Validation groups in Spring Boot - Step-by-Step Execution

Concept Flow - Validation groups

Define Validation Groups Interfaces

↓

Annotate Bean Fields with Groups

↓

Trigger Validation with Specific Group

↓

Validation Framework Checks Only That Group's Constraints

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Return Validation Result (Errors or Success)

Validation groups let you organize validation rules into sets and apply only the needed set when validating an object.

Execution Sample

Spring Boot

public interface CreateGroup {}
public interface UpdateGroup {}

public class User {
  @NotNull(groups = CreateGroup.class)
  private String name;
}

// Validate with CreateGroup

Defines two groups and applies @NotNull only when validating with CreateGroup.

Execution Table

Step	Action	Validation Group	Field Checked	Constraint	Result
1	Start validation	CreateGroup	name	@NotNull	Field 'name' must not be null
2	Field 'name' is null	CreateGroup	name	@NotNull	Validation fails
3	Start validation	UpdateGroup	name	@NotNull	Constraint not checked
4	Field 'name' is null	UpdateGroup	name	No constraint	Validation passes
5	End validation	-	-	-	Validation result returned

💡 Validation stops after checking constraints for the specified group only.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
validationGroup	-	CreateGroup	CreateGroup	UpdateGroup	UpdateGroup	-
field 'name'	null	null	null	null	null	null
validationResult	-	pending	fail	pending	pass	final result

Key Moments - 2 Insights

Why does validation fail with CreateGroup but pass with UpdateGroup when the field is null?

Because the @NotNull constraint is only applied to CreateGroup (see execution_table rows 1-4). UpdateGroup does not check this constraint.

Can multiple groups be validated at once?

Yes, you can specify multiple groups to validate, and all constraints in those groups will be checked.

Visual Quiz - 3 Questions

Look at the execution table, what is the validation result at Step 2 when validating with CreateGroup?

A Validation fails

B Constraint not checked

C Validation passes

D Validation pending

💡 Hint

Check the 'Result' column at Step 2 in the execution_table.

At which step does the validation framework skip the @NotNull constraint?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look for 'Constraint not checked' in the execution_table.

If the field 'name' was not null, how would the validation result change at Step 2?

A Validation would still fail

B Validation would pass

C Constraint would be ignored

D Validation would be pending

💡 Hint

Refer to the 'Constraint' and 'Result' columns in Step 2 of the execution_table.

Concept Snapshot

Validation groups let you assign constraints to named groups.
When validating, specify which group(s) to apply.
Only constraints in those groups run.
Useful to reuse the same bean with different rules.
Example: @NotNull(groups=CreateGroup.class) applies only when CreateGroup is validated.

Full Transcript

Validation groups in Spring Boot let you organize validation rules into sets called groups. You define interfaces as group names, then assign constraints to those groups on your bean fields. When you validate an object, you specify which group to use. The validation framework then checks only the constraints in that group. For example, a field might be @NotNull only for the CreateGroup, so if you validate with CreateGroup and the field is null, validation fails. But if you validate with UpdateGroup, that constraint is ignored and validation passes. This helps reuse the same bean with different validation rules depending on the context.

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