Servlet之ServletContext获取web上下文路径、全局参数、和Attribute（域）

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1)获取web上下文路径

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//获取ServletContext对象//this.getServletConfig().getServletContext();//等同于下面一句，因为创建getServletContext必须要通过getServletConfig对象ServletContext context = this.getServletContext();//获取web的上下文路径，String path = context.getContextPath();//请求重定向，这样的好处可以让获取的路径更加灵活。不用考虑项目名是否发生了变化。response.sendRedirect(context.getContextPath()+"/index.jsp");}}

2）获取全局参数

public class ServletContextDemo1 extends HttpServlet {/** * 获取全局参数 */public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { ServletContext context = this.getServletContext(); //根据参数名获取参数值 System.out.println(context.getInitParameter("MMM")); //获取所有的参数名，返回枚举类型 Enumeration<String> emn = context.getInitParameterNames(); while(emn.hasMoreElements()){ String paramName = emn.nextElement(); String paramValue = context.getInitParameter(paramName); System.out.println(paramName+"="+paramValue); }}}

3)和域相关

域：域对象在不同的资源之间来共享数据，保存数据，获取数据。

这个我使用了三个Servlet来说明这个问题，ScopeDemo1用于获取Attribute，ScopeDemo2用于设置Attribute，ScopeDemo3用于删除Attribute。

保存共享数据：

public class ScopeDemo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//首先创建ServletContext对象ServletContext context = this.getServletContext();//保存共享数据context.setAttribute("name", "zhangsan");//第一个参数为字符串，第二个是Object（也就是任意类型）System.out.println("设置成功");}}

获取恭喜数据：

public class ScopeDemo1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//创建ServletContext对象ServletContext context = this.getServletContext();//获取共享数据内容String name = (String)context.getAttribute("nnn");System.out.println(name);}}

删除共享数据：

public class ScopeDemo3 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//获取ServletContext对象ServletContext context = this.getServletContext();//删除共享数据context.removeAttribute("name");System.out.println("删除成功");}}

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