PropertySource Reload Spring Framework Boot Starters

Table of Contents

• Usage
• Repository
• Requirements and Downloads
• How to enable external property source reloading
• Spring Boot bootstrap configuration parameter:
• Reload Strategy
• PropertySourceReloadEvent
• Environment Changes
• Delete Configuration at Runtime
• Contributions
• Licenses

Usage

This starter can auto detect the external property source (current only support java properties file) change on the file system, and triggers the refresh process of the application.

Repository

Repository contains:

• propertysource-reload-spring-boot-starter the starter project which enables propertysource reload
• propertysource-reload-example an example demonstrating the usage of the starter

Requirements and Downloads

Requirements:

• Java 1.8
• Spring Framework Boot > 2.x.x

Gradle:

repositories {
    jcenter()
    mavenCentral()
}

dependencies {
  implementation 'io.github.topikachu:propertysource-reload-spring-boot-starter:0.0.7'
}

Maven:

<dependency>
    <groupId>io.github.topikachu</groupId>
    <artifactId>propertysource-reload-spring-boot-starter</artifactId>
    <version>0.0.7</version>
</dependency>

This starter requires the Spring Cloud Context . Add at least one Spring Cloud module, for example:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter</artifactId>
</dependency>

How to enable external property source reloading

1. Use annotation at class level
   @ReloadablePropertySource({ "config/a.properties", "config/b.properties" }) The starter only scans the packages same as or sub of the application's. It's NOT aware of @ComponentScan
2. Specify the configuration file in the bootstrap.properties or bootstrap.yaml:
   propertysource.reload.properties-files=config/foo.properties,config/bar.properties

Spring Boot bootstrap configuration parameter:

propertysource.reload.properties-files=
propertysource.reload.poll-interval=5s
propertysource.reload.strategy=refresh_environment
propertysource.reload.max-wait-for-shutdown=2s
propertysource.reload.max-wait-for-system-exit=10s
propertysource.reload.ignore-resource-not-found=true
propertysource.reload.ignore-resource-load-error=true

Once the content of the configuration file specified in propertysource.reload.properties-files is change, the application is reload automatically.

Reload Strategy

1. refresh_scope
   This is the default strategy. Execute ContextRefresher.refresh().
2. refresh_environment
   Execute ContextRefresher.refreshEnvironment().
3. exit_application
   Execute SpringApplication.exit()
4. exit_application_force
   Execute SpringApplication.exit() and System.exit()
5. restart
   Set management.endpoint.restart.enabled=true to enable this strategy. See RestartEndpoint#restart for details.

PropertySourceReloadEvent

There's a PropertySourceReloadEvent fired after each reload. To receive this event

	@EventListener(PropertySourceReloadEvent.class)
	public void onRefresh(PropertySourceReloadEvent event) {
		System.out.println(String.join(",", event.getKeys()));
		System.out.println(event.getFile().getName());
		System.out.println(event.getFileEvent());
	}

Environment Changes

Please read spring documentation for detail.
In a short description, the @ConfigurationProperties beans are rebind, but @Value are not by default. Any bean using @Value to inject the configuration must use @RefreshScope to receive the new change.

Delete Configuration at Runtime

It's very difficult to handle the configuration deletion. Try to always keep the keys at runtime. Another solution is to use "@RefreshScope" at any bean depending on the configuration may change during runtime.

Contributions

Contributions are welcome. Please respect the Code of Conduct.

Licenses

propertysource-reload-spring-boot-starter are licensed under the Apache 2.0 License. See LICENSE for details.