I have a project based on spring-integration . I want to use some of its class in other project ,i added reference to spring-integration based project class in other project all autowired object become null , as i am using new operator to create the object , how can i access the object using applicationContext from other project ?
You can't autowire beans that you create yourself (with new); you have to add them to a spring application context. Perhaps if you show your configuration and what you are trying to do, someone can help.
Related
I’m a newbie to mvc 5 dependency injection,I know that mvc 5 has a default parameterless constructor.But in dependency injection we create a constructor with a parameter, and IOC containers provide object to the parameter.my question is how does IOC containers like unity make mvc 5 understand the parametered constructor
The basic way that it works is that you ask the IoC container for a type ("resolve") and it will use reflection to look for the constructor (for Unity, the one with the most arguments if they are multiple constructors). It will then repeat the process for each of the argument types themselves, like a tree all the way down the dependency graph. Unity will be able to create instances of concrete types automatically but if the constructor uses an interface or abstract type then it needs to know which implementation to use so in these cases, you need to register the type beforehand:
Register:
e.g. container.RegisterType<IUserHelper, UserHelper>();
Resolve:
e.g. container.Resolve<IUserHelper>();
IOC containers do not work with MVC out of the box but extra libraries exist such as Unity.MVC5 which hook into the MVC pipeline so when MVC tries to create a controller, it uses the IoC container instead of newing up the controller directly (which would fail unless it is parameterless).
Here is an example:
public class MyController(IUserHelper userHelper, IRepository repository) : Controller
Then we could have:
public class MyRepository(IDbContext dbContext) : IRepository
and
public class MyDbContext () : IDbContext
If we use RegisterType to register the IUserHelper, IRepository and IDbContext then when MVC needs to create the controller, it will be able to build the controller complete with all the dependencies.
If I try to use the Message History bean from Spring Integration "int:message-history" when developing a Spring XD module, it fails when try to export the JMX bean.
I've seen that the naming strategy used is org.springframework.xd.dirt.module.jmx.ModuleObjectNamingStrategy
I already open a ticket for that https://jira.spring.io/browse/XD-3748
Is there any workaround for that? Like explicitly use another MBeanExporter and add a different name for the bean?
It's a bug in the ModuleObjectNamingStrategy; I'll see if I can come up with a work-around.
Thanks Gary, for now I have implemented other class like the ModuleObjectNamingStrategy and changed the mbean-exporters.xml to use that one if the bean is the messageHistoryConfigurer I create the ObjectName instance like:
String name = domain +":name=messageHistoryConfigurer";
ObjectName originalName = new ObjectName(name);
I'm currently writing a library where I want the user of my library to implement an interface. From within my library I'm calling this implementation.
I'm using ServiceLoader to instantiate the implementation provided by the integrator and it works just fine. The integrator calls a start() method in my library and in the end he gets something in return. The implementation is used to give me some things along the way that I need in order to get to the final result.
(I'm deliberately not using CDI or any other DI container 'cause I want to create a library that can be used anywhere. In a desktop application, a spring application an application using guice...)
Now I'm facing a problem. I'm creating a showcase in which I'm using my own library. It's a webapplication where I'm using jsf and CDI. When I instantiate the implementation provided in said webapp from within my library, I'm dealing with a non-container managed object. But since this implementation needs to use container managed objects I'm kinda screwed since this can never work.
Example:
Interface in lib:
public interface Example{
public abstract String getInfo();
}
Implementation in war:
public class ExampleImpl implements Example{
#Inject
private ManagedBean bean;
public String getInfo(){
return bean.getSomethingThatReturnsString();
}
}
As you can see this is a huge problem in the way my library is build since the bean will always be null... This means no one using a DI container can use my library. I know I can get the managedbean by doing a FacesContext lookup and get the managedbean but more importantly, my library isn't very well designed if you think about it.
So to conclude my question(s):
Is there any way I can make the serviceloader use a DI container to instantiate the class?
Anyone who knows a better way to fix my problem?
Anyone who knows a better way to get the things I need without making the integrator implement an interface but I can get information from the integrator?
I know this is a quite abstract question but I'm kinda stuck on this one.
Thanks in advance
As the implementation of Example is not performed within the CDI container the injection doesn't happen. What you can do is to lookup the bean manually using the BeanManager. According to the docs, the BeanManager is bound to the jndi name java:comp/BeanManager. Using the following code you can get the BeanManager within your implementation class and lookup the dependencies manually:
InitialContext context = new InitialContext();
BeanManager beanManager = (BeanManager) context.lookup("java:comp/BeanManager");
Set<Bean<?>> beans = beanManager.getBeans(YourBean.class, new AnnotationLiteral<Default>() {});
Bean<YourBean> provider = (Bean<YourBean>) beans.iterator().next();
CreationalContext<YourBean> cc = beanManager.createCreationalContext(provider);
YourBean yourBean = (YourBean) beanManager.getReference(provider, YourBean.class, cc);
where YourBean is the dependency you are looking for.
I'm having serious issues trying to send share custom objects between portlets in liferay. I have a Hook Plugin, with a servlet filter, which loads an object of Type MyCustomClass and inserts it into the request object as a parameter.
When i try to read this object in a portlet's render() i get a ClassCastException, though i am casting the object to the same class.
I understand that liferay plugins have different contexts, and i already tried to change the classloader before loading the object in the bean and portlet like this:
ClassLoader portalcl = PortalClassLoaderUtil.getClassLoader();
ClassLoader currentcl = Thread.currentThread().getContextClassLoader();
Thread.currentThread().setContextClassLoader(portalcl);
//do my stuff
Thread.currentThread().setContextClassLoader(currentcl);
however, it did not solved the problem, and the only way i found to solve the problem is to serialize the object into a json string, and deserialize it whenever i need it.
Isn't this kinda lame ? Does anyone know a better solution ?
Regards, DS
It sounds like the main problem you're seeing is that two different class loaders are loading the class which techncally makes them different classes (which it seems like you've already determined).
I haven't used LifeRay much but this has been a problem I've seen on other platforms as well. We were using WebSphere and solved this problem by putting the common MyCustomClass into a shared library that was on the server classpath. This way the server will load the class and make it available to all applications on the server through the server's single classloader. If you let each application load the class then you'll keep seeing this exception.
I installed Entity Framework 5.0 RC for Framework 4.0 in my project. But when I try to get data from Views I get error. EF tries creating table for this entity.
Use this on your application startup to turn off database initialization and migrations:
Database.SetInitializer<YourContextType>(null);
If you want to turn off database initialization/migration completely regardless of in which project you're using your Context you can add a static constructor to your context to call the initializer.
This ensures that the SetInitializer will be called once prior to the first construction/use of your context.
public class YourContext : DbContext
{
static YourContext()
{
// don't let EF modify the database schema...
Database.SetInitializer<YourContext >(null);
}
public YourContext() : base("name=YourContext")
{}
...
}
However, if you only want to do this in a select few projects, you're better off doing it explicitly via application startup - e.g. during your normal IoC setup, like suggested by Ladislav.