Configuration Metadata

Where we declare beans and it's dependency.The container knows what to instantiate and configure using configuration metadata .

Three ways to Configuring Metadata

  1. XML

    • Beans and their dependencies are declared in an XML file (commonly config.xml orapplicationContext.xml).
    • Spring container reads the XML file and creates objects accordingly.

  2. Java annotations

    • Done by annotating classes, methods, or fields.
    • Use @Component,@Autowired
    • @Autowired – Most common annotation; tells the IoC container to inject dependencies.

  3. Java code

    • @Configuration – Marks a class as a source for bean definitions.
    • @Bean – Indicates that a method’s return object should be managed by the IoC container.

Spring XML DI Example - Project Procedure

class Student{
        int id
        String name
       }
  1. Create Maven Project : Set up project structure using Maven.
  2. Add Dependencies : Add Spring Core and Spring Context in pom.xml.
  3. Create Bean (Student.java) : Plain Old Java Object (POJO) with properties id and name.

  4. Create Configuration File (config.xml) :Define the student1 bean and set properties. 

        <bean id="student1" class="com.core.Student"> </bean>

  5. Setter Injection : Use setter methods in Student.java to inject id and name.

  6. Main Class :
    • Load Spring ApplicationContext.
    • Retrieve Student bean and use it.
       ApplicationContext container= new ClassPathXmlApplicationContext("Config.xml");
       Object obj =container.getBean("student1");
       Student s1=(Student)obj;

Key Points:

Bean : An object managed by the IOC container.

DI – Container injects dependencies.

IoC – DI is Spring’s way of implementing IoC.


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Github Code : Configuration Metadata