How to Make Spring Boot Fail on Missing Environment Variables

May 06, 2021

Problem

By default, Spring Boot @ConfigurationProperties doesn’t fail when there are missing/unresolved environment variables defined in application properties. Instead, the property will be bound with the placeholder literal, e.g. "${ENV_VAR}".

Here’s a simple way to make your app fail to start if a missing/unresolved environment variable placeholder is detected using JSR-303 bean validation with Hibernate validator.

Solution

You will need to add this dependency: org.springframework.boot:spring-boot-starter-validation.

# application.yml
app:
  secret: ${ENV_VAR}

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.validation.annotation.Validated;
import javax.validation.constraints.AssertTrue;
import static org.springframework.util.StringUtils.hasText;

@Validated
@ConfigurationProperties("app")
public class Config {

    private String secret;

    @AssertTrue
    boolean isSecretValid() {
        return hasText(secret) && 
                !(secret.startsWith("${") && secret.endsWith("}"));
    }

    public String getSecret() {
        return secret;
    }

    public void setSecret(String secret) {
        this.secret = secret;
    }

}

See full code on GitHub here.

Example Failure Message

2021-05-05 20:48:32.579 ERROR 89318 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Binding to target org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'app' to com.davidagood.Config failed:

    Property: app.secretValid
    Value: false
    Reason: must be true


Action:

Update your application's configuration