.getNestedTypes()) {
if (nestedType.isInterface() != null && nestedType.isAssignableTo(myType)
&& nestedType.equals(myTYpe) == false) {
myInterfaceTypes.add(nestedType);
}
}
}
for (JClassType jClassType : myInterfaceTypes) {
MyInterfaceGenerator generator = new MyInterfaceGenerator();
generator.generate(logger, context, jClassType.getQualifiedSourceName());
}
}
// Other instantiator generation code for if () else if () .. constructs as
// explained below.
}
The MyIntefaceGenerator class is just like any other deferred binding generator. Except you call it directly within the above generator instead of via GWT.create. Once the generation of all known sub-types of MyInterface is done (when generating sub-types of MyInterface in the generator, make sure to make the classname have a unique pattern, such as MyInterface.class.getName() + "_MySpecialImpl"), simply create the Instantiator by again iterating through all known subtypes of MyInterface and creating a bunch of
if (clz.getName().equals(MySpecialDerivativeOfMyInterface)) { return (T) new MySpecialDerivativeOfMyInterface_MySpecialImpl();}
style of code. Lastly throw an exception so you can return a value in all cases.
Now where you'd call GWT.create(clz); instead do the following:
private static final Instantiator instantiator = GWT.create(Instantiator.class);
...
return instantiator.create(clz);
Also note that in your GWT module xml, you'll only define a generator for Instantiator, not for MyInterface generators:
<generate-with class="package.rebind.InstantiatorGenerator">
<when-type-assignable class="package.impl.Instantiator" />
</generate-with>
Bingo!
What exactly is the question - i am guessing you wish to pass parameters in addition to the class literal to a generator.
As you probably already know the class literal passed to GWT.create() is mostly a selector so that GWT can pick and execute a generator which in the end spits out a class. The easist way to pass a parameter to the generator is to use annotations in an interface and pass the interface.class to GWT.create(). Note of course the interface/class must extend the class literal passed into GWT.create().
class Selector{
}
#Annotation("string parameter...")
class WithParameter extends Selector{}
Selector instance = GWT.create( WithParameter.class )
Everything is possible..although may be difficult or even useless. As Jan has mentioned you should use a generator to do that. Basically you can create your interface the generator code which takes that interface and compile at creation time and gives you back the instance. An example could be:
//A marker interface
public interface Instantiable {
}
//What you will put in GWT.create
public interface ReflectionService {
public Instantiable newInstance(String className);
}
//gwt.xml, basically when GWT.create finds reflectionservice, use reflection generator
<generate-with class="...ReflectionGenerator" >
<when-type-assignable class="...ReflectionService" />
</generate-with>
//In not a client package
public class ReflectionGenerator extends Generator{
...
}
//A class you may instantiate
public class foo implements Instantiable{
}
//And in this way
ReflectionService service = GWT.create(ReflectionService.class);
service.newInstance("foo");
All you need to know is how to do the generator. I may tell you that at the end what you do in the generator is to create Java code in this fashion:
if ("clase1".equals(className)) return new clase1();
else if ("clase2".equals(className)) return new clase2();
...
At the final I thought, common I can do that by hand in a kind of InstanceFactory...
Best Regards
I was able to do what I think you're trying to do which is load a class and bind it to an event dynamically; I used a Generator to dynamically link the class to the event. I don't recommend it but here's an example if it helps:
http://francisshanahan.com/index.php/2010/a-simple-gwt-generator-example/
Not having looked through the code of rocket/gwittir (which you ought to do if you want to find out how they did it, it is opensource after all), i can only guess that they employ deferred binding in such a way that during compile time, they work out all calls to reflection, and statically generate all the code required to implement those call. So during run-time, you cant do different ones.
What you're trying to do is not possible in GWT.
While GWT does a good job of emulating Java at compile time the runtime is of course completely different. Most reflection is unsupported and it is not possible to generate or dynamically load classes at runtime.
I had a brief look into code for Gwittir and I think they are doing their "reflection stuff" at compile time. Here: http://code.google.com/p/gwittir/source/browse/trunk/gwittir-core/src/main/java/com/totsp/gwittir/rebind/beans/IntrospectorGenerator.java
You might be able to avoid the whole issue by doing it on the server side. Say with a service
witch takes String and returns some sort of a serializable super type.
On the server side you can do
return (MySerializableType)Class.forName("className").newInstance();
Depending on your circumstances it might not be a big performance bottleneck.