I have 3 classes , one is Activator and two others, 'mysqlConfiguration' and 'BinaryLogListner' where 'mysqlConfiguration' is injected into 'BinaryLogListner' using blueprint.
This is my blueprint (the injection part):
<bean id="binaryLogListnerBean" class="cdc.mysql.BinaryLogListner">
<property name="mysqlConfiguration" ref="configManagementMysql"></property>
</bean>
I want to start the BinaryLogListner when the bundle starts , so I instanciated it from the Activator class with :
BinaryLogListner binaryLogListner = new BinaryLogListner();
When i try to use 'mysqlConfiguration' which is injected into 'BinaryLogListner' I will get a null pointer Exception.
I want to know how to inject a bean into an activator, is this possible ?
Any thougts how to start beans in these situations?
In the Activator you instantiate the class using new BinaryLogListner(). So you simply get the plain class without any blueprint injects. These injects only work when the bean instance is created by blueprint.
Instead of an Activator you should simply use an init-method on any blueprint bean to react on the (blueprint) activation of the bundle.
Generally whenever you use blueprint in a bundle you should not also use an Activator.
Related
I am trying to export a spring bean as service using Spring's application context, I need to have them exported as "prototype" scope, but this is not possible due to OSGi Service registry caching the service as singleton.
Doing some research I came upon a post suggesting to use "session" scope to get around this issue. I am following this tutorial to get this working, but I am stuck with an issue that has to do with class loader not finding an interface.
Here's how I am declaring the bean
<osgi:service id="SimulationExporter" ref="simulationService" interface="org.geppetto.core.simulation.ISimulation"/>
<bean id="simulationService" scope="session" class="org.geppetto.simulation.SimulationService">
<aop:scoped-proxy proxy-target-class="false"/>
</bean>
When exporting the bean to another bundle, I get the following error
Caused by: java.lang.IllegalArgumentException: interface org.springframework.aop.scope.ScopedObject is not visible from class loader
at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:484)
at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:713)
at org.springframework.aop.framework.JdkDynamicAopProxy.getProxy(JdkDynamicAopProxy.java:117)
The bundle importing the service bean has the dependency org.springframework.aop-3.0.0.RELEASE , and this has also being copied to the virgo repository. Any ideas why would the class loader not find that interface that it needs for scope "session"?
Does your MANIFEST.MF include import packages for aop.scope?
If you are using Apache Felix to generate it try adding something like this:
<Import-Package>org.aopalliance.aop,org.springframework.aop,org.springframework.aop.scope,org.springframework.aop.framework,*</Import-Package>
I am using Spring's Application context for bean registry. I will be dependent on external jars for some services, which will be a part of routes.
Is there any way to let camel auto-register the beans that are available in the jar?
No, but you can call any java class from Camel using its bean component. You can specify a class name, and a method to invoke.
You can use the beanType attribute
<bean beanType="com.foo.MyClass" method="someNameHere"/>
Or in an uri
<to uri="bean:com.foo.MyClass?method=someNameHere"/>
If I have a bean defined in an xml file like so :
<bean id="myBean" class="com.myClass">
</bean>
Should "myBean" be autowired, ie should the class "com.myClass" be initialized by Spring ?
I have no Spring annotations in "com.myClass" but the class still seems to be initialized because it is declared in an xml file.
Yes, it is normal that your class to be initialised even though auto-wiring is not stated. The reason for this is:
Declared Spring beans have a life-cycle and the first step in this life-cycle is for Spring to initialise the bean.
The basic life-cycle is as follows:
Initialise Bean
Insert values
Calling certain methods depending on which interfaces you implement. This is useful for further custom initialisation and configuration.
Now your bean is ready for use by your application and will stay in the application context until your application context is destroyed.
Finally, if you implement the DisposableBean interface, the destroy method is called for any de-initialisation process that you may require.
This depends on whether you have any other beans that want Spring to inject myBean into them. If no one uses your bean, you can omit it.
As far as I understand When Using Dependency Injection all bean are initializing on Start.
<bean id="userPreferences" class="com.foo.UserPreferences">
</bean>
<!-- a singleton-scoped bean injected to the above bean -->
<bean id="userService" class="com.foo.SimpleUserService">
<!-- a reference to the userPreferences bean -->
<property name="userPreferences" ref="userPreferences"/>
</bean>
and the configuration above means that userService and userPreferences created when application starts. Is it correct?
When using Autowiring and using <context:component-scan>
public class SimpleUserService{
#Autowired
UserPreferences userPreferences;
//omitted
}
1) Is userPreference created on Application init?
2) What is the default scope for bean injected by autowire and how can we change it?
3) How affects bean creation and bean injection?
Hope I made myself clear.
First of all you should add #Service or #Component to the SimpleUserService class.
1 Yes, the ONE instance of UserPreferences is created at application intialization
2 Default scope is singleton, You can change it with the #Scope annotation (#See Spring Reference: 3.11.4.4 Specifying bean scope)
3 Component scan and XML configuration work in the same way (life cycle)
Maybe you should spend some time in understanding the Spring life cycle. You need to understand that Spring works a bit in this way (not 100% correct):
first it creates a pool of beans
then it injects the properties into the beans
But it does NOT work this way: taking a class, look what references it needs creating this references (recursive) and then creating the class.
If you understand this, then you will also understand, that the #Scope of a bean is defined at the bean declaration/class, but not at the references.
1) Is userPreference created on
Application init?
In either case userPreferences is initialized when Spring Context is loaded. You can change this behavior by adding lazy-init="true" to the bean configuration.
2) What is the default scope for bean
injected by autowire and how can we
change it?
The scope of what is injected is all beans loaded into Spring. If you import an XML configuration from another project, it too would be included. I'm not sure if you can limit your scope.
3) How affects bean creation and bean
injection?
Whether is autowired, or configured via XML, the behavior should be the same. I prefer explicitly defining dependencies over automatic annotations. Then again I also like strongly typed languages.
the configuration above means that userService and userPreferences created when application starts. Is it correct?
Yes
Is userPreference created on Application init?
Yes
What is the default scope for bean injected by autowire and how can we change it?
The default scope is always "singleton". This can be changed either using #Scope with #Bean or the scope XML attribute on <bean>.
How affects bean creation and bean injection?
This isn't a clear question. If you change the bean scope, you change when it gets created (start of application, on each request, on each session, etc). The wiring configuration remains the same, only the lifecycle changes.
The #autowired notation is an obsolete way to say #inject. THe latter is a feature of JavaEE 6.
stackoverflow.com/questions/7142622/what-is-the-difference-between-inject-and-autowired-in-spring-framework-which
I'm developing a web application on Apache Tomcat 6 with Hibernate and Spring, I'm using different XML configuration files to define my Spring beans (like the Hibernate DAO, Quartz scheduler and some other stuff). All these files are loaded at Tomcat start up via web.xml (ContextLoaderListener).
Now I'm not sure what is the recommended way to get access to my beans.
Should I write on class which provides the BeanFactory for all classes which should use a bean, or is it the better way to load the BeanFactory in each class.
BeanFactory bf = (BeanFactory) ContextLoader.getCurrentWebApplicationContext();
One of the core ideas of the spring framework is to minimize dependencies between classes. You'll get the most benefit by using this concept throughout your whole project. Each and every backend object should be defined as bean and can therefore use the dependency injection automatism.
If some of your Beans need to access the ApplicationContext directly (eg for requesting all Beans implementing some marker interface) you can implement the ApplicationContextAware interface, so still no factory is needed.
Use dependency injection instead. Create getters & setters in each controller class, and use your *-servlet.xml to inject the required beans via the <property> tag. No factory needed!