[JPMS] Letting spec module open target packages towards impl module instead of propagating lookup object

Author: gunnarmorling

java9/spec-modularity-patterns/acme-fieldreader-impl/src/main/java/acme/fieldreader/impl/AcmeBootstrapDelegate.java

@@ -6,7 +6,7 @@
 public class AcmeBootstrapDelegate implements BootstrapDelegate {
 
     @Override
-    public FieldValueReader getFieldValueReader(LookupProvider lookupProvider) {
-        return new FieldValueReaderImpl( lookupProvider );
+    public FieldValueReader getFieldValueReader(PackageOpener opener) {
+        return new FieldValueReaderImpl( opener );
     }
 }

java9/spec-modularity-patterns/acme-fieldreader-impl/src/main/java/acme/fieldreader/impl/FieldValueReaderImpl.java

@@ -1,24 +1,46 @@
 package acme.fieldreader.impl;
 
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodHandles.Lookup;
+
 import fieldreader.spec.FieldValueReader;
-import fieldreader.spec.bootstrap.BootstrapDelegate.LookupProvider;
+import fieldreader.spec.bootstrap.BootstrapDelegate.PackageOpener;
 
 public class FieldValueReaderImpl implements FieldValueReader {
 
-    private LookupProvider lookupProvider;
+    private final ClassValue<Lookup> lookups;
+
+    public FieldValueReaderImpl(PackageOpener moduleOpener) {
+        this.lookups = new ClassValue<Lookup>() {
+
+            @Override
+            protected Lookup computeValue(Class<?> type) {
+                if ( !getClass().getModule().canRead( type.getModule() ) ) {
+                    getClass().getModule().addReads( type.getModule() );
+                }
+
+                moduleOpener.openPackageIfNeeded(
+                        type.getModule(), type.getPackageName(), FieldValueReaderImpl.class.getModule()
+                );
 
-    public FieldValueReaderImpl(LookupProvider lookupProvider) {
-        this.lookupProvider = lookupProvider;
+                try {
+                    return MethodHandles.privateLookupIn( type, MethodHandles.lookup() );
+                }
+                catch (IllegalAccessException e) {
+                    throw new RuntimeException( e );
+                }
+            }
+        };
     }
 
     @Override
     public Object getFieldValue(Object o, String fieldName) {
         try {
-            return lookupProvider.getPrivateLookup( o )
+            return lookups.get( o.getClass() )
                     .unreflectVarHandle( o.getClass().getDeclaredField( fieldName ) )
                     .get( o );
         }
-        catch (Throwable e) {
+        catch (Exception e) {
             throw new RuntimeException( e );
         }
     }

java9/spec-modularity-patterns/fieldreader-spec/src/main/java/fieldreader/spec/FieldReaderApi.java

@@ -1,47 +1,29 @@
 package fieldreader.spec;
 
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.MethodHandles.Lookup;
 import java.util.ServiceLoader;
 
 import fieldreader.spec.bootstrap.BootstrapDelegate;
-import fieldreader.spec.bootstrap.BootstrapDelegate.LookupProvider;
+import fieldreader.spec.bootstrap.BootstrapDelegate.PackageOpener;
 
 public class FieldReaderApi {
 
-    private static final LookupProvider LOOKUP_PROVIDER = new LookupProviderImpl();
+    private static final PackageOpener PACKAGE_OPENER = new PackageOpenerImpl();
 
     public static FieldValueReader getFieldValueReader() {
         ServiceLoader<BootstrapDelegate> loader = ServiceLoader.load( BootstrapDelegate.class );
 
         return loader.findFirst()
                 .orElseThrow( () -> new IllegalStateException( "No provider of " + BootstrapDelegate.class.getName() + " available" ) )
-                .getFieldValueReader( LOOKUP_PROVIDER );
+                .getFieldValueReader( PACKAGE_OPENER );
     }
 
-    private static class LookupProviderImpl implements BootstrapDelegate.LookupProvider {
-
-        private final ClassValue<Lookup> classValue;
-
-        private LookupProviderImpl() {
-            classValue = new ClassValue<Lookup>() {
-
-                @Override
-                protected Lookup computeValue(Class<?> type) {
-                    FieldValueReader.class.getModule().addReads( type.getModule() );
-                    try {
-                        return MethodHandles.privateLookupIn( type, MethodHandles.lookup() );
-                    }
-                    catch (IllegalAccessException e) {
-                        throw new RuntimeException( e );
-                    }
-                }
-            };
-        }
+    private static class PackageOpenerImpl implements BootstrapDelegate.PackageOpener {
 
         @Override
-        public Lookup getPrivateLookup(Object o) {
-            return classValue.get( o.getClass() );
+        public void openPackageIfNeeded(Module targetModule, String targetPackage, Module specImplModule) {
+            if ( !targetModule.isOpen( targetPackage, specImplModule ) ) {
+                targetModule.addOpens( targetPackage, specImplModule );
+            }
         }
     }
 }

java9/spec-modularity-patterns/fieldreader-spec/src/main/java/fieldreader/spec/bootstrap/BootstrapDelegate.java

@@ -1,14 +1,12 @@
 package fieldreader.spec.bootstrap;
 
-import java.lang.invoke.MethodHandles.Lookup;
-
 import fieldreader.spec.FieldValueReader;
 
 public interface BootstrapDelegate {
 
-    FieldValueReader getFieldValueReader(LookupProvider lookupProvider);
+    FieldValueReader getFieldValueReader(PackageOpener opener);
 
-    public interface LookupProvider {
-        Lookup getPrivateLookup(Object o);
+    public interface PackageOpener {
+        void openPackageIfNeeded(Module targetModule, String targetPackage, Module specImplModule);
     }
 }