session保存作用域：一次会话范围都有效

Java的服务器端，有一块内存专门存储在session保存作用域的数据。

session保存作用域是和具体的某一个session对应的。

常用API：

• void session.setAttribute(k, v)
• Object session.getAttrivute(k) —> 返回的是Object类型的
• void removeAttribute(k)

代码示例

Demo04Servlet.java

// 演示向HttpSession保存数据
public class Demo04Servlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.getSession().setAttribute("uname", "lina");}
}

Demo05Servlet.java

// 演示从HttpSession保存作用域中获取数据
public class Demo05Servlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 它获取到的是Object类型Object unameObj = request.getSession().getAttribute("uname");System.out.println(unameObj);}
}

web.xml

<servlet><servlet-name>Demo04Servlet</servlet-name><servlet-class>com.atguigu.servlets.Demo04Servlet</servlet-class>
</servlet>
<servlet-mapping><servlet-name>Demo04Servlet</servlet-name><url-pattern>/demo04</url-pattern>
</servlet-mapping><servlet><servlet-name>Demo05Servlet</servlet-name><servlet-class>com.atguigu.servlets.Demo05Servlet</servlet-class>
</servlet>
<servlet-mapping><servlet-name>Demo05Servlet</servlet-name><url-pattern>/demo05</url-pattern>
<servlet-mapping>