1，jdbc.properties文件

driverClassName=oracle.jdbc.driver.OracleDriver
url=jdbc:oracle:thin:@localhost:1521:BDQN
username=wjb
password=wjb

2，读取properties文件

package cn.util;

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

public class ConfigManager {
    //读取jdbc.properties配置文件,单例模式 
    
    private static ConfigManager configManager;
    private static Properties properties;
    
    //单例模式必须用private构造方法，不能用public
    private ConfigManager(){
        String configFile = "jdbc.properties";
        properties = new Properties();
        InputStream is = ConfigManager.class.getClassLoader().getResourceAsStream(configFile);
        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    //提供一个入口获取ConfigManager,这个方法可以严格控制实例生成的个数
    public static ConfigManager getInstance(){
        //如果为空就创建一个自已的构造方法，获取ConfigManager
        if(configManager == null){
            configManager = new ConfigManager();
        }
        return configManager;
    }
    
    //以上只是获取了properties的KEY值，下面这个方法获取对应的value值
    public String getString (String key){
        return properties.getProperty(key);
    }
    
}

3，连接数据库的基类

package cn.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import cn.pojo.Dancer;
import cn.util.ConfigManager;

public class BaseDao {
    Connection connection = null;
    ResultSet rs = null;
    PreparedStatement pst = null;
    
//连接数据库的方法
    public boolean getConnection(){
        String driver = ConfigManager.getInstance().getString("driverClassName");
        String url = ConfigManager.getInstance().getString("url");
        String username = ConfigManager.getInstance().getString("username");
        String password = ConfigManager.getInstance().getString("password");
        
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        
        return true;
    }
    
    //增删改
    public int executeUpdate(String sql,Object[] param){
        int row = 0;
        if(this.getConnection()){
            try {
                pst = connection.prepareStatement(sql);
                for(int i = 0;i<param.length;i++){
                    pst.setObject(i+1, param[i]);
                }
                row = pst.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return row;
    }
    
    //查询
    public ResultSet executeQuery(String sql,Object[] param){
        if(this.getConnection()){
            try {
                pst = connection.prepareStatement(sql);
                for(int i=0;i<param.length;i++){
                    pst.setObject(i+1, param[i]);
                }
                rs = pst.executeQuery();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        return rs;
    }
    
    
}