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:
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:
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<T> 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:
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<Date> implements ContextualDeserializer { private final static Logger logger = LoggerFactory.getLogger(DateJsonDeserializer.class); private final static List<String> 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; } @Override public Date deserialize(JsonParser p, DeserializationContext ctxt) throws IOException { try { String dateValue = 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); } } @Override public 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 timezone if (tz != null) { DateFormat df = ctxt.getConfig().getDateFormat(); // one shortcut: with our custom format, can simplify handling a bit if (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) @JacksonAnnotation public @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 annotations private 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<Date> implements ContextualDeserializer { private final static Logger logger = LoggerFactory.getLogger(DateJsonDeserializer.class); private final static List<String> 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; } @Override public Date deserialize(JsonParser p, DeserializationContext ctxt) throws IOException { try { String dateValue = 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); } } @Override public 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 timezone if (tz != null) { DateFormat df = ctxt.getConfig().getDateFormat(); // one shortcut: with our custom format, can simplify handling a bit if (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-dd HH:mm:ss 时间格式
@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8") private Date joinedDate;
pattern
:日期格式
timezone
:时区
以上为个人经验,希望能给大家一个参考,也希望大家多多支持服务器之家。
原文链接:https://blog.csdn.net/qq_26881739/article/details/87862506