在Servlet的學習中，存在Listener這個技術點，本文主要講述使用HttpSessionActivationListener鈍化與活化Session中的實體。

鈍化 -- 將實體儲存到硬碟中（序列化）

活化 -- 將硬碟中的實體讀取到記憶體中（反序列化）

1、要鈍化與活化Session中的實體，首先要在該實體實現HttpSessionActivationListener和Serializable介面。

package com.liweijian.domain;

import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionEvent;
import java.io.Serializable;

/**
 * @Author:Liweijian
 * @Description: 鈍化與活化監聽器
 * @Date:Create in 15:55 2017/12/14 0014
 */
public class Customer implements HttpSessionActivationListener, Serializable{
    private String id;
    private String name;

    public void setId(String id) {
        this.id = id;
    }

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

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    //鈍化 -- 儲存到硬碟
    @Override
    public void sessionWillPassivate(HttpSessionEvent httpSessionEvent) {
        System.out.println("session被鈍化了..");
    }

    //活化 -- 讀取到記憶體
    @Override
    public void sessionDidActivate(HttpSessionEvent httpSessionEvent) {
        System.out.println("session被活化了..");
    }
}
 

<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <!-- maxIdleSwap:session中的物件多長時間不使用就鈍化 -->
    <!-- directory:鈍化後的物件的檔案寫到磁碟的哪個目錄下  配置鈍化的物件檔案在work/catalina/localhost/鈍化檔案 -->
    <Manager className="org.apache.catalina.session.PersistentManager" maxIdleSwap="1"> <!-- 1分鐘-->
        <Store className="org.apache.catalina.session.FileStore" directory="liweijian" />
    </Manager>
</Context>
 

      如果容器被關閉，也會鈍化。

package com.liweijian.web;

import com.liweijian.domain.Customer;

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;

/**
 * @Author:Liweijian
 * @Description: SessionActivationListener測試
 * @Date:Create in 16:08 2017/12/14 0014
 */
@WebServlet(name = "TestSessionActivationServlet")
public class TestSessionActivationServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();

        Customer customer = new Customer();
        customer.setId("200");
        customer.setName("wangwu");

        session.setAttribute("customer",customer);
    }
}
 

package com.liweijian.web;

import com.liweijian.domain.Customer;

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;

/**
 * @Author:Liweijian
 * @Description: 活化Customer
 * @Date:Create in 16:19 2017/12/14 0014
 */
@WebServlet(name = "TestSessionActivationServlet2")
public class TestSessionActivationServlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        Customer customer = (Customer) session.getAttribute("customer");
        String name = customer.getName();
        System.out.println(name);
    }
}

鈍化後的檔案在apache-tomcat-8.0.9\work\Catalina\localhost目錄下。