1.案例需求与效果
- 案例需求与效果：
访问index.html页面，点击页面上的加载所有联系人按钮，才使用ajax请求异步加载所有联系人列表。用户第一次访问从数据库中获取数据，以后都从redis缓存里面获取。
- 执行效果
服务器控制器信息
MySQL中的数据
Redis中数据
2.项目分析
3.准备数据
3.1复制原型目录web目录下
3.2表数据
-- 联系人 create table contact ( id int primary key auto_increment, name varchar(20) not null, -- 姓名 phone varchar(20), -- 电话 email varchar(50), -- 邮箱 birthday date -- 生日 ); insert into contact (name,phone,email,birthday) values ('孙悟空','13423431234','wukong@itcast.cn', '1993-11-23'), ('猪八戒','13525678909','bajie@itcast.cn', '1953-05-02'), ('白骨精','18642343123','xiaobai@itcast.cn', '1943-03-12'); select * from contact;
3.3导入的包
3.4实体类
package com.itheima.entity; import java.sql.Date; /** * 联系人实体类 */ public class Contact { private int id; //编号 private String name; //姓名 private String phone; //电话 private String email; //邮箱 private Date birthday; //生日 @Override public String toString() { return "Contact{" + "id=" + id + ", name='" + name + '\'' + ", phone='" + phone + '\'' + ", email='" + email + '\'' + ", birthday=" + birthday + '}'; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPhone() { return phone; } public void setPhone(String phone) { this.phone = phone; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } }
3.5工具类和配置文件
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <environments default="default"> <!--环境变量--> <environment id="default"> <!--事务管理器--> <transactionManager type="JDBC"/> <!--数据源--> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/day32"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments> <!--映射器--> <mappers> <mapper class="com.itheima.dao.ContactDao"/> </mappers> </configuration>
package com.itheima.utils; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.IOException; import java.io.InputStream; /** 会话工厂工具类 */ public class SessionFactoryUtils { private static SqlSessionFactory factory; static { //实例化工厂建造类 SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); //读取核心配置文件 try (InputStream inputStream = Resources.getResourceAsStream("sqlMapConfig.xml")) { //创建工厂对象 factory = builder.build(inputStream); } catch (IOException e) { e.printStackTrace(); } } /** 得到会话对象 @return 会话对象 */ public static SqlSession getSession() { return factory.openSession(); } /** 得到工厂对象 @return 会话工厂对象 */ public static SqlSessionFactory getSqlSessionFactory() { return factory; } }
3.6Jedis工具类和配置文件
jedis.properties
# 主机名 host=localhost # 端口号 port=6379 # 最大连接数 maxTotal=30 # 最长等待时间 maxWaitMillis=3000
JedisUtils.java
package com.itheima.utils; import redis.clients.jedis.Jedis; import redis.clients.jedis.JedisPool; import redis.clients.jedis.JedisPoolConfig; import java.util.ResourceBundle; /** * 创建Jedis工具类 */ public class JedisUtils { private static JedisPool pool; static { //读取src下的配置文件，得到ResourceBundle对象 ResourceBundle bundle = ResourceBundle.getBundle("jedis"); //得到所有的属性并且赋值 String host = bundle.getString("host"); //以下属性要转成整数类型 int port = Integer.parseInt(bundle.getString("port")); int maxTotal = Integer.parseInt(bundle.getString("maxTotal")); int maxWaitMillis = Integer.parseInt(bundle.getString("maxWaitMillis")); //创建配置对象 JedisPoolConfig config = new JedisPoolConfig(); config.setMaxWaitMillis(maxWaitMillis); config.setMaxTotal(maxTotal); //创建连接池对象 pool = new JedisPool(config, host, port); } /** * 从连接池中得到Jedis连接对象 */ public static Jedis getJedis() { return pool.getResource(); } }
4.项目结构
5.源代码
数据访问层
package com.itheima.dao; import com.itheima.entity.Contact; import org.apache.ibatis.annotations.Select; import java.util.List; /** 联系人数据访问层 */ public interface ContactDao { /** 查询所有联系人 */ @Select("select * from contact") List<Contact> findAll(); }
package com.itheima.dao.impl; import com.itheima.dao.ContactDao; import com.itheima.entity.Contact; import com.itheima.utils.SessionFactoryUtils; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import java.util.List; /** 联系人数据访问层 */ public class ContactDaoImpl implements ContactDao { private SqlSessionFactory factory = SessionFactoryUtils.getSqlSessionFactory(); /** 查询所有联系人 */ public List<Contact> findAll() { SqlSession session = factory.openSession(); ContactDao contactDao = session.getMapper(ContactDao.class); List<Contact> contacts = contactDao.findAll(); session.close(); return contacts; } }
业务层
package com.itheima.service; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.itheima.dao.ContactDao; import com.itheima.dao.impl.ContactDaoImpl; import com.itheima.entity.Contact; import com.itheima.utils.JedisUtils; import redis.clients.jedis.Jedis; import java.util.List; /** 业务层 */ public class ContactService { private ContactDao contactDao = new ContactDaoImpl(); /** 读取联系人的JSON数据 */ public String findAllContacts() { //1. 从redis中获取联系人列表 Jedis jedis = JedisUtils.getJedis(); String contacts = jedis.get("contacts"); //2. 判断数据是否为空，如果为空则调用DAO去MySQL找联系人，找到后转成JSON对象写入到redis中 if (contacts == null) { System.out.println("访问MySQL"); List<Contact> list = contactDao.findAll(); //转成JSON对象 try { contacts = new ObjectMapper().writeValueAsString(list); } catch (JsonProcessingException e) { e.printStackTrace(); } //写入到redis中 jedis.set("contacts", contacts); } else { System.out.println("访问Redis"); } //3.如果不为空，则从redis获取json数据。 return contacts; } }
Servlet
package com.itheima.servlet; import com.itheima.service.ContactService; 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 java.io.IOException; import java.io.PrintWriter; @WebServlet(name = "ContactServlet",urlPatterns = "/contact") public class ContactServlet extends HttpServlet { private ContactService contactService = new ContactService(); protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //指定为json类型 response.setContentType("text/json;charset=utf-8"); PrintWriter out = response.getWriter(); //调用业务类方法，得到所有联系人 String contacts = contactService.findAllContacts(); out.print(contacts); } }
页面
<!DOCTYPE html> <html lang="zh-CN"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>通讯录管理</title> <link href="css/bootstrap.min.css" rel="stylesheet"> <script src="js/jquery-3.3.1.min.js"></script> <script src="js/bootstrap.min.js"></script> </head> <body> <div class="container"> <br> <input id="btnLoad" type="button" class="btn btn-primary" value="加载联系人列表"> <input id="btnClear" type="button" class="btn btn-danger" value="清空联系人列表"> <hr> <table class="table table-bordered table-hover table-striped"> <thead> <tr class="success"> <th>编号</th> <th>姓名</th> <th>电话</th> <th>邮箱</th> <th>生日</th> </tr> </thead> <tbody id="contacts"> </tbody> </table> </div> </body> <script type="text/javascript"> $("#btnLoad").click(function () { //使用jquery和get方法去访问servlet $.get({ url: "contact", success: function (contacts) { var str = ""; if (contacts.length > 0) { //element表示每个元素 $.each(contacts, function (index, element) { str+= "<tr>"; str+= "<td>" + element.id + "</td>"; str+= "<td>" + element.name + "</td>"; str+= "<td>" + element.phone + "</td>"; str+= "<td>" + element.email + "</td>"; str+= "<td>" + element.birthday + "</td>"; str+= "</tr>"; }); //把所有行的加入tbody中 $("#contacts").html(str); } } }) }) //删除按钮 $("#btnClear").click(function () { //清空子元素 $("#contacts").empty(); }) </script> </html>
