You can configure a memory health check in Helidon SE. A memory health check will return a status of UP if the memory usage is below a certain threshold percentage and DOWN if the memory usage is above the threshold percentage. The default threshold percentage is 98%. To add the memory health check you need to add the dependency io.helidon.health:helidon-health-checks to your pom.xml file. This dependency contains three health checks: disk space usage, memory usage and dead lock detection.

To configure the memory health check you need to set the configuration property server.features.observe.observers.health.helidon.health.memory.thresholdPercent to the threshold percentage. Alternatively you can set the threshold percentage in your application code.

Suppose you want to return a response based on the Accept header of the request. If the Accept header is application/json you want to return a JSON response and if the Accept header is application/xml you want to return an XML response. You can use the isAccepted(MediaType) of the ServerRequestHeaders class to check if the value of the request header Accept is equal to the specified media type. The method returns true if the media type is defined for the request header Accept and false if not.

In order to convert an object to XML you need to add the dependency com.fasterxml.jackson.dataformat:jackson-dataformat-xml to your pom.xml file:

You can write an implementation of the interface EnvironmentPostProcessor to customize the Environment of a Spring Boot application. For example you can read an external configuration file and add its properties to the Environment. If you want to add some logging statement to the class then you need to make sure you pass a DeferredLogFactory to the constructor of the class. From this factory you can use the getLogger method to get a Log instance. This is needed, because the implementation of the interface EnvironmentPostProcessor is created before the logging system is initialized. By using the Log instances created from DeferredLogFactory Spring Boot will make sure the log messages are written when the logging system is initialized.

In Helidon SE you can enable a health check for the disk space usage. If the disk space usage is above a certain threshold then the health check will fail. To enable the disk space health check you need to add the dependency io.helidon.health:helidon-health-checks to your pom.xml file. The dependency contains three health checks: disk space usage, memory usage and dead lock detection.

To configure the disk space health check you need to set the configuration property server.features.observe.observers.health.helidon.health.diskSpace.thresholdPercent to the threshold percentage. Or programmatically set the value in your application code. The default value is 99.999, which means that in real life the health check will not fail. You need to set a lower percentage in order to see the health check fail. For example when you set the value to 95.0 then the health check will fail when the disk space usage is above 95% or less than 5% of the disk space is available. You can also configure the path to check for disk space usage. The default path is the current working directory, but it can be set to another path. You need to set the configuration property server.features.observe.observers.health.helidon.health.diskSpace.path to change the path.