1、ServletContext

web容器在启动的时候，它会为每个web程序都创立一个对应的ServletContext对象，它代表了以后web利用；
1、共享数据
我在这个Servlet中保留的数据，能够在另一个servlet中拿到
例子：给Servlet搁置数据

public class HelloServlet extends HttpServlet {    @Override   protected void doGet(HttpServletRequest req, HttpServletResponse response) throws                               ServletException, IOException {   //this.getInitParameter();//初始化参数   //this.getServletConfig();//Servlet配置   //this.getServletContext();//Servlet上下文    ServletContext context = this.getServletContext();    String username = "rygar";    context.setAttribute("username",username);    }@Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        super.doPost(req, resp);    }

在另一个Servlet去取进去

public class GetServlet extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        ServletContext context = this.getServletContext();        Object username = context.getAttribute("username");        resp.setContentType("text/html");        resp.setCharacterEncoding("UTF-8");        resp.getWriter().print(username);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        super.doPost(req, resp);    }}

web.xml配置

<servlet>    <servlet-name>hello</servlet-name>    <servlet-class>com.jialidun.servlet.HelloServlet</servlet-class></servlet><servlet-mapping>    <servlet-name>hello</servlet-name>    <servlet-class>hello</servlet-class></servlet-mapping><servlet>    <servlet-name>getc</servlet-name>    <servlet-class>com.jialidun.servlet.GetServlet</servlet-class></servlet><servlet-mapping>    <servlet-name>getc</servlet-name>    <servlet-class>getc</servlet-class></servlet-mapping>

2、获取初始化参数

<!--配置一些web利用初始化参数--><context-param>    <param-name>url</param-name>    <param-value>jdbc:mysql://localhost:3306/mybatis</param-value><context-param>

public class GetServlet extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws     ServletException, IOException {        ServletContext context = this.getServletContext();        String url = context.getInitParameter("url");        resp.getWriter().print(url);        }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        super.doPost(req, resp);    }}

3、申请转发

 @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {            ServletContext context = this.getServletContext();            RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp");//转发的申请门路        requestDispatcher.forward(req,resp);//调用forword实现申请转发 }

4、读取资源文件
Properties

在resources目录下新建properties
发现：都被打包到了同一个门路下：classes，咱们俗称这个门路为classpath
思路：须要一个文件流

username=root123password=123456

 @Override  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {      InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");//   /代表以后web我的项目      Properties prop = new Properties();      prop.load(is);      String username = prop.getProperty("username");      String password = prop.getProperty("password");      resp.getWriter().print(username+":"+password);   }

拜访测试后果