超市订单管理系统的实现（项目搭建---来自遇见狂神说）

一，项目搭建

1.搭建一个maven web项目

2.配置tomcat

3.测试项目是否能跑器来

4.配置pom.xml

jsp servlet mysql-connector-java jstl standard

5创建项目包结构

6.编写实体类

ORM映射

7.编写基础公共类

数据库配置文件db.properties

driver = com.mysql.jdbc.Driver
url   =jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8
username = root
password = root

编写dao里面的公共类
package com.sqt.dao;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Parameter;
import java.sql.*;
import java.util.Properties;

//操作数据库的公共类
public class BaseDao {

    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块，类加载的时候就初始化了
    static {
        Properties properties = new Properties();
        //通过类加载器读取资源
        InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver =properties.getProperty("driver");
        url    =properties.getProperty("url");
        username =properties.getProperty("root");
        password = properties.getProperty("password");
    }
    //获取数据库的链接
    public static Connection getConnection() {
        Connection  connection=null;
        try {

            Class.forName("driver");
             connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }
    //编写查询公共类(预编译的sql不用传参)
    public  static ResultSet excute(Connection  connection, String sql, Object[] params,ResultSet rs,PreparedStatement preparedStatement) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);
        for (int i=0;i <params.length;i++){
            //setOject是从1开始，而我们的数组是从0开始
            preparedStatement.setObject(i+1,params[i]);
        }
        rs = preparedStatement.executeQuery();
        return rs;
    }
    //编写增删改的公共区别
    public  static int excute(Connection  connection, String sql, Object[] params,PreparedStatement preparedStatement) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);
        for (int i=0;i <params.length;i++){
            //setOject是从1开始，而我们的数组是从0开始
            preparedStatement.setObject(i+1,params[i]);
        }
        int updateRows = preparedStatement.executeUpdate();
        return updateRows;
    }
    //释放资源，关闭链接
    public static boolean closeResource(Connection  connection,ResultSet rs,PreparedStatement preparedStatement){
        boolean flag =true;
      if(rs!=null){
          try {
              rs.close();
              //Gc回收
              rs =null;
          } catch (SQLException e) {
              e.printStackTrace();
              flag =false;
          }

      }
        if(connection!=null){
            try {
                connection.close();
                //Gc回收
                connection =null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag =false;
            }

        }
        if(preparedStatement!=null){
            try {
                preparedStatement.close();
                //Gc回收
                preparedStatement =null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag =false;
            }

        }
        return flag;
    }
}
编写编码过滤器

package com.sqt.filter;

import javax.servlet.*;
import java.io.IOException;

/**
 * @author mypc
 */
public class CharacterEncodingFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public 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");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}
web.xml文件

<filter>
    <filter-name>CharacterEncodingFilter</filter-name>
    <filter-class>com.sqt.filter.CharacterEncodingFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>CharacterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

8.导入静态资源