javabean|MVC|Filter|监听器|过滤器|JDBC

一、JavaBean

实体类

JavaBean有特定的写法

必须要有一个无参构造
属性必须私有化
必须有对应的get/set方法

一般用来和数据库的字段做映射

ORM：对象关系映射

表---->类
字段---->属性
行记录----->对象

id	name	age	address
1	tom	3	US
2	jerry	5	UK
3	kitty	4	Polan

class People{private int id;private Strig name;private int age;private String address;
}
class A{new People(1,"tom",3,"US")
}

二、MVC三层架构

Model View Controller 模型视图控制器

2.1 原先

用户直接访问控制层，控制层可以直接操作数据库

servlet--CRUD --->数据库
弊端：十分臃肿，不利于维护
servlet的代码中：处理请求、响应、视图跳转、处理JDBC、处理业务代码、处理逻辑代码架构思想：没有什么是加一层解决不了的
|
JDBC
|
MySQL  Oracle    SQL server.....

Model

业务处理：业务逻辑（service）
数据持久层：CRUD（DAO）

View

展示数据
提供链接发起的servlet请求（a,form,img）

Controller

接受用户的请求：request(请求参数，session信息…)
交给业务层处理对应的代码
控制视图的跳转

登录----接收用户的登录请求---->处理用户的请求(胡去哦去用户登录的参数，username，password) --->交给业务层处理登录业务（判断用户名密码是否正确）--->DAO层查询用户名和密码是否正确。

三、Filter

Filter：过滤器，用来过滤网站的数据。

处理中文乱码
登录验证…

导包

编写过滤器

导包不要倒错
```
import javax.servlet.*;
下的Filter
```

配置依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.example</groupId><artifactId>javaweb-filter</artifactId><version>1.0-SNAPSHOT</version><dependencies><dependency><groupId>javax.servlet</groupId><artifactId>servlet-api</artifactId><version>2.5</version></dependency><dependency><groupId>javax.servlet.jsp</groupId><artifactId>javax.servlet.jsp-api</artifactId><version>2.3.3</version></dependency><dependency><groupId>javax.servlet.jsp.jstl</groupId><artifactId>jstl-api</artifactId><version>1.2</version></dependency><dependency><groupId>org.apache.karaf.assemblies.features</groupId><artifactId>standard</artifactId><version>2.4.4</version></dependency>
<!--    链接数据库--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.25</version></dependency>
</dependencies>
</project>

实现Filter接口，重写方法

package org.raylene.filter;import javax.servlet.*;
import java.io.IOException;public class CharacterFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("filter已经初始化了");}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {servletRequest.setCharacterEncoding("utf-8");servletResponse.setCharacterEncoding("utf-8");servletResponse.setContentType("text/html;charset=utf-8");System.out.println("filter执行前");filterChain.doFilter(servletRequest,servletResponse);System.out.println("filter执行后。。。。");}
//服务器关闭的时候，过滤会销毁@Overridepublic void destroy() {System.out.println("filter已经销毁了");}
}

配置web.xml中Filter

<?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">
<servlet><servlet-name>showServlet</servlet-name><servlet-class>org.raylene.servlet.ShowServlet</servlet-class>
</servlet><servlet-mapping><servlet-name>showServlet</servlet-name><url-pattern>/show</url-pattern></servlet-mapping><servlet-mapping><servlet-name>showServlet</servlet-name><url-pattern>/servlet/show</url-pattern></servlet-mapping><filter><filter-name>fil</filter-name><filter-class>org.raylene.filter.CharacterFilter</filter-class></filter><filter-mapping><filter-name>fil</filter-name>
<!--        只要是/servlet下的所有请求，都会经过这个过滤器--><url-pattern>/servlet/*</url-pattern></filter-mapping>
</web-app>

四、监听器

参考文献：javaweb监听器

实现监听器

package org.raylene.listener;import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;public class OnlineCountListener implements HttpSessionListener {public void sessionCreated(HttpSessionEvent httpSessionEvent) {ServletContext servletContext = httpSessionEvent.getSession().getServletContext();Integer onlineCount = (Integer) servletContext.getAttribute("OnlineCount");if(onlineCount == null){onlineCount = new Integer(1);}else{int count = onlineCount.intValue();onlineCount = new Integer(count+1);}servletContext.setAttribute("OnlineCount",onlineCount);}public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {ServletContext servletContext = httpSessionEvent.getSession().getServletContext();Integer onlineCount = (Integer) servletContext.getAttribute("OnlineCount");if(onlineCount == null){onlineCount = new Integer(0);}else{int count = onlineCount.intValue();onlineCount = new Integer(count-1);}servletContext.setAttribute("OnlineCount",onlineCount);}
//    session的销毁
//    1，手动销毁  getsession().invalidate();
//    2，自动销毁}

在webxml中注册监听器

 <listener><listener-class>org.raylene.listener.OnlineCountListener</listener-class></listener>

根据情况看使用哪种或者不使用

五、过滤器、监听器的常见应用

监听器：GUI界面中减产使用

package org.raylene.listener;import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;public class TestPanel {public static void main(String[] args) {Frame frame = new Frame("测试面板");Panel panel = new Panel(null);frame.setLayout(null);frame.setBounds(50,50,500,500);frame.setBackground(Color.blue);panel.setBounds(100,100,200,200);panel.setBackground(Color.green);frame.add(panel);frame.setVisible(true);frame.addWindowListener(new WindowAdapter() {@Overridepublic void windowClosing(WindowEvent e) {System.exit(0);}});}
}

用户登录后才能进入主页，用户注销后不能进入主页！

Filter实现权限拦截

配置依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.example</groupId><artifactId>javaweb-filter</artifactId><version>1.0-SNAPSHOT</version><dependencies><dependency><groupId>javax.servlet</groupId><artifactId>servlet-api</artifactId><version>2.5</version></dependency><dependency><groupId>javax.servlet.jsp</groupId><artifactId>javax.servlet.jsp-api</artifactId><version>2.3.3</version></dependency><dependency><groupId>javax.servlet.jsp.jstl</groupId><artifactId>jstl-api</artifactId><version>1.2</version></dependency><dependency><groupId>org.apache.karaf.assemblies.features</groupId><artifactId>standard</artifactId><version>2.4.4</version></dependency>
<!--    链接数据库--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.25</version></dependency>
</dependencies>
</project>

编写对应的jsp页面（登录页面、登录成功页面，登录失败页面）

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<form action="/servlet/login" method="post"><input type="text" name="username"><input type="submit">
</form>
</body>
</html>

sys/success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<h1>主页</h1>
<a href="/login.jsp">注销</a>//下面这段java，可选择加或不加，不加的话，在首次登录界面可以防止直接进入成功界面，但是当点注销时，其实并无注销操作，所以注销后可直接进入登录成功界面。加了的话，会在每次登录成功后，注销时结束该会话，使得退出登录页面后，无法直接进入登录页面
<%pageContext.getSession().removeAttribute(Constant.USER_SESSION);
%>
</body>
</html>

error/err.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<h1>错误</h1>
<h1>权限不够</h1><a href="/login.jsp">返回登录页面</a>
</body>
</html>

编写对应的LoginServlet和LogoutServlet

静态常量

public class Constant {public final static String USER_SESSION = "USER_SESSION";
}

package org.raylene.servlet;import org.raylene.util.Constant;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class LoginServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获取前端请求的参数String username = req.getParameter("username");if(username.equals("Admin")){//登录成功req.getSession().setAttribute(Constant.USER_SESSION, req.getSession().getId());resp.sendRedirect("/sys/success.jsp");}else{resp.sendRedirect("/error/err.jsp");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

Logout

package org.raylene.servlet;import org.raylene.util.Constant;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class LogoutServlett extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {Object user_session = req.getSession().getAttribute(Constant.USER_SESSION);if(user_session != null){req.getSession().removeAttribute(Constant.USER_SESSION);resp.sendRedirect("/login.jsp");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

编写过滤器，防止其直接进入登录成功界面

package org.raylene.filter;import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class SysFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {HttpServletRequest req = (HttpServletRequest) servletRequest;HttpServletResponse resp = (HttpServletResponse) servletResponse;if(req.getSession().getAttribute("USER_SESSION")== null){resp.sendRedirect("/error/err.jsp");}filterChain.doFilter(req,resp);}@Overridepublic void destroy() {}
}

在web.xml中配置servlet和filter

   <servlet><servlet-name>login</servlet-name><servlet-class>org.raylene.servlet.LoginServlet</servlet-class></servlet><servlet-mapping><servlet-name>login</servlet-name><url-pattern>/servlet/login</url-pattern></servlet-mapping><servlet><servlet-name>logout</servlet-name><servlet-class>org.raylene.servlet.LogoutServlett</servlet-class></servlet><servlet-mapping><servlet-name>logout</servlet-name><url-pattern>/servlet/logout</url-pattern></servlet-mapping><filter><filter-name>sf</filter-name><filter-class>org.raylene.filter.SysFilter</filter-class></filter><filter-mapping><filter-name>sf</filter-name><url-pattern>/sys/*</url-pattern></filter-mapping>

六、JDBC

新建数据库

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添加依赖

<!--    mysql驱动-->
<dependencies><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.21</version></dependency>
</dependencies>

新建java文件

jdbc固定步骤

加载驱动
Class.forName(“com.mysql.cj.jdbc.Driver”);
链接数据库
Connection connection = DriverManager.getConnection(url, username, pwd);
向数据库发生sql的对象statement ：CRUD
Statement statement = connection.createStatement();
编写sql
String sql = “select * from users”;

执行sql

ResultSet resultSet = statement.executeQuery(sql);
int i = statement.executeUpdate(sql);

关闭资源

package org.raylene.test;import java.sql.*;public class TestJdbc {public static void main(String[] args) throws ClassNotFoundException, SQLException {//        配置信息String url = "jdbc:mysql://localhost:3306/jdbc?&useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8";String username = "root";String pwd = "yourpassword";//   1.  加载驱动Class.forName("com.mysql.cj.jdbc.Driver");
//        2.链接数据库Connection connection = DriverManager.getConnection(url, username, pwd);
//       3.向数据库发生sql的对象statement   ：CRUDStatement statement = connection.createStatement();
//        4.编写sqlString sql = "select * from users";
//        5.执行sqlResultSet resultSet = statement.executeQuery(sql);while (resultSet.next()) {System.out.println("id="+resultSet.getObject("id"));System.out.println("name="+resultSet.getObject("name"));System.out.println("pwd="+resultSet.getObject("password"));System.out.println("email="+resultSet.getObject("email"));System.out.println("birthday="+resultSet.getObject("birthday"));}
//        6.关闭资源resultSet.close();statement.close();connection.close();}
}

预编译sql

package org.raylene.test;import java.sql.*;
import java.util.Date;public class TestJdbc2 {public static void main(String[] args) throws ClassNotFoundException, SQLException {
//        配置信息String url = "jdbc:mysql://localhost:3306/jdbc?&useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8";String username = "root";String pwd = "GRL971215";//   1.  加载驱动Class.forName("com.mysql.cj.jdbc.Driver");
//        2.链接数据库Connection connection = DriverManager.getConnection(url, username, pwd);//        3.编写sqlString sql = "insert into users(id,name,password,email,birthday) values(?,?,?,?,?)";//       4. 预编译   向数据库发生sql的对象statement   ：CRUDPreparedStatement pst = connection.prepareStatement(sql);
//        5.执行sqlpst.setInt(1, 4);pst.setString(2, "hhh");pst.setString(3, "672");pst.setString(4, "sjva@qq.com");pst.setDate(5, new java.sql.Date(new Date().getTime()));int execute = pst.executeUpdate();if (execute > 0) {System.out.println("插入成功！");}
// 6.关闭资源pst.close();connection.close();}
}

事务

ACID

开启事务
事务提交
事务回滚
关闭事务

junit单元测试

<!--    单元测试--><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency>

简单使用

@Target({ElementType.ANNOTATION_TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)

@Test注解只有在运行时有效，只要加了这个注解的方法，就可以直接运行

package org.raylene.test;import org.junit.jupiter.api.Test;public class TestJdbc3 {@Testpublic void test(){System.out.println("hello");}
}

运行成功

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运行失败

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新建数据库

 CREATE TABLE `jdbc`.`account`( `id` INT NOT NULL AUTO_INCREMENT, `name` VARCHAR(40), `money` DECIMAL, PRIMARY KEY (`id`) ) ENGINE=INNODB CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci; INSERT INTO `jdbc`.`account` (`id`, `name`, `money`) VALUES ('1', 'A', '2000');
INSERT INTO `jdbc`.`account` (`id`, `name`, `money`) VALUES ('2', 'B', '10000');
INSERT INTO `jdbc`.`account` (`id`, `name`, `money`) VALUES ('3', 'C', '5000');

测试事务提交

package org.raylene.test;import org.junit.jupiter.api.Test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;public class TestJdbc3 {String url = null;String username =null;String pwd = null;Connection connection = null;@Testpublic void test() throws ClassNotFoundException, SQLException {//        配置信息url = "jdbc:mysql://localhost:3306/jdbc?&useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8";username = "root";pwd = "GRL971215";try {//   1.  加载驱动Class.forName("com.mysql.cj.jdbc.Driver");//        2.链接数据库connection = DriverManager.getConnection(url, username, pwd);//        3.编写sqlconnection.setAutoCommit(false);String sql = "update `account` set money = money - 100 where name = 'A';";connection.prepareStatement(sql).executeUpdate();//       制造错误int i = 1/0;String sql2 = "update `account` set money = money + 100 where name = 'B';";connection.prepareStatement(sql2).executeUpdate();//      以上两条语句都执行成功才提交connection.commit();System.out.println("success");}catch (Exception e){try{connection.rollback();}catch (SQLException e1){e1.printStackTrace();}}finally {connection.close();}
}
}