@RequestMapping for base paths in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @RequestMapping annotation in Spring Boot?

@RequestMapping is used to map web requests to specific handler classes or methods in Spring Boot. It defines the URL path and HTTP method that a controller or method will respond to.

beginner

How does <code>@RequestMapping</code> work when placed on a class level?

When @RequestMapping is placed on a class, it sets a base path for all the methods inside that class. Each method's path is appended to this base path.

beginner

Example: What URL will the method respond to if the class has <code>@RequestMapping("/api")</code> and the method has <code>@RequestMapping("/users")</code>?

The method will respond to requests at /api/users. The class-level path /api is combined with the method-level path /users.

intermediate

Can @RequestMapping specify HTTP methods? How?

Yes. You can specify HTTP methods like GET, POST, etc., using the method attribute, for example: @RequestMapping(value = "/path", method = RequestMethod.GET).

beginner

What happens if you omit the path in <code>@RequestMapping</code> at the class level?

<p>If omitted, the class does not set a base path, so method-level paths are treated as absolute from the root context.</p>

What does @RequestMapping("/app") on a class do?

A Sets a base URL path for all methods in the class

B Maps only GET requests to the class

C Defines a response type for the class

D Disables all mappings in the class

Class-level @RequestMapping sets a base path for all methods inside the class.

If a method has @RequestMapping("/list") and the class has @RequestMapping("/api"), what is the full path?

A /api

B /list

C /api/list

D /list/api

The method path is appended to the class base path, resulting in /api/list.

How do you specify that a method should only handle POST requests with @RequestMapping?

A httpMethod = POST

B method = "POST"

C type = POST

D method = RequestMethod.POST

Use method = RequestMethod.POST inside @RequestMapping to specify POST requests.

What happens if no @RequestMapping is on the class but methods have paths?

A Methods do not respond to any requests

B Methods respond at root-level paths

C Class path defaults to "/default"

D Application throws an error

Without a class-level path, method paths are absolute from the root.

Which annotation is a shortcut for @RequestMapping with GET method?

A @GetMapping

B @PostMapping

C @PutMapping

D @DeleteMapping

@GetMapping is a shortcut for @RequestMapping(method = RequestMethod.GET).

Explain how @RequestMapping at the class level affects the URL paths of methods inside the class.

Think about how a street address works with a building and apartment number.

Describe how to restrict a method to handle only POST requests using @RequestMapping.

Consider how a door might only open for certain visitors.

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