Ladies & Gents, I prototyped just a small app that could help you print out some basic environment related information by exposing a few Rest controller endpoints.

Running the app

The easiest way is to run the app using Spring boot maven plugin

$ mvn spring-boot:run \
  -Drun.jvmArguments="\
    -Dfoo=foo \
    -Dbar=bar \
    -Dbaz=baz \
    -Dserver.port=8080 \
    -agentlib:jdwp=transport=dt_socket,server=y,address=1044,suspend=n"

Here, we specify some Java properties that will be used by the application:

foo, bar, baz custom properties server.port – which is the way to instruct Spring Boot which port to use we also specify to start with remote debug capabilities (if we’d like to do some remote debugging with our IDE)

Rest controller exposing various system / spring properties

package rs.dodalovic.envprops;

import com.google.common.collect.ImmutableMap;
import lombok.AllArgsConstructor;
import lombok.val;
import org.springframework.core.env.Environment;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

@RestController
@AllArgsConstructor
public class EnvPropertiesController {
    private final Environment environment;

    @GetMapping("/sys/props")
    public Map<String, Object> getSysProperties() {
        val builder = ImmutableMap.builder();
        System.getProperties().stringPropertyNames().forEach(name -> {
            builder.put(name, environment.getProperty(name));
        });
        val systemProperties = builder.build();
        return ImmutableMap.of(
                "size", systemProperties.size(),
                "values", systemProperties
        );
    }

    @GetMapping("/sys/props/custom")
    public Map<String, Object> getCustomEnvProperties() {
        val builder = ImmutableMap.builder();
        builder.put("properties.key1", environment.getProperty("properties.key1"));
        builder.put("properties.key2", environment.getProperty("properties.key2"));

        builder.put("foo", environment.getProperty("foo"));
        builder.put("bar", environment.getProperty("bar"));
        builder.put("baz", environment.getProperty("baz"));

        val customProperties = builder.build();

        return ImmutableMap.of(
                "size", customProperties.size(),
                "values", customProperties
        );
    }

    @GetMapping("/sys/env")
    public Map<String, Object> get() {
        val env = System.getenv();
        return ImmutableMap.of(
                "size", env.size(),
                "values", env
        );
    }
}

Highlighted are lines used to get insights from running application environment. We are injecting Environment implementation which gives us access to environment properties, and application profiles.

Here's how application.properties look like:

properties.key1=properties.val1
properties.key2=properties.val2

In the application.properties (main Spring Boot configuration file) we define two custom Spring environment properties: properties.key1 and properties.key2.

Listing system properties

$ curl -s 'http://localhost:8080/sys/props' | jq .

Here's a response:

{
  "size": 63,
  "values": {
    "java.runtime.name": "Java(TM) SE Runtime Environment",
    "sun.boot.library.path": "/Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home/jre/lib",
    "java.vm.version": "25.121-b13"
    // ...
  }
}

Listing system environment

$ curl -s 'http://localhost:8080/sys/env' | jq .

Here's a response, once again:

{
  "size": 46,
  "values": {
    "M2": "/usr/local/Cellar/maven/3.5.0/libexec/bin",
    "GREP_COLOR": "1;33",
    "JENV_FORCEJDKHOME": "true"
    // ...
  }
}

Listing custom spring properties

$ curl -s 'http://localhost:8080/sys/props/custom' | jq .

A response would be something like:

{
  "size": 5,
  "values": {
    "properties.key1": "properties.val1",
    "properties.key2": "properties.val2",
    "foo": "foo",
    "bar": "bar",
    "baz": "baz"
  }
}

Here we see merged collection of environment properties we either passed via command line or defined in application.properties.

You can checkout source code from GitHub

That was all for today! Hope you liked it!