autodetect unsafe allocations metadata (#2883)

Author: riccardobl

jme3-core/src/main/java/com/jme3/util/PreserveReflection.java

@@ -43,4 +43,11 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.TYPE)
 public @interface PreserveReflection {
+    /**
+     * When true, metadata generators should also allow this type to be allocated
+     * without invoking a constructor.
+     *
+     * @return true to include unsafe allocation metadata
+     */
+    boolean allowUnsafeAllocation() default true;
 }

jme3-nativeimage-plugin/README.md

@@ -77,7 +77,14 @@ public class MyNiftyController {
 ```
 
 Classes annotated with `@PreserveReflection` are included by default when this
-plugin generates metadata. 
+plugin generates metadata. They are also marked as unsafe-allocatable by default.
+Disable that when a reflected type must always be constructed normally:
+
+```java
+@PreserveReflection(allowUnsafeAllocation = false)
+public class ConstructorOnlyEntryPoint {
+}
+```
 
 
 ## Default Resource Settings
@@ -134,6 +141,32 @@ jmeNativeImage {
 }
 ```
 
+### Unsafe Allocation
+
+The plugin automatically detects direct construction of known unsafe allocation
+container types, such as `SafeArrayList(SomeType.class)`, in compiled classes and
+adds unsafe allocation metadata for the corresponding `SomeType[]` array storage.
+By default, the container list contains `com.jme3.util.SafeArrayList`.
+
+You can also add explicit unsafe allocation entries:
+
+```groovy
+jmeNativeImage {
+    unsafeAllocatedType 'org.example.Foo'
+    unsafeAllocatedType 'org.example.Bar[]'
+    unsafeAllocatedType '[Lorg.example.Baz;'
+}
+```
+
+If a project has another container type with the same `Class`-first constructor
+pattern, add it to the detector:
+
+```groovy
+jmeNativeImage {
+    unsafeAllocationContainerType 'org.example.MyArrayStore'
+}
+```
+
 ### Proxy Interfaces
 
 If your application uses dynamic proxies, configure the interface set:

jme3-nativeimage-plugin/src/main/groovy/org/jmonkeyengine/gradle/nativeimage/JmeNativeImageExtension.groovy

@@ -14,6 +14,8 @@ class JmeNativeImageExtension {
     final ListProperty<String> additionalTargetTypes
     final ListProperty<String> additionalTargetAnnotations
     final ListProperty<List<String>> additionalProxyInterfaceSets
+    final ListProperty<String> additionalUnsafeAllocatedTypes
+    final ListProperty<String> additionalUnsafeAllocationContainerTypes
     final ListProperty<String> additionalResourceGlobs
     final Property<String> includeResourcesPattern
     final Property<String> excludeResourcesPattern
@@ -24,6 +26,8 @@ class JmeNativeImageExtension {
         additionalTargetTypes = objects.listProperty(String).convention([])
         additionalTargetAnnotations = objects.listProperty(String).convention([])
         additionalProxyInterfaceSets = objects.listProperty(List).convention([])
+        additionalUnsafeAllocatedTypes = objects.listProperty(String).convention([])
+        additionalUnsafeAllocationContainerTypes = objects.listProperty(String).convention([])
         additionalResourceGlobs = objects.listProperty(String).convention([])
         includeResourcesPattern = objects.property(String)
         excludeResourcesPattern = objects.property(String)
@@ -42,6 +46,14 @@ class JmeNativeImageExtension {
         additionalProxyInterfaceSets.add(interfaceClassNames.toList())
     }
 
+    void unsafeAllocatedType(String className) {
+        additionalUnsafeAllocatedTypes.add(className)
+    }
+
+    void unsafeAllocationContainerType(String className) {
+        additionalUnsafeAllocationContainerTypes.add(className)
+    }
+
     void resourceGlob(String glob) {
         additionalResourceGlobs.add(glob)
     }