在API平台中，自定义输出的序列化问题可以通过以下解决方法来解决：

1. 使用Jackson库自定义序列化器和反序列化器：

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CustomObjectMapper extends ObjectMapper {
    public CustomObjectMapper() {
        SimpleModule module = new SimpleModule();
        module.addSerializer(Date.class, new CustomDateSerializer());
        this.registerModule(module);
    }

    private static class CustomDateSerializer extends JsonSerializer {
        private static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        @Override
        public void serialize(Date date, JsonGenerator gen, SerializerProvider provider) throws IOException, JsonProcessingException {
            String formattedDate = dateFormat.format(date);
            gen.writeString(formattedDate);
        }
    }
}

// 在配置类中配置自定义的ObjectMapper
@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void configureMessageConverters(List> converters) {
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        converter.setObjectMapper(new CustomObjectMapper());
        converters.add(converter);
    }
}

2. 使用Gson库自定义序列化器和反序列化器：

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import org.springframework.http.converter.json.GsonHttpMessageConverter;

import java.lang.reflect.Type;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CustomGsonHttpMessageConverter extends GsonHttpMessageConverter {
    @Override
    protected Gson createGson() {
        GsonBuilder gsonBuilder = new GsonBuilder();
        gsonBuilder.registerTypeAdapter(Date.class, new CustomDateSerializer());
        return gsonBuilder.create();
    }

    private static class CustomDateSerializer implements JsonSerializer {
        private static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        @Override
        public JsonElement serialize(Date date, Type type, JsonSerializationContext context) {
            String formattedDate = dateFormat.format(date);
            return context.serialize(formattedDate);
        }
    }
}

// 在配置类中配置自定义的GsonHttpMessageConverter
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Override
    public void configureMessageConverters(List> converters) {
        converters.add(new CustomGsonHttpMessageConverter());
    }
}

这样，你就可以自定义输出对象的序列化规则，并在API平台中使用了。