#365 allow null to be injected

api/src/main/java/org/eclipse/microprofile/config/inject/ConfigProperty.java

@@ -102,6 +102,16 @@
 @Target({METHOD, FIELD, PARAMETER, TYPE})
 public @interface ConfigProperty {
     String UNCONFIGURED_VALUE="org.eclipse.microprofile.config.configproperty.unconfiguredvalue";
+    /**
+     * Provide a way to specify {@code null} value for a property. 
+     * e.g. The following example is to set the default value of {@code my.port} to null if the property is not specified in any config sources.
+     * <pre>
+     * &#064;Inject
+     * &#064;ConfigProperty(name="my.port" defaultValue=ConfigProperty.NULL_VALUE)
+     * String value;
+     * </pre>
+     */
+    String NULL_VALUE="org.eclipse.microprofile.config.configproperty.nullvalue";
     /**
      * The key of the config property used to look up the configuration value.
      * If it is not specified, it will be derived automatically as {@code <class_name>.<injection_point_name>},

api/src/main/java/org/eclipse/microprofile/config/inject/package-info.java

@@ -44,6 +44,6 @@
  * @author <a href="mailto:[email protected]">Emily Jiang</a>
  * 
  */
-@org.osgi.annotation.versioning.Version("1.0.1")
+@org.osgi.annotation.versioning.Version("1.1.0")
 package org.eclipse.microprofile.config.inject;
 

spec/src/main/asciidoc/configexamples.asciidoc

@@ -91,6 +91,11 @@ public class InjectedConfigUsageSample {
     @Inject
     @ConfigProperty(name="myprj.some.dynamic.timeout", defaultValue="100")
     private javax.inject.Provider<Long> timeout;
+    //Injects the value of the property myprj.name if specified in any of the configures, otherwise null will be injected. 
+    @Inject
+    @ConfigProperty(name="myprj.name" defaultValue=ConfigProperty.NULL_VALUE)
+    String name;
+
     //The following code injects an Array, List or Set for the `myPets` property,
     //where its value is a comma separated value ( myPets=dog,cat,dog\\,cat)
     @Inject @ConfigProperty(name="myPets") private String[] myArrayPets;

tck/src/main/java/org/eclipse/microprofile/config/tck/CDIPlainInjectionTest.java

@@ -46,6 +46,8 @@
 import org.testng.annotations.BeforeTest;
 import org.testng.annotations.Test;
 
+import junit.framework.Assert;
+
 /**
  * Test cases for CDI-based API that test retrieving values from the configuration.
  * The tests depend only on CDI 1.2.
@@ -95,6 +97,8 @@ public void canInjectSimpleValuesWhenDefined() {
         assertThat(bean.characterProperty, is(equalTo(Character.valueOf('c'))));
 
         assertThat(bean.doublePropertyWithDefaultValue, is(closeTo(3.1415, 0.1)));
+        Assert.assertNull("The property my.not.configured.nullable.property should be null", 
+                 ConfigProvider.getConfig().getOptionalValue("my.not.configured.nullable.property", String.class).orElse(null));
     }
 
     /*
@@ -126,6 +130,8 @@ public void injectedValuesAreEqualToProgrammaticValues() {
         assertThat(bean.doublePropertyWithDefaultValue, is(closeTo(
                 ConfigProvider.getConfig().getOptionalValue("my.not.configured.double.property", Double.class)
                         .orElse(3.1415), 0.1)));
+        Assert.assertNull("The injected field nullableConfigValue is null", bean.nullableConfigValue);
+
     }
 
     @Test
@@ -251,6 +257,10 @@ public static class SimpleValuesBean {
         @Inject
         @ConfigProperty(name="my.not.configured.double.property", defaultValue = "3.1415")
         private Double doublePropertyWithDefaultValue;
+        // the property is not configured in any ConfigSoources, so null will be used to set the filed
+        @Inject
+        @ConfigProperty(name="my.not.configured.nullable.property", defaultValue = ConfigProperty.NULL_VALUE)
+        private String nullableConfigValue;
 
     }