Spring Boot Controller - 枚举参数作为值

Question

我有一个弹簧启动控制器，我的参数之一是枚举。枚举有一个字符串值。我想将枚举的值和控制器作为参数传递给我枚举。这个可以吗？

 @RequestMapping(value = "/")
public MyResponse getResponse ( @RequestParam(value = "version") final ProjectVersion version ) {
   ...bla bla bla...
}

public enum ProjectVersion {
    VERSION_1 ("1.00")
    VERSION_2 ("2.00")

    private final String version;

    ProjectVersion ( String version ) {
        this.version = version;
    }

     @Override
     public String toString() {
        return this.version;
     }

}

我希望能够提出如下请求：

http://myhost.com/mypath?version=1.00

并在控制器中获取 ProjectVersion.VERSION_1

有什么想法吗？

Answer 1

这是不可能的。您必须创建自定义转换器才能将 String 转换为 ProjectVersion。

例如首先定义从String到ProjectVersion的转换器：

public class ProjectVersionConverter implements ConditionalGenericConverter {

  @Override
  public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
    return targetType.getType().equals(ProjectVersion.class);
  }

  @Override
  public Set<ConvertiblePair> getConvertibleTypes() {
    return Collections.singleton(new ConvertiblePair(String.class , ProjectVersion.class));
  }

  @Override
  public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
    return ProjectVersion.findByVersion((String)source);
  }
}

然后注册：

@Configuration
public class CustomWebMvcConfigurerAdapter extends WebMvcConfigurerAdapter {

  @Override
  public void addFormatters(FormatterRegistry registry) {
    registry.addConverter(new ProjectVersionConverter());
  }
}

如果将ProjectVersionConverter 定义为Spring bean，则可以跳过注册。 （此代码未经测试）。

Answer 2

因为您需要（对于每个请求）将参数传递给Controller 方法，所以干净的解决方案是使用HandlerMethodArgumentResolver，这样 Spring 容器可以将您的 ProjectVersion 参数动态注入到 Controller 方法中，如下所示：

ProjectVersionArgumentResolver类：

public class ProjectVersionArgumentResolver implements 
                                    HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter methodParameter) {
        return methodParameter.getParameterType().equals(ProjectVersion.class);
    }

    @Override
    public Object resolveArgument(MethodParameter methodParameter,
                   ModelAndViewContainer modelAndViewContainer,
                   NativeWebRequest nativeWebRequest,
                   WebDataBinderFactory webDataBinderFactory) throws Exception {

        return ProjectVersion.fromString(nativeWebRequest.getParameter("version"));
    }
}

Spring-boot ApplicationLauncher 类：

public class MyProjectApplicationLauncher extends WebMvcConfigurerAdapter {

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> 
                                           argumentResolvers) {
        //add the new resolver
        argumentResolvers.add(new MyMethodArgumentResolver());
    }

    public static void main(String[] args) {
        SpringApplication.run(MyProjectApplicationLauncher.class, args);
    }
} 

ProjectVersion类：

public enum ProjectVersion {

    //add your existing code

    //Add fromString method to convert string to enum 
    public static ProjectVersion fromString(String input) {
        for (ProjectVersion projectVersion : ProjectVersion.values()) {
          if (projectVersion.version.equals(input)) {
            return projectVersion;
          }
        }
        return null;
     }
}