web容器在启动的时候,它会为每个web程序都创建一个对应的ServletContext对象,它代表了当前的web应用;
作用:
1)共享数据,我在这个servlet中保存的数据,可以在另外一个servlet中拿到
HelloServlet
public class HelloServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
String username = "老尹"; // 数据
context.setAttribute("username",username); // 将一个数据保存在ServletContext中
}
}
getc
public class GetServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
// 获得ServletContext中放置的uaername数据,强转为String
String username = (String)context.getAttribute("username");
resp.setContentType("text/html"); // 设置文本格式
resp.setCharacterEncoding("utf-8"); // 设置字符格式
resp.getWriter().print("name" + username); // 输出信息到网页
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
2) 获取初始化参数
<context-param>
<param-name>url</param-name>
<param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
String url = context.getInitParameter("url");
resp.getWriter().print(url);
}
3)请求转发
gp的代码(gp是ServletDemo03的缩写)
package com.kuang.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class ServletDemo03 extends HelloServlet {
@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 {
doGet(req, resp);
}
}
图解重定向和转发:
重定向
转发
4:读取资源文件
Properties类
标签:ServletContext,ServletException,resp,req,IOException,context From: https://blog.51cto.com/u_15810109/5718727