[JAVA] About Spring DI related annotations

Types of Spring DI related annotations

Context Configuration Annotations   @Scope @Autowired @Resource @Inject @Required @Named @Order @PostConstruct @PreDestroy

@Scope

Generally, only one bean that automatically scans with @Component @Service @Repository is generated as a singleton, but you can use the @Scope annotation to change this. In other words, I will set the range of beans.

singleton-Return one bean per ʻIoC container prototype --Creates a new bean every time there is arequestand returns request-returns one bean perHTTP request object session-returns one bean perHTTP session object globalSession-Returns one bean forall sessions`  

Example

   @Component
   @Scope("prototype")
   Class Hoge { ... } 
   <bean id="hoge" class="aaa.java.bbb.ccc.hoge" scope="prototype" />

If you have Bean injected, you can use the following annotations.

@Autowired

Annotations belonging to Spring Framework Applies if the bean id or name matches. Type Driven Injection If some beans are searched, they are distinguished by the @Qualifier (name =" hoge ") annotation. Beans are basically injected for all attributes that are @Autowired.   --Applicable places: member variables, setter methods, constructs, general methods

@Resource

Annotations that can be used in Spring 2.5 and above and do not belong to the Spring Framework Find the bean that is injected by bean name. To use it, add jsr250-api.jar from the JSR.250 library to your classpath.   --Applicable places: member variables, setter methods

Maven settings

<dependency>
      <groupId>javax.annotation</groupId>
      <artifactId>jsr250-api</artifactId>
      <version>1.0</version>
</dependency>

@Inject

It can be used with Spring 3.0 or higher. It is recommended to use @Inject to configure apps that do not belong to a particular framework. To use it, add javax.inject-x.x.x.jar from the JSR.330 library to your classpath.   --Applicable places: member variables, setter methods, constructs, general methods

Maven settings

<dependency>
      <groupId>javax.inject</groupId>
      <artifactId>javax.inject</artifactId>
      <version>1</version>
</dependency>

@Required

It is used to write on the Setter method and set required properties. To use it, you can register the RequiredannotationBeanPostProcessor class as a bean or add the <context.annotation-config> setting.

Example

   package day1;
   public class Emp {
   private String ename;
   @Requried
   public void setEname( String ename ) { this.ename = ename; }
   public String getName() { return this.ename; }
   }

Beans.xml

<bean id="emp" class="day1.Emp" >
  <!--Error if the following properties are not set-->
  <!-- <property ename="ename" value="hoge" /> -->
</bean>

main()

   ApplicationContext ctx = new ClassPathXmlApplicationContext("Beans.xml");
   Emp emp = (Student) ctx.getBean("emp");
   System.out.println("Ename : " + emp.getEname());

When I run it, I get the following error:

>

#### **`Error`**
```ruby

   Property 'ename' is required for bean 'emp'

I'm a little tired@Named @Order @About PostConstruct tomorrow ...