Java中获取资源文件的方法总结

这里总结3中方法获取资源文件的

ServletContext
Class
ClassLoader

文件的位置

1. ServletContext#

public void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        PrintWriter pw = response.getWriter();
        ServletContext context = this.getServletContext();
        /**
         * 获取不同路径下的资源文件
         * servletContext是相对于项目的根目录的，这里为WebContent
         */
        InputStream  inputA = context.getResourceAsStream("/a.txt");
        InputStream inputB = context.getResourceAsStream("/WEB-INF/classes/cn/zydev/b.txt");
        InputStream inputC = context.getResourceAsStream("/WEB-INF/classes/c.txt");
         
        /**
         * 获取真实的磁盘路径
         */
        String realPath = context.getRealPath("/WEB-INF/classes/c.txt");
         
        /**
         * 获取指定目录下的文件（包括目录,深度为1级）
         */
        Set<String> rsc = context.getResourcePaths("/WEB-INF");
        String a = IOUtils.toString(inputA);
        String b = IOUtils.toString(inputB);
        String c = IOUtils.toString(inputC);
        pw.print(a+"<br/>");
        pw.print(b+"<br/>");
        pw.print(c+"<br/>");
        pw.print(realPath+"<br/>");
        pw.println(rsc);
    }

　　结果显示：

2. ClassLoader#

使用ClassLoader是相对于classes的

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        PrintWriter pw = response.getWriter();
        /**
         * ClassLoader是相对于classes参照的
         * 第一个斜杠可以不写，也可以写成./(熟悉Linux的应该很清楚）
         */
        ClassLoader cl = this.getClass().getClassLoader();
        InputStream inputA = cl.getResourceAsStream("/../../a.txt");
        InputStream inputB = cl.getResourceAsStream("/cn/zydev/b.txt");
        InputStream inputC = cl.getResourceAsStream("/c.txt");
        String a = IOUtils.toString(inputA);
        String b = IOUtils.toString(inputB);
        String c = IOUtils.toString(inputC);
        pw.print(a+"<br/>");
        pw.print(b+"<br/>");
        pw.print(c+"<br/>");
    }

　　得到结果：

3. class#

路径前斜杠表示相对于当前的class，不加斜杠相对于classes

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        PrintWriter pw = response.getWriter();
        Class cs = this.getClass();
        //不加斜杠表示相对于class（CServlet）
        InputStream inputA = cs.getResourceAsStream("../../../../a.txt");
        InputStream inputB = cs.getResourceAsStream("b.txt");
        //加斜杠，相对于classes
        InputStream inputC = cs.getResourceAsStream("/c.txt");
        String a = IOUtils.toString(inputA);
        String b = IOUtils.toString(inputB);
        String c = IOUtils.toString(inputC);
        pw.print(a+"<br/>");
        pw.print(b+"<br/>");
        pw.print(c+"<br/>");
    }