added foreign keys

src/main/java/jef/model/annotations/ForeignKey.java

@@ -0,0 +1,23 @@
+package jef.model.annotations;
+
+import jef.model.constraints.ForeignKeyConstraint;
+import jef.serializable.SerializableObject;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Documented
+@Target({ElementType.FIELD})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface ForeignKey {
+    String getterOrField();
+
+    Class<? extends SerializableObject> entity() default SerializableObject.class;
+
+    ForeignKeyConstraint.Action onUpdate() default ForeignKeyConstraint.Action.RESTRICT;
+
+    ForeignKeyConstraint.Action onDelete() default ForeignKeyConstraint.Action.CASCADE;
+}