Why Your Spring Boot DeepSeek API Key Stays Old and How to Fix It

Background: The "Stale" DeepSeek API Key Issue

When integrating the DeepSeek API into a Spring Boot application, the property deepseek.api-key was updated in application.properties, but the running code kept reading the old key, resulting in a 401 error ( API key: ****307b is invalid).

Investigation revealed that an environment variable deepseek_api_key=sk-旧密钥 was overriding the property because Spring Boot gives higher priority to environment variables.

Spring Boot Configuration Loading Priority

Spring Boot loads configuration sources in a specific order (high to low). Higher‑priority sources overwrite lower‑priority ones. The following diagram illustrates the hierarchy:

Five Common Pitfalls and Their Solutions

Pitfall 1: Environment Variable Overrides Configuration File

Problem : application.properties contains the new key, but the console prints the old key.

Cause : An OS environment variable deepseek_api_key is automatically mapped to deepseek.api-key and takes precedence.

Solution :

Windows: echo %deepseek_api_key% then set deepseek_api_key= to delete.

Linux/Mac: echo $deepseek_api_key then unset deepseek_api_key.

After removal, restart the application to verify the new value is loaded.

Pitfall 2: Configuration File Placed in Wrong Path

Problem : The file is under src/main/java/com/example/config, so Spring Boot cannot find it and uses default values.

Cause : Spring Boot only scans src/main/resources for application.properties or application.yml.

Solution :

Move application.properties to src/main/resources.

Project structure example:

src
 └─ main
     ├─ java      # source code
     └─ resources  # configuration files
         └─ application.properties

If a custom location is required, specify it in the startup command, e.g.:

@SpringBootApplication
public class QuestionnaireBackendApplication {
    public static void main(String[] args) {
        SpringApplication.run(QuestionnaireBackendApplication.class,
            "--spring.config.location=classpath:/config/application.properties");
    }
}

Pitfall 3: Configuration Class Lacks Setter Methods

Problem : DeepSeekConfig reads apiKey as null or default.

Cause : @ConfigurationProperties(prefix = "deepseek") requires JavaBean setters to inject values.

Solution : Add setters for all fields. Example:

@Configuration
@ConfigurationProperties(prefix = "deepseek")
public class DeepSeekConfig {
    private String apiKey;
    private String apiUrl = "https://api.deepseek.com/chat/completions";
    private String model = "deepseek-chat";
    private int timeout = 30000;

    public void setApiKey(String apiKey) { this.apiKey = apiKey; }
    public void setApiUrl(String apiUrl) { this.apiUrl = apiUrl; }
    public void setModel(String model) { this.model = model; }
    public void setTimeout(int timeout) { this.timeout = timeout; }

    @PostConstruct
    public void printConfig() {
        System.out.println("=== DeepSeek configuration ===");
        System.out.println("apiKey (masked): " + (apiKey == null ? "null" : apiKey.substring(0,6) + "****"));
        System.out.println("apiUrl: " + apiUrl);
        System.out.println("model: " + model);
    }
}

Pitfall 4: Wrong Profile Activation Causes Old Values

Problem : application-dev.properties contains an old key and overrides the main configuration.

Cause : spring.profiles.active=dev activates the dev profile, giving it higher priority.

Solution :

Remove or change the active profile if the main file should be used.

Edit the appropriate profile file ( application-dev.properties) with the correct key.

Alternatively, specify the profile at launch:

java -jar questionnaire-backend.jar --spring.profiles.active=prod

Pitfall 5: IDE Cache Leads to Stale Configuration

Problem : After editing deepseek.api-key, the application still reads the old value.

Cause : IDE (e.g., IntelliJ IDEA) caches compiled classes; the updated property file is not re‑compiled.

Solution :

Rebuild the project: IDEA → Build → Rebuild Project; Eclipse → Clean → Build Project.

Invalidate caches: IDEA → File → Invalidate Caches… → Invalidate and Restart.

Quick Validation: 3‑Line Snippet to Verify Configuration

@PostConstruct
public void printConfig() {
    System.out.println("=== Configuration Load Result ===");
    String maskedApiKey = apiKey == null ? "null (not loaded)" : apiKey.substring(0,6) + "****" + apiKey.substring(apiKey.length()-4);
    System.out.println("deepseek.api-key: " + maskedApiKey);
    System.out.println("deepseek.api-url: " + apiUrl);
    System.out.println("deepseek.model: " + model);
}

null → Configuration not injected (check setters, file location).

old value → Environment variable, command‑line argument, or active profile overriding.

new value → Configuration loaded successfully; further issues may lie elsewhere.