Validation groups in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are validation groups in Spring Boot?

Validation groups let you organize validation rules into sets. You can apply different rules in different situations by specifying which group to use.

beginner

How do you define a validation group in Spring Boot?

You create an empty interface to mark a group. For example:

public interface CreateGroup {}

This interface is used to tag validation annotations.

intermediate

How do you apply a validation group to a constraint annotation?

Add the groups attribute to the annotation with the group interface. Example:

@NotNull(groups = CreateGroup.class)

This means the rule runs only when validating the CreateGroup.

intermediate

How do you trigger validation for a specific group in Spring Boot controller?

Use @Validated(GroupName.class) on the method parameter. Example:

public ResponseEntity create(@Validated(CreateGroup.class) @RequestBody User user)

This runs validations for CreateGroup only.

beginner

Why use validation groups instead of one big validation set?

Validation groups let you reuse the same object with different rules for different actions, like creating or updating. This keeps validations clear and avoids conflicts.

What is the purpose of validation groups in Spring Boot?

A To organize validation rules for different scenarios

B To disable validation completely

C To automatically fix validation errors

D To generate database tables

Validation groups help organize and apply different validation rules depending on the use case.

How do you mark a validation group in Spring Boot?

A By writing XML configuration

B By creating a class with methods

C By adding annotations to the main class

D By creating an empty interface

Validation groups are defined as empty interfaces used as markers.

Which annotation attribute specifies the validation group for a constraint?

A groups

B target

C scope

D category

The 'groups' attribute on constraint annotations defines which validation groups apply.

How do you activate validation for a specific group in a controller method parameter?

A @Valid

B @Validated(Group.class)

C @Autowired

D @RequestMapping

Use @Validated with the group class to trigger group-specific validation.

What happens if you don't specify a validation group when validating?

A All groups run

B No validations run

C Default group validations run

D Validation throws an error

If no group is specified, the default validation group is used.

Explain how validation groups help manage different validation rules in Spring Boot.

Think about how you might want different rules when adding or editing data.

Describe the steps to create and use a validation group for a 'Create' operation in Spring Boot.

Start from defining the group, then tagging constraints, then activating validation.

Practice

1. What is the main purpose of using validation groups in Spring Boot?

easy

A. To automatically generate validation error messages

B. To group multiple objects for batch validation

C. To disable validation temporarily

D. To apply different validation rules to the same object based on context

Solution

1. Step 1: Understand validation groups concept

   Validation groups allow applying different sets of validation rules to the same object depending on the situation.

2. Step 2: Compare with other options

   Grouping objects or disabling validation are not the purpose of validation groups. Generating messages is separate.

3. Final Answer:

   To apply different validation rules to the same object based on context -> Option D

4. Quick Check:

   Validation groups = Different rules per context [OK]

Hint: Validation groups separate rules by use case [OK]

Common Mistakes:

• Thinking groups batch multiple objects
• Assuming groups disable validation
• Confusing groups with error message generation

2. Which of the following is the correct way to define a validation group interface in Spring Boot?

easy

A. @Group public interface CreateGroup {}

B. public class CreateGroup {}

C. public interface CreateGroup {}

D. interface CreateGroup extends Validation {}

Solution

1. Step 1: Recall validation group definition

   Validation groups are defined as empty interfaces without annotations or inheritance.

2. Step 2: Analyze options

   public interface CreateGroup {} correctly defines an empty interface. public class CreateGroup {} uses class, which is incorrect. @Group public interface CreateGroup {} uses a non-existent annotation. interface CreateGroup extends Validation {} extends a non-required interface.

3. Final Answer:

   public interface CreateGroup {} -> Option C

4. Quick Check:

   Groups = empty interfaces [OK]

Hint: Groups are simple empty interfaces [OK]

Common Mistakes:

• Using classes instead of interfaces
• Adding unnecessary annotations
• Extending unrelated interfaces

3. Given the code snippet:

@NotNull(groups = CreateGroup.class)
private String name;

@NotNull(groups = UpdateGroup.class)
private String id;

What happens when you validate the object with @Validated(CreateGroup.class)?

medium

A. Only the id field is validated for not null

B. Only the name field is validated for not null

C. Both name and id fields are validated for not null

D. No fields are validated because groups are ignored

Solution

1. Step 1: Understand group-based validation

   When validating with CreateGroup.class, only constraints assigned to that group run.

2. Step 2: Check which fields have CreateGroup

   The name field has @NotNull(groups = CreateGroup.class), so it is validated. The id field belongs to UpdateGroup, so it is skipped.

3. Final Answer:

   Only the name field is validated for not null -> Option B

4. Quick Check:

   Validate CreateGroup = only name checked [OK]

Hint: Validate with group runs only matching group constraints [OK]

Common Mistakes:

• Assuming all fields validate regardless of group
• Confusing group names
• Ignoring group parameter in validation

4. Consider this validation setup:

@NotNull(groups = Default.class)
private String email;

@NotBlank(groups = AdminGroup.class)
private String role;

Why does validation fail to check email when validating with @Validated(AdminGroup.class)?

medium

A. Because email is in the Default group, not AdminGroup

B. Because @NotNull is ignored in groups

C. Because role is not validated

D. Because @Validated does not support groups

Solution

1. Step 1: Identify groups assigned to fields

   The email field uses the Default group, while role uses AdminGroup.

2. Step 2: Understand validation group filtering

   When validating with AdminGroup.class, only constraints in that group run. email is skipped because it belongs to Default.

3. Final Answer:

   Because email is in the Default group, not AdminGroup -> Option A

4. Quick Check:

   Validation group filters constraints [OK]

Hint: Default group constraints don't run if validating other groups [OK]

Common Mistakes:

• Assuming Default group always validates
• Thinking @NotNull ignores groups
• Believing @Validated ignores groups

5. You want to validate a user object differently when creating and updating. You have CreateGroup and UpdateGroup. How do you apply validation groups to a Spring Boot controller method to validate only the create rules?

hard

A. Use @Validated(CreateGroup.class) on the method parameter

B. Use @Valid without groups on the method parameter

C. Use @Validated without parameters on the method parameter

D. Use @Validated(UpdateGroup.class) on the method parameter

Solution

1. Step 1: Recall how to specify validation groups

   To validate with a specific group, use @Validated(GroupName.class) on the method parameter.

2. Step 2: Match group to desired validation

   For create rules, use CreateGroup.class. Using @Valid or @Validated without parameters runs default group only.

3. Final Answer:

   Use @Validated(CreateGroup.class) on the method parameter -> Option A

4. Quick Check:

   Specify group in @Validated to run that group's rules [OK]

Hint: Add group class to @Validated to run specific validations [OK]

Common Mistakes:

• Using @Valid which ignores groups
• Omitting group class in @Validated
• Using wrong group class for validation