什么是servlet的init()方法用于？

Question

当我反编译GenericServlet并检查init()时,我看到以下代码.

public void init(ServletConfig servletconfig)
    throws ServletException
{
    config = servletconfig;
    init();
}

public void init()
    throws ServletException
{
}

这里实际做的init方法是什么？我错过了什么吗？

Answer 1

是的,它什么都不做.它可能是抽象的,但随后每个servlet都将被强制实现它.这样,默认情况下,没有任何操作init(),每个servlet都可以覆盖此行为.例如,您有两个servlet:

public PropertiesServlet extends HttpServlet {

   private Properties properties;

   @Override
   public void init() {
       // load properties from disk, do be used by subsequent doGet() calls
   }
}

和

public AnotherServlet extends HttpServlet {

   // you don't need any initialization here, 
   // so you don't override the init method.
}

Answer 2

来自javadoc:

/**
 *
 * A convenience method which can be overridden so that there's no need
 * to call <code>super.init(config)</code>.
 *
 * <p>Instead of overriding {@link #init(ServletConfig)}, simply override
 * this method and it will be called by
 * <code>GenericServlet.init(ServletConfig config)</code>.
 * The <code>ServletConfig</code> object can still be retrieved via {@link
 * #getServletConfig}. 
 *
 * @exception ServletException  if an exception occurs that
 *                  interrupts the servlet's
 *                  normal operation
 *
 */

所以它什么都不做,只是一个方便.