标签：text art etc val images exce try context super
生命周期：是一个程序的存在周期，servlet由于是受容器的管理，所以容器来决定其生命周期
public class LifeCycleServlet extends HttpServlet{ public void init() throws ServletException{ System.out.println("** 1、Servlet初始化 --> init()") ; } public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{ System.out.println("** 2、Servlet服务 --> doGet()、doPost()") ; } public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{ this.doGet(req,resp) ; } public void destroy(){ System.out.println("** 3、Servlet销毁 --> destory()") ; try{ Thread.sleep(3000) ; }catch(Exception e){} }/* public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException{ System.out.println("************ 服务 **************") ; } */ }
一个基本生命周期编译后，就可以在web-INF/web.xml中进行映射配置。下面直接在根目录下配置
<servlet>
<servlet-name>life</servlet-name>
<servlet-class>com.alice.servlet.LifeCycleServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>life</servlet-name>
<url-pattern>/LifeServlet</url-pattern>
访问路径为:
public class InitParamServlet extends HttpServlet { private String initParam = null ; // 用于保存初始化参数 public void init() throws ServletException{ System.out.println("*****************") ; } public void init(ServletConfig config) throws ServletException{ System.out.println("#######################") ; this.initParam = config.getInitParameter("ref") ; // 接收的初始化参数名称暂时为ref } public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{ System.out.println("** 初始化参数：" + this.initParam) ; } public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{ this.doGet(req,resp) ; } }
之后，要做web.xml中配置
<servlet>
<servlet-name>initparam</servlet-name>
<servlet-class>com.alice.servlet.InitParamServlet</servlet-class>
<init-param>
<param-name>ref</param-name>
<param-value>www.baidu.cn</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>initparam</servlet-name>
<url-pattern>/InitParamServlet</url-pattern>
</servlet-mapping>
如果一个servlet中覆写了两个init（）方法，只有在web.xml中配置了参数的初始化方法才可以起作用。
一般来说，取得初始化参数在一些系统架构中经常使用的。
servlet本身提供的只有request和response对象，要想取得session对象，则只能依靠request对象，因为session本身属于http协议范畴，而且在每次发生请求时，服务器都会自动为客户端设置一个cookie，session中要使用cookie机制，cookie又只能通过request取得，那么自然地session也只能通过request取得。
public class HttpSessionDemoServlet extends HttpServlet {
public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{
HttpSession ses = req.getSession() ;
System.out.println("SESSION ID --> " + ses.getId()) ;
ses.setAttribute("username","李李") ; // 设置session属性
System.out.println("username属性内容：" + ses.getAttribute("username")) ;
}
public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{
this.doGet(req,resp) ;
}
}
之后进行web.xml进行配置
<servlet> <servlet-name>sessiondemo</servlet-name> <servlet-class> com.alice.servlet.HttpSessionDemoServlet </servlet-class> </servlet> <servlet-mapping> <servlet-name>sessiondemo</servlet-name> <url-pattern>/HttpSessionDemoServlet</url-pattern> </servlet-mapping>
public class ServletContextDemoServlet extends HttpServlet {
public void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{
ServletContext app = super.getServletContext() ;
System.out.println("真实路径：" + app.getRealPath("/")) ;
}
public void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{
this.doGet(req,resp) ;
}
}
<servlet>
<servlet-name>applicationdemo</servlet-name>
<servlet-class>
com.alice.servlet.ServletContextDemoServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>applicationdemo</servlet-name>
<url-pattern>/ServletContextDemoServlet</url-pattern>
</servlet-mapping>
javaWeb中servlet开发(3)——Servlet生命周期
标签：text art etc val images exce try context super
原文地址：http://www.cnblogs.com/snowwang/p/6103179.html
