Custom query methods by naming convention in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method that finds users by their last name.

Spring Boot

List<User> findBy[1](String lastName);

Drag options to blanks, or click blank then click option'

ALastName

BAge

CId

DEmail

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase property names in method names.

Using unrelated property names.

The method name must include the property name 'LastName' to query by last name.

2fill in blank

medium

Complete the method name to find users older than a certain age.

Spring Boot

List<User> findByAge[1](int age);

Drag options to blanks, or click blank then click option'

AGreaterThan

BEquals

CContains

DStartsWith

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Equals' instead of 'GreaterThan' for comparison.

Using string-related keywords like 'Contains' for numeric fields.

The keyword 'GreaterThan' is used to find records with age greater than the given value.

3fill in blank

hard

Fix the error in the method name to find users by email ignoring case.

Spring Boot

User findByEmail[1](String email);

Drag options to blanks, or click blank then click option'

AStartsWith

BContains

CGreaterThan

DIgnoreCase

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Contains' or 'StartsWith' when case insensitivity is needed.

Omitting the case-insensitive keyword.

The correct keyword to ignore case sensitivity is 'IgnoreCase'.

4fill in blank

hard

Fill both blanks to find users by first name and last name.

Spring Boot

List<User> findBy[1]And[2](String firstName, String lastName);

Drag options to blanks, or click blank then click option'

AFirstName

BAge

CLastName

DEmail

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names.

Not capitalizing property names properly.

The method name must include both 'FirstName' and 'LastName' to query by these fields.

5fill in blank

hard

Fill all three blanks to find users by age greater than a value and email containing a string.

Spring Boot

List<User> findByAge[1]AndEmail[2][3](int age, String emailPart);

Drag options to blanks, or click blank then click option'

AGreaterThan

BContaining

CIgnoreCase

DStartsWith

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up keywords for numeric and string fields.

Forgetting to add 'IgnoreCase' for case insensitive search.

Use 'GreaterThan' for age comparison, 'Containing' for partial email match, and 'IgnoreCase' to ignore case in email.

Practice

1. What does a Spring Data JPA method named findByLastName do?

easy

A. Counts records where the lastName matches the given value

B. Deletes records where the lastName matches the given value

C. Checks if any record exists with the given lastName

D. Finds all records where the lastName matches the given value

Solution

1. Step 1: Understand the method prefix

   The prefix findBy in Spring Data JPA means it will search and return matching records.

2. Step 2: Analyze the property name

   The method uses LastName as the property to filter by, so it finds records with that lastName.

3. Final Answer:

   Finds all records where the lastName matches the given value -> Option D

4. Quick Check:

   findBy + property = find matching records [OK]

Hint: findBy means search and return matching records [OK]

Common Mistakes:

• Confusing findBy with deleteBy or countBy
• Thinking it returns a boolean instead of records
• Ignoring the property name after findBy

2. Which of the following is the correct syntax for a method that counts users by their age in Spring Data JPA?

easy

A. findCountByAge(int age);

B. countUsersByAge(int age);

C. countByAge(int age);

D. countAgeBy(int age);

Solution

1. Step 1: Identify the correct prefix for counting

   The correct prefix to count records is countBy.

2. Step 2: Check method naming pattern

   The method should be countByAge to count users filtered by age.

3. Final Answer:

   countByAge(int age); -> Option C

4. Quick Check:

   countBy + property = count matching records [OK]

Hint: Use countBy + property to count records [OK]

Common Mistakes:

• Adding extra words like Users in method name
• Using findCountBy which is invalid
• Placing property name after count instead of after By

3. Given the method existsByEmailAndStatus(String email, String status), what will it return if a user with email "[e-mail]" and status "active" exists?

medium

A. A list of users matching the email and status

B. true

C. false

D. The count of users matching the email and status

Solution

1. Step 1: Understand the method prefix

   The prefix existsBy returns a boolean indicating if any record matches the criteria.

2. Step 2: Analyze the condition

   The method checks if a user exists with the given email and status combined with And.

3. Final Answer:

   true -> Option B

4. Quick Check:

   existsBy + conditions returns boolean [OK]

Hint: existsBy returns true if matching record exists [OK]

Common Mistakes:

• Expecting a list instead of boolean
• Confusing existsBy with findBy
• Ignoring the combined conditions with And

4. Identify the error in this Spring Data JPA method declaration: List<User> findByNameOr(int age, String name);

medium

A. The method name is missing the property after 'Or'

B. The method should use 'And' instead of 'Or' for combining conditions

C. The order of parameters does not match the method name conditions

D. The return type should be boolean for 'findBy' methods

Solution

1. Step 1: Analyze the method name structure

   The method name uses 'Or' but does not specify the property after 'Or'. It should be like 'findByNameOrAge'.

2. Step 2: Check parameter order and names

   Parameters should match the properties in the method name order, but the main error is missing property after 'Or'.

3. Final Answer:

   The method name is missing the property after 'Or' -> Option A

4. Quick Check:

   Method names must specify property after 'Or' [OK]

Hint: After 'Or' or 'And', always specify property name [OK]

Common Mistakes:

• Leaving out property name after 'Or' or 'And'
• Mixing parameter order with method name order
• Using wrong return type for findBy methods

5. You want to create a method that finds all orders where the customer's city is "New York" and the order total is greater than 100. Which method name correctly follows Spring Data JPA naming conventions?

hard

A. findByCustomerCityAndOrderTotalGreaterThan(String city, double total);

B. findOrdersByCityAndTotalGreater(String city, double total);

C. findByCityAndOrderTotalGreaterThan(String city, double total);

D. findByCustomerCityAndOrderTotalGreater(String city, double total);

Solution

1. Step 1: Identify the correct property names

   The properties are nested: customer.city and orderTotal. The method name must reflect this exactly.

2. Step 2: Use correct keywords for comparison

   For 'greater than', the keyword is 'GreaterThan' in Spring Data JPA method names.

3. Step 3: Combine conditions with 'And'

   The method name should combine both conditions with 'And' and use full property paths.

4. Final Answer:

   findByCustomerCityAndOrderTotalGreaterThan(String city, double total); -> Option A

5. Quick Check:

   Use full property names + GreaterThan + And [OK]

Hint: Use full property names and 'GreaterThan' for > comparisons [OK]

Common Mistakes:

• Using incomplete property names
• Using 'Greater' instead of 'GreaterThan'
• Omitting 'By' after 'find'