Puzzle between modelAttribute and commandName in Spring FormTag

    平常用的时候form tag都是用commandName来设定form的对象上下文。
    看Spring例子的时候又发现了个modelAttribute，有着一样的功能。在国外的网站查了查，有如此的解释

 
/**
 * Set the name of the form attribute in the model.
 * May be a runtime expression.
 * @see #setModelAttribute
 */
public void setCommandName(String commandName) {
	this.modelAttribute = commandName;
}

发现modelAttribute取代了commandName属性

<form:form modelAttribute="user">
  <table>
    <tr>
      <td>First Name:</td>
      <td>
        <input path="firstName"/>
      </td>
    </tr>
    <tr>
      <td>Last Name:</td>
      <td>
        <input path="lastName"/>
      </td>
    </tr>
    <tr>
      <td colspan="2">
        <input type="submit" value="Save Changes"/>
      </td>
    </tr>
  </table>
</form:form>