Introduce portable @DateTimeFormat annotation [SPR-6313]

[spring-projects-issues]

Keith Donald opened SPR-6313 and commented

Proposal:

@DateTimeFormat - Declares that a field should be formatted as a date time.

/*
 * Copyright 2002-2009 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
 *
 *      http://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.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Declares that a field should be formatted as a date time.
 * Supports formatting by style pattern, ISO date time pattern, or custom format pattern string.
 * Can be applied to <code>java.util.Date</code>, <code>java.util.Calendar</code>, <code>java.long.Long</code>, or Joda Time fields.
 * <p>
 * For style-based formatting, set the {@link #style()} attribute to be the 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 '-'.
 * <p>
 * For ISO-based formatting, set the {@link #iso()} attribute to be the desired {@link ISO} format, such as {@link ISO#DATE}.
   <p>
 * For custom formatting, set the {@link #pattern()} attribute to be the DateTime pattern, such as <code>yyyy/mm/dd h:mm:ss a</code>.
 * <p>
 * Each attribute is mutually exclusive, so only set one attribute per annotation instance (the one most convenient one for your formatting needs).
 * When the pattern attribute is specified, it takes precedence over both the style and ISO attribute.
 * When the iso attribute is specified, if takes precedence over the style attribute.
 * When no annotation attributes are specified, the default format applied is style-based with a style code of 'SS' (short date, short time).
 * 
 * @author Keith Donald
 * @since 3.0
 * @see org.joda.time.format.DateTimeFormat
 */
@Target( { ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER })
@Retention(RetentionPolicy.RUNTIME)
public @interface DateTimeFormat {

	/**
	 * The style pattern to use to format the field.
	 * 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.
	 */
	String style() default "SS";

	/**
	 * The ISO pattern to use to format the field.
	 * The possible ISO patterns are defined in the {@link ISO} enum.
	 * Defaults to ISO.NONE, indicating this attribute should be ignored.
	 * Set this attribute when you wish to format your field in accordance with an ISO date time format.
	 */
	ISO iso() default ISO.NONE;

	/**
	 * The custom pattern to use to format the field.
	 * 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.
	 */
	String pattern() default "";

	/**
	 * Common ISO date time format patterns.
	 * @author Keith Donald
	 * @since 3.0
	 */
	public enum ISO {
		
		/** 
		 * The most common ISO Date Format <code>yyyy-MM-dd</code> e.g. 2000-10-31.
		 */
		DATE,

		/** 
		 * The most common ISO Time Format <code>hh:mm:ss.SSSZ</code> e.g. 01:30:00.000-05:00.
		 */
		TIME,

		/** 
		 * The most common ISO DateTime Format <code>yyyy-MM-dd'T'hh:mm:ss.SSSZ</code> e.g. 2000-10-31 01:30:00.000-05:00.
		 * The default if no annotation value is specified.
		 */
		DATE_TIME,
		
		/**
		 * Indicates that no ISO-based format pattern should be applied.
		 */
		NONE
		
	}
}

Example Usage

private static class TestBean {

	@DateTimeFormat(style="M-")
	private LocalDate localDateAnnotated;

	@DateTimeFormat(style="-M")
	private LocalTime localTimeAnnotated;

	@DateTimeFormat(style="FF")
	private LocalDateTime localDateTimeAnnotated;

	@DateTimeFormat(style="MS")
	private DateTime dateTimeAnnotated;

	@DateTimeFormat
	private DateTime dateTimeAnnotatedDefault;

	@DateTimeFormat(pattern="M/d/yy h:mm a")
	private DateTime dateTimeAnnotatedPattern;

	@DateTimeFormat(style="S-")
	private Date dateAnnotated;

	@DateTimeFormat(style="S-")
	private Calendar calendarAnnotated;

	@DateTimeFormat(style="S-")
	private Long millisAnnotated;

	@DateTimeFormat(iso=ISO.DATE)
	private LocalDate isoDate;

	@DateTimeFormat(iso=ISO.TIME)
	private LocalTime isoTime;

	@DateTimeFormat(iso=ISO.DATE_TIME)
	private DateTime isoDateTime;
}

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Affects: 3.0 RC1