Java体系知识之监听器&数据库连接池
(1)监听器使用
(2)数据库连接池使用
1 监听器
1.1 技术简介
(1)JavaWeb三大组件：
Servlet | Filter | Listener
Servlet：动态网页编程技术
Filter和Listener：高级特性，辅助Servlet工作，让web程序增色
Filter：过滤请求资源 req resp
Listener：监听域对象相关的内容
(2)Servlet三个域对象：
request：HttpServletRequest 请求对象 一次请求一次响应 转发
session：HttpSession 会话对象 多次请求
context：ServletContext 服务器对象|全局对象
(3)Listener：
监听域对象的创建和销毁
request：ServletRequestListener
session：HttpSessionListener
context：ServletContextListener
1.2 使用步骤
(1)Servlet：
创建一个类，继承HttpServlet类；
重写方法；
配置：
web.xml;
注解；@WebServlet("/xx")
(2)Filter：
创建一个类，实现Filter接口；
重写方法；
配置：
web.xml;
注解；@WebFilter("/xx")
(3)Listener：
创建一个类，实现对应接口；
重写方法；
配置：
web.xml;
注解；@WebListener
1.3 案例实现
1.3.1 HttpSessionListenerDemo
package com.javasm.listener;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import java.util.HashMap;
import java.util.Map;
public class HttpSessionListenerDemo implements HttpSessionListener {
Map<String, HttpSession> online = new HashMap<>();
@Override
public void sessionCreated(HttpSessionEvent se) {
HttpSession session = se.getSession();
String sessionId = session.getId();
online.put(sessionId, session);
System.out.println("有用户上线了：" + sessionId);
System.out.println("目前用户在线情况：" + online);
session.setMaxInactiveInterval(5);
}
@Override
public void sessionDestroyed(HttpSessionEvent se) {
HttpSession session = se.getSession();
String sessionId = session.getId();
online.remove(sessionId);
System.out.println("有用户下线了：" + sessionId);
System.out.println("目前用户在线情况：" + online);
}
}
1.3.2 ServletContextListenerDemo
package com.javasm.listener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
@WebListener
public class ServletContextListenerDemo implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("服务器启动时，触发该方法执行");
System.out.println("加载第三方资源");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("服务器关闭时，触发该方法执行");
System.out.println("销毁资源");
}
}
2 数据库连接池
2.1 技术简介
(1)池化技术：
复用资源
(2)JDBC使用步骤：
加载驱动；
创建连接；
有语句对象；
处理结果集；
关闭连接；
(3)数据库连接：
资源宝贵；
创建数据库连接：耗时；
高效管理的数据库连接，提高程序的操作性能；
数据库连接池
(4)数据库连接池：
负责分配、管理、释放数据库连接；
重复使用数据库连接资源；
(4)常用数据库连接：
C3P0；
DBCP；
Druid；
(5)案例演示：
Druid
(6)项目改造：
数据库连接资源的初始化和销毁，伴随服务器的开启和关闭执行
2.2 案例实现
2.2.1 DBUtils2
package com.javasm.finance.util;
import com.alibaba.druid.pool.DruidDataSource;
import java.sql.*;
import java.util.Properties;
public class DBUtils2 {
static String user;
static String pwd;
static String url;
static String driver;
static DruidDataSource dataSource = new DruidDataSource();
static {
Properties properties = new Properties();
try {
properties.load(DBUtils2.class.getClassLoader().getResourceAsStream("jdbc.properties"));
driver = properties.getProperty("jdbc.driver");
url = properties.getProperty("jdbc.url");
user = properties.getProperty("jdbc.user");
pwd = properties.getProperty("jdbc.pwd");
dataSource.setDriverClassName(driver);
dataSource.setUrl(url);
dataSource.setUsername(user);
dataSource.setPassword(pwd);
} catch (Exception e) {
e.printStackTrace();
}
}
public static DruidDataSource getDataSource() {
return dataSource;
}
public static Connection getConn() {
Connection connection = null;
try {
connection = dataSource.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return connection;
}
public static void getClose(Connection connection, Statement statement, PreparedStatement preparedStatement, ResultSet resultSet) {
try {
if (connection != null) connection.close();
if (statement != null) statement.close();
if (preparedStatement != null) preparedStatement.close();
if (resultSet != null) resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
2.2.2 DBListener
package com.javasm.finance.listener;
import com.alibaba.druid.pool.DruidDataSource;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import java.sql.SQLException;
@WebListener
public class DBListener implements ServletContextListener {
static DruidDataSource dataSource = new DruidDataSource();
@Override
public void contextInitialized(ServletContextEvent servletContextEvent) {
ServletContext servletContext = servletContextEvent.getServletContext();
String driver = servletContext.getInitParameter("jdbc.driver");
String url = servletContext.getInitParameter("jdbc.url");
String user = servletContext.getInitParameter("jdbc.user");
String pwd = servletContext.getInitParameter("jdbc.pwd");
dataSource.setDriverClassName(driver);
dataSource.setUrl(url);
dataSource.setUsername(user);
dataSource.setPassword(pwd);
try {
dataSource.init();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public static DruidDataSource getDataSource() {
return dataSource;
}
@Override
public void contextDestroyed(ServletContextEvent servletContextEvent) {
dataSource.close();
}
}
2.3 持久层实现类
2.3.1 内容概述
从数据库连接池中获取数据库连接资源
2.3.2 案例实现
package com.javasm.finance.dao.impl;
import com.javasm.finance.dao.UserDao;
import com.javasm.finance.entity.User;
import com.javasm.finance.listener.DBListener;
import com.javasm.finance.util.DBUtils2;
import org.apache.commons.dbutils.BasicRowProcessor;
import org.apache.commons.dbutils.GenerousBeanProcessor;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class UserDaoImpl implements UserDao {
QueryRunner runner = new QueryRunner(DBListener.getDataSource());
@Override
public User findLoginUser(String userName, String userPwd) throws SQLException {
String sql = "select user_id,user_name,user_pwd from fin_admin_user where user_name=? and user_pwd=?";
BeanHandler<User> beanHandler = new BeanHandler<>(User.class, new BasicRowProcessor(new GenerousBeanProcessor()));
User loginUser = runner.query(sql, beanHandler, userName, userPwd);
return loginUser;
}
@Override
public List<User> queryUser(Integer page, Integer pageSize, User user) throws SQLException {
String sql = "select user_id,user_name,role_id,reg_time,login_time,is_valid,head_img from fin_admin_user ";
boolean isWhere = true;
List paramList = new ArrayList();
if (user.getUserId() != null && !"".equals(user.getUserId())) {
if (isWhere) {
sql += "where ";
isWhere = false;
} else {
sql += "and ";
}
sql += "user_id=? ";
paramList.add(user.getUserId());
}
if (user.getUserName() != null && !"".equals(user.getUserName())) {
if (isWhere) {
sql += "where ";
isWhere = false;
} else {
sql += "and ";
}
sql += "user_name like ? ";
paramList.add("%" + user.getUserName() + "%");
}
sql += "limit " + (page - 1) * pageSize + "," + pageSize;
BeanListHandler<User> listHandler = new BeanListHandler<>(User.class, new BasicRowProcessor(new GenerousBeanProcessor()));
List<User> userList = runner.query(sql, listHandler, paramList.toArray());
return userList;
}
@Override
public long queryUserNum(User user) throws SQLException {
String sql = "select count(1) totalNum from fin_admin_user ";
boolean isWhere = true;
List paramList = new ArrayList();
if (user.getUserId() != null && !"".equals(user.getUserId())) {
if (isWhere) {
sql += "where ";
isWhere = false;
} else {
sql += "and ";
}
sql += "user_id=? ";
paramList.add(user.getUserId());
}
if (user.getUserName() != null && !"".equals(user.getUserName())) {
if (isWhere) {
sql += "where ";
isWhere = false;
} else {
sql += "and ";
}
sql += "user_name like ? ";
paramList.add("%" + user.getUserName() + "%");
}
ScalarHandler<Long> scalarHandler = new ScalarHandler<>();
long totalNum = runner.query(sql, scalarHandler, paramList.toArray());
return totalNum;
}
@Override
public int addUser(User user) throws SQLException {
String sql = "insert into fin_admin_user(user_name,user_pwd,role_id,reg_time,is_valid,head_img,version_id) values(?,1234,?,?,?,?,100)";
int rows = runner.update(sql, user.getUserName(), user.getRoleId(), user.getRegTime(), user.getIsValid(), user.getHeadImg());
return rows;
}
@Override
public User queryByUserId(Integer userId) throws SQLException {
String sql = "select user_id,user_name,user_pwd,role_id,reg_time,login_time,is_valid,head_img,version_id from fin_admin_user where user_id=?";
BeanHandler<User> beanHandler = new BeanHandler<>(User.class, new BasicRowProcessor(new GenerousBeanProcessor()));
User user = runner.query(sql, beanHandler, userId);
return user;
}
@Override
public User queryByUidAndVid(Integer userId, Integer versionId) throws SQLException {
String sql = "select user_id,user_name,user_pwd,role_id,reg_time,login_time,is_valid,head_img,version_id from fin_admin_user where user_id=? and version_id=?";
BeanHandler<User> beanHandler = new BeanHandler<>(User.class, new BasicRowProcessor(new GenerousBeanProcessor()));
User user = runner.query(sql, beanHandler, userId, versionId);
return user;
}
@Override
public int editUser(User user) throws SQLException {
String sql = "update fin_admin_user set user_name=?,user_pwd=?,role_id=?,reg_time=?,is_valid=?,head_img=?,version_id=?+1 where user_id=?";
int rows = runner.update(sql, user.getUserName(), user.getUserPwd(), user.getRoleId(), user.getRegTime(), user.getIsValid(), user.getHeadImg(), user.getVersionId(), user.getUserId());
return rows;
}
@Override
public int deleteUser(Integer userId) throws SQLException {
String sql = "delete from fin_admin_user where user_id=?";
int rows = runner.update(sql, userId);
return rows;
}
}
