Add validity assertions to Entity id accessors

Author: injectives

driver/src/main/java/org/neo4j/driver/internal/InternalEntity.java

@@ -46,6 +46,7 @@ public InternalEntity( long id, String elementId, Map<String,Value> properties )
     @Override
     public long id()
     {
+        assertValidId( id );
         return id;
     }
 
@@ -142,4 +143,12 @@ public <T> Iterable<T> values( Function<Value,T> mapFunction )
     {
         return Iterables.map( properties.values(), mapFunction );
     }
+
+    protected void assertValidId( long id )
+    {
+        if ( id < 0 )
+        {
+            throw new IllegalStateException( "id not available, please use elementId instead" );
+        }
+    }
 }

driver/src/main/java/org/neo4j/driver/internal/InternalRelationship.java

@@ -72,6 +72,7 @@ public void setStartAndEnd( long start, String startElementId, long end, String
     @Override
     public long startNodeId()
     {
+        assertValidId( start );
         return start;
     }
 
@@ -84,6 +85,7 @@ public String startNodeElementId()
     @Override
     public long endNodeId()
     {
+        assertValidId( end );
         return end;
     }