用戶管理系統工具類（servlet）

用戶管理系統工具類（連接，查詢，增刪改）（servlet+jdbc）

工具類具體實現了哪些功能：

• 連接功能，先在靜態代碼塊兒加載資源（Connection）這裏Class.forName有一個裝載類對象的作用，JDBC規範要求Driver類在使用前必須向DriverManger註冊自己。註冊過程在Driver類的靜態類已經實現。也就是說只要類被加載，就完成了向驅動管理器的註冊。
• 查詢功能，（executeQuery）由於在執行查詢方法時好多代碼都是相同的，所以我們把他包裝成一個類
• 增刪改功能，（executeUpdate）與查詢功能類似

package com.lxs.util;


import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class util {
    private static String driver;
    private static String url;
    private static String user;
    private static String password;

    static {
        Properties properties = new Properties();
        InputStream is = util.class.getClassLoader().getResourceAsStream("db.properties");
        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        user = properties.getProperty("user");
        password = properties.getProperty("password");
    }

    //獲取連接
    public static Connection getConnection() {
        Connection connection = null;
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, user, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }

    //查詢類方法
    public static ResultSet query(PreparedStatement preparedStatement, Connection connection, ResultSet resultSet, String sql, Object[] params) {
        try {
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < params.length; i++) {
                preparedStatement.setObject(i + 1, params[i]);
            }
            resultSet = preparedStatement.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return resultSet;
    }
    //增刪改方法
    public static int update(PreparedStatement preparedStatement, Connection connection, ResultSet resultSet, String sql, Object[] params) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i + 1, params[i]);
        }
        int update = preparedStatement.executeUpdate();
        return update;
    }

    //關閉資源
    public static boolean closeResource(PreparedStatement preparedStatement, Connection connection, ResultSet resultSet){

        boolean flag = true;
        if(resultSet != null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
                flag = false;
            }
        }
        if(preparedStatement != null){
            try {
                preparedStatement.close();

            } catch (SQLException e) {

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