Session

sessin是在服务器存一个东西，然后客户端会拿到一个ID，用这个ID去取东西。
每个人都有一个独特的ID
建一个SessionDemo01

@WebServlet("/s1")
public class SessionDemo01 extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //解决乱码问题
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=utf-8");
        //得到session
        HttpSession session =  req.getSession();
        //在session里面存东西
        session.setAttribute("name",new Person("亲将",1));
        //获取sessionid
        String id = session.getId();
        //判断session是不是新创建的
        if(session.isNew()){
            resp.getWriter().write("session创建成功，ID:"+id);
        }else{
            resp.getWriter().write("session以及在服务器中存在了,ID:"+id);
            resp.sendRedirect("/success.jsp");
        }



    }

session这节课的重要代码

//得到session
        HttpSession session =  req.getSession();
        //在session里面存东西
        session.setAttribute("name",new Person("亲将",1));
        //获取sessionid
        String id = session.getId();

用封装的方式获取SessionID

public class Person {
    private String name;
    private int age;

    public Person(){
    }
    public Person (String name,int age){
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name){
        this.name = name;
    }
    public int getAge(){
        return age;
    }
    public void setAgea(int age){
        this.age = age;
    }

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

在SessioDemo01中new一个person

  @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       //解决乱码问提i
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        //得到session
        HttpSession session = request.getSession();
        //得到name
        Person person = (Person) session.getAttribute("name");
        //在页面看到自己写的东西
        response.getWriter().print(person.getName() + " " + person.getAge());
    }
}