Druid工具類

基本要求

• 提供一個靜態代碼塊來加載配置文件，初始化連接池對象
• 獲取連接的方法：通過數據庫連接池獲取連接
• 釋放資源
• 獲取連接池的方法

配置文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/city
username=root
password=root
# 初始化連接數
initialSize=6
# 最大連接數
maxActive=10
# 最大等待時間
maxWait=3000
minIdle=3

工具類代碼

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class DruidUtils {

    private static DataSource dataSource;

    static {
        Properties properties = new Properties();
        ClassLoader classLoader = DruidUtils.class.getClassLoader();
        InputStream inputStream = classLoader.getResourceAsStream("druid.properties");

        try {
            properties.load(inputStream);
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static DataSource getDataSource() {
        return dataSource;
    }

    public static Connection getConnection() {
        try {
            return dataSource.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void close(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) {
        if (resultSet != null) {
            close(resultSet);
        }
        if (preparedStatement != null) {
            close(preparedStatement);
        }
        if (connection != null) {
            close(connection);
        }
    }

    public static void close(Connection connection, Statement statement) {
        if (statement != null) {
            close(statement);
        }
        if (connection != null) {
            close(connection);
        }
    }

    public static void close(Connection connection, Statement statement, ResultSet resultSet) {
        if (resultSet != null) {
            close(resultSet);
        }
        if (connection != null) {
            close(connection);
        }
        if (statement != null) {
            close(statement);
        }
    }

    public static void close(Statement statement) {
        try {
            statement.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void close(Connection connection) {
        try {
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void close(PreparedStatement preparedStatement) {
        try {
            preparedStatement.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void close(ResultSet resultSet) {
        try {
            resultSet.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

工具類測試

package jdbc;

import druid.DruidUtils;
import jdbcutils.JDBCUtil;

import java.sql.*;
import java.util.Scanner;

public class JDBCDemo {
    public static void main(String[] args) {
        Connection connection = DruidUtils.getConnection();
        String sql = "SELECT * FROM users";
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            preparedStatement = connection.prepareStatement(sql);
            resultSet = preparedStatement.executeQuery();

            while(resultSet.next()) {
                String name = resultSet.getString("name");
                String password = resultSet.getString("password");
                System.out.println(name + "  " + password);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DruidUtils.close(connection, preparedStatement, resultSet);
    }
}