出现的问题
我全局配置的时间格式是：yyyy-MM-dd HH:mm:ss
@JSONField注解配置的时间格式是：yyyy-MM-dd
最终的返回结果是：yyyy-MM-dd HH:mm:ss
问题：为啥不是以注解定义的时间格式为主呢？
先说答案，后面再分析：
FastJson的全局配置日期格式会导致@JSONField注解失效
使用建议：
1.若全局配置了日期格式，就不要使用@JSONField注解
2.若想使用@JSONField注解，就不要全局配置日期格式
一、FastJson全局配置代码如下
@Configuration public class FastJsonConverterConfig { @Bean public HttpMessageConverters fastJsonHttpMessageConverters() { FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter(); FastJsonConfig fastJsonConfig = new FastJsonConfig(); fastJsonConfig.setSerializerFeatures( SerializerFeature.WriteMapNullValue, SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteNullStringAsEmpty, SerializerFeature.WriteNullBooleanAsFalse // SerializerFeature.WriteDateUseDateFormat ); fastConverter.setFastJsonConfig(fastJsonConfig); //全局指定了日期格式 fastJsonConfig.setDateFormat("yyyy-MM-dd HH:mm:ss"); //该设置目的，为了兼容jackson fastConverter.setSupportedMediaTypes(Arrays.asList(MediaType.APPLICATION_JSON,MediaType.APPLICATION_JSON_UTF8,MediaType.APPLICATION_OCTET_STREAM)); HttpMessageConverter<?> converter = fastConverter; return new HttpMessageConverters(converter); } }
二、使用@JSONField注解的Java Bean代码如下
@Data public class UserCardInfoResponseModel { @JSONField(format = "yyyy-MM-dd") private Date validStartDate; }
三、源码分析
1.首先我们看下FastJson最终格式化字段值的方法，JSONSerializer.writeWithFormat(Object object, String format)
public class JSONSerializer extends SerializeFilterable {
/**
* format就是@JSONField注解中指定的format值
* object就是需要格式化的变量
*/
public final void writeWithFormat(Object object, String format) { if (object instanceof Date) {
//从当前类获取一个DateFormat，DateFormat就是用来格式化日期的类，再看看this.getDateFormat();的实现 DateFormat dateFormat = this.getDateFormat(); if (dateFormat == null) {
//只有当，当前类中的dateFormat为null时，才会使用JSONField注解中的format值初始化一个新的DateFormat
//那么我们可以肯定@JSONField注解没生效的原因就是,当前类中的dateFormat不为null dateFormat = new SimpleDateFormat(format, locale); dateFormat.setTimeZone(timeZone); } String text = dateFormat.format((Date) object); out.writeString(text); return; } if (object instanceof byte[]) { byte[] bytes = (byte[]) object; if ("gzip".equals(format) || "gzip,base64".equals(format)) { GZIPOutputStream gzipOut = null; try {z ByteArrayOutputStream byteOut = new ByteArrayOutputStream(); if (bytes.length < 512) { gzipOut = new GZIPOutputStream(byteOut, bytes.length); } else { gzipOut = new GZIPOutputStream(byteOut); } gzipOut.write(bytes); gzipOut.finish(); out.writeByteArray(byteOut.toByteArray()); } catch (IOException ex) { throw new JSONException("write gzipBytes error", ex); } finally { IOUtils.close(gzipOut); } } else if ("hex".equals(format)) { out.writeHex(bytes); } else { out.writeByteArray(bytes); } return; } if (object instanceof Collection) { Collection collection = (Collection) object; Iterator iterator = collection.iterator(); out.write('['); for (int i = 0; i < collection.size(); i++) { Object item = iterator.next(); if (i != 0) { out.write(','); } writeWithFormat(item, format); } out.write(']'); return; } write(object); } public DateFormat getDateFormat() {
if (dateFormat == null) { if (dateFormatPattern != null) {
//第一次调用该方法时，dateformat为null，满足第一个if条件
//那么只有当dateFormatPattern有值时，才会初始化一个dateFormat对象，
//那么问题来了，dateFormatPattern值是从哪里来的呢，答案就是从我们的全局配置中来的，我们继续往下看 dateFormat = new SimpleDateFormat(dateFormatPattern, locale); dateFormat.setTimeZone(timeZone); } } return dateFormat; } }
2.其次，我们来看使用我们FastJson全局配置的地方，FastJsonHttpMessageConverter.writeInternal(Object object, HttpOutputMessage outputMessage);
public class FastJsonHttpMessageConverter extends AbstractHttpMessageConverter<Object>// implements GenericHttpMessageConverter<Object> { @Override protected void writeInternal(Object object, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { ByteArrayOutputStream outnew = new ByteArrayOutputStream(); try { HttpHeaders headers = outputMessage.getHeaders(); //获取全局配置的filter SerializeFilter[] globalFilters = fastJsonConfig.getSerializeFilters(); List<SerializeFilter> allFilters = new ArrayList<SerializeFilter>(Arrays.asList(globalFilters)); boolean isJsonp = false; //不知道为什么会有这行代码， 但是为了保持和原来的行为一致，还是保留下来 Object value = strangeCodeForJackson(object); if (value instanceof FastJsonContainer) { FastJsonContainer fastJsonContainer = (FastJsonContainer) value; PropertyPreFilters filters = fastJsonContainer.getFilters(); allFilters.addAll(filters.getFilters()); value = fastJsonContainer.getValue(); } //revise 2017-10-23 , // 保持原有的MappingFastJsonValue对象的contentType不做修改 保持旧版兼容。 // 但是新的JSONPObject将返回标准的contentType：application/javascript ，不对是否有function进行判断 if (value instanceof MappingFastJsonValue) { if(!StringUtils.isEmpty(((MappingFastJsonValue) value).getJsonpFunction())){ isJsonp = true; } } else if (value instanceof JSONPObject) { isJsonp = true; } //我们看这里，fastJsonConfig就是我们全局配置的配置类，
//fastJsonConfig.getDateFormat()获取的就是我们全局配置的时间格式yyyy-MM-dd HH:mm:ss，然后我们看看JSON.writeJSONString方法 int len = JSON.writeJSONString(outnew, // fastJsonConfig.getCharset(), // value, // fastJsonConfig.getSerializeConfig(), // //fastJsonConfig.getSerializeFilters(), // allFilters.toArray(new SerializeFilter[allFilters.size()]), fastJsonConfig.getDateFormat(), // JSON.DEFAULT_GENERATE_FEATURE, // fastJsonConfig.getSerializerFeatures()); if (isJsonp) { headers.setContentType(APPLICATION_JAVASCRIPT); } if (fastJsonConfig.isWriteContentLength()) { headers.setContentLength(len); } outnew.writeTo(outputMessage.getBody()); } catch (JSONException ex) { throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex); } finally { outnew.close(); } } }
3.然后，我们看看初始化我们第1步说到类JSONSerializer的地方JSON.writeJSONString(....)
public abstract class JSON implements JSONStreamAware, JSONAware { public static final int writeJSONString(OutputStream os, // Charset charset, // Object object, // SerializeConfig config, // SerializeFilter[] filters, // String dateFormat, // int defaultFeatures, // SerializerFeature... features) throws IOException { SerializeWriter writer = new SerializeWriter(null, defaultFeatures, features); try {
//看这里,就是用来初始化JSONSerializer对象 JSONSerializer serializer = new JSONSerializer(writer, config); if (dateFormat != null && dateFormat.length() != 0) {
//然后在这里，将全局配置的日期格式dateFormat，设置到JSONSerializer中的
//到这里我们就应该很清楚整个的逻辑了 serializer.setDateFormat(dateFormat); serializer.config(SerializerFeature.WriteDateUseDateFormat, true); } if (filters != null) { for (SerializeFilter filter : filters) { serializer.addFilter(filter); } } serializer.write(object); int len = writer.writeToEx(os, charset); return len; } finally { writer.close(); } } }
四、保留下分析源码抓取的调用栈，方便下次阅读源码
WebMvcMetricsFilterdoFilterInternal WebMvcMetricsFilterfilterAndRecordMetrics ApplicationFilterChaininternalDoFilter WsFilterdoFilter ApplicationFilterChaindoFilter ApplicationFilterChaininternalDoFilter FrameworkServletservice FrameworkServletdoGet FrameworkServletprocessRequest DispatcherServletdoService() DispatcherServletdoDispatchmv = ha.handle(processedRequest, response, mappedHandler.getHandler()); AbstractHandlerMethodAdapterhandle(84) RequestMappingHandlerAdapterhandleInternal(761)mav = invokeHandlerMethod(request, response, handlerMethod); RequestMappingHandlerAdapterinvokeHandlerMethod(835) ServletInvocableHandlerMethodinvokeAndHandle(99) HandlerMethodReturnValueHandlerCompositehandleReturnValue(75) RequestResponseBodyMethodProcessorhandleReturnValue(171) AbstractMessageConverterMethodProcessorgenericConverter.write(outputValue, declaredType, selectedMediaType, outputMessage);(272) FastJsonHttpMessageConvertersuper.write(o, contentType, outputMessage);(184) AbstractHttpMessageConverterwriteInternal(t, outputMessage);(224) FastJsonHttpMessageConverterwriteInternal(246) **** JSONwriteJSONString(821) ===> JSONSerializerwriteWithFieldName ===> MapSerializerwrite() ===> JavaBeanSerializerfieldSerializer.writeValue(serializer, propertyValue); ===> FieldSerializerserializer.writeWithFormat(propertyValue, format); ===> **** JSONSerializerpublic final void writeWithFormat(Object object, String format) {}