项目搭建参照： JavaWeb——HelloServlet

ServletContext

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。

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。
- 放置数据的类

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

public class HelloServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {



//        this.getServletContext()      Servlet上下文
        ServletContext context = this.getServletContext();

        String name = "秦疆";//数据
        //将一个数据保存在了ServletContext中，名字为（键为）：username；值为：上面创建的name
        context.setAttribute("username",name);

        System.out.println("Hello");
    }
}

读取数据的类

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class GetServlet  extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String username = (String) context.getAttribute("username");
		//处理中文乱码
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        resp.getWriter().print("名字:"+username);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

web.xml

<servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>com.kuang.servlet.HelloServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>getc</servlet-name>
    <servlet-class>com.kuang.servlet.GetServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>getc</servlet-name>
    <url-pattern>/getc</url-pattern>
  </servlet-mapping>