code: public boolean delete() {
  		Table table = _getTable();
  		String[] pKeys = table.getPrimaryKey();
  		if (pKeys.length == 1) {	// 优化：主键大概率只有一个
  			Object id = attrs.get(pKeys[0]);
  			if (id == null)
  				throw new ActiveRecordException("Primary key " + pKeys[0] + " can not be null");
  			return deleteById(table, id);
  		}
  		
  		Object[] ids = new Object[pKeys.length];
  		for (int i=0; i<pKeys.length; i++) {
  			ids[i] = attrs.get(pKeys[i]);
  			if (ids[i] == null)
  				throw new ActiveRecordException("Primary key " + pKeys[i] + " can not be null");
  		}
  		return deleteById(table, ids);
  	}
docs: Delete model.