使用Spring 3.0,我可以创建一个可选的路径变量吗？

Question

使用Spring 3.0,我可以有一个可选的路径变量吗？

例如

@RequestMapping(value = "/json/{type}", method = RequestMethod.GET)
public @ResponseBody TestBean testAjax(
        HttpServletRequest req,
        @PathVariable String type,
        @RequestParam("track") String track) {
    return new TestBean();
}

在这里,我想/json/abc或/json称为相同的方法.
一个明显的解决方法是声明type为请求参数:

@RequestMapping(value = "/json", method = RequestMethod.GET)
public @ResponseBody TestBean testAjax(
        HttpServletRequest req,
        @RequestParam(value = "type", required = false) String type,
        @RequestParam("track") String track) {
    return new TestBean();
}

然后/json?type=abc&track=aa或/json?track=rr将工作

Answer 1

您不能拥有可选的路径变量,但您可以使用两个调用相同服务代码的控制器方法:

@RequestMapping(value = "/json/{type}", method = RequestMethod.GET)
public @ResponseBody TestBean typedTestBean(
        HttpServletRequest req,
        @PathVariable String type,
        @RequestParam("track") String track) {
    return getTestBean(type);
}

@RequestMapping(value = "/json", method = RequestMethod.GET)
public @ResponseBody TestBean testBean(
        HttpServletRequest req,
        @RequestParam("track") String track) {
    return getTestBean();
}

Answer 2

如果您在使用Spring 4.1和Java 8,你可以使用java.util.Optional它在支持@RequestParam,@PathVariable,@RequestHeader和@MatrixVariableSpring MVC中-

@RequestMapping(value = {"/json/{type}", "/json" }, method = RequestMethod.GET)
public @ResponseBody TestBean typedTestBean(
    @PathVariable Optional<String> type,
    @RequestParam("track") String track) {      
    if (type.isPresent()) {
        //type.get() will return type value
        //corresponds to path "/json/{type}"
    } else {
        //corresponds to path "/json"
    }       
}

Answer 3

众所周知,您还可以使用@PathVariable注释注入路径变量的Map.我不确定这个功能是否在Spring 3.0中可用或者是否稍后添加,但这是解决该示例的另一种方法:

@RequestMapping(value={ "/json/{type}", "/json" }, method=RequestMethod.GET)
public @ResponseBody TestBean typedTestBean(
    @PathVariable Map<String, String> pathVariables,
    @RequestParam("track") String track) {

    if (pathVariables.containsKey("type")) {
        return new TestBean(pathVariables.get("type"));
    } else {
        return new TestBean();
    }
}

Answer 4

你可以使用:

@RequestParam(value="somvalue",required=false)

对于可选参数而不是pathVariable

Answer 5

Spring 5 / Spring Boot 2示例：

阻塞

@GetMapping({"/dto-blocking/{type}", "/dto-blocking"})
public ResponseEntity<Dto> getDtoBlocking(
        @PathVariable(name = "type", required = false) String type) {
    if (StringUtils.isEmpty(type)) {
        type = "default";
    }
    return ResponseEntity.ok().body(dtoBlockingRepo.findByType(type));
}

反应性

@GetMapping({"/dto-reactive/{type}", "/dto-reactive"})
public Mono<ResponseEntity<Dto>> getDtoReactive(
        @PathVariable(name = "type", required = false) String type) {
    if (StringUtils.isEmpty(type)) {
        type = "default";
    }
    return dtoReactiveRepo.findByType(type).map(dto -> ResponseEntity.ok().body(dto));
}

Answer 6

Nicolai Ehmann 的评论和 wildloop 的答案的简化示例（适用于 Spring 4.3.3+），基本上您required = false现在可以使用：

  @RequestMapping(value = {"/json/{type}", "/json" }, method = RequestMethod.GET)
  public @ResponseBody TestBean testAjax(@PathVariable(required = false) String type) {
    if (type != null) {
      // ...
    }
    return new TestBean();
  }