Jackson反序列化@JsonFormat|Jackson反序列化@JsonFormat 不生效的解决方案 Jackson反序列化@JsonFormat不生效

今天在线上发现一个问题，在使用Jackson进行时间的反序列化时，配置的 @JsonFormat 没有生效
查看源码发现，Jackson在反序列化时间时，会判断json字段值类型，如下：

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由于在我们服务里，前端传时间值到后端时采用了时间戳的方式，json值被判断为数字类型，所以Jackson在反序列化时直接简单粗暴的方式处理，将时间戳转换为Date类型：

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为了能够按照正确的格式解析时间，抹去后面的时间点，精确到日，只好自定义一个时间解析器。自定义的时间解析器很好实现，网上已经有很多实例代码，只需要继承 JsonDeserializer 就可以。
问题的关键点在于，如何获取到注解上的时间格式，按照注解上的格式去解析，否则每个解析器的实现只能使用一种固定的格式去解析时间。
1. 所以第一步是获取注解上配置的信息想要获取字段对应的注解信息，只有找到相应的字段，然后通过字段属性获取注解信息，再通过注解信息获取配置的格式。
但找了很久，也没有在既有的参数里找到获取相关字段的方法，只能去翻看源码，最后在这里发现了获取字段信息的方法以及解析器的生成过程，源代码如下：
Jackson反序列化@JsonFormat|Jackson反序列化@JsonFormat 不生效的解决方案
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第一个红框表示解析器是在这里生成的，第二个红框就是获取注解信息的地方
2. 注解获取以后便创建自定义的时间解析器猜想，我们可不可以也实现这个类，重写生成解析器的方法？那就试试呗～我们在自定义的时间解析器上同样实现这个类，重写了生成时间解析器的方法，并初始化一些自定义的信息供解析时间使用（当然猜想是正确的，因为官方就是这么搞的，只是官方的是一个内部类实现的），具体代码如下：
时间解析器代码：

import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.databind.BeanProperty; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JsonDeserializer; import com.fasterxml.jackson.databind.deser.ContextualDeserializer; import com.fasterxml.jackson.databind.util.StdDateFormat; import com.google.common.collect.Lists; import com.tujia.rba.framework.core.remote.api.BizErrorCode; import com.tujia.rba.framework.core.remote.api.BizException; import java.io.IOException; import java.text.DateFormat; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.List; import java.util.Locale; import java.util.TimeZone; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang3.time.DateUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * @author 无名小生 Date: 2019-02-19 Time: 19:00 * @version $Id$ */public class DateJsonDeserializer extends JsonDeserializer implements ContextualDeserializer {private final static Logger logger = LoggerFactory.getLogger(DateJsonDeserializer.class); private final static List FORMATS = Lists.newArrayList("yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd HH:mm", "yyyyMMdd-HHmmss", "yyyy-MM-dd", "MM-dd", "HH:mm:ss", "yyyy-MM"); public final DateFormat df; public final String formatString; public DateJsonDeserializer() {this.df = null; this.formatString = null; }public DateJsonDeserializer(DateFormat df) {this.df = df; this.formatString = ""; }public DateJsonDeserializer(DateFormat df, String formatString) {this.df = df; this.formatString = formatString; }@Overridepublic Date deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {try {String dateValue = https://www.it610.com/article/p.getText(); if (df == null || StringUtils.isEmpty(dateValue)) {return null; }logger.info("使用自定义解析器解析字段:{}:时间:{}",p.getCurrentName(),p.getText()); Date date; if (StringUtils.isNumeric(dateValue)){date = new Date(Long.valueOf(dateValue)); }else {String[] patterns = FORMATS.toArray(new String[0]); date = DateUtils.parseDate(p.getText(),patterns); }return df.parse(df.format(date)); } catch (ParseException | SecurityException e) {logger.error("JSON反序列化，时间解析失败", e); throw new BizException(BizErrorCode.UNEXPECTED_ERROR); }}@Overridepublic JsonDeserializer createContextual(DeserializationContext ctxt, BeanProperty property) {if (property != null) {JsonFormat.Value format = ctxt.getAnnotationIntrospector().findFormat(property.getMember()); if (format != null) {TimeZone tz = format.getTimeZone(); // First: fully custom pattern?if (format.hasPattern()) {final String pattern = format.getPattern(); if (!FORMATS.contains(pattern)){FORMATS.add(pattern); }final Locale loc = format.hasLocale() ? format.getLocale() : ctxt.getLocale(); SimpleDateFormat df = new SimpleDateFormat(pattern, loc); if (tz == null) {tz = ctxt.getTimeZone(); }df.setTimeZone(tz); return new DateJsonDeserializer(df, pattern); }// But if not, can still override timezoneif (tz != null) {DateFormat df = ctxt.getConfig().getDateFormat(); // one shortcut: with our custom format, can simplify handling a bitif (df.getClass() == StdDateFormat.class) {final Locale loc = format.hasLocale() ? format.getLocale() : ctxt.getLocale(); StdDateFormat std = (StdDateFormat) df; std = std.withTimeZone(tz); std = std.withLocale(loc); df = std; } else {// otherwise need to clone, re-set timezone:df = (DateFormat) df.clone(); df.setTimeZone(tz); }return new DateJsonDeserializer(df); }}}return this; }}

至此，自定义时间解析器就完成了
但是，为了能够更灵活的控制时间的解析（例如：输入的时间格式和目标时间格式不同），我又重新自定义了一个时间解析的注解，基本仿照官方的 @Format 注解，具体代码如下
自定义时间解析注解：

import com.fasterxml.jackson.annotation.JacksonAnnotation; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import java.util.Locale; import java.util.TimeZone; /** * @author 无名小生 Date: 2019-02-21 Time: 11:03 * @version $Id$ */@Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER,ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@JacksonAnnotationpublic @interface DeserializeFormat {/*** Value that indicates that default {@link java.util.Locale}* (from deserialization or serialization context) should be used:* annotation does not define value to use.*/public final static String DEFAULT_LOCALE = "##default"; /*** Value that indicates that default {@link java.util.TimeZone}* (from deserialization or serialization context) should be used:* annotation does not define value to use.*/public final static String DEFAULT_TIMEZONE = "##default"; /*** 按照特定的时间格式解析*/public String pattern() default ""; /*** 目标格式* @return*/public String format() default ""; /*** Structure to use for serialization: definition of mapping depends on datatype,* but usually has straight-forward counterpart in data format (JSON).* Note that commonly only a subset of shapes is available; and if 'invalid' value* is chosen, defaults are usually used.*/public DeserializeFormat.Shape shape() default DeserializeFormat.Shape.ANY; /*** {@link java.util.Locale} to use for serialization (if needed).* Special value of {@link #DEFAULT_LOCALE}* can be used to mean "just use the default", where default is specified* by the serialization context, which in turn defaults to system* defaults ({@link java.util.Locale#getDefault()}) unless explicitly* set to another locale.*/public String locale() default DEFAULT_LOCALE; /*** {@link java.util.TimeZone} to use for serialization (if needed).* Special value of {@link #DEFAULT_TIMEZONE}* can be used to mean "just use the default", where default is specified* by the serialization context, which in turn defaults to system* defaults ({@link java.util.TimeZone#getDefault()}) unless explicitly* set to another locale.*/public String timezone() default DEFAULT_TIMEZONE; /*/**********************************************************/* Value enumeration(s), value class(es)/***********************************************************//*** Value enumeration used for indicating preferred Shape; translates* loosely to JSON types, with some extra values to indicate less precise* choices (i.e. allowing one of multiple actual shapes)*/public enum Shape{/*** Marker enum value that indicates "default" (or "whatever") choice; needed* since Annotations can not have null values for enums.*/ANY,/*** Value that indicates shape should not be structural (that is, not* {@link #ARRAY} or {@link #OBJECT}, but can be any other shape.*/SCALAR,/*** Value that indicates that (JSON) Array type should be used.*/ARRAY,/*** Value that indicates that (JSON) Object type should be used.*/OBJECT,/*** Value that indicates that a numeric (JSON) type should be used* (but does not specify whether integer or floating-point representation* should be used)*/NUMBER,/*** Value that indicates that floating-point numeric type should be used*/NUMBER_FLOAT,/*** Value that indicates that integer number type should be used* (and not {@link #NUMBER_FLOAT}).*/NUMBER_INT,/*** Value that indicates that (JSON) String type should be used.*/STRING,/*** Value that indicates that (JSON) boolean type* (true, false) should be used.*/BOOLEAN; public boolean isNumeric() {return (this == NUMBER) || (this == NUMBER_INT) || (this == NUMBER_FLOAT); }public boolean isStructured() {return (this == OBJECT) || (this == ARRAY); }}/*** Helper class used to contain information from a single {@link DeserializeFormat}* annotation.*/public static class Value{private final String pattern; private final String format; private final DeserializeFormat.Shape shape; private final Locale locale; private final String timezoneStr; // lazily constructed when created from annotationsprivate TimeZone _timezone; public Value() {this("", "", DeserializeFormat.Shape.ANY, "", ""); }public Value(DeserializeFormat ann) {this(ann.pattern(),ann.format(), ann.shape(), ann.locale(), ann.timezone()); }public Value(String p, String f, DeserializeFormat.Shape sh, String localeStr, String tzStr){this(p,f, sh,(localeStr == null || localeStr.length() == 0 || DEFAULT_LOCALE.equals(localeStr)) ?null : new Locale(localeStr),(tzStr == null || tzStr.length() == 0 || DEFAULT_TIMEZONE.equals(tzStr)) ?null : tzStr,null); }/*** @since 2.1*/public Value(String p, String f, DeserializeFormat.Shape sh, Locale l, TimeZone tz){pattern = p; format = f; shape = (sh == null) ? DeserializeFormat.Shape.ANY : sh; locale = l; _timezone = tz; timezoneStr = null; }/*** @since 2.4*/public Value(String p, String f, DeserializeFormat.Shape sh, Locale l, String tzStr, TimeZone tz){pattern = p; format = f; shape = (sh == null) ? DeserializeFormat.Shape.ANY : sh; locale = l; _timezone = tz; timezoneStr = tzStr; }/*** @since 2.1*/public DeserializeFormat.Value withPattern(String p,String f) {return new DeserializeFormat.Value(p, f, shape, locale, timezoneStr, _timezone); }/*** @since 2.1*/public DeserializeFormat.Value withShape(DeserializeFormat.Shape s) {return new DeserializeFormat.Value(pattern, format, s, locale, timezoneStr, _timezone); }/*** @since 2.1*/public DeserializeFormat.Value withLocale(Locale l) {return new DeserializeFormat.Value(pattern, format, shape, l, timezoneStr, _timezone); }/*** @since 2.1*/public DeserializeFormat.Value withTimeZone(TimeZone tz) {return new DeserializeFormat.Value(pattern, format, shape, locale, null, tz); }public String getPattern() { return pattern; }public String getFormat() { return format; }public DeserializeFormat.Shape getShape() { return shape; }public Locale getLocale() { return locale; }/*** Alternate access (compared to {@link #getTimeZone()}) which is useful* when caller just wants time zone id to convert, but not as JDK* provided {@link TimeZone}** @since 2.4*/public String timeZoneAsString() {if (_timezone != null) {return _timezone.getID(); }return timezoneStr; }public TimeZone getTimeZone() {TimeZone tz = _timezone; if (tz == null) {if (timezoneStr == null) {return null; }tz = TimeZone.getTimeZone(timezoneStr); _timezone = tz; }return tz; }/*** @since 2.4*/public boolean hasShape() { return shape != DeserializeFormat.Shape.ANY; }/*** @since 2.4*/public boolean hasPattern() {return (pattern != null) && (pattern.length() > 0); }/*** @since 2.4*/public boolean hasFormat() {return (format != null) && (format.length() > 0); }/*** @since 2.4*/public boolean hasLocale() { return locale != null; }/*** @since 2.4*/public boolean hasTimeZone() {return (_timezone != null) || (timezoneStr != null && !timezoneStr.isEmpty()); }}}

使用自定义解析注解的时间解析器

import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.databind.BeanProperty; import com.fasterxml.jackson.databind.DeserializationContext; import com.fasterxml.jackson.databind.JsonDeserializer; import com.fasterxml.jackson.databind.deser.ContextualDeserializer; import com.fasterxml.jackson.databind.util.StdDateFormat; import com.google.common.collect.Lists; import com.tujia.rba.framework.core.remote.api.BizErrorCode; import com.tujia.rba.framework.core.remote.api.BizException; import java.io.IOException; import java.text.DateFormat; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; import java.util.List; import java.util.Locale; import java.util.TimeZone; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang3.time.DateUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * @author 无名小生 Date: 2019-02-19 Time: 19:00 * @version $Id$ */public class DateJsonDeserializer extends JsonDeserializer implements ContextualDeserializer {private final static Logger logger = LoggerFactory.getLogger(DateJsonDeserializer.class); private final static List FORMATS = Lists.newArrayList("yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd HH:mm", "yyyyMMdd-HHmmss", "yyyy-MM-dd", "MM-dd", "HH:mm:ss","yyyy-MM"); public final DateFormat df; public final String formatString; public DateJsonDeserializer() {this.df = null; this.formatString = null; }public DateJsonDeserializer(DateFormat df) {this.df = df; this.formatString = ""; }public DateJsonDeserializer(DateFormat df, String formatString) {this.df = df; this.formatString = formatString; }@Overridepublic Date deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {try {String dateValue = https://www.it610.com/article/p.getText(); if (df == null || StringUtils.isEmpty(dateValue)) {return null; }Date date; if (StringUtils.isNumeric(dateValue)){date = new Date(Long.valueOf(dateValue)); }else {String[] formatArray = FORMATS.toArray(new String[0]); date = DateUtils.parseDate(p.getText(),formatArray); }return df.parse(df.format(date)); } catch (ParseException | SecurityException e) {logger.error("JSON反序列化，时间解析失败", e); throw new BizException(BizErrorCode.UNEXPECTED_ERROR); }}@Overridepublic JsonDeserializer createContextual(DeserializationContext ctxt, BeanProperty property) {if (property != null) {//JsonFormat.Value format = ctxt.getAnnotationIntrospector().findFormat(property.getMember()); DeserializeFormat deFormat = property.getAnnotation(DeserializeFormat.class); DeserializeFormat.Value format = (deFormat == null)? null : new DeserializeFormat.Value(deFormat); if (format != null) {TimeZone tz = format.getTimeZone(); // First: fully custom pattern?if (format.hasPattern() && !FORMATS.contains(format.getPattern())){FORMATS.add(format.getPattern()); }if (format.hasFormat()) {final String dateFormat = format.getFormat(); final Locale loc = format.hasLocale() ? format.getLocale() : ctxt.getLocale(); SimpleDateFormat df = new SimpleDateFormat(dateFormat, loc); if (tz == null) {tz = ctxt.getTimeZone(); }df.setTimeZone(tz); return new DateJsonDeserializer(df, dateFormat); }// But if not, can still override timezoneif (tz != null) {DateFormat df = ctxt.getConfig().getDateFormat(); // one shortcut: with our custom format, can simplify handling a bitif (df.getClass() == StdDateFormat.class) {final Locale loc = format.hasLocale() ? format.getLocale() : ctxt.getLocale(); StdDateFormat std = (StdDateFormat) df; std = std.withTimeZone(tz); std = std.withLocale(loc); df = std; } else {// otherwise need to clone, re-set timezone:df = (DateFormat) df.clone(); df.setTimeZone(tz); }return new DateJsonDeserializer(df); }}}return this; }}

@JsonFormat的使用实体类字段中添加@JsonFormat注解（），返回 yyyy-MM-ddHH:mm:ss时间格式