ava Bean

 

✅ 1. What is a Java Bean (Simplified)

Think of a Java Bean like a container to hold data — for example: name, email, age, etc.

🎯 Rules for Java Bean:

1. It should have private variables

2. It should have public getters and setters

3. It should have a no-argument constructor

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🔧 Example: Customer Java Bean

java
public class Customer {
    private String name;   // private variable
    private int age;

    // No-argument constructor
    public Customer() {}

    // Getter
    public String getName() {
        return name;
    }

    // Setter
    public void setName(String name) {
        this.name = name;
    }

    // Getter
    public int getAge() {
        return age;
    }

    // Setter
    public void setAge(int age) {
        this.age = age;
    }
}

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💡 How do you use this Java Bean?

You can create an object and set/get values using the setters and getters:

java
Customer customer = new Customer();
customer.setName("Mitesh");
customer.setAge(30);

System.out.println(customer.getName());  // Output: Mitesh
System.out.println(customer.getAge());   // Output: 30

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✅ 2. What is a Spring Bean?

A Spring Bean is just a Java object that is created and managed by the Spring Framework.

Spring takes care of:

• Creating the object

• Injecting dependencies

• Managing the lifecycle

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🧪 Real Example with Spring Boot

📦 Step 1: Create a simple class

java
@Component  // Tells Spring to manage this class as a bean
public class HelloService {
    public String sayHello() {
        return "Hello from Spring Bean!";
    }
}

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🚀 Step 2: Use this bean in another class

java
@RestController
public class HelloController {

    private final HelloService helloService;

    // Spring injects HelloService automatically (this is called Dependency Injection)
    public HelloController(HelloService helloService) {
        this.helloService = helloService;
    }

    @GetMapping("/hello")
    public String hello() {
        return helloService.sayHello();
    }
}

📌 Now, when you run the Spring Boot app and open http://localhost:8080/hello, it shows:

csharp
Hello from Spring Bean!

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🧠 Summary

Concept	Purpose	Example
Java Bean	Holds data (like a data model)	Customer with get/set
Spring Bean	Object created and managed by Spring Framework	HelloService, @Component