Question

我使用Spring MVC Annotations创建一个JSON Rest API，其定义方法如下：

@RequestMapping(value = "/authenticate", method = RequestMethod.POST)
public @ResponseBody AuthenticationResponse authenticate(@RequestBody final DeviceInformation deviceInformation)
            throws AuthenticationException {
    return createAuthenticationResponse(deviceInformation, false);
}

为了处理不同的客户端版本，我想通过使用注释来排除或包含序列化bean的属性，如

class AuthenticationResponse {
    @InterfaceVersion(max = 2) 
    String old;

    @InterfaceVersion(min = 3)
    String new;
}

因此，如果客户端使用InterfaceVersion 2调用，他将无法获得 new 属性，如果他使用3调用，则他将无法获得旧属性。

我已经发现Jackson库（Spring为JSON使用）提供了JsonView，JsonFilter等功能，但我无法弄清楚我在哪里以及如何配置这些东西。

Answer 1

我使用@JsonFilter选择性地过滤掉同一个对象的属性，Spring当时没有（当然还没有？）支持这个，所以我注册了一个自定义MappingJackson2HttpMessageConverter来检查返回类型，如果是过滤器包装类型，我将过滤器取出并应用它。

public class JsonFilterAwareMappingJackson2HttpMessageConverter extends
    MappingJackson2HttpMessageConverter {

private boolean prefixJson = false;

@Override
public void setPrefixJson(boolean prefixJson) {
    this.prefixJson = prefixJson;
    super.setPrefixJson(prefixJson);
}

@Override
protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
        throws IOException, HttpMessageNotReadableException {

    JavaType javaType = getJavaType(clazz);
    try {
        return this.getObjectMapper().readValue(inputMessage.getBody(), javaType);
    }
    catch (IOException ex) {
        logger.error("Could not read JSON: " + ex.getMessage());
        throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
    }

}

@Override
protected void writeInternal(Object object, HttpOutputMessage outputMessage)
        throws IOException, HttpMessageNotWritableException {
    JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType());
    ObjectMapper objectMapper = getObjectMapper();
    JsonGenerator jsonGenerator =
            objectMapper.getJsonFactory().createJsonGenerator(outputMessage.getBody(), encoding);

    // A workaround for JsonGenerators not applying serialization features
    // https://github.com/FasterXML/jackson-databind/issues/12
    if (objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
        jsonGenerator.useDefaultPrettyPrinter();
    }

    try {
        if (this.prefixJson) {
            jsonGenerator.writeRaw("{} && ");
        }

        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        if (object instanceof FilterAppliedJsonObject) {
            FilterAppliedJsonObject viewObject = FilterAppliedJsonObject.class.cast(object);
            objectMapper.setFilters(viewObject.getFilters());
            objectMapper.writeValue(jsonGenerator, viewObject.getObject()); 
        } else if (object == null) {
            jsonGenerator.writeNull();

        } else {
            objectMapper.writeValue(jsonGenerator, object); 
        }
    }
    catch (JsonProcessingException ex) {
        logger.error("Could not write JSON: " + ex.getMessage());
        throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
    }
}

}

我尽可能多地使用java @config而不是xml配置，所以我这样做：

@Override
public void configureMessageConverters(
        List<HttpMessageConverter<?>> converters) {
    converters.add(new JsonFilterAwareMappingJackson2HttpMessageConverter());
    super.configureMessageConverters(converters);
}

如果你想在xml

中注册这种转换，我认为this post会对你有所帮助

过滤Jackson JSON的属性

1 个答案: