Careeroza

Returning JSON

Return Objects, Get JSON

Return a Java object, a List or a Map and Jackson converts it to JSON automatically. Java records are ideal for API responses: short, immutable, and every component becomes a JSON field.

package com.shopease.product;

import java.math.BigDecimal;

public record Product(Long id, String name, String description,
                      BigDecimal price, int stock, String category) {}
@RestController
@RequestMapping("/api/products")
public class ProductController {

    private final List<Product> products = List.of(
        new Product(1L, "Boat Rockerz 450", "Wireless headphones", new BigDecimal("1499.00"), 25, "Electronics"),
        new Product(2L, "Clean Code", "Book by Robert C. Martin", new BigDecimal("599.00"), 40, "Books"));

    @GetMapping
    public List<Product> all() {
        return products;
    }
}

The Response

Example

curl -s http://localhost:8080/api/products

Example output

[
  {"id":1,"name":"Boat Rockerz 450","description":"Wireless headphones","price":1499.00,"stock":25,"category":"Electronics"},
  {"id":2,"name":"Clean Code","description":"Book by Robert C. Martin","price":599.00,"stock":40,"category":"Books"}
]
Java typeJSON
record / class with gettersobject { }
List, array, Setarray [ ]
Map<String, ?>object
String, numbers, boolean, nullJSON string, number, boolean, null
LocalDate / LocalDateTimeISO string, e.g. "2026-01-15"

Practice

Exercise: Add GET /api/products/in-stock that returns only products with stock greater than 0.

Show answer
@GetMapping("/in-stock")
public List<Product> inStock() {
    return products.stream()
            .filter(p -> p.stock() > 0)
            .toList();
}