java 学习笔记 读取配置文件的三种方式

package com.itheima.servlet.cfg;
 
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Properties;
import java.util.ResourceBundle;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
public class LoaderCfgServletDemo1 extends HttpServlet {
 
	//第一种方式,可以加载所有目录下的内容,但只用于web项目
	//test11();
	//test12();//ppp
	//test13();
	//第二种方式  ResouceBundle专门用于读取properties文件的，
    //只用于加载类路径classes目录下的文件
	//java项目和web项目都可以用
	//test21();
	//test22();//基名  ppp
 
	//第三种方式  就是用ClassLoader类加载器
	//得到类加载器的方法   LoaderCfgServletDemo1.class.getClassLoader()
	//类加载器一上来定位的目录是classes
	//test31();
	//test32();
	//test33();
	//曾经的回顾
	//test34();
 
	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//test11();
		//test12();
		//test13();
		//test21();
		//test22();
		//test31();
		//test32();
		//test33();
		//test34();
	}
	 //pp
	public  void test34() throws IOException, FileNotFoundException {
		ClassLoader cl = LoaderCfgServletDemo1.class.getClassLoader();
		URL url  = cl.getResource("cfg.properties");//协议+主机名(包含端口)+资源地址
		//System.out.println(url.getPath());
 
		Properties p = new Properties();
		p.load(new FileInputStream(url.getPath()));
		System.out.println(p.getProperty("p"));
	}
   //pppp
	public  void test33() throws IOException, FileNotFoundException {
		ClassLoader cl = LoaderCfgServletDemo1.class.getClassLoader();
		//这是相对于classes这个目录而言，找它的上一级
		InputStream is = cl.getResourceAsStream("../cfg.properties");
		Properties p = new Properties();
		p.load(is);
		System.out.println(p.getProperty("p"));
	}
	//pp
	public  void test32() throws IOException, FileNotFoundException {
		ClassLoader cl = LoaderCfgServletDemo1.class.getClassLoader();
		InputStream is = cl.getResourceAsStream("cfg.properties");//如何写路径
		Properties p = new Properties();
		p.load(is);
		System.out.println(p.getProperty("p"));
	}
	//ppp
	public  void test31() throws IOException, FileNotFoundException {
		ClassLoader cl = LoaderCfgServletDemo1.class.getClassLoader();
		InputStream is = cl.getResourceAsStream("com/itheima/servlet/cfg/cfg.properties");//如何写路径
		Properties p = new Properties();
		p.load(is);
		System.out.println(p.getProperty("p"));
	}
	//ppp
	public  void test22() throws IOException, FileNotFoundException {
		ResourceBundle rb = ResourceBundle.getBundle("com.itheima.servlet.cfg.cfg");//基名(包名.文件名（不带扩展名）)
		System.out.println(rb.getString("p"));
	}
	//pp
	public  void test21() throws IOException, FileNotFoundException {
		ResourceBundle rb = ResourceBundle.getBundle("cfg");//基名
		System.out.println(rb.getString("p"));
	}
	public  void test13() throws IOException, FileNotFoundException {
		//1第一种  ,用/代表当前应用  pppp
		String path =getServletContext().getRealPath("/WEB-INF/cfg.properties");
		//System.out.println(path);
		Properties p  = new Properties();
		p.load(new FileInputStream(path));
 
		System.out.println(p.getProperty("p"));
	}
	public  void test12() throws IOException, FileNotFoundException {
		//1第一种  ,用/代表当前应用  ppp
		String path =getServletContext().getRealPath("/WEB-INF/classes/com/itheima/servlet/cfg/cfg.properties");
		//System.out.println(path);
		Properties p  = new Properties();
		p.load(new FileInputStream(path));
 
		System.out.println(p.getProperty("p"));
	}
	private void test11() throws IOException, FileNotFoundException {
		//1第一种  ,用/代表当前应用  pp
		String path =getServletContext().getRealPath("/WEB-INF/classes/cfg.properties");
		//System.out.println(path);
		Properties p  = new Properties();
		p.load(new FileInputStream(path));
		System.out.println(p.getProperty("p"));
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doGet(request, response);
	}
 
}