The spring can be used to resolve collaborators automatically by inspecting contents of the ApplicationContext.
The Autowiring has the following advantages in spring:
1. Reduces requirement for specifying properties or construction arguments.
2. Updates configuration while evolving of objects. To understand this lets consider an example: modifying would not be required in configuration of a dependency while adding it to a class.
3. Switching to explicit wiring when code base is stable can be neglected.
List the limitations of auto wiring.
Autowiring has the following limitations :
1. Overriding and auto wiring are caused due to dependency in property and constructor argument setting.
2. Less precise as compared to explicit wiring.
3. Tools that generate documentation using a spring might not have access to wiring information.
4. There is a possibility of clash between bean definitions and argument or method to be wired.
5. The problem does not occur much in case of maps, arrays and collection and cannot be resolved randomly for dependencies which expect one value.
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| Oracle Spring MVC Recently Asked Interview Questions Answers |
In scenarios where you have to avoid using auto wiring, what are the other options that can be explored to achieve the same?
In scenarios where using autowiring is prohibited, the following replacements can achive the same :
1. Abandon autowiring for favor of explicit wiring.
2. Avoid autowiring for a bean definition by setting the autowire-candidate for attributes to false as
described in the next section.
3. Set a single bean definition as the primary candidate by setting the primary attribute of its <bean/> element to true.
4. When Java 5 or later is used, implementation needs more fine-grained control available with annotation-based configuration.
How do you call the multiple life cycle mechanisms configured for the same bean?
Multiple lifecycle mechanisms which are configured for the same bean, with different initialization methods, are called by the following ways :
1. Methods annotated with use of @PostConstruct.
2. afterPropertiesSet() as stated by the InitializingBean callback interface.
3. Custom configuration init() method
Destroy methods are called in the same order as follows :
1. Methods annotated with the use of @PreDestroy.
2. destroy() as stated by the DisposableBean callback interface.
3. destroy() method with custom configuration.
What are the methods associated with the FactoryBean interface?
Following are the methods associated with factory bean interface:
1. Object getObject() : This returns an instance of the object which the factory creates. This instance can possibly be shared, depending on the factory returns singletons or prototypes.
2. Boolean isSingleton() : This returns true if this FactoryBean returns singletons, otherwise false.
3. Class getObjectType() : This returns the object type returned by the getObject() method or null if the type is unknown in advance.
What are the functionalities provided by the context package to enhance the BeanFactory functionality?
The functionalities provided by context package are as follows:
1. Message access in i18n-style, through the MessageSource interface.
2. Resource access such as URLs and files, through which, the ResourceLoader interface, can be accessed and used.
3. Publication of events, through the beans that allow, implementing the ApplicationListener interface. It is done through the use, of the ApplicationEventPublisher interface.
4. Multiple loading contexts, allowing each to be focused on one particular layer, such as the web layer of an application, through the HierarchicalBeanFactory interface.
How can you achieve Internationalization using MessageSource?
Internationnalization using message source can be achieved by the following :
1. String get Mesage(String code, Objct[] args, String default, Local loc) :
The basic method used for retrieving a message from the MessageSource. When no message is to be found for the specified locale, the default message is used.
2. String getMessage(String code, Objct[] args, Locale loc) :
Essentially the same as the last method, but with a difference, no default message is specified; if the message cannot be found, a NoSuchMessageException is shown.
3. String getMessage(MessageSourceResolvable resolvable, Local locale) :
Properties used for the preceding methods are also wrapped in a class named MessageSourceResolvable, which you can use with this method.
Enlist and explain the main methods associated with the Resource interface.
Methods associated with resource interface are as follows:
1. getInputStream() : It locates and opens the resource, returning an InputStream to read from the resource.
2. exists() : Returns a boolean which indicates whether this resource actually exists in physical form.
3. isOpen() : Returns a boolean which indicates whether this resource represents a handle with an open stream.
4. getDescription() : Returns a description for this resource, which is used for error output when working with the resource.
Give some examples where property editing is used in spring.
Following are the examples for property editing in spring :
1. Setting of properties on beans is done by using PropertyEditors. To mention java.lang.string as the value for a property of some bean you're declaring in XML file, Spring will use the ClassEditor to try resolving the parameter to a Class object.
2. Passing HTTP request parameters in Spring's MVC framework can be done using all kinds of PropertyEditors that can be manually bind in all subclasses of the CommandController.
Explain the main AOP concepts and terminology.
The main AOP concepts are as follows:
1. Aspect : A modularization of a concern that cuts through multiple classes.
2. Join point : It is a point during which the execution of a programming, such as the execution of method or handling of an exception.
3. Advice : An action taken by an aspect for a particular join point.
4. Point cut : A predicate that is matched to join points.
5. Introduction : Declaration of additional methods or fields on behalf of a type.
6. Target object : Object which is advised by one or more aspects.
7. AOP proxy : An object which is created by AOP framework for implementing the aspect contracts.
8. Weaving : Linking of aspects with other application types or objects to create an advised object.
What is Weaving in Spring?
Weaving is the process of linking aspect with other application types or object to create an advised object. This can be performed at compile time, runtime and load time. In spring framework weaving is performed at runtime.
What is AOP Proxy?
AOP proxy is an object to implement the aspect contracts (advice method executions and so on). The AOP proxy is object is created by the AOP framework. In spring framework AOP proxy is JDK dynamic proxy or CGLIB proxy.
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