Fixes #542, add some docs on the substrate build items

core/deployment/src/main/java/org/jboss/shamrock/deployment/builditem/substrate/ReflectiveClassBuildItem.java

@@ -21,6 +21,9 @@
 
 import org.jboss.builder.item.MultiBuildItem;
 
+/**
+ * Used to register a class for reflection in substrate
+ */
 public final class ReflectiveClassBuildItem extends MultiBuildItem {
 
     private final List<String> className;

core/deployment/src/main/java/org/jboss/shamrock/deployment/builditem/substrate/RuntimeReinitializedClassBuildItem.java

@@ -18,6 +18,10 @@
 
 import org.jboss.builder.item.MultiBuildItem;
 
+/**
+ * A class that will be reinitialized at runtime by Substrate. This will result in the static
+ * initializer running twice.
+ */
 public final class RuntimeReinitializedClassBuildItem extends MultiBuildItem {
 
     private final String className;

core/deployment/src/main/java/org/jboss/shamrock/deployment/builditem/substrate/SubstrateResourceBuildItem.java

@@ -22,6 +22,9 @@
 
 import org.jboss.builder.item.MultiBuildItem;
 
+/**
+ * A build item that indicates that a static resource should be included in the native image
+ */
 public final class SubstrateResourceBuildItem extends MultiBuildItem {
 
     private final List<String> resources;

core/deployment/src/main/java/org/jboss/shamrock/deployment/builditem/substrate/SubstrateResourceBundleBuildItem.java

@@ -18,6 +18,9 @@
 
 import org.jboss.builder.item.MultiBuildItem;
 
+/**
+ * Indicates that a resource bundle should be included in the native image
+ */
 public final class SubstrateResourceBundleBuildItem extends MultiBuildItem {
 
     private final String bundleName;

core/deployment/src/main/java/org/jboss/shamrock/deployment/builditem/substrate/SubstrateSystemPropertyBuildItem.java

@@ -18,6 +18,9 @@
 
 import org.jboss.builder.item.MultiBuildItem;
 
+/**
+ * A system property that will be set at native image build time
+ */
 public final class SubstrateSystemPropertyBuildItem extends MultiBuildItem {
 
     private final String key;

docs/src/main/asciidoc/extension-authors-guide.adoc

@@ -396,3 +396,31 @@ public class PersistenceAndShamrockConfigTest {
 ----
 
 <1> This tells JUnit that the Protean deployment should fail with a specific exception
+
+
+== Native Image Support
+
+There Shamrock provides a lot of build items that control aspects of the native image build. This allows for extensions
+to programmatically perform tests such as registering classes for reflection or adding static resources to the native
+image. Some of these build items are listed below:
+
+`org.jboss.shamrock.deployment.builditem.substrate.SubstrateResourceBuildItem`::
+ Includes static resources into the native image.
+
+`org.jboss.shamrock.deployment.builditem.substrate.RuntimeReinitializedClassBuildItem`::
+A class that will be reinitialized at runtime by Substrate. This will result in the static initializer running twice.
+
+`org.jboss.shamrock.deployment.builditem.substrate.SubstrateSystemPropertyBuildItem`::
+A system property that will be set at native image build time.
+
+`org.jboss.shamrock.deployment.builditem.substrate.SubstrateResourceBundleBuildItem`::
+Includes a resource bundle in the native image.
+
+`org.jboss.shamrock.deployment.builditem.substrate.ReflectiveClassBuildItem`::
+Registers a class for reflection in Substrate. Constructors are always registered, while methods and fields are optional.
+
+`org.jboss.shamrock.deployment.builditem.substrate.RuntimeInitializedClassBuildItem`::
+A class that will be initialized at runtime rather than build time. This will cause the build to fail if the class is initialized as part of the native image build process, so care must be taken.
+
+`org.jboss.shamrock.deployment.builditem.substrate.SubstrateConfigBuildItem`::
+A convenience feature that allows you to control most of the above features from a single build item.