#1297 - ENH: Add DtoQuery ... such that we can map native SQL queries automatically into "DTO beans"

src/main/java/io/ebeaninternal/server/dto/DtoMetaConstructor.java

@@ -0,0 +1,67 @@
+package io.ebeaninternal.server.dto;
+
+import io.ebeaninternal.server.type.DataReader;
+import io.ebeaninternal.server.type.ScalarType;
+import io.ebeaninternal.server.type.TypeManager;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.lang.reflect.Constructor;
+import java.sql.SQLException;
+
+class DtoMetaConstructor {
+
+	private final Class<?>[] types;
+	private final MethodHandle handle;
+  private final ScalarType<?>[] scalarTypes;
+
+	DtoMetaConstructor(TypeManager typeManager, Constructor<?> constructor, Class<?> someClass) throws NoSuchMethodException, IllegalAccessException {
+
+    this.types = constructor.getParameterTypes();
+    this.scalarTypes = new ScalarType[types.length];
+    for (int i = 0; i < types.length; i++) {
+      scalarTypes[i] = typeManager.getScalarType(types[i]);
+    }
+
+    MethodHandles.Lookup lookup = MethodHandles.publicLookup();
+		this.handle = lookup.findConstructor(someClass, typeFor(types));
+	}
+
+	private MethodType typeFor(Class<?>[] types) {
+		return MethodType.methodType(void.class, types);
+	}
+
+  Class<?>[] getTypes() {
+    return types;
+  }
+
+  int getArgCount() {
+    return types.length;
+  }
+
+  Object defaultConstructor() {
+    try {
+      return handle.invokeWithArguments();
+    } catch (Throwable e) {
+      throw new RuntimeException("Unexpected error invoking constructor", e);
+    }
+  }
+
+	public Object process(DataReader dataReader) throws SQLException {
+    Object[] values = new Object[scalarTypes.length];
+    for (int i = 0; i < scalarTypes.length; i++) {
+      values[i] = scalarTypes[i].read(dataReader);
+    }
+    return invoke(values);
+  }
+
+	private Object invoke(Object... args) {
+	  try {
+	    return handle.invokeWithArguments(args);
+    } catch (Throwable e) {
+	    throw new RuntimeException("Unexpected error invoking constructor", e);
+    }
+	}
+
+}