mysql jdbc

天要将以前一个项目的数据连接改成从properties文件中配置。找了好久，网上也不少，可就是读取文件时总是找不到文件在哪（我放在classes目录下了）。最后终于成功，记下，以做纪念。 

package com.web.connection;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Conn {
    private String fileName="/db.properties";//这里是指放在classes下，如果有包的话，前面加包名即可。例：/com/web/db.properties
    private String driver = "";
    private String url = "";
    private String username ="";
    private String password = "";
    Connection conn=null;


    public  Connection  getConn(){
        Properties p = new Properties();
        try {
            InputStream in = Conn.class.getResourceAsStream(fileName);//这里有人用new FileInputStream(fileName),不过这种方式找不到配置文件。有人说是在classes下，我调过了，不行。
            p.load(in);
            in.close();
            if(p.containsKey("driver")){
                this.driver = p.getProperty("driver");
            }
            if(p.containsKey("url")){
                this.url = p.getProperty("url");
            }
            if(p.containsKey("user")){
                this.username = p.getProperty("user");
            }
            if(p.containsKey("password")){
                this.password = p.getProperty("password");
            }
        } catch (IOException ex) {
            Logger.getLogger(Conn.class.getName()).log(Level.SEVERE, null, ex);
        }
        System.out.println(p.getProperty("driver"));
       try {
            Class.forName(this.driver);
            conn = DriverManager.getConnection(this.url,this.username,this.password);
        } catch (SQLException ex) {
            ex.printStackTrace();
            System.out.print("获取连接异常");
        } catch (ClassNotFoundException ex) {
            System.out.print("加载驱动出错");
            ex.printStackTrace();;
        }
        return conn;
    }
}

网上文章常见的几种读取.properties文件的方式

1、使用java.util.Properties类的load()方法 示例：

InputStream in = lnew BufferedInputStream(new FileInputStream(name));
Properties p = new Properties();
p.load(in);

2、使用java.util.ResourceBundle类的getBundle()方法 
示例：

ResourceBundle rb = ResourceBundle.getBundle(name, Locale.getDefault());

用ResourceBundle读取.properties文件可避免路径问题 
            我在jar里读取.properties文件时，总是找不到文件路径，后来用ResourceBundle读取.properties文件即可避免路径问题，代码如下： 
     

//process为文件名，切记不要加 .properties， URL是文件里的键名 

    ResourceBundle bundle = ResourceBundle.getBundle("com.ihandy.smsoc.app.process");
   String s = bundle.getString("URL");
System.out.println(s);
pURL = s;

3、使用java.util.PropertyResourceBundle类的构造函数 
示例： 

InputStream in = new BufferedInputStream(new FileInputStream(name));
ResourceBundle rb = new PropertyResourceBundle(in);

4、使用class变量的getResourceAsStream()方法 
示例： 

InputStream in = 类名.class.getResourceAsStream(name);
Properties p = new Properties();
p.load(in);

5、使用class.getClassLoader()所得到的java.lang.ClassLoader的getResourceAsStream()方法 示例： 

InputStream in = 类名.class.getClassLoader().getResourceAsStream(name);
Properties p = new Properties();
p.load(in);

6、使用java.lang.ClassLoader类的getSystemResourceAsStream()静态方法 示例： 

InputStream in = ClassLoader.getSystemResourceAsStream(name);
Properties p = new Properties();
p.load(in);

7、Servlet中可以使用javax.servlet.ServletContext的getResourceAsStream()方法 示例： 

InputStream in = context.getResourceAsStream(path);
Properties p = new Properties();
p.load(in);