abstractmessagesource.java

spring的源代码

/*
 * Copyright 2002-2005 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.context.support;

import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.context.HierarchicalMessageSource;
import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceResolvable;
import org.springframework.context.NoSuchMessageException;
import org.springframework.util.ObjectUtils;

/**
 * Abstract implementation of the HierarchicalMessageSource interface,
 * implementing common handling of message variants, making it easy
 * to implement a specific strategy for a concrete MessageSource.
 *
 * <p>Subclasses must implement the abstract <code>resolveCode</code>
 * method. For efficient resolution of messages without arguments, the
 * <code>resolveCodeWithoutArguments</code> method should be overridden
 * as well, resolving messages without a MessageFormat being involved.
 *
 * <p><b>Note:</b> By default, message texts are only parsed through
 * MessageFormat if arguments have been passed in for the message. In case
 * of no arguments, message texts will be returned as-is. As a consequence,
 * you should only use MessageFormat escaping for messages with actual
 * arguments, and keep all other messages unescaped. If you prefer to
 * escape all messages, set the "alwaysUseMessageFormat" flag to "true".
 *
 * <p>Supports not only MessageSourceResolvables as primary messages
 * but also resolution of message arguments that are in turn
 * MessageSourceResolvables themselves.
 *
 * <p>This class does not implement caching of messages per code, thus
 * subclasses can dynamically change messages over time. Subclasses are
 * encouraged to cache their messages in a modification-aware fashion,
 * allowing for hot deployment of updated messages.
 *
 * @author Juergen Hoeller
 * @author Rod Johnson
 * @see #resolveCode(String, java.util.Locale)
 * @see #resolveCodeWithoutArguments(String, java.util.Locale)
 * @see #setAlwaysUseMessageFormat
 * @see java.text.MessageFormat
 */
public abstract class AbstractMessageSource implements HierarchicalMessageSource {

	protected final Log logger = LogFactory.getLog(getClass());

	private MessageSource parentMessageSource;

	private boolean useCodeAsDefaultMessage = false;

	private boolean alwaysUseMessageFormat = false;

	/**
	 * Cache to hold already generated MessageFormats per message.
	 * Used for passed-in default messages. MessageFormats for resolved
	 * codes are cached on a specific basis in subclasses.
	 */
	private final Map cachedMessageFormats = new HashMap();


	public void setParentMessageSource(MessageSource parent) {
		this.parentMessageSource = parent;
	}

	public MessageSource getParentMessageSource() {
		return parentMessageSource;
	}

	/**
	 * Set whether to use the message code as default message instead of
	 * throwing a NoSuchMessageException. Useful for development and debugging.
	 * Default is "false".
	 * <p>Note: In case of a MessageSourceResolvable with multiple codes
	 * (like a FieldError) and a MessageSource that has a parent MessageSource,
	 * do <i>not</i> activate "useCodeAsDefaultMessage" in the <i>parent</i>:
	 * Else, you'll get the first code returned as message by the parent,
	 * without attempts to check further codes.
	 * <p>To be able to work with "useCodeAsDefaultMessage" turned on in the parent,
	 * AbstractMessageSource and AbstractApplicationContext contain special checks
	 * to delegate to the internal <code>getMessageInternal</code> method if available.
	 * In general, it is recommended to just use "useCodeAsDefaultMessage" during
	 * development and not rely on it in production in the first place, though.
	 * @see #getMessage(String, Object[], Locale)
	 * @see #getMessageInternal
	 * @see org.springframework.validation.FieldError
	 */
	public void setUseCodeAsDefaultMessage(boolean useCodeAsDefaultMessage) {
		this.useCodeAsDefaultMessage = useCodeAsDefaultMessage;
	}

	/**
	 * Return whether to use the message code as default message instead of
	 * throwing a NoSuchMessageException. Useful for development and debugging.
	 * Default is "false".
	 * <p>Alternatively, consider overriding the <code>getDefaultMessage</code>
	 * method to return a custom fallback message for an unresolvable code.
	 * @see #getDefaultMessage(String)
	 */
	protected boolean isUseCodeAsDefaultMessage() {
		return useCodeAsDefaultMessage;
	}

	/**
	 * Set whether to always apply the MessageFormat rules, parsing even
	 * messages without arguments.
	 * <p>Default is "false": Messages without arguments are by default
	 * returned as-is, without parsing them through MessageFormat.
	 * Set this to "true" to enforce MessageFormat for all messages,
	 * expecting all message texts to be written with MessageFormat escaping.
	 * <p>For example, MessageFormat expects a single quote to be escaped
	 * as "''". If your message texts are all written with such escaping,
	 * even when not defining argument placeholders, you need to set this
	 * flag to "true". Else, only message texts with actual arguments
	 * are supposed to be written with MessageFormat escaping.
	 * @see java.text.MessageFormat
	 */
	public void setAlwaysUseMessageFormat(boolean alwaysUseMessageFormat) {
		this.alwaysUseMessageFormat = alwaysUseMessageFormat;
	}

	/**
	 * Return whether to always apply the MessageFormat rules, parsing even
	 * messages without arguments.
	 */
	protected boolean isAlwaysUseMessageFormat() {
		return alwaysUseMessageFormat;
	}


	public final String getMessage(String code, Object[] args, String defaultMessage, Locale locale) {
		String msg = getMessageInternal(code, args, locale);
		if (msg != null) {
			return msg;
		}
		if (defaultMessage == null) {
			String fallback = getDefaultMessage(code);
			if (fallback != null) {
				return fallback;
			}
		}
		return renderDefaultMessage(defaultMessage, args, locale);
	}

	public final String getMessage(String code, Object[] args, Locale locale) throws NoSuchMessageException {
		String msg = getMessageInternal(code, args, locale);
		if (msg != null) {
			return msg;
		}
		String fallback = getDefaultMessage(code);
		if (fallback != null) {
			return fallback;
		}
		throw new NoSuchMessageException(code, locale);
	}

	public final String getMessage(MessageSourceResolvable resolvable, Locale locale)
			throws NoSuchMessageException {

		String[] codes = resolvable.getCodes();
		if (codes == null) {
			codes = new String[0];
		}
		for (int i = 0; i < codes.length; i++) {
			String msg = getMessageInternal(codes[i], resolvable.getArguments(), locale);
			if (msg != null) {
				return msg;
			}
		}
		if (resolvable.getDefaultMessage() != null) {
			return renderDefaultMessage(resolvable.getDefaultMessage(), resolvable.getArguments(), locale);
		}
		if (codes.length > 0) {
			String fallback = getDefaultMessage(codes[0]);
			if (fallback != null) {
				return fallback;
			}
		}
		throw new NoSuchMessageException(codes.length > 0 ? codes[codes.length - 1] : null, locale);
	}


	/**
	 * Resolve the given code and arguments as message in the given Locale,
	 * returning null if not found. Does <i>not</i> fall back to the code
	 * as default message. Invoked by getMessage methods.
	 * @param code the code to lookup up, such as 'calculator.noRateSet'
	 * @param args array of arguments that will be filled in for params
	 * within the message
	 * @param locale the Locale in which to do the lookup
	 * @return the resolved message, or <code>null</code> if not found
	 * @see #getMessage(String, Object[], String, Locale)
	 * @see #getMessage(String, Object[], Locale)