16 域对象4 Application域

- 日理万妓 2023-09-27 15:59 91阅读 0赞

Application域

有效范围

当前web服务内,跨请求,跨会话

生命周期

创建 项目启动

使用 项目运行任何时间有效

销毁 项目关闭

测试代码

Application域中放入数据

package com.msb.testApplication;
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;
    /**
     * @Author: Ma HaiYang
     * @Description: MircoMessage:Mark_7001
     */
    @WebServlet(urlPatterns = "/addToApplication.do")
    public class Servlet1 extends HttpServlet {
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            // 向Application域中添加数据
            ServletContext application = req.getServletContext();
            List<String> x=new ArrayList<>();
            Collections.addAll(x, "a","b","c");
            application.setAttribute("list", x);
            application.setAttribute("gender","girl");
            application.setAttribute("name","晓明");
        }
    }

![f04e13efd29de417cc51528872399bd8.gif][]

![94d2684473713bf1c6755d69531582b6.gif][]

Application域中读取数据

package com.msb.testApplication;
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    import java.util.List;
    /**
     * @Author: Ma HaiYang
     * @Description: MircoMessage:Mark_7001
     */
    @WebServlet(urlPatterns="/readFromApplication.do")
    public class Servlet2 extends HttpServlet {
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            ServletContext application = this.getServletContext();
            // 从application域中读取数据
            List<String> list =(List<String>) application.getAttribute("list");
            System.out.println(list);
            System.out.println(application.getAttribute("gender"));
            System.out.println(application.getAttribute("name"));
        }
    }

![fa465ec345f0383bca6cf6842a916c88.gif][]

![a6cb9b4fc6ebf47911d25137f59f9781.gif][]

[f04e13efd29de417cc51528872399bd8.gif]: https://img-blog.csdnimg.cn/img_convert/f04e13efd29de417cc51528872399bd8.gif
[94d2684473713bf1c6755d69531582b6.gif]: https://img-blog.csdnimg.cn/img_convert/94d2684473713bf1c6755d69531582b6.gif
[fa465ec345f0383bca6cf6842a916c88.gif]: https://img-blog.csdnimg.cn/img_convert/fa465ec345f0383bca6cf6842a916c88.gif
[a6cb9b4fc6ebf47911d25137f59f9781.gif]: https://img-blog.csdnimg.cn/img_convert/a6cb9b4fc6ebf47911d25137f59f9781.gif