springcloud采坑-jason序列化

提纲：

1.出现的场景。

2.报错内容和代码追踪。

3.原因。

4.三种解决方案。

1. 出现的场景：

服务端提供一个springcloud接口。
客户端通过feign调用该接口，返回值为一个列表的CompanyDTO,DTO中有一个Date对象。
调用出错。

2. 报错如下：

Caused by: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize value of type java.util.Date from String "2017-12-08 09:20:53": not a valid representation (error: Failed to parse Date value '2017-12-08 09:20:53': Can not parse date "2017-12-08 09:20:53Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null))
 at [Source: java.io.PushbackInputStream@2041c1b0; line: 1, column: 554] (through reference chain: com.qts.base.result.ResponseData["data"]->java.util.ArrayList[0]->com.qts.company.api.dto.CompanyDTO["applyRefundTime"]); nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type java.util.Date from String "2017-12-08 09:20:53": not a valid representation (error: Failed to parse Date value '2017-12-08 09:20:53': Can not parse date "2017-12-08 09:20:53Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null))
 at [Source: java.io.PushbackInputStream@2041c1b0; line: 1, column: 554] (through reference chain: com.qts.base.result.ResponseData["data"]->java.util.ArrayList[0]->com.qts.company.api.dto.CompanyDTO["applyRefundTime"])
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:228)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:213)
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:95)
	at org.springframework.cloud.netflix.feign.support.SpringDecoder.decode(SpringDecoder.java:59)
	at org.springframework.cloud.netflix.feign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:47)
	at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:165)
	... 75 more
Caused by: com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type java.util.Date from String "2017-12-08 09:20:53": not a valid representation (error: Failed to parse Date value '2017-12-08 09:20:53': Can not parse date "2017-12-08 09:20:53Z": while it seems to fit format 'yyyy-MM-dd'T'HH:mm:ss.SSS'Z'', parsing fails (leniency? null))
 at [Source: java.io.PushbackInputStream@2041c1b0; line: 1, column: 554] (through reference chain: com.qts.base.result.ResponseData["data"]->java.util.ArrayList[0]->com.qts.company.api.dto.CompanyDTO["applyRefundTime"])
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:74)
	at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:1410)
	at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:926)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:822)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:791)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateBasedDeserializer._parseDate(DateDeserializers.java:172)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:259)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:242)
	at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:499)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:101)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:357)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:277)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26)
	at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:499)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:101)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:357)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2913)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:225)
	... 80 more

从AbstractJackson2HttpMessageConverter.java:225的readJavaType方法开始。
DateDeserializers.java的deserialize中，有一段核心逻辑：this._customFormat.parse(str)。问题来了：_customFormat是从哪里来的？

protected Date _parseDate(JsonParser p, DeserializationContext ctxt) throws IOException {
            if (this._customFormat != null) {
                JsonToken t = p.getCurrentToken();
                if (t == JsonToken.VALUE_STRING) {
                    String str = p.getText().trim();
                    if (str.length() == 0) {
                        return (Date)this.getEmptyValue(ctxt);
                    }

                    DateFormat var5 = this._customFormat;
                    synchronized(this._customFormat) {
                        Date var10000;
                        try {
                            var10000 = this._customFormat.parse(str);
                        } catch (ParseException var8) {
                            return (Date)ctxt.handleWeirdStringValue(this.handledType(), str, "expected format \"%s\"", new Object[]{this._formatString});
                        }

                        return var10000;
                    }
                }
            }

            return super._parseDate(p, ctxt);
        }

DateBasedDeserializer中的_customFormat，通过ctxt.getConfig()获取，DeserializationContext是配置的上下文。

protected abstract static class DateBasedDeserializer<T> extends StdScalarDeserializer<T> implements ContextualDeserializer {
        protected final DateFormat _customFormat;
        protected final String _formatString;

        protected abstract DateDeserializers.DateBasedDeserializer<T> withDateFormat(DateFormat var1, String var2);

        public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property) throws JsonMappingException {
            if (property != null) {
                Value format = this.findFormatOverrides(ctxt, property, this.handledType());
                if (format != null) {
                    TimeZone tz = format.getTimeZone();
                    Locale loc;
                    if (format.hasPattern()) {
                        String pattern = format.getPattern();
                        loc = format.hasLocale() ? format.getLocale() : ctxt.getLocale();
                        SimpleDateFormat df = new SimpleDateFormat(pattern, loc);
                        if (tz == null) {
                            tz = ctxt.getTimeZone();
                        }

                        df.setTimeZone(tz);
                        return this.withDateFormat(df, pattern);
                    }

                    if (tz != null) {
                        DateFormat df = ctxt.getConfig().getDateFormat();
                        Object df;
                        if (df.getClass() == StdDateFormat.class) {
                            loc = format.hasLocale() ? format.getLocale() : ctxt.getLocale();
                            StdDateFormat std = (StdDateFormat)df;
                            std = std.withTimeZone(tz);
                            std = std.withLocale(loc);
                            df = std;
                        } else {
                            df = (DateFormat)df.clone();
                            ((DateFormat)df).setTimeZone(tz);
                        }

                        return this.withDateFormat((DateFormat)df, this._formatString);
                    }
                }
            }

            return this;
        }
    }

我们看下getDateFormat的具体实现，最终是通过MapperConfig中的BaseSettings获取。

    public final DateFormat getDateFormat() {
        return this._base.getDateFormat();
    }

3.具体原因是Jason只支持一下几种格式：

"yyyy-MM-dd'T'HH:mm:ss.SSSZ"  
 "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"  
 "EEE, dd MMM yyyy HH:mm:ss zzz"  
 "yyyy-MM-dd"

4.解决方案：

4.1设置客户端的DateFormat。

public class MyDateFormat extends DateFormat {

    private DateFormat dateFormat;

    private SimpleDateFormat format1 = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");

    public MyDateFormat(DateFormat dateFormat) {
        this.dateFormat = dateFormat;
    }

    @Override
    public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
        return dateFormat.format(date, toAppendTo, fieldPosition);
    }

    @Override
    public Date parse(String source, ParsePosition pos) {

        Date date = null;

        try {

            date = format1.parse(source, pos);
        } catch (Exception e) {

            date = dateFormat.parse(source, pos);
        }

        return date;
    }

    // 主要还是装饰这个方法
    @Override
    public Date parse(String source) throws ParseException {

        Date date = null;

        try {

            // 先按我的规则来
            date = format1.parse(source);
        } catch (Exception e) {

            // 不行，那就按原先的规则吧
            date = dateFormat.parse(source);
        }

        return date;
    }

    // 这里装饰clone方法的原因是因为clone方法在jackson中也有用到
    @Override
    public Object clone() {
        Object format = dateFormat.clone();
        return new MyDateFormat((DateFormat) format);
    }
}

并在启动的时候加入。

@Configuration
public class WebConfig {

	@Autowired
	private Jackson2ObjectMapperBuilder jackson2ObjectMapperBuilder;
	
	@Bean
	public MappingJackson2HttpMessageConverter MappingJsonpHttpMessageConverter() {

		ObjectMapper mapper = jackson2ObjectMapperBuilder.build();

		// ObjectMapper为了保障线程安全性，里面的配置类都是一个不可变的对象
		// 所以这里的setDateFormat的内部原理其实是创建了一个新的配置类
		DateFormat dateFormat = mapper.getDateFormat();
		mapper.setDateFormat(new MyDateFormat(dateFormat));

		MappingJackson2HttpMessageConverter mappingJsonpHttpMessageConverter = new MappingJackson2HttpMessageConverter(
				mapper);
		return mappingJsonpHttpMessageConverter;
	}
}

4.2解决方案2

可以通过代码，那就可以通过配置。。。

#spring.mvc.date-format=yyyy-MM-dd HH:mm:ss
#spring.jackson.time-zone=GMT+8
#spring.jackson.date-format=yyyy-MM-dd HH:mm:ss
#spring.jackson.deserialization.accept_empty_string_as_null_object=true

4.3解决方案3

在字段的setter上加上注解，这种方法比较麻烦。

public class DateJsonDeserializer extends JsonDeserializer<Date> {

    /**
     * @see JsonDeserializer#deserialize(JsonParser,
     *      DeserializationContext)
     */
    @Override
    public Date deserialize(JsonParser parser, DeserializationContext context)
            throws IOException, JsonProcessingException {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            return sdf.parse(parser.getValueAsString());
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}

然后在DTO的字段上增加注解：

    @JsonDeserialize(using = DateJsonDeserializer.class)
    private Date applyRefundTime;

参考文章：

https://blog.csdn.net/qq906627950/article/details/79503801

http://wujiu.iteye.com/blog/2244537

springcloud采坑-jason序列化

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