web项目使用，类加载器读文件、servletContext对象读文件区别
      1、servletContext有getResourceAsStream根据文件获取输入流、getRealPath根据文件获取绝对路径方法，servletContext获取的是tomcat发布的工程目录下，
即E:\软件\work\apache-tomcat-7.0.40\webapps\store_v2.0路径下。
   2、类加载器只有getResourceAsStream根据文件获取输入流方法，获取的路径在tomcat发布的工程项目下WEB-INF下class路径，
即E:\软件\work\apache-tomcat-7.0.40\webapps\store_v2.0\WEB-INF\classes路径下。
   以下为代码实例，说明：代码中的db.properties文件位于工程的src目录下

[Java] 纯文本查看 复制代码

/**
         * 使用ServletContext中的getResourceAsStream读取.
         * @throws FileNotFoundException
         * @throws IOException
         */
        private void test2() throws FileNotFoundException, IOException {
        
                // 获得ServletContext:
                ServletContext context = this.getServletContext();
                InputStream is = context.getResourceAsStream("/WEB-INF/classes/db.properties");
                Properties properties = new Properties();
                properties.load(is);
                
                String driverClass = properties.getProperty("driverClass");
                String url = properties.getProperty("url");
                String username = properties.getProperty("username");
                String password = properties.getProperty("password");
                
                System.out.println(driverClass);
                System.out.println(url);
                System.out.println(username);
                System.out.println(password);
        }


/**
         * 使用ServletContext中的getRealPath读取.
         * @throws FileNotFoundException
         * @throws IOException
         */
        private void test3() throws FileNotFoundException, IOException {
                // 获得ServletContext:
                ServletContext context = this.getServletContext();
                String realPath = context.getRealPath("/WEB-INF/classes/db.properties");
                // 获得该文件的磁盘绝对路径.
                System.out.println(realPath);
                InputStream is = new FileInputStream(realPath);
                
                Properties properties = new Properties();
                properties.load(is);
                
                String driverClass = properties.getProperty("driverClass");
                String url = properties.getProperty("url");
                String username = properties.getProperty("username");
                String password = properties.getProperty("password");
                
                System.out.println(driverClass);
                System.out.println(url);
                System.out.println(username);
                System.out.println(password);
}


/**
         * 使用类的加载器来读取文件
         * @throws IOException
         */
public static void readFile() throws IOException{
                // 使用类的加载器来读取文件.
                // 类的加载器用来加载class文件,将class文件加载到内存.
                InputStream is = ReadFileUtils.class.getClassLoader().getResourceAsStream("db.properties");
                Properties properties = new Properties();
                properties.load(is);
                
                String driverClass = properties.getProperty("driverClass");
                String url = properties.getProperty("url");
                String username = properties.getProperty("username");
                String password = properties.getProperty("password");
                
                System.out.println(driverClass);
                System.out.println(url);
                System.out.println(username);
                System.out.println(password);
        }

web项目使用，类加载器读文件、servletContext对象读文件区别
      1、servletContext有getResourceAsStream根据文件获取输入流、getRealPath根据文件获取绝对路径方法，servletContext获取的是tomcat发布的工程目录下，
即E:\软件\work\apache-tomcat-7.0.40\webapps\store_v2.0路径下。
   2、类加载器只有getResourceAsStream根据文件获取输入流方法，获取的路径在tomcat发布的工程项目下WEB-INF下class路径，
即E:\软件\work\apache-tomcat-7.0.40\webapps\store_v2.0\WEB-INF\classes路径下。
   以下为代码实例，说明：代码中的db.properties文件位于工程的src目录下

[Java] 纯文本查看 复制代码

/**
         * 使用ServletContext中的getResourceAsStream读取.
         * @throws FileNotFoundException
         * @throws IOException
         */
        private void test2() throws FileNotFoundException, IOException {
        
                // 获得ServletContext:
                ServletContext context = this.getServletContext();
                InputStream is = context.getResourceAsStream("/WEB-INF/classes/db.properties");
                Properties properties = new Properties();
                properties.load(is);
                
                String driverClass = properties.getProperty("driverClass");
                String url = properties.getProperty("url");
                String username = properties.getProperty("username");
                String password = properties.getProperty("password");
                
                System.out.println(driverClass);
                System.out.println(url);
                System.out.println(username);
                System.out.println(password);
        }


/**
         * 使用ServletContext中的getRealPath读取.
         * @throws FileNotFoundException
         * @throws IOException
         */
        private void test3() throws FileNotFoundException, IOException {
                // 获得ServletContext:
                ServletContext context = this.getServletContext();
                String realPath = context.getRealPath("/WEB-INF/classes/db.properties");
                // 获得该文件的磁盘绝对路径.
                System.out.println(realPath);
                InputStream is = new FileInputStream(realPath);
                
                Properties properties = new Properties();
                properties.load(is);
                
                String driverClass = properties.getProperty("driverClass");
                String url = properties.getProperty("url");
                String username = properties.getProperty("username");
                String password = properties.getProperty("password");
                
                System.out.println(driverClass);
                System.out.println(url);
                System.out.println(username);
                System.out.println(password);
}


/**
         * 使用类的加载器来读取文件
         * @throws IOException
         */
public static void readFile() throws IOException{
                // 使用类的加载器来读取文件.
                // 类的加载器用来加载class文件,将class文件加载到内存.
                InputStream is = ReadFileUtils.class.getClassLoader().getResourceAsStream("db.properties");
                Properties properties = new Properties();
                properties.load(is);
                
                String driverClass = properties.getProperty("driverClass");
                String url = properties.getProperty("url");
                String username = properties.getProperty("username");
                String password = properties.getProperty("password");
                
                System.out.println(driverClass);
                System.out.println(url);
                System.out.println(username);
                System.out.println(password);
        }