我有控制器：
@RequestMapping(method = RequestMethod.GET)
public String getViewRailwayService(@RequestParam long id,Model model) {
model.addAttribute("railwayService",railwayServiceRepository.findOne(id));
return "admin/railwayService/view";
}
和jsp页面：
...
它运行正常,但我很困惑,当railwayServiceRepository.findOne(id)返回null时,NullPointerException不会抛出.
最佳答案
不确定StackOverflow wiki on Expression Language是否值得信赖(我一直试图在官方规格中找到它,但还没有运气),但是：
原文链接：https://www.f2er.com/spring/432292.htmlEL relies on the JavaBeans specification when it comes to accessing properties. In JSP,the following expression:
${user.name}does basically the same as the following in “raw” scriptlet code (the below example is for simplicity,in reality the reflection API is used to obtain the methods and invoke them):
<%
User user = (User) pageContext.findAttribute("user");
if (user != null) {
String name = user.getName();
if (name != null) {
out.print(name);
}
}
%>
(…) Please note that it thus doesn’t print “null” when the value is null nor throws a
NullPointerExceptionunlike as when using scriptlets. In other words,EL is null-safe.
