0Pricing
Spring Boot 4 Microservices & REST APIs · Lektion

CRUD-Operationen mit REST

Implementieren Sie Create-, Read-, Update- und Delete-Operationen für Ihre Entities über REST-Endpunkte.

CRUD-Operationen mit REST ist eine kostenlose Spring Boot 4 Microservices & REST APIs-Lektion auf CoddyKit. Dies ist Lektion 5 von 6. Du kannst die komplette Lektion unten kostenlos lesen – dann übst du sie direkt im Browser mit einem integrierten Code-Editor und einem KI-Tutor rund um die Uhr. Sie ist Teil des Spring Boot 4 Microservices & REST APIs-Lernpfads, und dein Fortschritt wird über Web und CoddyKit-App synchronisiert. Der Spring Boot 4 Microservices & REST APIs-Kurs umfasst insgesamt 6 Lektionen.

Teile dieser Lektion wurden noch nicht übersetzt und werden auf Englisch angezeigt.

CRUD Operations: The Basics

Welcome to implementing CRUD operations with Spring Boot! CRUD stands for Create, Read, Update, and Delete.

These are the four fundamental operations for persistent storage, allowing you to manage data in your application.

In REST APIs, each CRUD operation typically maps to a specific HTTP method.

Mapping CRUD to HTTP Methods

Understanding how CRUD maps to HTTP methods is key for RESTful design:

  • Create (C): Handled by POST requests.
  • Read (R): Handled by GET requests.
  • Update (U): Handled by PUT requests.
  • Delete (D): Handled by DELETE requests.

We'll use a simple Product entity and its ProductRepository from previous lessons.

Implementing Create (POST)

To create a new resource, we use the POST HTTP method. In Spring Boot, this is handled by the @PostMapping annotation.

The new product data is sent in the request body, which Spring automatically maps to our Product object using @RequestBody.

Create Product Example

Here's how you'd create an endpoint to add a new product. Run it, then try adding a product via a tool like Postman (e.g., POST to /api/products with JSON body {"name": "Laptop", "price": 1200.0}).

package com.coddykit.crud;

import jakarta.persistence.*;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.*;
import org.springframework.beans.factory.annotation.Autowired;

@Entity
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private double price;
    public Product() {}
    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public double getPrice() { return price; }
    public void setPrice(double price) { this.price = price; }
}

@Repository
interface ProductRepository extends JpaRepository<Product, Long> {}

@RestController
@RequestMapping("/api/products")
class ProductController {
    @Autowired
    private ProductRepository productRepository;

    @PostMapping
    public Product createProduct(@RequestBody Product product) {
        return productRepository.save(product);
    }
}

@SpringBootApplication
class CrudApplication {
    public static void main(String[] args) {
        SpringApplication.run(CrudApplication.class, args);
    }
}

Implementing Read (GET)

Reading resources is done with the GET HTTP method. We'll create two types of read operations:

  • Get all products: Maps to @GetMapping.
  • Get a single product by ID: Maps to @GetMapping("/{id}") using a @PathVariable.

When fetching by ID, we use Optional to handle cases where the product might not exist.

Read Products Example

This code adds methods to fetch all products and a single product by its ID. Notice the use of ResponseEntity to return a 404 if a product isn't found.

package com.coddykit.crud;

import jakarta.persistence.*;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import java.util.List;
import java.util.Optional;

@Entity
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private double price;
    public Product() {}
    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public double getPrice() { return price; }
    public void setPrice(double price) { this.price = price; }
}

@Repository
interface ProductRepository extends JpaRepository<Product, Long> {}

@RestController
@RequestMapping("/api/products")
class ProductController {
    @Autowired
    private ProductRepository productRepository;

    @GetMapping
    public List<Product> getAllProducts() {
        return productRepository.findAll();
    }

    @GetMapping("/{id}")
    public ResponseEntity<Product> getProductById(@PathVariable Long id) {
        Optional<Product> product = productRepository.findById(id);
        return product.map(ResponseEntity::ok)
                      .orElseGet(() -> ResponseEntity.notFound().build());
    }
}

@SpringBootApplication
class CrudApplication {
    public static void main(String[] args) {
        SpringApplication.run(CrudApplication.class, args);
    }
}

Implementing Update (PUT)

To update an existing resource, we use the PUT HTTP method, annotated with @PutMapping.

The endpoint typically includes the resource's ID in the path (/{id}) to identify which item to update, and the updated data is sent in the @RequestBody.

Update Product Example

This method updates an existing product. It first checks if the product exists using the ID from the path. If found, it updates the fields from the request body and saves it.

package com.coddykit.crud;

import jakarta.persistence.*;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import java.util.Optional;

@Entity
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private double price;
    public Product() {}
    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public double getPrice() { return price; }
    public void setPrice(double price) { this.price = price; }
}

@Repository
interface ProductRepository extends JpaRepository<Product, Long> {}

@RestController
@RequestMapping("/api/products")
class ProductController {
    @Autowired
    private ProductRepository productRepository;

    @PutMapping("/{id}")
    public ResponseEntity<Product> updateProduct(
        @PathVariable Long id, @RequestBody Product productDetails) {
        Optional<Product> product = productRepository.findById(id);
        if (product.isPresent()) {
            Product existingProduct = product.get();
            existingProduct.setName(productDetails.getName());
            existingProduct.setPrice(productDetails.getPrice());
            return ResponseEntity.ok(productRepository.save(existingProduct));
        } else {
            return ResponseEntity.notFound().build();
        }
    }
}

@SpringBootApplication
class CrudApplication {
    public static void main(String[] args) {
        SpringApplication.run(CrudApplication.class, args);
    }
}

Implementing Delete (DELETE)

To remove a resource, we use the DELETE HTTP method, annotated with @DeleteMapping.

Similar to update, the ID of the resource to delete is passed as a @PathVariable. After deletion, it's common to return a 204 No Content status.

Delete Product Example

This method deletes a product by ID. It finds the product and, if present, deletes it. Returning ResponseEntity.noContent().build() is a good practice for successful deletions.

package com.coddykit.crud;

import jakarta.persistence.*;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import java.util.Optional;

@Entity
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private double price;
    public Product() {}
    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public double getPrice() { return price; }
    public void setPrice(double price) { this.price = price; }
}

@Repository
interface ProductRepository extends JpaRepository<Product, Long> {}

@RestController
@RequestMapping("/api/products")
class ProductController {
    @Autowired
    private ProductRepository productRepository;

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteProduct(@PathVariable Long id) {
        Optional<Product> product = productRepository.findById(id);
        if (product.isPresent()) {
            productRepository.delete(product.get());
            return ResponseEntity.noContent().build();
        } else {
            return ResponseEntity.notFound().build();
        }
    }
}

@SpringBootApplication
class CrudApplication {
    public static void main(String[] args) {
        SpringApplication.run(CrudApplication.class, args);
    }
}

Quick Check: HTTP Methods

Which HTTP method is typically used to update an existing resource in a REST API, and which one is for creating a new resource?

Recap: CRUD with REST

You've successfully learned how to implement all four CRUD operations using Spring Boot REST controllers!

  • Create: Use @PostMapping.
  • Read: Use @GetMapping (for all or by ID).
  • Update: Use @PutMapping.
  • Delete: Use @DeleteMapping.

These are the building blocks for almost any data-driven API. Next, we'll explore validation and error handling!

Häufig gestellte Fragen

Ist die Lektion „CRUD-Operationen mit REST“ kostenlos?

Ja — der vollständige Text von „CRUD-Operationen mit REST“ ist hier im Web kostenlos zu lesen. Um sie interaktiv zu üben (integrierter Code-Editor und 24/7 KI-Tutor) und den Rest des Spring Boot 4 Microservices & REST APIs-Kurses freizuschalten, upgrade auf CoddyKit PRO. Der Spring Boot 4 Microservices & REST APIs-Kurs umfasst insgesamt 6 Lektionen.

Was lerne ich in „CRUD-Operationen mit REST“?

Implementieren Sie Create-, Read-, Update- und Delete-Operationen für Ihre Entities über REST-Endpunkte. Du übst Spring Boot 4 Microservices & REST APIs mit praktischem Code, den du direkt im Browser ausführst, und ein 24/7 KI-Tutor beantwortet deine Fragen während du die Lektion bearbeitest.

Brauche ich Erfahrung, um Spring Boot 4 Microservices & REST APIs zu starten?

Keine Vorkenntnisse erforderlich. Spring Boot 4 Microservices & REST APIs auf CoddyKit ist für Anfänger bis fortgeschrittene Lernende strukturiert, sodass du hier starten oder von Anfang an beginnen und in deinem eigenen Tempo voranschreiten kannst. Dies ist Lektion 5 von 6.

Wie lange dauert die Lektion „CRUD-Operationen mit REST“?

Die meisten CoddyKit-Lektionen dauern etwa 5–10 Minuten. Jede ist kompakt und interaktiv, sodass du stetig Fortschritte machst und genau dort weitermachst, wo du aufgehört hast – im Web und in der App.

Kann ich in dieser Spring Boot 4 Microservices & REST APIs-Lektion Code schreiben und ausführen?

Ja. Jede Spring Boot 4 Microservices & REST APIs-Lektion enthält einen integrierten Code-Editor, sodass du echten Code direkt in deinem Browser schreibst und ausführst und sofort KI-Feedback erhältst — ohne lokale Einrichtung erforderlich.

Alle Lektionen in diesem Kurs

  1. H2-Datenbank und JPA integrieren
  2. Einführung in Spring Data JPA
  3. Entities und Repositories erstellen
  4. Entitäten und Repositories definieren
  5. CRUD-Operationen mit REST
  6. CRUD-Operationen ausführen
← Zurück zu Spring Boot 4 Microservices & REST APIs