jdbc.driver_class=oracle.jdbc.driver.OracleDriver
jdbc.connection.url=jdbc:oracle:thin:@localhost:1521:orcl
jdbc.connection.username=scott
jdbc.connection.password=tiger

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

//读取配置文件（属性文件）的工具类
public class ConfigManager {
 private static ConfigManager configManager;
 // properties.load(inputStream);读取属性文件
 private static Properties properties;

 // 在构造工具类时，进行配置文件的读取
 private ConfigManager() {
  String configFile = "database.properties";
  properties = new Properties();
  InputStream is = ConfigManager.class.getClassLoader()
    .getResourceAsStream(configFile);
  try {
   // 读取配置文件
   properties.load(is);
   is.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }

 // 通过单例模式设置实例化个数
 public static ConfigManager getInstance() {
  if (configManager == null) {
   configManager = new ConfigManager();
  }
  return configManager;
 }

 // 通过key获取对应的value
 public String getString(String key) {
  return properties.getProperty(key);
 }
}

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

import com.book.util.ConfigManager;

//基类：数据库操作通用类
public class BaseDao {
 protected Connection conn;
 protected PreparedStatement ps;
 protected Statement stmt;
 protected ResultSet rs;

 // 获取数据库连接
 public boolean getConnection() {
  // // 读取配置信息
  String driver = ConfigManager.getInstance().getString(
    "jdbc.driver_class");
  String url = ConfigManager.getInstance().getString(
    "jdbc.connection.url");
  String username = ConfigManager.getInstance().getString(
    "jdbc.connection.username");
  String password = ConfigManager.getInstance().getString(
    "jdbc.connection.password");
  // 加载JDBC驱动
  try {
   Class.forName(driver);
   // 与数据库建立连接
   conn = DriverManager.getConnection(url, username, password);
  } catch (ClassNotFoundException e) {
   return false;
  } catch (SQLException e) {
   return false;
  }
  return true;
 }

 // 增删改的通用方法
 public int executeUpdate(String sql, Object[] params) {
  int updateRows = 0;
  getConnection();
  try {
   ps = conn.prepareStatement(sql);
   // 填充占位符
   for (int i = 0; i < params.length; i++) {
    ps.setObject(i + 1, params[i]);
    System.out.println(i + 1 + "---" + params[i]);
   }
   System.out.println(sql);
   updateRows = ps.executeUpdate();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return updateRows;

 }

 // 查询
 public ResultSet executeSQL(String sql, Object[] params) {
  getConnection();
  try {
   ps = conn.prepareStatement(sql);

   // 填充占位符
   for (int i = 0; i < params.length; i++) {
    ps.setObject(i + 1, params[i]);
   }
   rs = ps.executeQuery();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return rs;

 }

 // 关闭资源
 public void closeAll(){
  try {
   if(rs!=null){
    rs.close();
   }
   if(stmt!=null){
    stmt.close();
   }
   if(ps!=null){
    ps.close();
   }
   if(conn!=null){
    conn.close();
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }
 }
}