code: @Override
      public void setProperty(String paramString, Object paramObject)
      {
          checkClosed();
          if (getProperties() == null)
          {
              this.properties = new HashMap<String, Object>();
          }
  
          this.properties.put(paramString, paramObject);
          getPersistenceDelegator().populateClientProperties(this.properties);
      }
docs: Set an entity manager property or hint. If a vendor-specific property or
  hint is not recognized, it is silently ignored.
  
  @param propertyName
  name of property or hint
  @param value
  @throws IllegalArgumentException
  if the second argument is not valid for the implementation
  @see javax.persistence.EntityManager#setProperty(java.lang.String,
  java.lang.Object)