@RequestMapping for base paths in Spring Boot - Mini Project: Build & Apply

Using @RequestMapping for Base Paths in Spring Boot

📖 Scenario: You are building a simple Spring Boot web application that manages greetings. You want to organize your controller so that all greeting-related URLs start with the same base path.

🎯 Goal: Create a Spring Boot controller class with a base path using @RequestMapping at the class level, and add methods to handle specific greeting requests under that base path.

📋 What You'll Learn

Create a controller class named GreetingController

Use @RequestMapping at the class level with the base path /greetings

Add a method hello() mapped to /hello that returns the string Hello, World!

Add a method goodbye() mapped to /goodbye that returns the string Goodbye, World!

💡 Why This Matters

🌍 Real World

Organizing controller URLs with base paths helps keep your web application routes clean and easy to manage.

💼 Career

Understanding how to use @RequestMapping for base paths is essential for building REST APIs and web applications in Spring Boot, a common skill for Java backend developers.

1

Create the GreetingController class

Create a public class named GreetingController annotated with @RestController.

Spring Boot

@RestController
// Your code here

Hint

Use @RestController to make the class a REST controller.

2

Add @RequestMapping base path to the class

Add @RequestMapping("/greetings") annotation to the GreetingController class to set the base path for all methods.

Spring Boot

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;

@RestController
// Add @RequestMapping with base path "/greetings" here
public class GreetingController {

}

Hint

Place @RequestMapping("/greetings") above the class declaration.

3

Add hello() method mapped to /hello

Inside GreetingController, add a public method named hello annotated with @RequestMapping("/hello") that returns the string Hello, World!.

Spring Boot

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;

@RestController
@RequestMapping("/greetings")
public class GreetingController {
    // Add hello() method with @RequestMapping("/hello") here
}

Hint

Use @RequestMapping("/hello") above the method and return the exact string.

4

Add goodbye() method mapped to /goodbye

Add a public method named goodbye annotated with @RequestMapping("/goodbye") that returns the string Goodbye, World! inside GreetingController.

Spring Boot

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;

@RestController
@RequestMapping("/greetings")
public class GreetingController {

    @RequestMapping("/hello")
    public String hello() {
        return "Hello, World!";
    }

    // Add goodbye() method with @RequestMapping("/goodbye") here
}

Hint

Use @RequestMapping("/goodbye") above the method and return the exact string.

Practice

1. What does placing @RequestMapping("/api") on a Spring Boot controller class do?

easy

A. Automatically maps all methods to the root URL /.

B. Defines the HTTP method type for all requests in the class.

C. Sets a base URL path for all request methods inside the class.

D. Disables URL mapping for the controller.

Solution

1. Step 1: Understand class-level @RequestMapping

   When @RequestMapping is placed on a controller class, it sets a base URL path prefix for all methods inside.

2. Step 2: Effect on method-level mappings

   Each method's path is appended to this base path, organizing URLs under a common root.

3. Final Answer:

   Sets a base URL path for all request methods inside the class. -> Option C

4. Quick Check:

   Class-level @RequestMapping sets base path = A [OK]

Hint: Class-level @RequestMapping sets base path prefix [OK]

Common Mistakes:

• Confusing base path with HTTP method type
• Thinking it maps all methods to root path
• Assuming it disables mapping

2. Which of the following is the correct way to set a base path /users for a Spring Boot controller using @RequestMapping?

easy

A. @RequestMapping("/users") on each method only

B. @RequestMapping(path = "/users") on the class

C. @RequestMapping(method = "users") on the class

D. @RequestMapping(basePath = "/users") on the class

Solution

1. Step 1: Check correct syntax for base path

   The correct attribute to set the path is path or directly the value in @RequestMapping. Using @RequestMapping(path = "/users") is valid and clear.

2. Step 2: Validate other options

   @RequestMapping("/users") on each method only sets path only on methods, not base path. @RequestMapping(method = "users") on the class incorrectly uses method attribute for path. @RequestMapping(basePath = "/users") on the class uses a non-existent attribute basePath.

3. Final Answer:

   @RequestMapping(path = "/users") on the class -> Option B

4. Quick Check:

   Use path attribute with leading slash [OK]

Hint: Use path="/yourBase" with leading slash on class [OK]

Common Mistakes:

• Using wrong attribute like method= for path
• Using wrong attribute name like basePath
• Setting base path only on methods

3. Given the controller class below, what is the full URL path to access the getUser() method?

@RequestMapping("/api")
public class UserController {
  @RequestMapping("/user")
  public String getUser() { return "user"; }
}

medium

A. /user

B. /user/api

C. /api

D. /api/user

Solution

1. Step 1: Identify class-level base path

   The class has @RequestMapping("/api"), so all method paths start with /api.

2. Step 2: Append method-level path

   The method getUser() has @RequestMapping("/user"), so the full path is /api + /user = /api/user.

3. Final Answer:

   /api/user -> Option D

4. Quick Check:

   Base path + method path = full URL [OK]

Hint: Combine class and method paths with slashes [OK]

Common Mistakes:

• Ignoring class-level path
• Mixing order of paths
• Missing leading slash

4. What is wrong with this controller code?

@RequestMapping("api")
public class ProductController {
  @RequestMapping("/list")
  public String listProducts() { return "products"; }
}

medium

A. Class must be annotated with @RestController or @Controller.

B. Missing leading slash in class-level @RequestMapping path.

C. Method-level @RequestMapping cannot have a path.

D. Method must return ResponseEntity, not String.

Solution

1. Step 1: Identify missing controller annotation

   The class is missing @Controller or @RestController. Without it, the class is not registered as a handler despite having @RequestMapping.

2. Step 2: Validate other options

   Method-level paths are allowed. Leading slash is optional (Spring prepends it). Returning String is valid for view names or with @ResponseBody.

3. Final Answer:

   Class must be annotated with @RestController or @Controller. -> Option A

4. Quick Check:

   Controller annotation required [OK]

Hint: Use @RestController or @Controller on controller classes [OK]

Common Mistakes:

• Missing @RestController or @Controller annotation
• Thinking method paths are disallowed
• Confusing @Controller with @RestController requirement

5. You want all endpoints in your controller to start with /shop, and inside you have a method mapped to /items. Which of these setups correctly maps the full URL /shop/items and why?

Option A:
@RequestMapping("/shop")
public class ShopController {
  @RequestMapping("/items")
  public String getItems() { return "items"; }
}

Option B:
@RequestMapping("/shop/items")
public class ShopController {
  @RequestMapping
  public String getItems() { return "items"; }
}

Option C:
@RequestMapping
public class ShopController {
  @RequestMapping("/shop/items")
  public String getItems() { return "items"; }
}

Option D:
@RequestMapping(shop)
public class ShopController {
  @RequestMapping(items)
  public String getItems() { return "items"; }
}

hard

A. Option A correctly sets base path and method path with leading slashes.

B. Option B sets full path on class, method has no path, works fine.

C. Option C sets full path on method only, class has no base path.

D. Option D misses leading slashes, so paths are invalid.

Solution

1. Step 1: Identify the correct configuration

   The setup with class-level @RequestMapping("/shop") and method-level @RequestMapping("/items") combines to /shop/items with full syntax validity (parentheses, quotes, leading slashes).

2. Step 2: Examine incorrect configurations

   The full class path setup lacks parentheses on method @RequestMapping (syntax error). The full method path setup lacks parentheses on class @RequestMapping (syntax error). The no-slash setup lacks quotes on shop and items (syntax error).

3. Final Answer:

   Option A correctly sets base path and method path with leading slashes. -> Option A

4. Quick Check:

   Base path + method path + valid syntax = full URL [OK]

Hint: Use leading slashes on class and method paths for clarity [OK]

Common Mistakes:

• Missing parentheses in @RequestMapping
• Missing quotes around path values
• Omitting leading slashes on paths