Controller CRUD

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Goal

Replace the beginner ItemController with a new one that delegates to ItemService and exposes three endpoints: GET /items, GET /items/{id}, and POST /items. After this page you can exercise all three with curl.

Prerequisites

• Service layer

Replace ItemController

Open src/main/java/com/example/itemsapi/ItemController.java and replace its contents:

package com.example.itemsapi;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import jakarta.validation.Valid;
import java.util.List;

@RestController
@RequestMapping("/items")
public class ItemController {

    private final ItemService service;

    public ItemController(ItemService service) {
        this.service = service;
    }

    @GetMapping
    public List<Item> list() {
        return service.list();
    }

    @GetMapping("/{id}")
    public Item get(@PathVariable Long id) {
        return service.get(id);
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Item create(@Valid @RequestBody Item item) {
        return service.create(item);
    }
}

Annotation breakdown:

Annotation	Effect
@RequestMapping("/items")	All methods in this class share the /items prefix
@GetMapping	Handles GET /items
@GetMapping("/{id}")	Handles GET /items/{id}; {id} is bound to the id parameter
@PathVariable Long id	Extracts the {id} segment and converts it to a Long
@PostMapping	Handles POST /items
@ResponseStatus(HttpStatus.CREATED)	Returns HTTP 201 on success instead of the default 200
@RequestBody Item item	Deserializes the JSON request body into an Item object
@Valid	Triggers Bean Validation on the item before the method body runs

Verify: run and test

Start the app:

./mvnw spring-boot:run

In a second terminal, exercise all three endpoints:

# GET /items — empty list on a fresh start
curl http://localhost:8080/items

[]

# POST /items — create an item
curl -X POST http://localhost:8080/items \
  -H 'Content-Type: application/json' \
  -d '{"name":"pen"}'

{"id":1,"name":"pen"}

# GET /items — list now includes the item
curl http://localhost:8080/items

[{"id":1,"name":"pen"}]

# GET /items/1 — retrieve by id
curl http://localhost:8080/items/1

{"id":1,"name":"pen"}

Stop the server with Ctrl-C.

At this point blank-name POST requests and requests for non-existent IDs return Spring's default error body. Page 06 replaces that with clean JSON error responses.

Next → Validation and errors