JavaWeb-Cookie和Session基本用法

Cookie

Cookie：有时也用其复数形式 Cookies。类型为“小型文本文件”，是某些网站为了辨别用户身份，进行Session跟踪而储存在用户本地终端上的数据（通常经过加密），由用户客户端计算机暂时或永久保存的信息

cookie使用实例

public class CookieDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决中文乱码
        req.setCharacterEncoding("GBK");
        resp.setCharacterEncoding("GBK");

        PrintWriter out = resp.getWriter();

        //服务器从客户端获取cookie
        Cookie[] cookies = req.getCookies();

        //判断cookie是否存在
        if(cookies!=null){
            out.write("您上一次访问的时间是：");

            for (Cookie cookie : cookies) {
                //获取cookie的名字
                if (cookie.getName().equals("loginTime")) {
                    //获取cookie中的值
                    long loginTime = Long.parseLong(cookie.getValue());
                    Date date = new Date(loginTime);
                    out.write(date.toLocaleString());
                }
            }
        }else {
            out.write("这是您第一次访问本站");
        }

        //服务器给客户端发一个cookie
        Cookie cookie = new Cookie("loginTime", System.currentTimeMillis()+"");
        //设置cookie的有效期(单位:s)
        cookie.setMaxAge(5*60);
        resp.addCookie(cookie);
    }

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

运行效果图：
第一次运行：

第二次运行：

Session

Session：在计算机中，尤其是在网络应用中，称为“会话控制”。Session对象存储特定用户会话所需的属性及配置信息。这样，当用户在应用程序的Web页之间跳转时，存储在Session对象中的变量将不会丢失，而是在整个用户会话中一直存在下去。当用户请求来自应用程序的 Web页时，如果该用户还没有会话，则Web服务器将自动创建一个 Session对象。当会话过期或被放弃后，服务器将终止该会话。

session使用实例1

public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码
        req.setCharacterEncoding("GBK");
        resp.setCharacterEncoding("GBK");
        resp.setContentType("text/html");
        //获取session
        HttpSession session = req.getSession();
        PrintWriter out = resp.getWriter();
        //获取sessionID
        String id = session.getId();
        //给session中存入数据
        session.setAttribute("name",new Person("小梁",20));
        //判断session是不是新创建的
        if(session.isNew()){
            out.write("Session创建成功！");
        }else
            out.write("Session已存在！SessionID="+id);
    }

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

运行效果图：

session使用实例2

//创建一个实例对象
public class Person {
    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Person() {
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

//获取session值
public class SessionDemo02 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码
        req.setCharacterEncoding("GBK");
        resp.setCharacterEncoding("GBK");
        resp.setContentType("text/html;charset=GBK");
        //获取session
        HttpSession session = req.getSession();
        PrintWriter out = resp.getWriter();

        Person person = (Person) session.getAttribute("name");
        out.write(person.toString());
    }

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

运行效果图：

手动注销session：session.invalidate();
设置session有效期：需要在xml配置中配置Session-config的值，如下

Web.xml配置：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"
         metadata-complete="true">
    <servlet>
        <servlet-name>CookieDemo01</servlet-name>
        <servlet-class>com.teng.servlet.CookieDemo01</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CookieDemo01</servlet-name>
        <url-pattern>/c1</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>CookieDemo02</servlet-name>
        <servlet-class>com.teng.servlet.CookieDemo02</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CookieDemo02</servlet-name>
        <url-pattern>/c2</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>SessionDemo01</servlet-name>
        <servlet-class>com.teng.servlet.SessionDemo01</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>SessionDemo01</servlet-name>
        <url-pattern>/s1</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>SessionDemo02</servlet-name>
        <servlet-class>com.teng.servlet.SessionDemo02</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>SessionDemo02</servlet-name>
        <url-pattern>/s2</url-pattern>
    </servlet-mapping>

    <!--时间单位：min-->
    <session-config>
        <session-timeout>1</session-timeout>
    </session-config>
</web-app>

Maven添加依赖

<!--        Servlet依赖-->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
    </dependency>
    <!--        JSP依赖-->
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.3.3</version>
    </dependency>