[Solved] Given this Spring Boot code snippet, what will be printed when the application runs? @Component class A { public A() { System.out.println("A created"); } } @Component class B { public B(A a) { System.... | Spring Boot

Spring Boot - Inversion of Control and Dependency Injection

Given this Spring Boot code snippet, what will be printed when the application runs?

 @Component class A { public A() { System.out.println("A created"); } }
 @Component class B { public B(A a) { System.out.println("B created with " + a); } }

AOnly A created

BA created\nB created with A@<hashcode>

CB created with null\nA created

DCompilation error due to missing annotations

Step-by-Step Solution

Solution:

Step 1: Understand bean creation order
Spring creates bean A first, printing "A created". Then it creates B, injecting A, printing "B created with A@".
Step 2: Eliminate wrong outputs
B created with null\nA created is wrong because B cannot get null for A. Only A created misses B creation. Compilation error due to missing annotations is wrong; annotations are correct.
Final Answer:
A created\nB created with A@<hashcode> -> Option B
Quick Check:
Bean creation order = A then B with injected A [OK]

Quick Trick: Beans are created in dependency order, dependencies injected automatically [OK]

Common Mistakes:

Assuming dependencies are null during injection
Thinking beans are created in random order
Missing that constructor runs on bean creation

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More Spring Boot Quizzes

Given this Spring Boot code snippet, what will be printed when the application runs?

Step 1: Understand bean creation order

Step 2: Eliminate wrong outputs

Final Answer:

Quick Check:

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