Spring Filter components in auto scanning
by In this Spring auto component scanning tutorial, you learn about how to make Spring auto scan your components. In this article, we show you how to do component filter in auto scanning process.
Category: Spring Framework
Spring Auto scanning components
Normally you declare all the beans or components in XML bean configuration file, so that Spring container can detect and register your beans or components. Actually, Spring is able to auto scan, detect and instantiate your beans from pre-defined project package, no more tedious beans declaration in in XML file. Following is a simple Spring project, including a customer service and dao layer. Let’s explore the different between declare components manually and auto components scanning in Spring.
Constructor injection type ambiguities in Spring
In Spring framework, when your class contains multiple constructors with same number of arguments, it will always cause the constructor injection argument type ambiguities issue. To fix it, you should always specify the exact data type for constructor, via type attribute. Note: It’s always a good practice to explicitly declared the data type for each constructor argument, to avoid constructor injection type ambiguities issue above.
Spring 3 and JSR-330 @Inject and @Named example
Since Spring 3.0, Spring supports for the standard JSR 330: Dependency Injection for Java. In Spring 3 application, you can uses standard: 1 – @Inject instead of Spring’s @Autowired to inject a bean, 2 – @Named instead of Spring’s @Component to declare a bean. Those JSR-330 standard annotations are scanned and retrieved the same way as Spring annotations, the integration just happened automatically, as long as the following jar in your classpath.
Spring DI via setter method
A simple Spring example to show you how to dependency inject a bean via setter method, the most common used DI method.
Spring Dependency Injection (DI)
In Spring frameowork, Dependency Injection (DI) design pattern is used to define the object dependencies between each other. It exits in two major types : 1 – Setter Injection – it will injects the dependency via a setter method, 2 – Constructor Injection – it will injects the dependency via a constructor.
[org.springframework.context.annotation.AnnotationConfigBeanDefinitionParser] are only available on JDK 1.5 and higher
Follow the Stackoverflow question about: Spring/Java error: namespace element ‘annotation-config’ … on JDK 1.5 and higher to find the solution for fixing the error: java.lang.IllegalStateException: Context namespace element ‘annotation-config’ and its parser class [org.springframework.context.annotation.AnnotationConfigBeanDefinitionParser] are only available on JDK 1.5 and higher
Spring DI via constructor
Uses Spring to dependency inject a bean via constructor. 1. IOutputGenerator An interface and implementation class of it. 2. Helper class A helper class, later …
Spring Autowiring @Qualifier example
In Spring, @Qualifier means, which bean is qualify to autowired on a field. When you have multiple similar beans are declared in bean configuration file, will Spring know which particular bean should autowired? To fix above problem, you need @Quanlifier to tell Spring about which bean should autowired.
Spring Auto-Wiring Beans with @Autowired annotation
In last Spring auto-wiring in XML example, it will autowired the matched property of any bean in current Spring container. In most cases, you may need autowired property in a particular bean only. In Spring, you can use @Autowired annotation to auto wire bean on the setter method, constructor or a field. Moreover, it can autowired property in a particular bean. Note: the @Autowired annotation is auto wire the bean by matching data type.