Servlet之ServletContext获取web上下文路径、全局参数、和Attribute(域)
2017-01-28 23:20
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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");
}
}
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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