I have UI object that wraps JPA entity and in constructor of that UI object I do lazy loading of some properties. In that same constructor I need to know what JsonView is currently active so I dont lazy load some fields that are not needed if say its the List view.
Is there way to find out from constructor what is current active JsonView at runtime. Or is there any other way to achieve what I described above.
My current plan
create custom serializer that during serialization will call setJsonView(Class jsonView) of the object that it serializes. All my objects that serialized will have to support that method. Inside that metid I can do lazy loading based on now known json view. Something like this:
public class JsonViewSerializer extends JsonSerializer<BaseSerializableEntity> {
#Override
public void serialize(BaseSerializableEntity value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
value.setJsonView(provider.getSerializationView());
// need to pass serialization to base class...
}
}
Currently active view is accessible via context object (SerializerProvider or DeserializationContext), using method getActiveView().
Related
I have a Dictionary that will be populated with data from the database at startup, with a method that takes the key as a parameter, and returns the value. How to make the dictionary publicly accessible to all controllers? After searching, I learned that I would need to use Dependency Injection, but I'm failing at implementing it. Any resource that can get me on track is highly appreciated.
There are many ways to implement your question with/without DI. One of which is to write a static class that will be filled upon app startup.
No dependency injection:
Declare a static class that contains your dictionary. By being static there would only be 1 instance on app start.
public static class StaticDictionary {
public Dictionary<string,int> MyDictionary {get;set;}
}
In your Startup.cs - Configure method, append your db context in the parameters.
public void Configure(..., YourDbContext dbContext)
In the Configure method again, append your code that fills the dictionary.
public void Configure(..., YourDbContext dbContext){
...
// no need to modify the code above this, just append the fill dictionary code
foreach(var item in dbContext.TableName.ToList()){
StaticDictionary.MyDictionary.Add(...);
}
}
In your controllers, you could access StaticDictionary without DI.
public IActionResult Index{
var something = StaticDictionary.MyDictionary["Something"];
return View();
}
I am using javassist library for modify class files.
I want to modify interface to abstract class
for example,
original :
public interface javax.servlet.Servlet {
public void init(ServletConfig config) throws ServletException;
}
modified :
public abstract javax.servlet.Servlet {
public void init(ServletConfig config) throws ServletException {
System.out.println(config.getServletContext().getServerInfo());
callMethod(); // this is implemented original method
}
}
How can i apply this solution like aop(before, after)?
I think the first problem with your approach is that when you try to modify your interface using Javassist you are attempting to redefine an interface that has been already loaded by the class loader.
One option might be to do a bit of classloader tricks: create a new classloader that doesn't have your existing interface loaded (parent is the system classloader) and have Javassist load through that (use aCtClass.toClass() method that takes a ClassLoader argument). However is not really something I would do since to manage properly more than one ClassLoader is not that easy.
There might be a better way to achieve your goal, and creating new classes might be a better design. You could create a new class that implements everything you need and then extends the required interface.
Moreover I suggest you to take also a look at dynamic proxies that could be an option as well. Their biggest advantage is that you don't need any 3rd party libraries to create them.
(or "Using LocationInterceptionAspect and IInstanceScopedAspect together")
Using Postsharp I'm trying to inject a property into a target class using 'IntroduceMember' and then using the 'OnGetValue' functionality of LocationInterceptionAspect dynamically give it a value on inspection.
Originally I thought that I'd need two separate aspects, one for the field injection and one for the location interception but managed to combine the two by implementing the IInstanceScopedAspect interface and inheriting from LocationInterceptionAspect.
The problem is that if I set a breakpoint I will see the property that's been injected, but if I set another breakpoint in the OnGetValue method (that gets fired for each property on the class) I can't see it...
Here's some sample code:
[Serializable]
class DALDecoratorWrapper : LocationInterceptionAspect, IInstanceScopedAspect
{
public override void OnGetValue(LocationInterceptionArgs args)
{
if (args.LocationName == "Type")
{
args.Value = "computed value here";
}
args.ProceedGetValue();
}
[IntroduceMember(OverrideAction = MemberOverrideAction.OverrideOrFail)]
public String Type { get; set; }
I was also hoping there was a better way of doing this than overriding OnGetValue as that's called for each getter where really I want to only target the getter of the property that's been injected
Cheers
I am developing a Windows Phone 7 app and am using the MVVM pattern. I have a need to pass a parameter to the contructor of the ViewModel for a page. All my datacontexts and binding are done in XAML. Through my research I've seen that I need to do so using a dependency injector such as NInject.
Here's a little detail on whats going on:
I have a page with a ListPicker that lists various tasks. Each task has a unique TaskID. When an item is selected I need to open another page that will show the selected Tasks detail. My ViewModel and binding is all done and works if I use a static TaskID in the ViewModel but of course I need to use a variable.
I've setup NInject in the project and the various classes needed such as ViewModelLocator and my NInjectModule as shown here:
public class LighthouseNInjectModule : NinjectModule
{
public override void Load()
{
this.Bind<TaskViewModel>().ToSelf().WithConstructorArgument("TaskID", 2690);
}
}
Note that I have hardcoded a TaskID here and using this code this value properly gets injected into my constructor. Of course, this is hardcoded and I need to get the TaskID for the selected ListPicker item. I know how to get the selected ID from the ListPicker but how do I make NInject aware of it so when my class constructor is run it will have the correct value?
Here is the basic definition of my ViewModel class showing use of the Injector attribute.
public class TaskViewModel : INotifyPropertyChanged
{
[Inject]
public TaskViewModel(int TaskID)
{
//run function to get data using TaskID
}
}
WithConstructorArgument has another oveload that accepts a lazy evaluated Func<Context, object>.
I have looked at the Dozer's FAQs and docs, including the SourceForge forum, but I didn't see any good tutorial or even a simple example on how to implement a custom BeanFactory.
Everyone says, "Just implement a BeanFactory". How exactly do you implement it?
I've Googled and all I see are just jars and sources of jars.
Here is one of my BeanFactories, I hope it helps to explain the common pattern:
public class LineBeanFactory implements BeanFactory {
#Override
public Object createBean(final Object source, final Class<?> sourceClass, final String targetBeanId) {
final LineDto dto = (LineDto) source;
return new Line(dto.getCode(), dto.getElectrified(), dto.getName());
}
}
And the corresponding XML mapping:
<mapping>
<class-a bean-factory="com.floyd.nav.web.ws.mapping.dozer.LineBeanFactory">com.floyd.nav.core.model.Line</class-a>
<class-b>com.floyd.nav.web.contract.dto.LineDto</class-b>
</mapping>
This way I declare that when a new instance of Line is needed then it should create it with my BeanFactory. Here is a unit test, that can explain it:
#Test
public void Line_is_created_with_three_arg_constructor_from_LineDto() {
final LineDto dto = createTransientLineDto();
final Line line = (Line) this.lineBeanFactory.createBean(dto, LineDto.class, null);
assertEquals(dto.getCode(), line.getCode());
assertEquals(dto.getElectrified(), line.isElectrified());
assertEquals(dto.getName(), line.getName());
}
So Object source is the source bean that is mapped, Class sourceClass is the class of the source bean (I'm ignoring it, 'cause it will always be a LineDto instance). String targetBeanId is the ID of the destination bean (too ignored).
A custom bean factory is a class that has a method that creates a bean. There are two "flavours"
a) static create method
SomeBean x = SomeBeanFactory.createSomeBean();
b) instance create method
SomeBeanFactory sbf = new SomeBeanFactory();
SomeBean x = sbf.createSomeBean();
You would create a bean factory if creating and setting up your bean requires some tricky logic, like for example initial value of certain properties depend on external configuration file. A bean factory class allows you to centralize "knowledge" about how to create such a tricky bean. Other classes just call create method without worying how to correctly create such bean.
Here is an actual implementation. Obviously it does not make a lot of sense, since Dozer would do the same without the BeanFactory, but instead of just returning an object, you could initialized it somehow differently.
public class ComponentBeanFactory implements BeanFactory {
#Override
public Object createBean(Object source, Class<?> sourceClass,
String targetBeanId) {
return new ComponentDto();
}
}
Why do you need a BeanFactory anyways? Maybe that would help understanding your question.