超市订单管理系统 准备工作 部署和pojo Dao Filter

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306?useUnicode=true&characterEncoding=utf-8
username=root
password=123456

2.编写数据库公共类

package com.kevin.dao;

import javax.imageio.IIOException;
import java.io.IOException;
import java.io.InputStream;
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();
        //通过类加载器读取对应的资源
        final 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("username");
        password = properties.getProperty("password");
    }

    //获取数据库的连接
    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  三个基本对象和最基本的sql参数
    public static ResultSet execute(Connection connection, String sql, Object[] params, ResultSet resultSet, PreparedStatement preparedStatement) throws SQLException {
        //编写预编译的sql，在后面直接执行就可以了
        preparedStatement = connection.prepareStatement(sql);

        for (int i = 0; i < params.length; i++) {
            //serObject,占位符从1开始，但是我们的数组是从0开始！
        }
        resultSet = preparedStatement.executeQuery();
        return resultSet;
    }

    //编写增删改公共方法
    public static int execute(Connection connection, String sql, Object[] params, PreparedStatement preparedStatement) throws SQLException {
        //编写预编译的sql，在后面直接执行就可以了
        preparedStatement = connection.prepareStatement(sql);

        for (int i = 0; i < params.length; i++) {
            //serObject,占位符从1开始，但是我们的数组是从0开始！
        }
        int updateRows = preparedStatement.executeUpdate();
        return updateRows;
    }

    //释放资源，关闭数据库连接
    public static boolean closeResource(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) {
        boolean flag = true;

        if (resultSet != null) {
            try {
                resultSet.close();
                //GC回收
                resultSet = 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;
    }
}

3.编写字符编码过滤器

package com.kevin.filter;

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


public class CharacterEncodingFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");

        chain.doFilter(request, response);
    }

    public void destroy() {

    }
}

  
    CharacterEncodingFilter
    com.kevin.filter.CharacterEncodingFilter
  
  
    CharacterEncodingFilter
    /*