GraphQL APIs with Spring Boot · Lesson

Updating and Deleting Data

Develop mutations for modifying existing data and removing records from your system.

Updating and Deleting Data is a free GraphQL APIs with Spring Boot lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the GraphQL APIs with Spring Boot learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Changing Your Data

So far, you've learned to fetch data with queries and add new data with mutations. But what about modifying or removing existing records?

In this lesson, we'll dive into how GraphQL mutations allow you to update and delete data, making your applications fully dynamic.

GraphQL Update Mutation (SDL)

An update mutation modifies an existing record. It usually requires an identifier (like an ID) to specify which record to change, and then the fields you want to update.

Here's how you might define an updateBook mutation in your GraphQL schema (SDL):

type Mutation { updateBook(id: ID!, title: String, author: String, year: Int): Book }

Designing Update Input Types

For cleaner mutations, especially with many fields, it's good practice to use an Input Type. This bundles all arguments into a single object.

An Input Type is similar to a regular type but uses the input keyword.

input UpdateBookInput { id: ID! title: String author: String year: Int } type Mutation { updateBook(input: UpdateBookInput!): Book }

Spring Boot: Update Resolver

In your Spring Boot application, you'll create a Java method that acts as the resolver for the updateBook mutation.

This method will take the necessary arguments (like the book's ID and new details) and perform the update logic, often interacting with a database or service.

public Book updateBook(String id, String title, String author, Integer year) { // ... logic to find and update the book ... return updatedBook; }

Implementing Update Logic

Let's see a simple Java example of how an update might work. We'll use an in-memory list to simulate a data store.

Notice how we find the book by ID and then modify its properties.

public class Main {
  static class Book {
    String id;
    String title;
    public Book(String id, String title) {
      this.id = id;
      this.title = title;
    }
    public String getId() { return id; }
    public String getTitle() { return title; }
    public void setTitle(String title) { this.title = title; }
    @Override
    public String toString() { return "Book[id=" + id + ", title='" + title + "']"; }
  }

  private static java.util.List<Book> books = new java.util.ArrayList<>();

  public static void main(String[] args) {
    books.add(new Book("1", "Original Title"));
    books.add(new Book("2", "Another Book"));

    System.out.println("Before update:");
    books.forEach(System.out::println);

    // Simulate update logic
    String targetId = "1";
    String newTitle = "Updated Title";
    
    books.stream()
         .filter(b -> b.getId().equals(targetId))
         .findFirst()
         .ifPresent(book -> book.setTitle(newTitle));

    System.out.println("\nAfter update:");
    books.forEach(System.out::println);
  }
}

GraphQL Delete Mutation (SDL)

Deleting data is simpler. You typically only need to provide the unique ID of the record you wish to remove.

The delete mutation usually returns the ID of the deleted item, or a boolean indicating success.

type Mutation { deleteBook(id: ID!): ID }

Spring Boot: Delete Resolver

Similar to updating, a delete mutation in Spring Boot will have a corresponding Java method.

This method will receive the ID of the item to be deleted and perform the removal operation.

public String deleteBook(String id) { // ... logic to find and delete the book ... return id; }

Implementing Delete Logic

Here's a basic Java example of a delete operation. We'll remove a book from our in-memory list based on its ID.

The removeIf method is a concise way to delete elements that match a condition.

public class Main {
  static class Book {
    String id;
    String title;
    public Book(String id, String title) {
      this.id = id;
      this.title = title;
    }
    public String getId() { return id; }
    public String getTitle() { return title; }
    @Override
    public String toString() { return "Book[id=" + id + ", title='" + title + "']"; }
  }

  private static java.util.List<Book> books = new java.util.ArrayList<>();

  public static void main(String[] args) {
    books.add(new Book("1", "Book to Delete"));
    books.add(new Book("2", "Another Book"));

    System.out.println("Before delete:");
    books.forEach(System.out::println);

    // Simulate delete logic
    String targetId = "1";
    books.removeIf(book -> book.getId().equals(targetId));

    System.out.println("\nAfter delete:");
    books.forEach(System.out::println);
  }
}

Handling Missing Records

What happens if you try to update or delete a record that doesn't exist?

Your resolver should check if the ID exists.
If not found, it can return null or throw a specific GraphQL error (more on error handling in a later course!).
This prevents unexpected behavior and informs the client.

Quick Check: Mutation Operations

You've learned about different types of GraphQL operations. Let's test your understanding!

Recap: Mastered Data Changes!

Congratulations! You've learned how to implement powerful data modification features:

Update Mutations: Used to modify existing data records, identified by a unique ID.
Delete Mutations: Used to remove data records from your system, also identified by a unique ID.
Spring Boot Resolvers: How to map these mutations to Java methods for backend logic.

With queries, create, update, and delete mutations, you now have a full set of tools to build dynamic GraphQL APIs!

Frequently asked questions

Is the “Updating and Deleting Data” lesson free?

Yes — the full text of “Updating and Deleting Data” is free to read here on the web, and the GraphQL APIs with Spring Boot course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the GraphQL APIs with Spring Boot course, upgrade to CoddyKit PRO.

What will I learn in “Updating and Deleting Data”?

Develop mutations for modifying existing data and removing records from your system. You practise GraphQL APIs with Spring Boot with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start GraphQL APIs with Spring Boot?

No prior experience is required. GraphQL APIs with Spring Boot on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Updating and Deleting Data” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this GraphQL APIs with Spring Boot lesson?

Yes. Every GraphQL APIs with Spring Boot lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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