javaWeb-Servlet(一)

/**
 *查看Servlet接口中的方法
 */
public class AServlet implements Servlet {
    /*
     *它也是生命周期方法
     *它会在Servlet被销毁之前调用，并且它只会被调用一次！ 
     */
    @Override
    public void destroy() {
        System.out.println("destory().....");
    }
    
    /*
     * 可以用来获取Servlet的配置信息
     */
    @Override
    public ServletConfig getServletConfig() {
        System.out.println("getServletConfig().........");
        return null;
    }
    
    /*
     *获取Servlet信息 
     */
    @Override
    public String getServletInfo() {
        System.out.println("getServletInfo()......");
        return null;
    }
    
    /*
     * 它是生命周期方法
     * 它会在Servlet对象创建之后马上执行，并只执行一次！(出声之后调用)
     */
    @Override
    public void init(ServletConfig arg0) throws ServletException {
        System.out.println("init()....");
    }

    /*
     * 它是生命周期方法
     * 它会被调用多次！
     * 每次处理请求都是在调用这个方法
     */
    @Override
    public void service(ServletRequest request, ServletResponse response) 
            throws ServletException, IOException {
        System.out.println("service()......");
    }

 <servlet>
    <servlet-name>AServlet</servlet-name>
    <servlet-class>cn.itcast.web.servlet.AServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>AServlet</servlet-name>
    <url-pattern>/AServlet</url-pattern>
  </servlet-mapping>

1. public void init(ServletConfig config) throws ServletException  
2. public abstract void service(ServletRequest req,ServletResponse res) throws ServletException, java.io.IOException
3. public void destroy()
　

@Override
    public void destroy() {
        // NOOP by default
    }

    /**
     * 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
     */
    @Override
    public String getInitParameter(String name) {
        return getServletConfig().getInitParameter(name);
    }

    /**
     * Returns the names of the servlet‘s initialization parameters as an
     * <code>Enumeration</code> of <code>String</code> objects, or an empty
     * <code>Enumeration</code> if the servlet has no initialization parameters.
     * See {@link ServletConfig#getInitParameterNames}.
     * <p>
     * This method is supplied for convenience. It gets the parameter names from
     * the servlet‘s <code>ServletConfig</code> object.
     * 
     * @return Enumeration an enumeration of <code>String</code> objects
     *         containing the names of the servlet‘s initialization parameters
     */
    @Override
    public Enumeration<String> getInitParameterNames() {
        return getServletConfig().getInitParameterNames();
    }

    /**
     * Returns this servlet‘s {@link ServletConfig} object.
     * 
     * @return ServletConfig the <code>ServletConfig</code> object that
     *         initialized this servlet
     */
    @Override
    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
     */
    @Override
    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
     */
    @Override
    public String getServletInfo() {
        return "";
    }