Use application.properties to configure the application

core/deployment/src/main/java/io/quarkus/deployment/steps/ConfigurationSetup.java

@@ -57,6 +57,7 @@
 import io.quarkus.deployment.recording.ObjectLoader;
 import io.quarkus.deployment.util.ServiceUtil;
 import io.quarkus.runtime.annotations.ConfigPhase;
+import io.quarkus.runtime.configuration.ApplicationPropertiesConfigSource;
 import io.quarkus.runtime.configuration.CidrAddressConverter;
 import io.quarkus.runtime.configuration.ConverterFactory;
 import io.quarkus.runtime.configuration.DefaultConfigSource;
@@ -180,6 +181,17 @@ private static <T> void withConverterHelper(final SmallRyeConfigBuilder builder,
         }
     }
 
+    /**
+     * Add a config sources for {@code application.properties}.
+     */
+    @BuildStep
+    void setUpConfigFile(BuildProducer<RunTimeConfigurationSourceBuildItem> configSourceConsumer) {
+        configSourceConsumer.produce(new RunTimeConfigurationSourceBuildItem(
+                ApplicationPropertiesConfigSource.InJar.class.getName(), OptionalInt.empty()));
+        configSourceConsumer.produce(new RunTimeConfigurationSourceBuildItem(
+                ApplicationPropertiesConfigSource.InFileSystem.class.getName(), OptionalInt.empty()));
+    }
+
     /**
      * Write the default run time configuration.
      */

core/runtime/src/main/java/io/quarkus/runtime/configuration/ApplicationPropertiesConfigSource.java

@@ -0,0 +1,90 @@
+package io.quarkus.runtime.configuration;
+
+import java.io.BufferedReader;
+import java.io.Closeable;
+import java.io.FileNotFoundException;
+import java.io.IOError;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Properties;
+
+import io.smallrye.config.PropertiesConfigSource;
+
+/**
+ * A configuration source for {@code application.properties}.
+ */
+public abstract class ApplicationPropertiesConfigSource extends PropertiesConfigSource {
+    private static final long serialVersionUID = -4694780118527396798L;
+
+    static final String APPLICATION_PROPERTIES = "application.properties";
+
+    ApplicationPropertiesConfigSource(InputStream is, int ordinal) {
+        super(readProperties(is), APPLICATION_PROPERTIES, ordinal);
+    }
+
+    private static Map<String, String> readProperties(final InputStream is) {
+        if (is == null) {
+            return Collections.emptyMap();
+        }
+        try (Closeable ignored = is) {
+            try (InputStreamReader isr = new InputStreamReader(is, StandardCharsets.UTF_8)) {
+                try (BufferedReader br = new BufferedReader(isr)) {
+                    final Properties properties = new Properties();
+                    properties.load(br);
+                    return (Map<String, String>) (Map) properties;
+                }
+            }
+        } catch (IOException e) {
+            throw new IOError(e);
+        }
+    }
+
+    public static final class InJar extends ApplicationPropertiesConfigSource {
+        public InJar() {
+            super(openStream(), 250);
+        }
+
+        private static InputStream openStream() {
+            ClassLoader cl = Thread.currentThread().getContextClassLoader();
+            if (cl == null) {
+                cl = ApplicationPropertiesConfigSource.class.getClassLoader();
+            }
+            InputStream is;
+            if (cl == null) {
+                is = ClassLoader.getSystemResourceAsStream(APPLICATION_PROPERTIES);
+            } else {
+                is = cl.getResourceAsStream(APPLICATION_PROPERTIES);
+            }
+            return is;
+        }
+    }
+
+    public static final class InFileSystem extends ApplicationPropertiesConfigSource {
+        public InFileSystem() {
+            super(openStream(), 260);
+        }
+
+        private static InputStream openStream() {
+            final Path path = Paths.get("config", APPLICATION_PROPERTIES);
+            if (Files.exists(path)) {
+                try {
+                    return Files.newInputStream(path);
+                } catch (NoSuchFileException | FileNotFoundException e) {
+                    return null;
+                } catch (IOException e) {
+                    throw new IOError(e);
+                }
+            } else {
+                return null;
+            }
+        }
+    }
+}

core/runtime/src/main/java/io/quarkus/runtime/configuration/TemporaryConfigSourceProvider.java

@@ -0,0 +1,17 @@
+package io.quarkus.runtime.configuration;
+
+import java.util.Arrays;
+
+import org.eclipse.microprofile.config.spi.ConfigSource;
+import org.eclipse.microprofile.config.spi.ConfigSourceProvider;
+
+/**
+ * This is a temporary hack until the class loader mess is worked out.
+ */
+public class TemporaryConfigSourceProvider implements ConfigSourceProvider {
+    public Iterable<ConfigSource> getConfigSources(final ClassLoader forClassLoader) {
+        return Arrays.asList(
+                new ApplicationPropertiesConfigSource.InJar(),
+                new ApplicationPropertiesConfigSource.InFileSystem());
+    }
+}

core/runtime/src/main/resources/META-INF/services/org.eclipse.microprofile.config.spi.ConfigSourceProvider

@@ -0,0 +1 @@
+io.quarkus.runtime.configuration.TemporaryConfigSourceProvider