Java-GenricServlet

public abstract class GenericServlet
    implements Servlet, ServletConfig, java.io.Serializable
{

    private transient ServletConfig config;
    /**
     * Does nothing. All of the servlet initialization
     * is done by one of the <code>init</code> methods.
     */
    //空构造函数，所有的servlet初始化已经被init函数执行
    public GenericServlet() { }

   /**
     * Called by the servlet container to indicate to a servlet that the
     * servlet is being taken out of service.  See {@link Servlet#destroy}.
     */
    //servlet容器调用，表明servlet被移除服务
    public void destroy() {
    }
    /**
     * Returns a <code>String</code> containing the value of the named
     * initialization parameter, or <code>null</code> if the parameter does
     * not exist.  See {@link ServletConfig#getInitParameter}.
     * <p>This method is supplied for convenience. It gets the
     * value of the named parameter from the servlet's
     * <code>ServletConfig</code> object.
     * @param name 		a <code>String</code> specifying the name
     *				of the initialization parameter
     * @return String 		a <code>String</code> containing the value
     *				of the initialization parameter
     */
    //获得初始化参数name的值
    public String getInitParameter(String name) {
    	return getServletConfig().getInitParameter(name);
    }
    //初始化参数枚举
    public Enumeration getInitParameterNames() {
    	return getServletConfig().getInitParameterNames();
    }
    /**
     * Returns this servlet's {@link ServletConfig} object.
     * @return ServletConfig 	the <code>ServletConfig</code> object that initialized this servlet
     */
    //获得servlet的初始化对象
    public ServletConfig getServletConfig() {
	return config;
    }
    /**
     * Returns a reference to the {@link ServletContext} in which this servlet
     * is running.  See {@link ServletConfig#getServletContext}.
     * <p>This method is supplied for convenience. It gets the
     * context from the servlet's <code>ServletConfig</code> object.
     * @return ServletContext 	the <code>ServletContext</code> object passed to this servlet by the <code>init</code>method
     */
    //返回正在运行的servlet的ServletContext，
    public ServletContext getServletContext() {
    	return getServletConfig().getServletContext();
    }
    /**
     * Returns information about the servlet, such as  author, version, and copyright.
     * By default, this method returns an empty string.  Override this method
     * to have it return a meaningful value.  See {@link Servlet#getServletInfo}.
     * @return String 		information about this servlet, by default an empty string
     */
    //获得Servlet信息
    public String getServletInfo() {
    	return "";
    }
    /**
     * Called by the servlet container to indicate to a servlet that the
     * servlet is being placed into service.  See {@link Servlet#init}.
     * <p>This implementation stores the {@link ServletConfig}  object it receives from the servlet container for later use. When overriding this form of the method, call
     * <code>super.init(config)</code>.
     * @param config 			the <code>ServletConfig</code> object that contains configutation information for this servlet
     * @exception ServletException 	if an exception occurs that interrupts the servlet's normal operation
     * @see UnavailableException
     */
    //servlet容器进行调用，表明这个Servlet被放置进服务
    public void init(ServletConfig config) throws ServletException {
    	this.config = config;
    	this.init();
    }

    /**
     * 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
     */

    public void init() throws ServletException {

    }
    /**
     * Writes the specified message to a servlet log file, prepended by the
     * servlet's name.  See {@link ServletContext#log(String)}.
     * @param msg 	a <code>String</code> specifying
     *			the message to be written to the log file
     */
     //写Servlet名和信息日志
    public void log(String msg) {
    	getServletContext().log(getServletName() + ": "+ msg);
    }
    /**
     * Writes an explanatory message and a stack trace
     * for a given <code>Throwable</code> exception
     * to the servlet log file, prepended by the servlet's name.
     * See {@link ServletContext#log(String, Throwable)}.
     * @param message 		a <code>String</code> that describes the error or exception
     * @param t			the <code>java.lang.Throwable</code> error or exception
     */

    public void log(String message, Throwable t) {
	getServletContext().log(getServletName() + ": " + message, t);
    }
    /**
     * Called by the servlet container to allow the servlet to respond to
     * a request.  See {@link Servlet#service}.
     *
     * <p>This method is declared abstract so subclasses, such as
     * <code>HttpServlet</code>, must override it.
     * @param req 	the <code>ServletRequest</code> object	that contains the client's request
     * @param res 	the <code>ServletResponse</code> object that will contain the servlet's response
     * @exception ServletException 	if an exception occurs that interferes with the servlet's normal operation occurred
     * @exception IOException 		if an input or output exception occurs
     */
    //servlet 容器调用来运行Servlet 对请求进行回复
    public abstract void service(ServletRequest req, ServletResponse res)
	throws ServletException, IOException;
    /**
     * Returns the name of this servlet instance.
     * See {@link ServletConfig#getServletName}.
     * @return          the name of this servlet instance
     */
    //Servlet名称
    public String getServletName() {
        return config.getServletName();
    }
}