ConfigController.java

package org.zalando.catwatch.backend.web.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.Map;
import java.util.Properties;
import java.util.SortedMap;
import java.util.TreeMap;

import static org.springframework.http.MediaType.APPLICATION_JSON_VALUE;
import static org.springframework.web.bind.annotation.RequestMethod.GET;

@Controller
public class ConfigController {

    private final Environment env;

    @Autowired
    public ConfigController(Environment env) {
        this.env = env;
    }

    @RequestMapping(value = "/config", method = GET, produces = { APPLICATION_JSON_VALUE })
    @ResponseBody
    public Map<String, String> config() throws Exception {
        Properties properties = new Properties();
        properties.load(getClass().getResourceAsStream("/application-public.properties"));
        
        SortedMap<String,  String> result = new TreeMap<>();
        properties.stringPropertyNames().stream().forEach(name -> result.put(name, env.getProperty(name)));
        return result;
    }

}