Pointcut expressions in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to match all methods in the service package.

Spring Boot

execution(* com.example.service..*[1]*(..))

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

Aset

Bget

C*

Dfind

Attempts:

3 left

💡 Hint

Common Mistakes

Using a specific method name instead of a wildcard.

Omitting the wildcard causes no methods to match.

The * wildcard matches any method name in the specified package.

2fill in blank

medium

Complete the code to match all public methods in any class.

Spring Boot

execution(public [1] *(..))

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

AString

B*

Cint

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Specifying a return type limits matched methods.

Using a specific type misses other methods.

The * wildcard matches any return type, so all public methods are matched.

3fill in blank

hard

Fix the error in the pointcut to match all methods in classes ending with 'Controller'.

Spring Boot

execution(* *[1]Controller.*(..))

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

A*

B.

C..

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '.' matches only one character, not any prefix.

Using '..' is for packages, not class names.

The * wildcard matches any package or class prefix before 'Controller'.

4fill in blank

hard

Fill both blanks to match all methods in the repository package with any return type.

Spring Boot

execution([1] com.example.repository..[2]*(..))

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

A*

Bpublic

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using specific return types limits matches.

Using access modifiers restricts methods unnecessarily.

The first * matches any return type, and the second * matches any method name.

5fill in blank

hard

Fill all three blanks to match any public method in classes under service package with names starting with 'save'.

Spring Boot

execution([1] [2].service..[3]save*(..))

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

Apublic

Bcom.example

C*

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong access modifier restricts matches.

Incorrect package name causes no matches.

Missing wildcard before 'save' limits class matches.

public matches access modifier, com.example is the base package, and * matches any class name prefix before 'save'.

Practice

1. What does a pointcut expression in Spring Boot primarily do?

easy

A. Create new methods dynamically at runtime

B. Define the database connection settings

C. Select methods where extra code (advice) should run

D. Replace existing methods with new implementations

Solution

1. Step 1: Understand the purpose of pointcut expressions

   Pointcut expressions specify where additional code, called advice, should be applied in existing methods without changing those methods.

2. Step 2: Differentiate from other concepts

   They do not create or replace methods, nor configure databases. Their role is to select join points (methods) for advice.

3. Final Answer:

   Select methods where extra code (advice) should run -> Option C

4. Quick Check:

   Pointcut expression = Select methods for advice [OK]

Hint: Pointcuts pick methods to add code without changing them [OK]

Common Mistakes:

• Confusing pointcuts with method creation
• Thinking pointcuts configure databases
• Believing pointcuts replace method code

2. Which of the following is the correct syntax to match all methods in package com.example.service using a pointcut expression?

easy

A. execution(* com.example.service..*(..))

B. execution(com.example.service.*.*(..))

C. execution(* com.example.service.*(..))

D. execution(* com.example.service.*.*(..))

Solution

1. Step 1: Understand the execution syntax

   The syntax execution(* com.example.service.*.*(..)) matches any return type, any class in the package com.example.service, and any method with any parameters.

2. Step 2: Analyze other options

   execution(com.example.service.*.*(..)) misses the wildcard for return type. execution(* com.example.service..*(..)) uses double dot .. which matches subpackages, not just the package. execution(* com.example.service.*(..)) misses the class wildcard.

3. Final Answer:

   execution(* com.example.service.*.*(..)) -> Option D

4. Quick Check:

   Use * for any class and method in package [OK]

Hint: Use * for any class and method in a package [OK]

Common Mistakes:

• Omitting the return type wildcard *
• Using .. instead of * for classes
• Missing method wildcard *

3. Given the pointcut expression execution(public * com.example.repo.*Repository.find*(..)), which methods will it match?

medium

A. All methods named 'find' in any class in com.example.repo

B. All public methods starting with 'find' in any class ending with 'Repository' in package com.example.repo

C. All public methods in any class in com.example.repo

D. Only methods named exactly 'find' in any class ending with 'Repository'

Solution

1. Step 1: Break down the expression

   public * means any public return type, com.example.repo.*Repository matches classes ending with 'Repository' in the package, and find*(..) matches methods starting with 'find' with any parameters.

2. Step 2: Match options to expression meaning

   All public methods starting with 'find' in any class ending with 'Repository' in package com.example.repo correctly describes all public methods starting with 'find' in classes ending with 'Repository' in the package. Others are either too broad or too narrow.

3. Final Answer:

   All public methods starting with 'find' in any class ending with 'Repository' in package com.example.repo -> Option B

4. Quick Check:

   execution(public * com.example.repo.*Repository.find*(..)) = All public methods starting with 'find' in any class ending with 'Repository' in package com.example.repo [OK]

Hint: Look for wildcards * and method name patterns carefully [OK]

Common Mistakes:

• Ignoring method name prefix 'find*'
• Confusing class name pattern *Repository
• Missing public modifier effect

4. Identify the error in this pointcut expression: execution(* com.example..service.*(..)

medium

A. Missing closing parenthesis at the end

B. Incorrect use of double dots '..' in package name

C. Wildcard '*' cannot be used for method names

D. Return type '*' is invalid

Solution

1. Step 1: Check syntax completeness

   The expression is missing a closing parenthesis ')' at the end, which is required to close the execution() expression.

2. Step 2: Validate other parts

   Double dots '..' are valid to match subpackages, '*' is valid for method names, and '*' is valid for return type.

3. Final Answer:

   Missing closing parenthesis at the end -> Option A

4. Quick Check:

   Check parentheses balance in execution() [OK]

Hint: Count parentheses carefully in pointcut expressions [OK]

Common Mistakes:

• Forgetting closing parenthesis
• Misunderstanding '..' usage
• Thinking '*' is invalid for methods or return types

5. You want to create a pointcut expression that matches all methods in any class within com.app.service and its subpackages, but only methods that have exactly two parameters of any type. Which expression is correct?

hard

A. execution(* com.app.service..*.*(*, *))

B. execution(* com.app.service.*.*(..))

C. execution(* com.app.service..*.*(.., ..))

D. execution(* com.app.service..*.*(*))

Solution

1. Step 1: Understand package and subpackage matching

   com.app.service..* matches classes in the package and all subpackages.

2. Step 2: Match method parameters exactly

   (* , *) means exactly two parameters of any type. (..) means any number of parameters, so it's incorrect here.

3. Step 3: Analyze options

   execution(* com.app.service..*.*(*, *)) correctly matches all classes in package and subpackages with exactly two parameters. Others either match any number of parameters or wrong parameter counts.

4. Final Answer:

   execution(* com.app.service..*.*(*, *)) -> Option A

5. Quick Check:

   Use (*, *) for exactly two parameters [OK]

Hint: Use (*, *) to match exactly two parameters [OK]

Common Mistakes:

• Using (..) to match exact parameter count
• Confusing single * with .. for subpackages
• Missing commas between parameters