001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.context;
018
019import java.util.Locale;
020
021import org.springframework.lang.Nullable;
022
023/**
024 * Strategy interface for resolving messages, with support for the parameterization
025 * and internationalization of such messages.
026 *
027 * <p>Spring provides two out-of-the-box implementations for production:
028 * <ul>
029 * <li>{@link org.springframework.context.support.ResourceBundleMessageSource}: built
030 * on top of the standard {@link java.util.ResourceBundle}, sharing its limitations.
031 * <li>{@link org.springframework.context.support.ReloadableResourceBundleMessageSource}:
032 * highly configurable, in particular with respect to reloading message definitions.
033 * </ul>
034 *
035 * @author Rod Johnson
036 * @author Juergen Hoeller
037 * @see org.springframework.context.support.ResourceBundleMessageSource
038 * @see org.springframework.context.support.ReloadableResourceBundleMessageSource
039 */
040public interface MessageSource {
041
042        /**
043         * Try to resolve the message. Return default message if no message was found.
044         * @param code the message code to look up, e.g. 'calculator.noRateSet'.
045         * MessageSource users are encouraged to base message names on qualified class
046         * or package names, avoiding potential conflicts and ensuring maximum clarity.
047         * @param args an array of arguments that will be filled in for params within
048         * the message (params look like "{0}", "{1,date}", "{2,time}" within a message),
049         * or {@code null} if none
050         * @param defaultMessage a default message to return if the lookup fails
051         * @param locale the locale in which to do the lookup
052         * @return the resolved message if the lookup was successful, otherwise
053         * the default message passed as a parameter (which may be {@code null})
054         * @see #getMessage(MessageSourceResolvable, Locale)
055         * @see java.text.MessageFormat
056         */
057        @Nullable
058        String getMessage(String code, @Nullable Object[] args, @Nullable String defaultMessage, Locale locale);
059
060        /**
061         * Try to resolve the message. Treat as an error if the message can't be found.
062         * @param code the message code to look up, e.g. 'calculator.noRateSet'.
063         * MessageSource users are encouraged to base message names on qualified class
064         * or package names, avoiding potential conflicts and ensuring maximum clarity.
065         * @param args an array of arguments that will be filled in for params within
066         * the message (params look like "{0}", "{1,date}", "{2,time}" within a message),
067         * or {@code null} if none
068         * @param locale the locale in which to do the lookup
069         * @return the resolved message (never {@code null})
070         * @throws NoSuchMessageException if no corresponding message was found
071         * @see #getMessage(MessageSourceResolvable, Locale)
072         * @see java.text.MessageFormat
073         */
074        String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException;
075
076        /**
077         * Try to resolve the message using all the attributes contained within the
078         * {@code MessageSourceResolvable} argument that was passed in.
079         * <p>NOTE: We must throw a {@code NoSuchMessageException} on this method
080         * since at the time of calling this method we aren't able to determine if the
081         * {@code defaultMessage} property of the resolvable is {@code null} or not.
082         * @param resolvable the value object storing attributes required to resolve a message
083         * (may include a default message)
084         * @param locale the locale in which to do the lookup
085         * @return the resolved message (never {@code null} since even a
086         * {@code MessageSourceResolvable}-provided default message needs to be non-null)
087         * @throws NoSuchMessageException if no corresponding message was found
088         * (and no default message was provided by the {@code MessageSourceResolvable})
089         * @see MessageSourceResolvable#getCodes()
090         * @see MessageSourceResolvable#getArguments()
091         * @see MessageSourceResolvable#getDefaultMessage()
092         * @see java.text.MessageFormat
093         */
094        String getMessage(MessageSourceResolvable resolvable, Locale locale) throws NoSuchMessageException;
095
096}