Support multiple parsing patterns in @DateTimeFormat

Prior to this commit, @DateTimeFormat only supported a single format
for parsing date time values via the style, iso, and pattern attributes.

This commit introduces a new fallbackPatterns attribute that can be
used to configure multiple fallback patterns for parsing date time
values. This allows applications to accept multiple input formats for
date time values.

For example, if you wish to use the ISO date format for parsing and
printing but allow for lenient parsing of user input for various
additional date formats, you could annotate a field or method parameter
with configuration similar to the following.

    @DateTimeFormat(
        iso = ISO.DATE,
        fallbackPatterns = { "M/d/yy", "dd.MM.yyyy" }
    )

Closes gh-20292

spring-context/src/main/java/org/springframework/format/annotation/DateTimeFormat.java

@@ -26,17 +26,20 @@ import java.lang.annotation.Target;
  * Declares that a field or method parameter should be formatted as a date or time.
  *
  * <p>Supports formatting by style pattern, ISO date time pattern, or custom format pattern string.
- * Can be applied to {@code java.util.Date}, {@code java.util.Calendar}, {@code Long} (for
- * millisecond timestamps) as well as JSR-310 <code>java.time</code> and Joda-Time value types.
+ * Can be applied to {@link java.util.Date}, {@link java.util.Calendar}, {@link Long} (for
+ * millisecond timestamps) as well as JSR-310 {@code java.time} and Joda-Time value types.
  *
- * <p>For style-based formatting, set the {@link #style} attribute to be the style pattern code.
+ * <p>For style-based formatting, set the {@link #style} attribute to the desired style pattern code.
  * The first character of the code is the date style, and the second character is the time style.
  * Specify a character of 'S' for short style, 'M' for medium, 'L' for long, and 'F' for full.
- * A date or time may be omitted by specifying the style character '-'.
+ * The date or time may be omitted by specifying the style character '-' &mdash; for example,
+ * 'M-' specifies a medium format for the date with no time.
  *
- * <p>For ISO-based formatting, set the {@link #iso} attribute to be the desired {@link ISO} format,
- * such as {@link ISO#DATE}. For custom formatting, set the {@link #pattern} attribute to be the
- * DateTime pattern, such as {@code "yyyy/MM/dd hh:mm:ss a"}.
+ * <p>For ISO-based formatting, set the {@link #iso} attribute to the desired {@link ISO} format,
+ * such as {@link ISO#DATE}.
+ *
+ * <p>For custom formatting, set the {@link #pattern} attribute to a date time pattern, such as
+ * {@code "yyyy/MM/dd hh:mm:ss a"}.
  *
  * <p>Each attribute is mutually exclusive, so only set one attribute per annotation instance
  * (the one most convenient for your formatting needs).
@@ -48,8 +51,19 @@ import java.lang.annotation.Target;
  * with a style code of 'SS' (short date, short time).</li>
  * </ul>
  *
+ * <h3>Time Zones</h3>
+ * <p>Whenever the {@link #style} or {@link #pattern} attribute is used, the
+ * {@linkplain java.util.TimeZone#getDefault() default time zone} of the JVM will
+ * be used when formatting {@link java.util.Date} values. Whenever the {@link #iso}
+ * attribute is used when formatting {@link java.util.Date} values, {@code UTC}
+ * will be used as the time zone. The same time zone will be applied to any
+ * {@linkplain #fallbackPatterns fallback patterns} as well. In order to enforce
+ * consistent use of {@code UTC} as the time zone, you can bootstrap the JVM with
+ * {@code -Duser.timezone=UTC}.
+ *
  * @author Keith Donald
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 3.0
  * @see java.time.format.DateTimeFormatter
  * @see org.joda.time.format.DateTimeFormat
@@ -60,34 +74,59 @@ import java.lang.annotation.Target;
 public @interface DateTimeFormat {
 
 	/**
-	 * The style pattern to use to format the field.
-	 * <p>Defaults to 'SS' for short date time. Set this attribute when you wish to format
-	 * your field in accordance with a common style other than the default style.
+	 * The style pattern to use to format the field or method parameter.
+	 * <p>Defaults to 'SS' for short date, short time. Set this attribute when you
+	 * wish to format your field or method parameter in accordance with a common
+	 * style other than the default style.
+	 * @see #fallbackPatterns
 	 */
 	String style() default "SS";
 
 	/**
-	 * The ISO pattern to use to format the field.
-	 * <p>The possible ISO patterns are defined in the {@link ISO} enum.
+	 * The ISO pattern to use to format the field or method parameter.
+	 * <p>Supported ISO patterns are defined in the {@link ISO} enum.
 	 * <p>Defaults to {@link ISO#NONE}, indicating this attribute should be ignored.
-	 * Set this attribute when you wish to format your field in accordance with an ISO format.
+	 * Set this attribute when you wish to format your field or method parameter
+	 * in accordance with an ISO format.
+	 * @see #fallbackPatterns
 	 */
 	ISO iso() default ISO.NONE;
 
 	/**
-	 * The custom pattern to use to format the field.
-	 * <p>Defaults to empty String, indicating no custom pattern String has been specified.
-	 * Set this attribute when you wish to format your field in accordance with a custom
-	 * date time pattern not represented by a style or ISO format.
+	 * The custom pattern to use to format the field or method parameter.
+	 * <p>Defaults to empty String, indicating no custom pattern String has been
+	 * specified. Set this attribute when you wish to format your field or method
+	 * parameter in accordance with a custom date time pattern not represented by
+	 * a style or ISO format.
 	 * <p>Note: This pattern follows the original {@link java.text.SimpleDateFormat} style,
 	 * as also supported by Joda-Time, with strict parsing semantics towards overflows
 	 * (e.g. rejecting a Feb 29 value for a non-leap-year). As a consequence, 'yy'
 	 * characters indicate a year in the traditional style, not a "year-of-era" as in the
 	 * {@link java.time.format.DateTimeFormatter} specification (i.e. 'yy' turns into 'uu'
-	 * when going through that {@code DateTimeFormatter} with strict resolution mode).
+	 * when going through a {@code DateTimeFormatter} with strict resolution mode).
+	 * @see #fallbackPatterns
 	 */
 	String pattern() default "";
 
+	/**
+	 * The set of custom patterns to use as a fallback in case parsing fails for
+	 * the primary {@link #pattern}, {@link #iso}, or {@link #style} attribute.
+	 * <p>For example, if you wish to use the ISO date format for parsing and
+	 * printing but allow for lenient parsing of user input for various date
+	 * formats, you could configure something similar to the following.
+	 * <pre style="code">
+	 * {@literal @}DateTimeFormat(iso = ISO.DATE, fallbackPatterns = { "M/d/yy", "dd.MM.yyyy" })
+	 * </pre>
+	 * <p>Fallback patterns are only used for parsing. They are not used for
+	 * printing the value as a String. The primary {@link #pattern}, {@link #iso},
+	 * or {@link #style} attribute is always used for printing. For details on
+	 * which time zone is used for fallback patterns, see the
+	 * {@linkplain DateTimeFormat class-level documentation}.
+	 * <p>Fallback patterns are not supported for Joda-Time value types.
+	 * @since 5.3.5
+	 */
+	String[] fallbackPatterns() default {};
+
 
 	/**
 	 * Common ISO date time format patterns.
@@ -95,20 +134,20 @@ public @interface DateTimeFormat {
 	enum ISO {
 
 		/**
-		 * The most common ISO Date Format {@code yyyy-MM-dd},
-		 * e.g. "2000-10-31".
+		 * The most common ISO Date Format {@code yyyy-MM-dd} &mdash; for example,
+		 * "2000-10-31".
 		 */
 		DATE,
 
 		/**
-		 * The most common ISO Time Format {@code HH:mm:ss.SSSXXX},
-		 * e.g. "01:30:00.000-05:00".
+		 * The most common ISO Time Format {@code HH:mm:ss.SSSXXX} &mdash; for example,
+		 * "01:30:00.000-05:00".
 		 */
 		TIME,
 
 		/**
-		 * The most common ISO DateTime Format {@code yyyy-MM-dd'T'HH:mm:ss.SSSXXX},
-		 * e.g. "2000-10-31T01:30:00.000-05:00".
+		 * The most common ISO Date Time Format {@code yyyy-MM-dd'T'HH:mm:ss.SSSXXX}
+		 * &mdash; for example, "2000-10-31T01:30:00.000-05:00".
 		 */
 		DATE_TIME,
 

spring-context/src/main/java/org/springframework/format/datetime/DateFormatter.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,17 +27,21 @@ import java.util.Map;
 import java.util.TimeZone;
 
 import org.springframework.format.Formatter;
+import org.springframework.format.annotation.DateTimeFormat;
 import org.springframework.format.annotation.DateTimeFormat.ISO;
 import org.springframework.lang.Nullable;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
  * A formatter for {@link java.util.Date} types.
- * Allows the configuration of an explicit date pattern and locale.
+ * <p>Supports the configuration of an explicit date time pattern, timezone,
+ * locale, and fallback date time patterns for lenient parsing.
  *
  * @author Keith Donald
  * @author Juergen Hoeller
  * @author Phillip Webb
+ * @author Sam Brannen
  * @since 3.0
  * @see SimpleDateFormat
  */
@@ -56,9 +60,15 @@ public class DateFormatter implements Formatter<Date> {
 	}
 
 
+	@Nullable
+	private Object source;
+
 	@Nullable
 	private String pattern;
 
+	@Nullable
+	private String[] fallbackPatterns;
+
 	private int style = DateFormat.DEFAULT;
 
 	@Nullable
@@ -74,19 +84,33 @@ public class DateFormatter implements Formatter<Date> {
 
 
 	/**
-	 * Create a new default DateFormatter.
+	 * Create a new default {@code DateFormatter}.
 	 */
 	public DateFormatter() {
 	}
 
 	/**
-	 * Create a new DateFormatter for the given date pattern.
+	 * Create a new {@code DateFormatter} for the given date time pattern.
 	 */
 	public DateFormatter(String pattern) {
 		this.pattern = pattern;
 	}
 
 
+	/**
+	 * Set the source of the configuration for this {@code DateFormatter} &mdash;
+	 * for example, an instance of the {@link DateTimeFormat @DateTimeFormat}
+	 * annotation if such an annotation was used to configure this {@code DateFormatter}.
+	 * <p>The supplied source object will only be used for descriptive purposes
+	 * by invoking its {@code toString()} method &mdash; for example, when
+	 * generating an exception message to provide further context.
+	 * @param source the source of the configuration
+	 * @since 5.3.5
+	 */
+	public void setSource(Object source) {
+		this.source = source;
+	}
+
 	/**
 	 * Set the pattern to use to format date values.
 	 * <p>If not specified, DateFormat's default style will be used.
@@ -96,7 +120,19 @@ public class DateFormatter implements Formatter<Date> {
 	}
 
 	/**
-	 * Set the ISO format used for this date.
+	 * Set additional patterns to use as a fallback in case parsing fails for the
+	 * configured {@linkplain #setPattern pattern}, {@linkplain #setIso ISO format},
+	 * {@linkplain #setStyle style}, or {@linkplain #setStylePattern style pattern}.
+	 * @param fallbackPatterns the fallback parsing patterns
+	 * @since 5.3.5
+	 * @see DateTimeFormat#fallbackPatterns()
+	 */
+	public void setFallbackPatterns(String... fallbackPatterns) {
+		this.fallbackPatterns = fallbackPatterns;
+	}
+
+	/**
+	 * Set the ISO format to use to format date values.
 	 * @param iso the {@link ISO} format
 	 * @since 3.2
 	 */
@@ -105,7 +141,7 @@ public class DateFormatter implements Formatter<Date> {
 	}
 
 	/**
-	 * Set the style to use to format date values.
+	 * Set the {@link DateFormat} style to use to format date values.
 	 * <p>If not specified, DateFormat's default style will be used.
 	 * @see DateFormat#DEFAULT
 	 * @see DateFormat#SHORT
@@ -118,8 +154,10 @@ public class DateFormatter implements Formatter<Date> {
 	}
 
 	/**
-	 * Set the two character to use to format date values. The first character used for
-	 * the date style, the second is for the time style. Supported characters are
+	 * Set the two characters to use to format date values.
+	 * <p>The first character is used for the date style; the second is used for
+	 * the time style.
+	 * <p>Supported characters:
 	 * <ul>
 	 * <li>'S' = Small</li>
 	 * <li>'M' = Medium</li>
@@ -136,7 +174,7 @@ public class DateFormatter implements Formatter<Date> {
 	}
 
 	/**
-	 * Set the TimeZone to normalize the date values into, if any.
+	 * Set the {@link TimeZone} to normalize the date values into, if any.
 	 */
 	public void setTimeZone(TimeZone timeZone) {
 		this.timeZone = timeZone;
@@ -159,12 +197,43 @@ public class DateFormatter implements Formatter<Date> {
 
 	@Override
 	public Date parse(String text, Locale locale) throws ParseException {
-		return getDateFormat(locale).parse(text);
+		try {
+			return getDateFormat(locale).parse(text);
+		}
+		catch (ParseException ex) {
+			if (!ObjectUtils.isEmpty(this.fallbackPatterns)) {
+				for (String pattern : this.fallbackPatterns) {
+					try {
+						DateFormat dateFormat = configureDateFormat(new SimpleDateFormat(pattern, locale));
+						// Align timezone for parsing format with printing format if ISO is set.
+						if (this.iso != null && this.iso != ISO.NONE) {
+							dateFormat.setTimeZone(UTC);
+						}
+						return dateFormat.parse(text);
+					}
+					catch (ParseException ignoredException) {
+						// Ignore fallback parsing exceptions since the exception thrown below
+						// will include information from the "source" if available -- for example,
+						// the toString() of a @DateTimeFormat annotation.
+					}
+				}
+			}
+			if (this.source != null) {
+				throw new ParseException(
+					String.format("Unable to parse date time value \"%s\" using configuration from %s", text, this.source),
+					ex.getErrorOffset());
+			}
+			// else rethrow original exception
+			throw ex;
+		}
 	}
 
 
 	protected DateFormat getDateFormat(Locale locale) {
-		DateFormat dateFormat = createDateFormat(locale);
+		return configureDateFormat(createDateFormat(locale));
+	}
+
+	private DateFormat configureDateFormat(DateFormat dateFormat) {
 		if (this.timeZone != null) {
 			dateFormat.setTimeZone(this.timeZone);
 		}

spring-context/src/main/java/org/springframework/format/datetime/DateTimeFormatAnnotationFormatterFactory.java

 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,10 +16,12 @@
 
 package org.springframework.format.datetime;
 
+import java.util.ArrayList;
 import java.util.Calendar;
 import java.util.Collections;
 import java.util.Date;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 import org.springframework.context.support.EmbeddedValueResolutionSupport;
@@ -34,6 +36,7 @@ import org.springframework.util.StringUtils;
  * Formats fields annotated with the {@link DateTimeFormat} annotation using a {@link DateFormatter}.
  *
  * @author Phillip Webb
+ * @author Sam Brannen
  * @since 3.2
  * @see org.springframework.format.datetime.joda.JodaDateTimeFormatAnnotationFormatterFactory
  */
@@ -68,15 +71,30 @@ public class DateTimeFormatAnnotationFormatterFactory  extends EmbeddedValueReso
 
 	protected Formatter<Date> getFormatter(DateTimeFormat annotation, Class<?> fieldType) {
 		DateFormatter formatter = new DateFormatter();
+		formatter.setSource(annotation);
+		formatter.setIso(annotation.iso());
+
 		String style = resolveEmbeddedValue(annotation.style());
 		if (StringUtils.hasLength(style)) {
 			formatter.setStylePattern(style);
 		}
-		formatter.setIso(annotation.iso());
+
 		String pattern = resolveEmbeddedValue(annotation.pattern());
 		if (StringUtils.hasLength(pattern)) {
 			formatter.setPattern(pattern);
 		}
+
+		List<String> resolvedFallbackPatterns = new ArrayList<>();
+		for (String fallbackPattern : annotation.fallbackPatterns()) {
+			String resolvedFallbackPattern = resolveEmbeddedValue(fallbackPattern);
+			if (StringUtils.hasLength(resolvedFallbackPattern)) {
+				resolvedFallbackPatterns.add(resolvedFallbackPattern);
+			}
+		}
+		if (!resolvedFallbackPatterns.isEmpty()) {
+			formatter.setFallbackPatterns(resolvedFallbackPatterns.toArray(new String[0]));
+		}
+
 		return formatter;
 	}
 

spring-context/src/main/java/org/springframework/format/datetime/standard/DateTimeContext.java

 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,7 +29,7 @@ import org.springframework.lang.Nullable;
 /**
  * A context that holds user-specific <code>java.time</code> (JSR-310) settings
  * such as the user's Chronology (calendar system) and time zone.
- * A {@code null} property value indicate the user has not specified a setting.
+ * <p>A {@code null} property value indicates the user has not specified a setting.
  *
  * @author Juergen Hoeller
  * @since 4.0
@@ -81,8 +81,8 @@ public class DateTimeContext {
 
 
 	/**
-	 * Get the DateTimeFormatter with the this context's settings
-	 * applied to the base {@code formatter}.
+	 * Get the DateTimeFormatter with this context's settings applied to the
+	 * base {@code formatter}.
 	 * @param formatter the base formatter that establishes default
 	 * formatting rules, generally context-independent
 	 * @return the contextual DateTimeFormatter

spring-context/src/main/java/org/springframework/format/datetime/standard/DateTimeContextHolder.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -69,9 +69,8 @@ public final class DateTimeContextHolder {
 		return dateTimeContextHolder.get();
 	}
 
-
 	/**
-	 * Obtain a DateTimeFormatter with user-specific settings applied to the given base Formatter.
+	 * Obtain a DateTimeFormatter with user-specific settings applied to the given base formatter.
 	 * @param formatter the base formatter that establishes default formatting rules
 	 * (generally user independent)
 	 * @param locale the current user locale (may be {@code null} if not known)

spring-context/src/main/java/org/springframework/format/datetime/standard/DateTimeFormatterFactory.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,7 +18,6 @@ package org.springframework.format.datetime.standard;
 
 import java.time.format.DateTimeFormatter;
 import java.time.format.FormatStyle;
-import java.time.format.ResolverStyle;
 import java.util.TimeZone;
 
 import org.springframework.format.annotation.DateTimeFormat.ISO;
@@ -34,6 +33,7 @@ import org.springframework.util.StringUtils;
  *
  * @author Juergen Hoeller
  * @author Phillip Webb
+ * @author Sam Brannen
  * @since 4.0
  * @see #createDateTimeFormatter()
  * @see #createDateTimeFormatter(DateTimeFormatter)
@@ -180,11 +180,7 @@ public class DateTimeFormatterFactory {
 	public DateTimeFormatter createDateTimeFormatter(DateTimeFormatter fallbackFormatter) {
 		DateTimeFormatter dateTimeFormatter = null;
 		if (StringUtils.hasLength(this.pattern)) {
-			// Using strict parsing to align with Joda-Time and standard DateFormat behavior:
-			// otherwise, an overflow like e.g. Feb 29 for a non-leap-year wouldn't get rejected.
-			// However, with strict parsing, a year digit needs to be specified as 'u'...
-			String patternToUse = StringUtils.replace(this.pattern, "yy", "uu");
-			dateTimeFormatter = DateTimeFormatter.ofPattern(patternToUse).withResolverStyle(ResolverStyle.STRICT);
+			dateTimeFormatter = DateTimeFormatterUtils.createStrictDateTimeFormatter(this.pattern);
 		}
 		else if (this.iso != null && this.iso != ISO.NONE) {
 			switch (this.iso) {

spring-context/src/main/java/org/springframework/format/datetime/standard/DateTimeFormatterUtils.java

+/*
+ * Copyright 2002-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.format.datetime.standard;
+
+import java.time.format.DateTimeFormatter;
+import java.time.format.ResolverStyle;
+
+import org.springframework.util.StringUtils;
+
+/**
+ * Internal {@link DateTimeFormatter} utilities.
+ *
+ * @author Juergen Hoeller
+ * @since 5.3.5
+ */
+abstract class DateTimeFormatterUtils {
+
+	static DateTimeFormatter createStrictDateTimeFormatter(String pattern) {
+		// Using strict parsing to align with Joda-Time and standard DateFormat behavior:
+		// otherwise, an overflow like e.g. Feb 29 for a non-leap-year wouldn't get rejected.
+		// However, with strict parsing, a year digit needs to be specified as 'u'...
+		String patternToUse = StringUtils.replace(pattern, "yy", "uu");
+		return DateTimeFormatter.ofPattern(patternToUse).withResolverStyle(ResolverStyle.STRICT);
+	}
+
+}

spring-context/src/main/java/org/springframework/format/datetime/standard/Jsr310DateTimeFormatAnnotationFormatterFactory.java

 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,8 +24,10 @@ import java.time.OffsetTime;
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 import java.time.temporal.TemporalAccessor;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 import org.springframework.context.support.EmbeddedValueResolutionSupport;
@@ -40,6 +42,7 @@ import org.springframework.util.StringUtils;
  * JSR-310 <code>java.time</code> package in JDK 8.
  *
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 4.0
  * @see org.springframework.format.annotation.DateTimeFormat
  */
@@ -93,8 +96,17 @@ public class Jsr310DateTimeFormatAnnotationFormatterFactory extends EmbeddedValu
 	@Override
 	@SuppressWarnings("unchecked")
 	public Parser<?> getParser(DateTimeFormat annotation, Class<?> fieldType) {
+		List<String> resolvedFallbackPatterns = new ArrayList<>();
+		for (String fallbackPattern : annotation.fallbackPatterns()) {
+			String resolvedFallbackPattern = resolveEmbeddedValue(fallbackPattern);
+			if (StringUtils.hasLength(resolvedFallbackPattern)) {
+				resolvedFallbackPatterns.add(resolvedFallbackPattern);
+			}
+		}
+
 		DateTimeFormatter formatter = getFormatter(annotation, fieldType);
-		return new TemporalAccessorParser((Class<? extends TemporalAccessor>) fieldType, formatter);
+		return new TemporalAccessorParser((Class<? extends TemporalAccessor>) fieldType,
+				formatter, resolvedFallbackPatterns.toArray(new String[0]), annotation);
 	}
 
 	/**

spring-context/src/main/java/org/springframework/format/datetime/standard/TemporalAccessorParser.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,16 +24,20 @@ import java.time.OffsetDateTime;
 import java.time.OffsetTime;
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
 import java.time.temporal.TemporalAccessor;
 import java.util.Locale;
 
 import org.springframework.format.Parser;
+import org.springframework.lang.Nullable;
+import org.springframework.util.ObjectUtils;
 
 /**
  * {@link Parser} implementation for a JSR-310 {@link java.time.temporal.TemporalAccessor},
- * using a {@link java.time.format.DateTimeFormatter}) (the contextual one, if available).
+ * using a {@link java.time.format.DateTimeFormatter} (the contextual one, if available).
  *
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 4.0
  * @see DateTimeContextHolder#getFormatter
  * @see java.time.LocalDate#parse(CharSequence, java.time.format.DateTimeFormatter)
@@ -49,6 +53,12 @@ public final class TemporalAccessorParser implements Parser<TemporalAccessor> {
 
 	private final DateTimeFormatter formatter;
 
+	@Nullable
+	private final String[] fallbackPatterns;
+
+	@Nullable
+	private final Object source;
+
 
 	/**
 	 * Create a new TemporalAccessorParser for the given TemporalAccessor type.
@@ -57,14 +67,49 @@ public final class TemporalAccessorParser implements Parser<TemporalAccessor> {
 	 * @param formatter the base DateTimeFormatter instance
 	 */
 	public TemporalAccessorParser(Class<? extends TemporalAccessor> temporalAccessorType, DateTimeFormatter formatter) {
+		this(temporalAccessorType, formatter, null, null);
+	}
+
+	TemporalAccessorParser(Class<? extends TemporalAccessor> temporalAccessorType, DateTimeFormatter formatter,
+		@Nullable String[] fallbackPatterns, @Nullable Object source) {
 		this.temporalAccessorType = temporalAccessorType;
 		this.formatter = formatter;
+		this.fallbackPatterns = fallbackPatterns;
+		this.source = source;
 	}
 
 
 	@Override
 	public TemporalAccessor parse(String text, Locale locale) throws ParseException {
-		DateTimeFormatter formatterToUse = DateTimeContextHolder.getFormatter(this.formatter, locale);
+		try {
+			return doParse(text, locale, this.formatter);
+		}
+		catch (DateTimeParseException ex) {
+			if (!ObjectUtils.isEmpty(this.fallbackPatterns)) {
+				for (String pattern : this.fallbackPatterns) {
+					try {
+						DateTimeFormatter fallbackFormatter = DateTimeFormatterUtils.createStrictDateTimeFormatter(pattern);
+						return doParse(text, locale, fallbackFormatter);
+					}
+					catch (DateTimeParseException ignoredException) {
+						// Ignore fallback parsing exceptions since the exception thrown below
+						// will include information from the "source" if available -- for example,
+						// the toString() of a @DateTimeFormat annotation.
+					}
+				}
+			}
+			if (this.source != null) {
+				throw new DateTimeParseException(
+					String.format("Unable to parse date time value \"%s\" using configuration from %s", text, this.source),
+					text, ex.getErrorIndex());
+			}
+			// else rethrow original exception
+			throw ex;
+		}
+	}
+
+	private TemporalAccessor doParse(String text, Locale locale, DateTimeFormatter formatter) throws DateTimeParseException {
+		DateTimeFormatter formatterToUse = DateTimeContextHolder.getFormatter(formatter, locale);
 		if (LocalDate.class == this.temporalAccessorType) {
 			return LocalDate.parse(text, formatterToUse);
 		}

spring-context/src/test/java/org/springframework/format/datetime/DateFormattingTests.java

 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.format.datetime;
 
+import java.text.ParseException;
 import java.util.ArrayList;
 import java.util.Calendar;
 import java.util.Date;
@@ -25,16 +26,23 @@ import java.util.Locale;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import org.springframework.beans.MutablePropertyValues;
+import org.springframework.beans.TypeMismatchException;
 import org.springframework.context.i18n.LocaleContextHolder;
+import org.springframework.core.convert.ConversionFailedException;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.format.annotation.DateTimeFormat;
 import org.springframework.format.annotation.DateTimeFormat.ISO;
 import org.springframework.format.support.FormattingConversionService;
+import org.springframework.validation.BindingResult;
 import org.springframework.validation.DataBinder;
+import org.springframework.validation.FieldError;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -42,10 +50,11 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Phillip Webb
  * @author Keith Donald
  * @author Juergen Hoeller
+ * @author Sam Brannen
  */
 public class DateFormattingTests {
 
-	private FormattingConversionService conversionService;
+	private final FormattingConversionService conversionService = new FormattingConversionService();
 
 	private DataBinder binder;
 
@@ -57,7 +66,6 @@ public class DateFormattingTests {
 	}
 
 	private void setup(DateFormatterRegistrar registrar) {
-		conversionService = new FormattingConversionService();
 		DefaultConversionService.addDefaultConverters(conversionService);
 		registrar.registerFormatters(conversionService);
 
@@ -87,34 +95,34 @@ public class DateFormattingTests {
 	@Test
 	void testBindLongAnnotated() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("millisAnnotated", "10/31/09");
+		propertyValues.add("styleMillis", "10/31/09");
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
-		assertThat(binder.getBindingResult().getFieldValue("millisAnnotated")).isEqualTo("10/31/09");
+		assertThat(binder.getBindingResult().getFieldValue("styleMillis")).isEqualTo("10/31/09");
 	}
 
 	@Test
 	void testBindCalendarAnnotated() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("calendarAnnotated", "10/31/09");
+		propertyValues.add("styleCalendar", "10/31/09");
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
-		assertThat(binder.getBindingResult().getFieldValue("calendarAnnotated")).isEqualTo("10/31/09");
+		assertThat(binder.getBindingResult().getFieldValue("styleCalendar")).isEqualTo("10/31/09");
 	}
 
 	@Test
 	void testBindDateAnnotated() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotated", "10/31/09");
+		propertyValues.add("styleDate", "10/31/09");
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
-		assertThat(binder.getBindingResult().getFieldValue("dateAnnotated")).isEqualTo("10/31/09");
+		assertThat(binder.getBindingResult().getFieldValue("styleDate")).isEqualTo("10/31/09");
 	}
 
 	@Test
 	void testBindDateArray() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotated", new String[]{"10/31/09 12:00 PM"});
+		propertyValues.add("styleDate", new String[]{"10/31/09 12:00 PM"});
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
 	}
@@ -122,10 +130,10 @@ public class DateFormattingTests {
 	@Test
 	void testBindDateAnnotatedWithError() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotated", "Oct X31, 2009");
+		propertyValues.add("styleDate", "Oct X31, 2009");
 		binder.bind(propertyValues);
-		assertThat(binder.getBindingResult().getFieldErrorCount("dateAnnotated")).isEqualTo(1);
-		assertThat(binder.getBindingResult().getFieldValue("dateAnnotated")).isEqualTo("Oct X31, 2009");
+		assertThat(binder.getBindingResult().getFieldErrorCount("styleDate")).isEqualTo(1);
+		assertThat(binder.getBindingResult().getFieldValue("styleDate")).isEqualTo("Oct X31, 2009");
 	}
 
 	@Test
@@ -133,19 +141,19 @@ public class DateFormattingTests {
 	void testBindDateAnnotatedWithFallbackError() {
 		// TODO This currently passes because of the Date(String) constructor fallback is used
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotated", "Oct 031, 2009");
+		propertyValues.add("styleDate", "Oct 031, 2009");
 		binder.bind(propertyValues);
-		assertThat(binder.getBindingResult().getFieldErrorCount("dateAnnotated")).isEqualTo(1);
-		assertThat(binder.getBindingResult().getFieldValue("dateAnnotated")).isEqualTo("Oct 031, 2009");
+		assertThat(binder.getBindingResult().getFieldErrorCount("styleDate")).isEqualTo(1);
+		assertThat(binder.getBindingResult().getFieldValue("styleDate")).isEqualTo("Oct 031, 2009");
 	}
 
 	@Test
 	void testBindDateAnnotatedPattern() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotatedPattern", "10/31/09 1:05");
+		propertyValues.add("patternDate", "10/31/09 1:05");
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
-		assertThat(binder.getBindingResult().getFieldValue("dateAnnotatedPattern")).isEqualTo("10/31/09 1:05");
+		assertThat(binder.getBindingResult().getFieldValue("patternDate")).isEqualTo("10/31/09 1:05");
 	}
 
 	@Test
@@ -156,16 +164,17 @@ public class DateFormattingTests {
 		registrar.setFormatter(dateFormatter);
 		setup(registrar);
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotatedPattern", "10/31/09 1:05");
+		propertyValues.add("patternDate", "10/31/09 1:05");
 		binder.bind(propertyValues);
-		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
-		assertThat(binder.getBindingResult().getFieldValue("dateAnnotatedPattern")).isEqualTo("10/31/09 1:05");
+		BindingResult bindingResult = binder.getBindingResult();
+		assertThat(bindingResult.getErrorCount()).isEqualTo(0);
+		assertThat(bindingResult.getFieldValue("patternDate")).isEqualTo("10/31/09 1:05");
 	}
 
 	@Test
 	void testBindDateTimeOverflow() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("dateAnnotatedPattern", "02/29/09 12:00 PM");
+		propertyValues.add("patternDate", "02/29/09 12:00 PM");
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(1);
 	}
@@ -200,10 +209,10 @@ public class DateFormattingTests {
 	@Test
 	void testBindNestedDateAnnotated() {
 		MutablePropertyValues propertyValues = new MutablePropertyValues();
-		propertyValues.add("children[0].dateAnnotated", "10/31/09");
+		propertyValues.add("children[0].styleDate", "10/31/09");
 		binder.bind(propertyValues);
 		assertThat(binder.getBindingResult().getErrorCount()).isEqualTo(0);
-		assertThat(binder.getBindingResult().getFieldValue("children[0].dateAnnotated")).isEqualTo("10/31/09");
+		assertThat(binder.getBindingResult().getFieldValue("children[0].styleDate")).isEqualTo("10/31/09");
 	}
 
 	@Test
@@ -247,35 +256,127 @@ public class DateFormattingTests {
 	}
 
 
+	@Nested
+	class FallbackPatternTests {
+
+		@ParameterizedTest(name = "input date: {0}")
+		@ValueSource(strings = {"2021-03-02", "2021.03.02", "20210302", "3/2/21"})
+		void styleCalendar(String propertyValue) {
+			String propertyName = "styleCalendarWithFallbackPatterns";
+			MutablePropertyValues propertyValues = new MutablePropertyValues();
+			propertyValues.add(propertyName, propertyValue);
+			binder.bind(propertyValues);
+			BindingResult bindingResult = binder.getBindingResult();
+			assertThat(bindingResult.getErrorCount()).isEqualTo(0);
+			assertThat(bindingResult.getFieldValue(propertyName)).isEqualTo("3/2/21");
+		}
+
+		@ParameterizedTest(name = "input date: {0}")
+		@ValueSource(strings = {"2021-03-02", "2021.03.02", "20210302", "3/2/21"})
+		void styleDate(String propertyValue) {
+			String propertyName = "styleDateWithFallbackPatterns";
+			MutablePropertyValues propertyValues = new MutablePropertyValues();
+			propertyValues.add(propertyName, propertyValue);
+			binder.bind(propertyValues);
+			BindingResult bindingResult = binder.getBindingResult();
+			assertThat(bindingResult.getErrorCount()).isEqualTo(0);
+			assertThat(bindingResult.getFieldValue(propertyName)).isEqualTo("3/2/21");
+		}
+
+		@ParameterizedTest(name = "input date: {0}")
+		@ValueSource(strings = {"2021-03-02", "2021.03.02", "20210302", "3/2/21"})
+		void patternDate(String propertyValue) {
+			String propertyName = "patternDateWithFallbackPatterns";
+			MutablePropertyValues propertyValues = new MutablePropertyValues();
+			propertyValues.add(propertyName, propertyValue);
+			binder.bind(propertyValues);
+			BindingResult bindingResult = binder.getBindingResult();
+			assertThat(bindingResult.getErrorCount()).isEqualTo(0);
+			assertThat(bindingResult.getFieldValue(propertyName)).isEqualTo("2021-03-02");
+		}
+
+		@ParameterizedTest(name = "input date: {0}")
+		@ValueSource(strings = {"2021-03-02", "2021.03.02", "20210302", "3/2/21"})
+		void isoDate(String propertyValue) {
+			String propertyName = "isoDateWithFallbackPatterns";
+			MutablePropertyValues propertyValues = new MutablePropertyValues();
+			propertyValues.add(propertyName, propertyValue);
+			binder.bind(propertyValues);
+			BindingResult bindingResult = binder.getBindingResult();
+			assertThat(bindingResult.getErrorCount()).isEqualTo(0);
+			assertThat(bindingResult.getFieldValue(propertyName)).isEqualTo("2021-03-02");
+		}
+
+		@Test
+		void patternDateWithUnsupportedPattern() {
+			String propertyValue = "210302";
+			String propertyName = "patternDateWithFallbackPatterns";
+			MutablePropertyValues propertyValues = new MutablePropertyValues();
+			propertyValues.add(propertyName, propertyValue);
+			binder.bind(propertyValues);
+			BindingResult bindingResult = binder.getBindingResult();
+			assertThat(bindingResult.getErrorCount()).isEqualTo(1);
+			FieldError fieldError = bindingResult.getFieldError(propertyName);
+			assertThat(fieldError.unwrap(TypeMismatchException.class))
+				.hasMessageContaining("for property 'patternDateWithFallbackPatterns'")
+				.hasCauseInstanceOf(ConversionFailedException.class).getCause()
+					.hasMessageContaining("for value '210302'")
+					.hasCauseInstanceOf(IllegalArgumentException.class).getCause()
+						.hasMessageContaining("Parse attempt failed for value [210302]")
+						.hasCauseInstanceOf(ParseException.class).getCause()
+							// Unable to parse date time value "210302" using configuration from
+							// @org.springframework.format.annotation.DateTimeFormat(
+							// pattern=yyyy-MM-dd, style=SS, iso=NONE, fallbackPatterns=[M/d/yy, yyyyMMdd, yyyy.MM.dd])
+							.hasMessageContainingAll(
+								"Unable to parse date time value \"210302\" using configuration from",
+								"@org.springframework.format.annotation.DateTimeFormat",
+								"yyyy-MM-dd", "M/d/yy", "yyyyMMdd", "yyyy.MM.dd");
+		}
+	}
+
+
 	@SuppressWarnings("unused")
 	private static class SimpleDateBean {
 
 		private Long millis;
 
-		private Long millisAnnotated;
+		private Long styleMillis;
 
-		@DateTimeFormat(style="S-")
-		private Calendar calendarAnnotated;
+		@DateTimeFormat(style = "S-")
+		private Calendar styleCalendar;
 
-		@DateTimeFormat(style="S-")
-		private Date dateAnnotated;
+		@DateTimeFormat(style = "S-", fallbackPatterns = { "yyyy-MM-dd", "yyyyMMdd", "yyyy.MM.dd" })
+		private Calendar styleCalendarWithFallbackPatterns;
+
+		@DateTimeFormat(style = "S-")
+		private Date styleDate;
+
+		@DateTimeFormat(style = "S-", fallbackPatterns = { "yyyy-MM-dd", "yyyyMMdd", "yyyy.MM.dd" })
+		private Date styleDateWithFallbackPatterns;
+
+		@DateTimeFormat(pattern = "M/d/yy h:mm")
+		private Date patternDate;
 
-		@DateTimeFormat(pattern="M/d/yy h:mm")
-		private Date dateAnnotatedPattern;
+		@DateTimeFormat(pattern = "yyyy-MM-dd", fallbackPatterns = { "M/d/yy", "yyyyMMdd", "yyyy.MM.dd" })
+		private Date patternDateWithFallbackPatterns;
 
-		@DateTimeFormat(iso=ISO.DATE)
+		@DateTimeFormat(iso = ISO.DATE)
 		private Date isoDate;
 
-		@DateTimeFormat(iso=ISO.TIME)
+		@DateTimeFormat(iso = ISO.DATE, fallbackPatterns = { "M/d/yy", "yyyyMMdd", "yyyy.MM.dd" })
+		private Date isoDateWithFallbackPatterns;
+
+		@DateTimeFormat(iso = ISO.TIME)
 		private Date isoTime;
 
-		@DateTimeFormat(iso=ISO.DATE_TIME)
+		@DateTimeFormat(iso = ISO.DATE_TIME)
 		private Date isoDateTime;
 
 		private final List<SimpleDateBean> children = new ArrayList<>();
 
+
 		public Long getMillis() {
-			return millis;
+			return this.millis;
 		}
 
 		public void setMillis(Long millis) {
@@ -283,48 +384,80 @@ public class DateFormattingTests {
 		}
 
 		@DateTimeFormat(style="S-")
-		public Long getMillisAnnotated() {
-			return millisAnnotated;
+		public Long getStyleMillis() {
+			return this.styleMillis;
+		}
+
+		public void setStyleMillis(@DateTimeFormat(style="S-") Long styleMillis) {
+			this.styleMillis = styleMillis;
+		}
+
+		public Calendar getStyleCalendar() {
+			return this.styleCalendar;
+		}
+
+		public void setStyleCalendar(Calendar styleCalendar) {
+			this.styleCalendar = styleCalendar;
+		}
+
+		public Calendar getStyleCalendarWithFallbackPatterns() {
+			return this.styleCalendarWithFallbackPatterns;
+		}
+
+		public void setStyleCalendarWithFallbackPatterns(Calendar styleCalendarWithFallbackPatterns) {
+			this.styleCalendarWithFallbackPatterns = styleCalendarWithFallbackPatterns;
+		}
+
+		public Date getStyleDate() {
+			return this.styleDate;
 		}
 
-		public void setMillisAnnotated(@DateTimeFormat(style="S-") Long millisAnnotated) {
-			this.millisAnnotated = millisAnnotated;
+		public void setStyleDate(Date styleDate) {
+			this.styleDate = styleDate;
 		}
 
-		public Calendar getCalendarAnnotated() {
-			return calendarAnnotated;
+		public Date getStyleDateWithFallbackPatterns() {
+			return this.styleDateWithFallbackPatterns;
 		}
 
-		public void setCalendarAnnotated(Calendar calendarAnnotated) {
-			this.calendarAnnotated = calendarAnnotated;
+		public void setStyleDateWithFallbackPatterns(Date styleDateWithFallbackPatterns) {
+			this.styleDateWithFallbackPatterns = styleDateWithFallbackPatterns;
 		}
 
-		public Date getDateAnnotated() {
-			return dateAnnotated;
+		public Date getPatternDate() {
+			return this.patternDate;
 		}
 
-		public void setDateAnnotated(Date dateAnnotated) {
-			this.dateAnnotated = dateAnnotated;
+		public void setPatternDate(Date patternDate) {
+			this.patternDate = patternDate;
 		}
 
-		public Date getDateAnnotatedPattern() {
-			return dateAnnotatedPattern;
+		public Date getPatternDateWithFallbackPatterns() {
+			return this.patternDateWithFallbackPatterns;
 		}
 
-		public void setDateAnnotatedPattern(Date dateAnnotatedPattern) {
-			this.dateAnnotatedPattern = dateAnnotatedPattern;
+		public void setPatternDateWithFallbackPatterns(Date patternDateWithFallbackPatterns) {
+			this.patternDateWithFallbackPatterns = patternDateWithFallbackPatterns;
 		}
 
 		public Date getIsoDate() {
-			return isoDate;
+			return this.isoDate;
 		}
 
 		public void setIsoDate(Date isoDate) {
 			this.isoDate = isoDate;
 		}
 
+		public Date getIsoDateWithFallbackPatterns() {
+			return this.isoDateWithFallbackPatterns;
+		}
+
+		public void setIsoDateWithFallbackPatterns(Date isoDateWithFallbackPatterns) {
+			this.isoDateWithFallbackPatterns = isoDateWithFallbackPatterns;
+		}
+
 		public Date getIsoTime() {
-			return isoTime;
+			return this.isoTime;
 		}
 
 		public void setIsoTime(Date isoTime) {
@@ -332,7 +465,7 @@ public class DateFormattingTests {
 		}
 
 		public Date getIsoDateTime() {
-			return isoDateTime;
+			return this.isoDateTime;
 		}
 
 		public void setIsoDateTime(Date isoDateTime) {
@@ -340,7 +473,7 @@ public class DateFormattingTests {
 		}
 
 		public List<SimpleDateBean> getChildren() {
-			return children;
+			return this.children;
 		}
 	}