【Servlet】session保存作用域

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

java 复制代码

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

Demo05Servlet.java

java 复制代码

// 演示从HttpSession保存作用域中获取数据
public class Demo05Servlet extends HttpServlet {
    @Override
    protected 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

xml 复制代码

<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>