关于java:Servlet之ServletContext和ServletConfig

ServletContext

1、作用
解决不同用户之间数据共享问题
2、特点

• 由服务器创立
• 所有用户共享同一个ServletContext对象
• 所有的Servlet都能够拜访到ServletContext中的属性
• 每一个web我的项目对应的是一个ServletContext

3、 用法

public class ContextServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //3种形式获取ServletContext对象
        ServletContext sc1 = this.getServletContext();//罕用
        ServletContext sc2 = this.getServletConfig().getServletContext();
        ServletContext sc3 = request.getSession().getServletContext();
        //设置属性
        sc1.setAttribute("name","zhangsan");
    }
}

public class ContextServlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取ServletContext对象
        ServletContext sc = this.getServletContext();
        //获取在contextServlet类中设置的属性
        String name = (String) sc.getAttribute("name");
        System.out.println(name);//zhangsan
    }
}