DefaultMessageResolver.java

/*
 * Copyright 2004-2009 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.ui.message;

import java.util.Locale;
import java.util.Map;

import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceResolvable;
import org.springframework.core.style.ToStringCreator;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.ParseException;
import org.springframework.expression.ParserContext;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.support.StandardEvaluationContext;

final class DefaultMessageResolver implements MessageResolver, MessageSourceResolvable {

	private Severity severity;

	private String[] codes;

	private Map<String, Object> args;

	private String defaultText;

	private ExpressionParser expressionParser;

	public DefaultMessageResolver(Severity severity, String[] codes, Map<String, Object> args, String defaultText,
			ExpressionParser expressionParser) {
		this.severity = severity;
		this.codes = codes;
		this.args = args;
		this.defaultText = defaultText;
		this.expressionParser = expressionParser;
	}

	// implementing MessageResolver

	public Message resolveMessage(MessageSource messageSource, Locale locale) {
		String messageString = messageSource.getMessage(this, locale);
		Expression message;
		try {
			message = expressionParser.parseExpression(messageString, ParserContext.TEMPLATE_EXPRESSION);
		} catch (ParseException e) {
			throw new MessageResolutionException("Failed to parse message expression", e);
		}
		try {
			StandardEvaluationContext context = new StandardEvaluationContext();
			context.setRootObject(args);
			context.addPropertyAccessor(new MessageArgumentAccessor(messageSource, locale));
			String text = (String) message.getValue(context);
			return new TextMessage(severity, text);
		} catch (EvaluationException e) {
			throw new MessageResolutionException("Failed to evaluate expression to generate message text", e);
		}
	}

	// implementing MessageSourceResolver

	public String[] getCodes() {
		return codes;
	}

	public Object[] getArguments() {
		return null;
	}

	public String getDefaultMessage() {
		return defaultText;
	}

	public String toString() {
		return new ToStringCreator(this).append("severity", severity).append("codes", codes).append("defaultText",
				defaultText).toString();
	}

	private static class TextMessage implements Message {

		private Severity severity;

		private String text;

		public TextMessage(Severity severity, String text) {
			this.severity = severity;
			this.text = text;
		}

		public Severity getSeverity() {
			return severity;
		}

		public String getText() {
			return text;
		}

	}

	static class MessageArgumentAccessor implements PropertyAccessor {

		private MessageSource messageSource;
		
		private Locale locale;

		public MessageArgumentAccessor(MessageSource messageSource, Locale locale) {
			this.messageSource = messageSource;
			this.locale = locale;
		}

		public boolean canRead(EvaluationContext context, Object target, String name) throws AccessException {
			return (((Map) target).containsKey(name));
		}

		public TypedValue read(EvaluationContext context, Object target, String name) throws AccessException {
			Object o = ((Map) target).get(name);
			if (o instanceof MessageSourceResolvable) {
				String message = messageSource.getMessage((MessageSourceResolvable) o, locale);
				return new TypedValue(message);
			} else {
				return new TypedValue(o);
			}
		}
		
		public boolean canWrite(EvaluationContext context, Object target, String name) throws AccessException {
			return false;
		}

		public void write(EvaluationContext context, Object target, String name, Object newValue)
				throws AccessException {
			throw new UnsupportedOperationException("Should not be called");
		}
		
		public Class[] getSpecificTargetClasses() {
			return new Class[] { Map.class };
		}

	}

}