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Understanding API Parameters in Spring Boot

Understanding API Parameters in Spring Boot

When designing APIs in Spring Boot, it's essential to understand how to handle different types of parameters. These parameters define how data is sent from the client to the server. Let's break down the common types of parameters used in API development, with examples and cURL commands.

1. Types of Parameters

Parameter Type Location Use Case Example Format Annotation in Spring Boot
Query Param URL after `?` Filtering, Pagination ?key=value @RequestParam
Path Param In the URL path Identifying specific resource /resource/{id} @PathVariable
Form Param Form-encoded body Simple form submissions key=value @RequestParam
Request Body JSON or raw data in body Complex objects or large payloads JSON or XML @RequestBody

2. Examples

1. Query Parameters


@GetMapping("/api/products")
public ResponseEntity<List<Product>> getProducts(@RequestParam String category) {
    return ResponseEntity.ok(productService.getProducts(category));
}

cURL:

curl -X GET "http://localhost:8080/api/products?category=electronics"

2. Path Parameters


@GetMapping("/api/products/{id}")
public ResponseEntity<Product> getProductById(@PathVariable Long id) {
    return ResponseEntity.ok(productService.getProductById(id));
}

cURL:

curl -X GET "http://localhost:8080/api/products/123"

3. Form Parameters


@PostMapping("/api/products")
public ResponseEntity<Product> createProduct(@RequestParam String name, @RequestParam double price) {
    return ResponseEntity.ok(productService.createProduct(name, price));
}

cURL:

curl -X POST "http://localhost:8080/api/products" -d "name=phone&price=50000"

4. Request Body (JSON)


@PostMapping("/api/products")
public ResponseEntity<Product> createProduct(@RequestBody Product product) {
    return ResponseEntity.ok(productService.createProduct(product));
}

cURL:

curl -X POST "http://localhost:8080/api/products" -H "Content-Type: application/json" -d '{"name":"phone","price":50000}'

Conclusion

Understanding how to handle query, path, form, and body parameters is essential for building robust APIs in Spring Boot. By selecting the right parameter type for the right scenario, you can create efficient, scalable, and well-structured applications.

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