What is @PathVariable in Spring Boot?

@PathVariable is one of the most commonly used annotations in Spring Boot REST APIs.

It is used to:

• Read values from URL path
• Capture dynamic URL parameters
• Pass resource identifiers like IDs

It helps create clean and RESTful URLs.

Simple Definition

@PathVariable is used to extract values from URL path and bind them to method parameters.

@PathVariable = Reads dynamic values from URL path.

Why is @PathVariable Needed?

In REST APIs, resources are identified using URLs.

Example:

/api/courses/1

Here:

• 1 is dynamic value
• Represents course ID

@PathVariable extracts this value automatically.

Basic Example

@GetMapping("/courses/{id}")
public Course getCourse(
        @PathVariable Long id) {

    return courseService.getById(id);
}

If request is:

GET /courses/10

Then:

id = 10

Spring automatically maps URL value to method parameter.

Real-Time Example

Suppose we are developing Dhanish Empower.

Frontend wants course details.

Frontend sends:

GET /api/courses/5

Here:

• 5 is course ID
• @PathVariable captures it

How @PathVariable Works Internally

1. Client sends HTTP request.
2. Spring matches URL pattern.
3. Dynamic value is extracted.
4. Value is converted into required datatype.
5. Method parameter receives value.

Internal Flow Diagram

Client Request
        ↓
URL Pattern Matching
        ↓
@PathVariable Extraction
        ↓
Datatype Conversion
        ↓
Controller Method

URL Mapping Example

@GetMapping("/users/{id}")

URL:

/users/100

Extracted Value:

id = 100

Example with Multiple Path Variables

@GetMapping("/users/{userId}/orders/{orderId}")
public String getOrder(
        @PathVariable Long userId,
        @PathVariable Long orderId) {

    return "User: " + userId
            + ", Order: " + orderId;
}

Request:

/users/10/orders/200

Result:

userId = 10
orderId = 200

Custom Variable Name Example

@GetMapping("/courses/{courseId}")
public Course getCourse(
        @PathVariable("courseId") Long id) {

    return courseService.getById(id);
}

Here:

• URL variable = courseId
• Method parameter = id

Supported Datatypes

@PathVariable supports:

• String
• Long
• Integer
• UUID
• Custom datatypes

@PathVariable with PUT Example

@PutMapping("/courses/{id}")
public Course updateCourse(
        @PathVariable Long id,
        @RequestBody Course course) {

    return courseService.update(id, course);
}

Here:

• @PathVariable reads ID
• @RequestBody reads JSON data

@PathVariable vs @RequestParam

@PathVariable vs @RequestBody

REST API Design Best Practice

Use resource IDs in path variables:

/api/courses/1

instead of:

/api/getCourse?id=1

because path variables create cleaner RESTful URLs.

Common Errors

1. Variable Name Mismatch

@GetMapping("/courses/{id}")
public Course getCourse(
        @PathVariable Long courseId)

Error occurs because:

• URL variable = id
• Method parameter = courseId

Fix:

@PathVariable("id") Long courseId

2. Invalid Datatype

Example:

/courses/abc

when expecting:

Long id

causes datatype conversion error.

Advantages of @PathVariable

• Creates clean RESTful URLs
• Easy resource identification
• Improves API readability
• Simplifies URL handling
• Supports dynamic URLs
• Improves frontend-backend communication

Production-Level Importance

@PathVariable is heavily used in:

• REST APIs
• Microservices
• Banking systems
• E-commerce platforms
• Cloud-native applications

Almost every enterprise REST API uses path variables.

Interview Answer

@PathVariable is used in Spring Boot to extract values from URL paths and bind them to method parameters.

It is commonly used to identify resources such as IDs.

Example:

/api/courses/1

where 1 is extracted using @PathVariable.

Short Interview Answer

@PathVariable extracts dynamic values from URL path.

Frequently Asked Questions

What is the purpose of @PathVariable?

To read dynamic values from URL paths.

Can multiple path variables be used?

Yes.

Which HTTP methods commonly use @PathVariable?

GET, PUT, DELETE.

What is difference between @PathVariable and @RequestParam?

@PathVariable reads URL path values, while @RequestParam reads query parameters.

Can @PathVariable work with different datatypes?

Yes, Spring automatically converts datatypes.

Conclusion

@PathVariable is one of the most important annotations in Spring Boot REST API development.

It helps create clean RESTful URLs, improves API readability, and simplifies resource identification.

It is widely used in enterprise applications, microservices, and cloud-native systems.