bthelen / spring-property-load

Spring Required Property Loading Sample

Purpose

The purpose of this repo is to demonstrate how to force SpringBoot to short-circuit loading when a specified property is unavailable. This technique is useful when you want to keep an application from starting if it does not have a certain set of configuration.

Relevant Configuration Details

Refer to comments in SampleConfiguration.java to understand which property is required for the application to load:

@Configuration
@ConfigurationProperties(prefix = "message.default")
@Validated // required to tell Spring to validate this Configuration on load
public class SampleConfiguration {
    // If SpringBoot cannot find message.default.sample SOMEWHERE (Environment Variables, Properties Files,
    // or Config Server), this application will refuse to start.
    @NotNull
    private String sample;

    public String getSample() {
        return sample;
    }

    public void setSample(String sample) {
        this.sample = sample;
    }
}

Notice that the property message.default.sample exists only in the files application-local.yml or application-test.yml. This means that in the way this application is setup currently it will only load if the local or test Spring profile is active.

How To Use This Repo To Demo

• Check out the source code:

$ git clone https://github.com/bthelen/spring-property-load.git 
$ cd spring-property-load

• Try to run without activating one of those profiles

$ mvn spring-boot:run -DskipTests

• Notice the application failed to start
• Run with activating the profile

$ mvn spring-boot:run -DskipTests -Dspring.profiles.active=local

• Notice the application did start
• Check the actuator endpoint to inspect the environment -- notice message.default.sample is in there

$ curl localhost:8080/actuator/env

How to use This Repo To Show Spring Cloud Config Server Integration on Pivotal Cloud Foundry

• Make sure you are logged on to a foundation where you have access to cf push and you have the ability to cf create-service an instance of Spring Cloud Config Server.

• Create a config server instance pointing to a sample git repo that includes message.default.sample in application-cloud.yml

$ cf create-service p-config-server standard config-server -c '{"git": {"uri": "https://github.com/bthelen/spring-config-repo.git" }}'

• Review the file application-cloud.yml to see that message.default.sample is there.
• Compile the sample

$ mvn clean install -Dspring.profiles.active=test

• Push the sample

$ cf push

• Notice it does load, even though local not test Spring profile is active
• Recall that Pivotal Cloud Foundry automatically activates a Spring profile called cloud
  • Review the log of the application start

  $ cf logs spring-property-load --recent

  • You should see a line similar to the following that shows the configuration contained in application-cloud.yml was loaded into the Spring Boot context.

  2019-03-29T10:39:10.97-0500 [APP/PROC/WEB/0] OUT 2019-03-29 15:39:10.973  INFO 23 --- [           main] b.c.PropertySourceBootstrapConfiguration : Located property source: CompositePropertySource {name='configService', propertySources=[MapPropertySource {name='configClient'}, MapPropertySource {name='https://github.com/bthelen/spring-config-repo.git/application-cloud.yml'}, MapPropertySource {name='https://github.com/bthelen/spring-config-repo.git/application.yml'}]}

• Check the actuator endpoint to inspect the environment -- notice message.default.sample is in there

$ curl <route-to-your-app-on-PCF>/actuator/env

• Now unbind the application from the Spring Cloud Config Server

$ cf unbind-service spring-property-load config-server

• Attempt to restart the app

$ cf restart spring-property-load

• Notice that application failed to start because message.default.sample was not available.