从@PathVariable DomainObject 到字符串的转换器?(使用 ControllerLinkBuilder.methodOn) [英] Converter from @PathVariable DomainObject to String? (using ControllerLinkBuilder.methodOn)

问题描述

我正在尝试使用非字符串类型调用 Spring 的 ControllerLinkBuilder.methodOn()，但总是失败.而且我不知道要使用哪种Converter 以及在哪里注册.

I'm trying to call Spring's ControllerLinkBuilder.methodOn() with a non-String type, which always fails. And I don't know which kind of Converter to use and where to register it.

这是我的控制器:

@RestController
@RequestMapping("/companies")
class CompanyController {

    @RequestMapping(value="/{c}", method=RequestMethod.GET)
    void getIt(@PathVariable Company c) {
        System.out.println(c);
        Link link = linkTo(methodOn(getClass()).getIt(c));
    }

}

System.out.println(c) 运行良好.我的 Company 域对象从数据库中获取.(我正在使用 DomainClassConverter)

The System.out.println(c) works well. My Company Domain object get's fetched from DB. (I'm using DomainClassConverter)

但另一种方式不起作用:ConverterNotFoundException:找不到能够从@PathVariable Company 类型转换为String 类型的转换器

But the other way doesn't work: ConverterNotFoundException: No converter found capable of converting from type @PathVariable Company to type String

我是否只需要一个 Converter?我应该在哪里注册?我在 WebMvcConfigurationSupport 的 addFormatters(FormatterRegistry registry) 方法中尝试了一些东西，但它确实显示了相同的错误.但毕竟我不确定我到底尝试了什么......

Do I just need a Converter<Company, String>? And where should I register it? I tried something within the addFormatters(FormatterRegistry registry) method of WebMvcConfigurationSupport, but it did just display the same error. But after all I'm not sure what exactly I tried...

推荐答案

找到了解决方案".它需要大量的复制&从 Spring 的类粘贴，但至少它有效！

Found a "solution". It requires a lot copy & paste from Spring's classes, but at least it works!

基本上我必须复制 org.springframework.hateoas.mvc.AnnotatedParametersParameterAccessor 并更改两行:

Basically I had to copy org.springframework.hateoas.mvc.AnnotatedParametersParameterAccessor and change two lines:

class AnnotatedParametersParameterAccessor {
    ...
    static class BoundMethodParameter {
        // OLD: (with this one you can't call addConverter())
        // private static final ConversionService CONVERSION_SERVICE = new DefaultFormattingConversionService();
        // NEW:
        private static final FormattingConversionService CONVERSION_SERVICE = new DefaultFormattingConversionService();

        ...

        public BoundMethodParameter(MethodParameter parameter, Object value, AnnotationAttribute attribute) {
            ...
            // ADD:
            CONVERSION_SERVICE.addConverter(new MyNewConverter());
    }

    ...
}

这个类被 ControllerLinkBuilderFactory 使用.所以我不得不复制 &也贴一下.

This class get's used by ControllerLinkBuilderFactory. So I had to copy & paste that, too.

ControllerLinkBuilder 使用了这个.也复制 &粘贴.

And this one get's used by ControllerLinkBuilder. Also copy & paste.

我的 Converter 只做 myDomainObject.getId().toString():

public class MyNewConverter implements Converter<Company, String> {
    @Override
    public String convert(Company source) {
        return source.getId().toString();
    }   
}

现在您可以在控制器中使用复制和粘贴的 ControllerLinkBuilder 并且它按预期工作！

Now you can use the copy&pasted ControllerLinkBuilder inside the controller and it works as expected!

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