ClassLoader
不能以“/”开头，
ClassLoader.getSystemResourceAsStream("abc.properties");//从classpath根获取
Class
加斜杠是从Classpath根，不加是从类所在目录。
Demo.class.getResourceAsStream("/abc.properties");//根目录下
ResourcePatternResolver
较灵活
//new ClassPathResource("abc.properties"); 也可以
//(new DefaultResourceLoader()).getResource("classpath:abc.properties");
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
Resource resource = resolver.getResource("classpath:" + "abc.properties");