servlet的ServletConfig接口

ServletConfig接口

　　　　　　

A servlet configuration object used by a servlet container to pass information to a servlet during initialization.

servlet 容器使用的 servlet 配置对象，该对象在初始化期间将信息传递给 servlet。

web.xml配置

  <servlet>
  	<servlet-name>hello</servlet-name>
  	<servlet-class>com.qf.servlet.HelloServlet3</servlet-class>
  	<init-param>
  		<param-name>name</param-name>
  		<param-value>wxf</param-value>
  	</init-param>
  	<init-param>
  		<param-name>age</param-name>
  		<param-value>24</param-value>
  	</init-param>
  </servlet>
  <servlet-mapping>
  	<servlet-name>hello</servlet-name>
  	<url-pattern>/*</url-pattern>
  </servlet-mapping>

servlet类编写

 public class HelloServlet extends HttpServlet {

     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         System.out.println("doGet");
         testServletConfig();
     }

     public void testServletConfig() {

         //得到servlet配置对象 专门用于在配置servlet的信息
         ServletConfig config = getServletConfig();

         //获取到的是配置servlet里面servlet-name 的文本内容
         String servletName = config.getServletName();
         System.out.println("servletName==="+servletName);
         System.out.println("-----------");

         //获取ServletContext
         ServletContext context = config.getServletContext();
         String path = context.getContextPath();
         System.out.println("path==="+path);
         System.out.println("-----------");

         //获取某一具体的参数
         String name = config.getInitParameter("name");
         System.out.println("name==="+name);
         System.out.println("-----------");

         //获取所有的参数名称
         Enumeration<String> names = config.getInitParameterNames();
         //遍历取出所有的参数名称
         while (names.hasMoreElements()) {
             String key = (String) names.nextElement();
             String value = config.getInitParameter(key);
             System.out.println("key==="+key + "   value==="+value);

         }
     }
 }

url（http://localhost:8080/HelloServlet/hello）访问后控制台输出

doGet
servletName===hello
-----------
path===/HelloServlet
-----------
name===wxf
-----------
key===name   value===wxf
key===age   value===24

ServletConfig的作用：可以在web.xml的<init-param>标签中配置一些变量值，并在servlet中根据param-name获取