解決方案：

@Configuration
public class FastJsonConfiguration extends WebMvcConfigurationSupport {

      
        @Override
        public void configureMessageConverters(List<HttpMessageConverter<?>> converters){
 
            //建立fastJson訊息轉換器
            FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
            //建立配置類
            FastJsonConfig fastJsonConfig = new FastJsonConfig();
           
            fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);
            //處理中文亂碼問題
            List<MediaType> fastMediaTypes = new ArrayList<>();
            fastMediaTypes.add(MediaType.APPLICATION_JSON_UTF8);
            fastJsonHttpMessageConverter.setSupportedMediaTypes(fastMediaTypes);
            fastJsonHttpMessageConverter.setFastJsonConfig(fastJsonConfig);
            converters.add(fastJsonHttpMessageConverter);
        }
}