1）带占位符的URL是Spring3.0新增的功能，该功能在SpringMVC向REST目标挺进发展过程中具有里程碑的意义。
2）通过@PathVariable可以将URL中占位符参数绑定到控制器处理方法的入参中：URL中的{
xxx}占位符可以通过@PathVariable("xxx")绑定到操作方法的入参中。在HelloWord.java中添加testPathVariable方法：
package com.dx.springlearn.handlers;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;@Controller@RequestMapping("class_requestmapping")public class HelloWord { private static String SUCCESS = "success"; @RequestMapping("/testPathVariable/{id}") public String testPathVariable(@PathVariable(value = "id", required = true) Integer id) { System.out.println("testPathVariable: id: " + id); return SUCCESS; }} index.jsp添加链接：