Spring boot Ambiguous handler

Question

I use Spring Boot. I created theses two method:

@RequestMapping(value = "/user/{userId}", method = RequestMethod.GET) public UserAppDto getNameByUserId(@PathVariable("userId") Long userId) { return userService.getByUserId(userId); } @RequestMapping(value = "/user/{username}", method = RequestMethod.GET) public UserAppDto getNameByUsername(@PathVariable("username") String username) { return userService.getNameByUsername(username); }

When i try to log in the web application, i get:

java.lang.IllegalStateException: Ambiguous handler methods mapped for HTTP path 'http://localhost:8080/rest/user/bsmith': {public com.zenar.dto.UserAppDto com.zenar.controller.UserController.getNameByUsername(java.lang.String), public com.zenar.dto.UserAppDto com.zenar.controller.UserController.getNameByUserId(java.lang.Long)}

Seem like, it's not able to do difference on the data type.

So need to modify URL? Any fix in the latest release?

In HTTP there is only text. Spring does some conversion but only a real human would know that 123 is not a username (who says someone doesn't create a user with that as a username). You might be able to get it to work by including a regex to limit somethings but I wouldn't count on it. — M. Deinum
– M. Deinum, Commented May 2, 2016 at 12:48

Jesper · Accepted Answer · 2016-05-02 13:30:02Z

According to Spring MVC documentation, when a URL matches multiple patterns, a sort is used to find The Most Specific Match:

A pattern with a lower count of URI variables and wild cards is considered more specific. For example /hotels/{hotel}/* has 1 URI variable and 1 wild card and is considered more specific than /hotels/{hotel}/** which as 1 URI variable and 2 wild cards.

If two patterns have the same count, the one that is longer is considered more specific. For example /foo/bar* is longer and considered more specific than /foo/*.

When two patterns have the same count and length, the pattern with fewer wild cards is considered more specific. For example /hotels/{hotel} is more specific than /hotels/*.

After applying these rules, when Spring MVC couldn't decide which one is more specific, it will throw that exception. One way for fixing this problem is to make one of them More specific:

@RequestMapping(value = "/user/{userId:\\d+}", method = RequestMethod.GET) public UserAppDto getNameByUserId(@PathVariable("userId") Long userId) { return userService.getByUserId(userId); }

The trick here is that you can specify a regular expression in the URI pattern that matches only digits.

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