【源碼分析】FastJson全局配置日期格式致使@JSONField(format = "yyyy-MM-dd")註解失效

出現的問題

我全局配置的時間格式是：yyyy-MM-dd HH:mm:ss

@JSONField註解配置的時間格式是：yyyy-MM-dd

最終的返回結果是：yyyy-MM-dd HH:mm:ss

問題：爲啥不是以註解定義的時間格式爲主呢？

先說答案，後面再分析：

FastJson的全局配置日期格式會致使@JSONField註解失效

使用建議：

1.若全局配置了日期格式，就不要使用@JSONField註解

2.若想使用@JSONField註解，就不要全局配置日期格式

 

1、FastJson全局配置代碼以下

@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"); //該設置目的，爲了兼容jackson
        fastConverter.setSupportedMediaTypes(Arrays.asList(MediaType.APPLICATION_JSON,MediaType.APPLICATION_JSON_UTF8,MediaType.APPLICATION_OCTET_STREAM));
        HttpMessageConverter<?> converter = fastConverter;
        return new HttpMessageConverters(converter);
    }
}

 

2、使用@JSONField註解的Java Bean代碼以下

@Data
public class UserCardInfoResponseModel {

    @JSONField(format = "yyyy-MM-dd") private Date validStartDate;

}

 

3、源碼分析

1.首先咱們看下FastJson最終格式化字段值的方法，JSONSerializer.writeWithFormat(Object object, String format)

public class JSONSerializer extends SerializeFilterable {
　　
　　/**
　　* format就是@JSONField註解中指定的format值
　　* object就是須要格式化的變量
　　*/
　　public final void writeWithFormat(Object object, String format) {
        if (object instanceof Date) {
　　　　　　　//從當前類獲取一個DateFormat，DateFormat就是用來格式化日期的類，再看看this.getDateFormat();的實現　
            DateFormat dateFormat = this.getDateFormat();
            if (dateFormat == null) {
　　　　　　　//只有當，當前類中的dateFormat爲null時，纔會使用JSONField註解中的format值初始化一個新的DateFormat
　　　　　　　//那麼咱們能夠確定@JSONField註解沒生效的緣由就是,當前類中的dateFormat不爲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) {
　　　　　　　//第一次調用該方法時，dateformat爲null，知足第一個if條件
　　　　　　　//那麼只有當dateFormatPattern有值時，纔會初始化一個dateFormat對象，
　　　　　　　//那麼問題來了，dateFormatPattern值是從哪裏來的呢，答案就是從咱們的全局配置中來的，咱們繼續往下看
                dateFormat = new SimpleDateFormat(dateFormatPattern, locale);
                dateFormat.setTimeZone(timeZone);
            }
        }

        return dateFormat;
    }

}

 

2.其次，咱們來看使用咱們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();

            //獲取全局配置的filter
            SerializeFilter[] globalFilters = fastJsonConfig.getSerializeFilters();
            List<SerializeFilter> allFilters = new ArrayList<SerializeFilter>(Arrays.asList(globalFilters));

            boolean isJsonp = false;

            //不知道爲何會有這行代碼， 可是爲了保持和原來的行爲一致，仍是保留下來
            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對象的contentType不作修改 保持舊版兼容。
            // 可是新的JSONPObject將返回標準的contentType：application/javascript ，不對是否有function進行判斷
            if (value instanceof MappingFastJsonValue) {
                if(!StringUtils.isEmpty(((MappingFastJsonValue) value).getJsonpFunction())){
                    isJsonp = true;
                }
            } else if (value instanceof JSONPObject) {
                isJsonp = true;
            }

　　　　　　　//咱們看這裏，fastJsonConfig就是咱們全局配置的配置類，
　　　　　　　//fastJsonConfig.getDateFormat()獲取的就是咱們全局配置的時間格式yyyy-MM-dd HH:mm:ss，而後咱們看看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.而後，咱們看看初始化咱們第1步說到類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 {
　　　　　　//看這裏,就是用來初始化JSONSerializer對象
            JSONSerializer serializer = new JSONSerializer(writer, config);
            
            if (dateFormat != null && dateFormat.length() != 0) {
　　　　　　　//而後在這裏，將全局配置的日期格式dateFormat，設置到JSONSerializer中的
　　　　　　　//到這裏咱們就應該很清楚整個的邏輯了
                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();
        }
    }
}

 

4、保留下分析源碼抓取的調用棧，方便下次閱讀源碼

WebMvcMetricsFilter\doFilterInternal
WebMvcMetricsFilter\filterAndRecordMetrics
ApplicationFilterChain\internalDoFilter
WsFilter\doFilter
ApplicationFilterChain\doFilter
ApplicationFilterChain\internalDoFilter
FrameworkServlet\service
FrameworkServlet\doGet
FrameworkServlet\processRequest
DispatcherServlet\doService()
DispatcherServlet\doDispatch\mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
AbstractHandlerMethodAdapter\handle(84)
RequestMappingHandlerAdapter\handleInternal(761)\mav = invokeHandlerMethod(request, response, handlerMethod);
RequestMappingHandlerAdapter\invokeHandlerMethod(835)
ServletInvocableHandlerMethod\invokeAndHandle(99)
HandlerMethodReturnValueHandlerComposite\handleReturnValue(75)
RequestResponseBodyMethodProcessor\handleReturnValue(171)
AbstractMessageConverterMethodProcessor\genericConverter.write(outputValue, declaredType, selectedMediaType, outputMessage);(272)
FastJsonHttpMessageConverter\super.write(o, contentType, outputMessage);(184)
AbstractHttpMessageConverter\writeInternal(t, outputMessage);(224)
FastJsonHttpMessageConverter\writeInternal(246)
****  JSON\writeJSONString(821)
===>
JSONSerializer\writeWithFieldName
===>
MapSerializer\write()
===>
JavaBeanSerializer\fieldSerializer.writeValue(serializer, propertyValue);
===>
FieldSerializer\serializer.writeWithFormat(propertyValue, format);
===>
**** JSONSerializer\public final void writeWithFormat(Object object, String format) {}