@Documented
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ApiVersion {
    /**
     * 版本號
     * @return
     */
    int value() default 1;
}

@RefreshScope
@Data
@ConfigurationProperties(prefix = "api.version")
public class ApiVersionProperties {

    boolean enabled;
}

public class ApiRequestHandlerMapping extends RequestMappingHandlerMapping {

    @Override
    protected RequestCondition<ApiVersionCondition> getCustomTypeCondition(Class<?> handlerType) {
        ApiVersion apiVersion = AnnotationUtils.findAnnotation(handlerType, ApiVersion.class);
        return createCondition(apiVersion);
    }

    @Override
    protected RequestCondition<ApiVersionCondition> getCustomMethodCondition(Method method) {
        ApiVersion apiVersion = AnnotationUtils.findAnnotation(method, ApiVersion.class);
        return createCondition(apiVersion);
    }

    private RequestCondition<ApiVersionCondition> createCondition(ApiVersion apiVersion) {
        return apiVersion == null ? null : new ApiVersionCondition(apiVersion.value());
    }
}

public class ApiVersionCondition implements RequestCondition<ApiVersionCondition> {
    /**
     * extract the version part from url. example [v0-9]
     */
    private final static Pattern VERSION_PREFIX_PATTERN = Pattern.compile("v(\\d+)/");

    private int apiVersion;


    public ApiVersionCondition(int apiVersion) {
        this.apiVersion = apiVersion;
    }

    /**
     *  // 和另外一個請求匹配條件合并，具體合并邏輯由實現(xiàn)類提供
     * @param other
     * @return
     */
    @Override
    public ApiVersionCondition combine(ApiVersionCondition other) {
        // latest defined would be take effect, that means, methods definition with
        // override the classes definition
        return new ApiVersionCondition(other.getApiVersion());
    }

    /**
     * 	// 檢查當(dāng)前請求匹配條件和指定請求request是否匹配，如果不匹配返回null，
     * 	// 如果匹配，生成一個新的請求匹配條件，該新的請求匹配條件是當(dāng)前請求匹配條件
     * 	// 針對指定請求request的剪裁。
     * 	// 舉個例子來講，如果當(dāng)前請求匹配條件是一個路徑匹配條件，包含多個路徑匹配模板，
     * 	// 并且其中有些模板和指定請求request匹配，那么返回的新建的請求匹配條件將僅僅
     * 	// 包含和指定請求request匹配的那些路徑模板。
     * @param request
     * @return
     */
    @Override
    public ApiVersionCondition getMatchingCondition(HttpServletRequest request) {
        Matcher m = VERSION_PREFIX_PATTERN.matcher(request.getRequestURI());
        if (m.find()) {
            Integer version = Integer.valueOf(m.group(1));
            // when applying version number bigger than configuration, then it will take
            if (version >= this.apiVersion) {
                // effect
                return this;
            }

        }
        return null;
    }

    /**
     *  針對指定的請求對象request比較兩個請求匹配條件。
     *  該方法假定被比較的兩個請求匹配條件都是針對該請求對象request調(diào)用了
     *  #getMatchingCondition方法得到的，這樣才能確保對它們的比較
     *  是針對同一個請求對象request，這樣的比較才有意義(最終用來確定誰是
     *  更匹配的條件)。
     * @param other
     * @param request
     * @return
     */
    @Override
    public int compareTo(ApiVersionCondition other, HttpServletRequest request) {
        // when more than one configured version number passed the match rule, then only
        // the biggest one will take effect.
        return other.getApiVersion() - this.apiVersion;
    }

    public int getApiVersion() {
        return apiVersion;
    }
}

@Configuration
@EnableConfigurationProperties(ApiVersionProperties.class)
@ConditionalOnProperty(
        value = {"api.version.enabled"},
        matchIfMissing = true
)
public class WebConfig implements WebMvcRegistrations {

    @Override
    public RequestMappingHandlerMapping getRequestMappingHandlerMapping() {
        return new ApiRequestHandlerMapping();
    }
}

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.example.springbootgray.apiversion.WebConfig,\

@RestController
@ApiVersion(value = 1)
@RequestMapping("/api/{version}")