更新与删除数据
开发用于修改现有数据和从系统中删除记录的变更。
更新与删除数据 是 CoddyKit 上的免费 GraphQL APIs with Spring Boot 课时。 这是第 3 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 GraphQL APIs with Spring Boot 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 GraphQL APIs with Spring Boot 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
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
IDexists. - If not found, it can return
nullor 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!
常见问题解答
「更新与删除数据」课时是免费的吗？
是的 — 「更新与删除数据」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 GraphQL APIs with Spring Boot 课程的其余内容，请升级到 CoddyKit PRO。 GraphQL APIs with Spring Boot 课程共包含 4 节课。
「更新与删除数据」这节课中我会学到什么？
开发用于修改现有数据和从系统中删除记录的变更。 你通过在浏览器中直接运行的动手代码来练习 GraphQL APIs with Spring Boot，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 GraphQL APIs with Spring Boot 需要有经验吗？
无需任何先前经验。CoddyKit 上的 GraphQL APIs with Spring Boot 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 3 节课，共 4 节。
「更新与删除数据」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 GraphQL APIs with Spring Boot 课中编写并运行代码吗？
能。每节 GraphQL APIs with Spring Boot 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。