@PreAuthorize annotation in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

The @PreAuthorize annotation is used to check if a user has the required permissions before allowing access to a method. It helps secure methods by defining access rules using expressions.

beginner

How do you enable the use of @PreAuthorize annotations in a Spring Boot application?

You enable @PreAuthorize by adding @EnableMethodSecurity (or @EnableGlobalMethodSecurity(prePostEnabled = true) in older versions) to a configuration class. This activates method-level security checks.

intermediate

What kind of expressions can you use inside @PreAuthorize?

You can use Spring Expression Language (SpEL) expressions like hasRole('ADMIN'), hasAuthority('permission'), or complex logical expressions combining roles and permissions.

beginner

Example: What does @PreAuthorize("hasRole('ADMIN')") do?

It allows only users with the role ADMIN to access the annotated method. If the user lacks this role, access is denied before the method runs.

intermediate

Can @PreAuthorize check conditions based on method parameters?

Yes, @PreAuthorize can use method parameters in expressions, for example: @PreAuthorize("#userId == authentication.principal.id") to allow access only if the user ID matches the logged-in user.

What annotation must be added to enable @PreAuthorize in Spring Boot?

A <code>@EnableMethodSecurity</code>

B <code>@EnableWebSecurity</code>

C <code>@SpringBootApplication</code>

D <code>@ComponentScan</code>

@EnableMethodSecurity activates method-level security including @PreAuthorize.

Which expression checks if a user has the role 'USER' inside @PreAuthorize?

A hasRole('USER')

B hasAuthority('USER')

C isAuthenticated()

D permitAll()

hasRole('USER') checks if the user has the role named USER.

What happens if a user fails the @PreAuthorize check?

A Method runs but returns null

B Access is denied and method is not executed

C User is redirected automatically

D Method runs with limited permissions

If the @PreAuthorize condition is false, access is denied and the method does not run.

Can @PreAuthorize use method parameters in its expression?

A Only if parameters are primitive types

B No, it only checks user roles

C Yes, using parameter names with #

D Only in controller classes

You can reference method parameters by name with a # prefix inside @PreAuthorize.

Which of these is a valid @PreAuthorize expression?

A isAnonymous() or hasAuthority('USER')

B permitAll()

C allUsers()

D hasRole('ADMIN') and #id == authentication.principal.id

You can combine role checks and parameter checks with logical operators in @PreAuthorize.

Explain how the @PreAuthorize annotation secures a method in Spring Boot.

Think about how you stop someone from entering a room unless they have a key.

Describe how you would restrict a method to only allow access to users with a specific role and matching user ID parameter.

Combine role check and parameter check in one expression.

Practice

1. What is the main purpose of the @PreAuthorize annotation in Spring Boot?

easy

A. To inject dependencies into a method

B. To log method execution time automatically

C. To restrict access to methods based on user roles or permissions before execution

D. To handle exceptions thrown by a method

Solution

1. Step 1: Understand the role of @PreAuthorize

   This annotation is used to check if a user has the right role or permission before allowing method execution.

2. Step 2: Compare with other options

   Logging, dependency injection, and exception handling are unrelated to @PreAuthorize.

3. Final Answer:

   To restrict access to methods based on user roles or permissions before execution -> Option C

4. Quick Check:

   Access control = A [OK]

Hint: Remember: @PreAuthorize controls access before method runs [OK]

Common Mistakes:

• Confusing @PreAuthorize with logging or exception handling
• Thinking it injects dependencies
• Assuming it runs after method execution

2. Which of the following is the correct syntax to allow only users with role 'ADMIN' to access a method using @PreAuthorize?

easy

A. @PreAuthorize("denyAll()")

B. @PreAuthorize("hasRole('ADMIN')")

C. @PreAuthorize("permitAll()")

D. @PreAuthorize("hasAuthority('USER')")

Solution

1. Step 1: Identify the correct expression for role checking

   The expression hasRole('ADMIN') checks if the user has the 'ADMIN' role.

2. Step 2: Verify other options

   hasAuthority('USER') checks for a different role, permitAll() allows everyone, and denyAll() denies everyone.

3. Final Answer:

   @PreAuthorize("hasRole('ADMIN')") -> Option B

4. Quick Check:

   Role check syntax = D [OK]

Hint: Use hasRole('ROLE_NAME') to restrict by role [OK]

Common Mistakes:

• Using wrong role name or authority
• Confusing hasRole with hasAuthority
• Using permitAll() when restriction is needed

3. Given the method below, what will happen if a user with role 'USER' calls it?

@PreAuthorize("hasRole('ADMIN')")
public String adminOnly() {
    return "Welcome Admin";
}

medium

A. Access denied error is thrown before method runs

B. The method executes and returns 'Welcome Admin'

C. The method executes but returns null

D. The method executes and returns 'Welcome User'

Solution

1. Step 1: Understand the role restriction

   The method requires the user to have 'ADMIN' role to run.

2. Step 2: Check user role and effect

   User has 'USER' role, not 'ADMIN', so access is denied before method runs.

3. Final Answer:

   Access denied error is thrown before method runs -> Option A

4. Quick Check:

   Role mismatch causes denial = A [OK]

Hint: If role missing, @PreAuthorize blocks method [OK]

Common Mistakes:

• Assuming method runs anyway
• Thinking it returns null instead of error
• Confusing roles 'USER' and 'ADMIN'

4. Identify the error in this usage of @PreAuthorize:

@PreAuthorize("hasRole(ADMIN)")
public void secureMethod() { }

medium

A. Annotation should be @PostAuthorize instead

B. Method must return a value to use @PreAuthorize

C. No error, syntax is correct

D. Missing quotes around 'ADMIN' in hasRole expression

Solution

1. Step 1: Check syntax of hasRole expression

   The role name must be a string inside quotes: hasRole('ADMIN').

2. Step 2: Verify other options

   Return type is not required, @PreAuthorize is correct annotation, so no other errors.

3. Final Answer:

   Missing quotes around 'ADMIN' in hasRole expression -> Option D

4. Quick Check:

   Role names need quotes = C [OK]

Hint: Always put role names in quotes inside hasRole() [OK]

Common Mistakes:

• Omitting quotes around role names
• Confusing @PreAuthorize with @PostAuthorize
• Thinking method must return a value

5. How would you use @PreAuthorize to allow access only if the user has either 'ADMIN' role or 'MANAGER' authority?

hard

A. @PreAuthorize("hasRole('ADMIN') or hasAuthority('MANAGER')")

B. @PreAuthorize("hasRole('ADMIN') and hasAuthority('MANAGER')")

C. @PreAuthorize("hasRole('ADMIN')") @PreAuthorize("hasAuthority('MANAGER')")

D. @PreAuthorize("permitAll()")

Solution

1. Step 1: Understand logical operators in @PreAuthorize

   Use or to allow access if either condition is true.

2. Step 2: Analyze options

   @PreAuthorize("hasRole('ADMIN') or hasAuthority('MANAGER')") uses or correctly; @PreAuthorize("hasRole('ADMIN') and hasAuthority('MANAGER')") requires both roles which is stricter; @PreAuthorize("hasRole('ADMIN')") @PreAuthorize("hasAuthority('MANAGER')") is invalid to use two annotations; @PreAuthorize("permitAll()") allows everyone.

3. Final Answer:

   @PreAuthorize("hasRole('ADMIN') or hasAuthority('MANAGER')") -> Option A

4. Quick Check:

   Use 'or' for either role or authority = B [OK]

Hint: Combine roles with 'or' inside one @PreAuthorize [OK]

Common Mistakes:

• Using 'and' instead of 'or' when either role suffices
• Trying to stack multiple @PreAuthorize annotations
• Using permitAll() which allows everyone