学步园

一般情况配置文件有两种，一是：用properties，二是用XML。当配置文件内容之间有关系时用XML，反之，用properties

ServletContext（）；如果在WobRoot下面，就直接“/dbconfig.properties”

当配置文件在不同的目录下，会有不同读取方式

package com.heng.test;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Test extends HttpServlet {
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		test3();
	}
	//通过servletContext的getRealPath得到资源的绝对路径后，再通过传统方式读取（好处是可以获取资源的名称，应用在下载文件时）
	private void test3() throws IOException {
		String path = this.getServletContext().getRealPath("/WEB-INF/classes/dbconfig.properties");
		
		String filename = path.substring(path.lastIndexOf("\\")+1);
		System.out.println("当前读取到的资源名称是："+filename);
		
		FileInputStream fis = new FileInputStream(path);
		Properties prop = new Properties();
		prop.load(fis);
		
		String url = prop.getProperty("url");
		String usern = prop.getProperty("username");
		String pwd = prop.getProperty("password");
		
		System.out.println(url);
		System.out.println(usern);
		System.out.println(pwd);
	}
	//配置文件在WebRoot下面时
	private void test2() throws IOException {
		InputStream is = this.getServletContext().getResourceAsStream("/dbconfig.properties");
		Properties prop = new Properties();
		prop.load(is);
		
		String url = prop.getProperty("url");
		String usern = prop.getProperty("username");
		String pwd = prop.getProperty("password");
		
		System.out.println(url);
		System.out.println(usern);
		System.out.println(pwd);
	}
	//配置文件在src下面时
	private void test1() throws IOException {
		InputStream is = this.getServletContext().getResourceAsStream("/WEB-INF/classes/dbconfig.properties");
		Properties prop = new Properties();
		prop.load(is);
		
		String url = prop.getProperty("url");
		String usern = prop.getProperty("username");
		String pwd = prop.getProperty("password");
		
		System.out.println(url);
		System.out.println(usern);
		System.out.println(pwd);
	}
	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doGet(request, response);
	}

}

如果配置文件在普通类下，那么可以通过类加载器来读。。。。如下所示

public class UserDao {
	private static Properties dbconfig = new Properties();

	//以下代码虽然可以读取文件的数据，但是无法获取更新后的数据。
	static {
		try {
			InputStream is = UserDao.class.getClassLoader().getResourceAsStream("dbconfig.properties");
			Properties prop = new Properties();
			prop.load(is);
			
		} catch (Exception e) {
			throw new ExceptionInInitializerError();
		}
	}