Hi,
Unfortunately I'm using this functionality only in my test application
to check how does these all "spring things" work in Wicket. So probably
I can't help you much.
One thing about a prototype-scoped beans, which is interesting. I have a
very simple bean class to test injection:
package example.spring;
public class SimpleBean {
private static int counter = 0;
private String welcome;
public SimpleBean() {
this.welcome = "Welcome text from a default constructor: " +
(++counter);
System.out.println("Constructor A - " + counter);
}
public SimpleBean(String welcome) {
this.welcome = welcome + " " + (++counter);
System.out.println("Constructor B - " + counter);
}
public String getWelcome() {
return welcome;
}
}
I've created a static counter to check how many instances of this class
is created and simple output to observe bean creation.
In my applicationContext.xml there is an entry:
<bean id="simpleBean" class="example.spring.SimpleBean"
scope="prototype">
<constructor-arg>
<value>This is a sample welcome text for Spring bean</value>
</constructor-arg>
</bean>
And I inject this bean into my MyTestPage:
@SpringBean
private SimpleBean simpleBean;
public MyTestPage() {
super();
System.out.println(simpleBean.getWelcome());
}
When I enter this page first time in a browser there is the following
output:
Constructor B - 1
Constructor A - 2
Constructor B - 3
This is a sample welcome text for Spring bean 3
So as you can see there are 3 calls to SimpleBean constructor, including
one default constructor call (so it looks like 3 instances of this class
was created). Each time I enter MyTestPage SimpleBean counter is
incremented three times:
Constructor B - 4
Constructor A - 5
Constructor B - 6
This is a sample welcome text for Spring bean 6
etc...
The question is: is it a normal behaviour or a bug in
wicket-spring-annot (or somewhere in my code :))?
When I comment a default no-argument constructor code, I've received an
error:
java.lang.IllegalArgumentException: Superclass has no null constructors but no
arguments were given
at net.sf.cglib.proxy.Enhancer.emitConstructors(Enhancer.java:718)
at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer.java:499)
at
net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
at
net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216)
at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:285)
at
org.apache.wicket.proxy.LazyInitProxyFactory.createProxy(LazyInitProxyFactory.java:138)
at
org.apache.wicket.spring.injection.annot.AnnotProxyFieldValueFactory.getFieldValue(AnnotProxyFieldValueFactory.java:102)
at org.apache.wicket.injection.Injector.inject(Injector.java:109)
at
org.apache.wicket.injection.ConfigurableInjector.inject(ConfigurableInjector.java:40)
at
org.apache.wicket.injection.ComponentInjector.onInstantiation(ComponentInjector.java:54)
at
org.apache.wicket.Application.notifyComponentInstantiationListeners(Application.java:919)
at org.apache.wicket.Component.<init>(Component.java:606)
at org.apache.wicket.MarkupContainer.<init>(MarkupContainer.java:111)
at org.apache.wicket.Page.<init>(Page.java:195)
at org.apache.wicket.markup.html.WebPage.<init>(WebPage.java:99)
Is a "null constructor" necessary for "bean" class?
BTW: In Wicket 1.2.6 prototype-scoped beans does not work. I was wrong
in my last mail, it seems that they work as singletons.
Best regards,
Daniel
Rüdiger Schulz wrote:
> Hello,
>
> I can't say anything about request or session scoped beans.
> But I am interested in how you use prototype-scoped beans. Do you use
> them to store the state of your Wicket-components? I have some
> problems with that (which I posted earlier)...
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