Java_JDBC连接数据库_使用读取配置文件的方式

 package com.homewoek3_4.dao;

 import java.io.IOException;
 import java.io.InputStream;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.Properties;

 /**
  * 数据库连接通用类
  * @author Administrator
  */
 public abstract class BaseDao {
     private static final String path = "database.properties";
     private static String DB_DRIVER;
     private static String DB_URL;
     private static String DB_USER;
     private static String DB_PWD;

     protected Connection conn = null;
     protected PreparedStatement ps = null;
     protected ResultSet rs = null;

     static {
         Properties pro = new Properties();
         InputStream io = BaseDao.class.getClassLoader().getResourceAsStream(path);
         try {
             //读取配置文件
             pro.load(io);
         } catch (IOException e) {
             e.printStackTrace();
         }
         DB_DRIVER = pro.getProperty("DB_DRIVER");
         DB_URL = pro.getProperty("DB_URL");
         DB_USER = pro.getProperty("DB_USER");
         DB_PWD = pro.getProperty("DB_PWD");
         try {
             //加载驱动类
             Class.forName(DB_DRIVER);
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         }
     }
     /**
      * 打开数据库连接
      */
     protected void openConn() {
         try {
             conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PWD);
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }
     /**
      * 关闭数据库连接
      */
     protected void closeConn() {
         try {
             if (rs != null) {
                 rs.close();
             }
             if (ps != null) {
                 ps.close();
             }
             if (conn != null) {
                 conn.close();
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }
     /**
      * 增删改
      * @param sql
      * @param obj
      * @return
      */
     protected int executeUpdate(String sql, Object...obj) {
         int result = -1;
         this.openConn();
         try {
             ps = conn.prepareStatement(sql);
             if (obj != null) {
                 for (int i = 0; i < obj.length; i++) {
                     ps.setObject(i+1, obj[i]);
                 }
             }
             result = ps.executeUpdate();
         } catch (SQLException e) {
             e.printStackTrace();
         }
         return result;
     }
     /**
      * 查询
      * @param sql
      * @param obj
      * @return
      */
     protected void executeQuery(String sql, Object...obj) {
         this.openConn();
         try {
             ps = conn.prepareStatement(sql);
             if (obj != null) {
                 for (int i = 0; i < obj.length; i++) {
                     ps.setObject(i+1, obj[i]);
                 }
             }
             rs = ps.executeQuery();
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }
 }

创建database.properties文件，注意：后缀名一定是properties。此格式的文件在MyEclipse中图标会变，这点很容易写错，要注意。

 DB_DRIVER=com.mysql.jdbc.Driver
 DB_URL=jdbc:mysql://localhost:3306/Pet?useUnicode=true&characterEncoding=utf8&useSSL=true
 DB_USER=root
 DB_PWD=111111