【原】Java解析resources文件夹下properties文件、连接数据库

孟船长 2022-10-09 发布于内蒙古

展开全文

为了项目容易管理，我们经常将变量统一放在resources文件夹下，以.properties文件进行存储。最常见的就是在进行数据库连接时配置的数据库连接数据。

1 解析.properties配置文件
2 从数据库查询数据

1 解析配置文件.properties

先在resources文件夹下新建jdbc.properties文件

jdbc.driver = com.mysql.jdbc.Driver
jdbc.url =  jdbc:mysql://localhost:3306/myDatabase
jdbc.username = root
jdbc.password = hwsofts08

代码

package com.autotesting;

import java.io.IOException;
import java.util.Properties;

public  class Test {
    public static void main(String[] args) {
        Properties properties = new Properties();
        try {
            properties.load(Test.class.getClassLoader().getResourceAsStream("jdbc.properties"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        String url = properties.getProperty("jdbc.url");
        String username = properties.getProperty("jdbc.username");
        String password = properties.getProperty("jdbc.password");
        System.out.println("url is: " + url);
        System.out.println("username is: " + username);
        System.out.println("password is: " + password);
    }
}

执行结果：

连接数据库查询数据

为了连接MySQL数据库，需要先下载mysql-connector-javajar包。

下载地址：

https:///artifact/mysql/mysql-connector-java/8.0.30

下载完成后，将mysql-connector-java-8.0.30.jar文件复制到lib文件夹下，然后右键选择Add as Library

语句

select * from student where sid = 18;

代码：

package com.autotesting;

import java.io.File;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Properties;

public  class ConnData {
    public static void main(String[] args) {
        String sql = "select * from student where sid = ?;";
        Properties properties = new Properties();
        try {
            properties.load(new FileInputStream(new File("src/main/resources/jdbc.properties")));
            // 获取jdbc.properties文件中的数据
            String url = properties.getProperty("jdbc.url");
            String username = properties.getProperty("jdbc.username");
            String password = properties.getProperty("jdbc.password");
            // 获取Connection
            Connection connection = DriverManager.getConnection(url, username, password);
            // 获取PreparedStatement
            PreparedStatement preparedStatement = connection.prepareStatement(sql);
            // 设置条件字段值
            preparedStatement.setObject(1, 18);
            // 调用查询方法获取结果集
            ResultSet resultSet = preparedStatement.executeQuery();
            // 从结果集获取查询数据
            while(resultSet.next()){
                String nameValue = resultSet.getObject("sname").toString();
                String genderValue = resultSet.getObject("gender").toString();
                String sidValue = resultSet.getObject("sid").toString();
                System.out.println("sname is "+ nameValue + "; gender is " + genderValue + "; sid is " + sidValue);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}