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();} //pppublic  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"));}    //pppppublic  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"));} //pppublic  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"));} //ppppublic  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"));}//pppublic  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  ppppString 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  pppString 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  ppString 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);}}