/*
* Copyright 2014 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.xd.integration.hadoop.expression;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.Expression;
import org.springframework.expression.MethodResolver;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.util.Assert;
/**
* Helper class to work with a spel expressions resolving values
* from a {@link Message}. A {@link StandardEvaluationContext} is expected and
* {@link MessagePartitionKeyMethodResolver} and {@link MessagePartitionKeyPropertyAccessor}
* registered with it.
*
* @author Janne Valkealahti
*
*/
public class MessageExpressionMethods {
private final StandardEvaluationContext context;
/**
* Instantiates a new message expression methods with
* a {@link StandardEvaluationContext}.
*
* @param evaluationContext the spel evaluation context
*/
public MessageExpressionMethods(StandardEvaluationContext evaluationContext) {
this(evaluationContext, false, false);
}
/**
* Instantiates a new message expression methods with
* a {@link StandardEvaluationContext}.
*
* @param evaluationContext the spel evaluation context
* @param autoCustomize auto customize method resolver and property accessor
* @param replaceMethodResolver replace context method resolver
*/
public MessageExpressionMethods(StandardEvaluationContext evaluationContext, boolean autoCustomize, boolean replaceMethodResolver) {
Assert.notNull(evaluationContext, "Evaluation context cannot be null");
if (autoCustomize) {
MethodResolver methodResolver = new MessagePartitionKeyMethodResolver();
if (replaceMethodResolver) {
List<MethodResolver> methodResolvers = new ArrayList<MethodResolver>();
methodResolvers.add(methodResolver);
evaluationContext.setMethodResolvers(methodResolvers);
} else {
evaluationContext.addMethodResolver(methodResolver);
}
}
if (autoCustomize) {
evaluationContext.addPropertyAccessor(new MessagePartitionKeyPropertyAccessor());
}
this.context = evaluationContext;
}
/**
* Gets the value.
*
* @param <T> the generic type
* @param expression the expression
* @param desiredResultType the desired result type
* @return the value
* @throws EvaluationException the evaluation exception
*/
public <T> T getValue(Expression expression, Message<?> message, Class<T> desiredResultType)
throws EvaluationException {
Assert.notNull(expression, "Expression cannot be null");
return expression.getValue(context, new MessageWrappedMessage(message), desiredResultType);
}
public static class MessageWrappedMessage implements Message<Object> {
private final Message<?> delegate;
public MessageWrappedMessage(Message<?> delegate) {
this.delegate = delegate;
}
@Override
public Object getPayload() {
return delegate.getPayload();
}
@Override
public MessageHeaders getHeaders() {
return delegate.getHeaders();
}
public String dateFormat(String pattern) {
SimpleDateFormat format = new SimpleDateFormat(pattern);
return format.format(getHeaders().getTimestamp());
}
}
}