Unlocking the Power of Message Properties in Spring Boot: Get all Key-Value Pairs as JSON for Selected Locale

As a Spring Boot developer, you’re no stranger to the importance of handling internationalization and localization in your applications. One crucial aspect of this is dealing with message properties, which contain key-value pairs that are used to display text and other content to users in different languages. In this article, we’ll explore how to retrieve all message properties key-value pairs as JSON for a selected locale in Spring Boot, and dive into the benefits and best practices of this approach.

Why Do We Need to Get All Message Properties as JSON?

In a typical Spring Boot application, you might have multiple message properties files, each containing a set of key-value pairs for a specific locale. For example, you might have a `messages.properties` file for English, a `messages_fr.properties` file for French, and so on. When a user requests a resource in a specific locale, Spring Boot uses the corresponding message properties file to resolve the text and display it accordingly.

However, what if you need to retrieve all the message properties for a selected locale as a single JSON object? This could be useful in scenarios where you need to:

• Display all the available text and content for a specific locale in a single view
• Provide a JSON endpoint for a frontend application to fetch and display localized content
• Generate a report or export data that includes all the localized text and content

In the following sections, we’ll explore how to achieve this using Spring Boot’s built-in features and some clever coding.

Step 1: Configure Spring Boot for Internationalization

Before we dive into retrieving message properties as JSON, let’s ensure that our Spring Boot application is configured to handle internationalization and localization correctly.

In your `application.properties` file, add the following configuration:

spring.messages.basename=messages
spring.messages.encoding=UTF-8
spring.mvc.locale-resolver=default

This sets up the message properties file naming convention, encoding, and locale resolver. The `basename` property specifies the prefix for your message properties files, while the `encoding` property sets the character encoding to UTF-8. The `locale-resolver` property enables the default locale resolver, which uses the `Accept-Language` header to determine the user’s preferred locale.

Step 2: Create a Service to Load Message Properties

Create a new service class, e.g., `MessagePropertyService`, to load the message properties for a given locale:

@Service
public class MessagePropertyService {

  @Autowired
  private ResourceBundleMessageSource messageSource;

  public Map<String, String> getMessageProperties(Locale locale) {
    ResourceBundle bundle = messageSource.getResourceBundle(locale);
    Map<String, String> messageProperties = new HashMap<>();

    for (String key : bundle.keySet()) {
      messageProperties.put(key, bundle.getString(key));
    }

    return messageProperties;
  }
}

This service uses the `ResourceBundleMessageSource` to load the message properties for a given locale. It then iterates over the key-value pairs in the resource bundle and builds a `Map` of message properties.

Step 3: Create a Controller to Return JSON Response

Create a new controller class, e.g., `MessagePropertyController`, to handle requests for message properties as JSON:

@RestController
@RequestMapping("/api/message-properties")
public class MessagePropertyController {

  @Autowired
  private MessagePropertyService messagePropertyService;

  @GetMapping("/{locale}")
  public ResponseEntity<Map<String, String>> getMessageProperties(@PathVariable Locale locale) {
    Map<String, String> messageProperties = messagePropertyService.getMessageProperties(locale);
    return ResponseEntity.ok(messageProperties);
  }
}

This controller has a single endpoint, `/api/message-properties/{locale}`, which accepts a `locale` path variable. It uses the `MessagePropertyService` to load the message properties for the specified locale and returns the result as a JSON object.

Testing the Endpoint

Start your Spring Boot application and use a tool like Postman or cURL to test the endpoint. For example, to retrieve the message properties for the `fr` locale, send a GET request to `http://localhost:8080/api/message-properties/fr`.

The response should contain a JSON object with all the message properties for the French locale, like this:

{
  "hello.world": "Bonjour le monde!",
  "goodbye.world": "Au revoir le monde!",
  "welcome.message": "Bienvenue sur notre site!"
}

Bonus: Handling Nested Message Properties

In some cases, you might have nested message properties, where a property value is a reference to another property. For example:

welcome.message=Bonjour sur notre site {site.name}!
site.name=Mon Site

To handle this scenario, you can modify the `MessagePropertyService` to recursively resolve nested properties:

public Map<String, String> getMessageProperties(Locale locale) {
  ResourceBundle bundle = messageSource.getResourceBundle(locale);
  Map<String, String> messageProperties = new HashMap<>();

  for (String key : bundle.keySet()) {
    String value = bundle.getString(key);
    value = resolveNestedProperties(value, bundle);
    messageProperties.put(key, value);
  }

  return messageProperties;
}

private String resolveNestedProperties(String value, ResourceBundle bundle) {
  Pattern pattern = Pattern.compile("\\{([a-zA-Z.]+)\\}");
  Matcher matcher = pattern.matcher(value);
  while (matcher.find()) {
    String propertyKey = matcher.group(1);
    String propertyValue = bundle.getString(propertyKey);
    value = value.replace("{" + propertyKey + "}", propertyValue);
  }
  return value;
}

This modified service uses a regular expression to detect and replace nested property references with their corresponding values.

Conclusion

In this article, we’ve explored how to retrieve all message properties key-value pairs as JSON for a selected locale in Spring Boot. By configuring internationalization and localization, creating a service to load message properties, and creating a controller to return JSON responses, we’ve achieved a flexible and scalable solution for handling localized content in our applications.

By following these steps and best practices, you’ll be well-equipped to handle the complexities of internationalization and localization in your Spring Boot applications, and provide a seamless experience for users around the world.

Summary of Key Takeaways

Step	Description
1	Configure Spring Boot for internationalization and localization
2	Create a service to load message properties for a given locale
3	Create a controller to return message properties as JSON
Bonus	Handle nested message properties using recursive resolution

Remember to test and iterate on your implementation to ensure it meets the specific needs of your application and users. Happy coding!

Frequently Asked Question

Are you struggling to retrieve all message properties key-value pairs as JSON for a selected locale in your Spring Boot application? Worry not! We’ve got you covered with these frequently asked questions and answers.