读取配置文件的3中方式

3个不同位置的配置文件：a.properties位于WebRoot的根目录，b.properties位于src的下，c.properties位于src中的com.neu包中。其中a.properties中的内容是hello=helloa，b.properties中的内容是hello=hellob，c.properties中的内容是hello=helloc；

如图所示：



ServletContextDemo5.java文件中的程序：

运行：

package com.neu;

import java.io.FileInputStream;
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;
//读取配置文件的3中方式
public class ServletContextDemo5 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

// test31(request,response);
// test30(request,response);
// test20(request,response);
test10(request,response);
}

//请不要把Tomcat等服务器装在有空格的目录中
//类加载器读取:只能读取classes或者类路径中的任意资源。但不适合读取特别大的资源。 b c
private void test31(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
ClassLoader cl = ServletContextDemo5.class.getClassLoader();//得到类加载器
URL url = cl.getResource("com/neu/c.properties");
String path = url.getPath();
InputStream in = new FileInputStream(path);
Properties props = new Properties();
props.load(in);
System.out.println(props.getProperty("hello"));
}

//类加载器读取:只能读取classes或者类路径中的任意资源。但不适合读取特别大的资源。b c
private void test30(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
ClassLoader cl = ServletContextDemo5.class.getClassLoader();//得到类加载器
// InputStream in = cl.getResourceAsStream("b.properties");
InputStream in = cl.getResourceAsStream("com/neu/c.properties");
Properties props = new Properties();
props.load(in);
System.out.println(props.getProperty("hello"));
}

//利用ResourceBundle读取:b c,不能读a,只能读取properties文件
private void test20(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
// ResourceBundle rb = ResourceBundle.getBundle("b");
ResourceBundle rb = ResourceBundle.getBundle("com.neu.c");
System.out.println(rb.getString("hello"));
}

//利用ServletContext读取:a b c
//可以读取应用中任何位置上的资源。使用限制:只能在web应用中用
private void test10(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
// String path = getServletContext().getRealPath("/a.properties");
// String path = getServletContext().getRealPath("//WEB-INF/classes/b.properties");
String path = getServletContext().getRealPath("/WEB-INF/classes/com/neu/c.properties");

InputStream in = new FileInputStream(path);
Properties props = new Properties();
props.load(in);
System.out.println(props.getProperty("hello"));
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

}

}

运行：http://localhost:8080/ServletDemo/servlet/ServletContextDemo5

结果：服务器的控制台输出：helloc