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我第一次在 Rest Web 服务中使用 Optional 将路径参数设为可选。

@RequestMapping(value = {"/hosts","/hosts/{name}"}, method = RequestMethod.GET, produces = "application/json")
public ResponseEntity<Object> getHosts(@PathVariable Optional<String> name) {
    if(name.isPresent()) {
        return service.getHosts(name.get());
    } else {
        return service.getHosts(null);
    }
}

当我使用不带参数的 API 时，它工作正常。

但是当我给出参数时，它会引发以下异常：

org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.String' to required type 'java.util.Optional'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [java.util.Optional]: no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterSupport.doConvert(TypeConverterSupport.java:74)
    at org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:47)
    at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:603)
    at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:104)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:129)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)

我花了很长时间调试这个但无法克服这个错误。任何帮助表示赞赏。

谢谢，

4

1 回答 1

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只需将“mvc:annotation-driven/>”添加到您的 xml 文件中即可使其工作。

于 2018-07-17T22:55:14.653 回答