/*
* Copyright 2002-2016 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.integration.handler;
import org.springframework.expression.Expression;
import org.springframework.expression.ParseException;
import org.springframework.messaging.Message;
import org.springframework.util.Assert;
/**
* A {@link MessageProcessor} implementation that evaluates a SpEL expression
* with the Message itself as the root object within the evaluation context.
*
* @author Mark Fisher
* @author Artem Bilan
* @author Gary Russell
* @since 2.0
*/
public class ExpressionEvaluatingMessageProcessor<T> extends AbstractMessageProcessor<T> {
private final Expression expression;
private final Class<T> expectedType;
/**
* Create an {@link ExpressionEvaluatingMessageProcessor} for the given expression.
* @param expression The expression.
*/
public ExpressionEvaluatingMessageProcessor(Expression expression) {
this(expression, null);
}
/**
* Create an {@link ExpressionEvaluatingMessageProcessor} for the given expression
* and expected type for its evaluation result.
* @param expression The expression.
* @param expectedType The expected type.
*/
public ExpressionEvaluatingMessageProcessor(Expression expression, Class<T> expectedType) {
Assert.notNull(expression, "The expression must not be null");
try {
this.expression = expression;
this.expectedType = expectedType;
}
catch (ParseException e) {
throw new IllegalArgumentException("Failed to parse expression.", e);
}
}
/**
* Create an {@link ExpressionEvaluatingMessageProcessor} for the given expression.
* @param expression a SpEL expression to evaluate.
* @since 5.0
*/
public ExpressionEvaluatingMessageProcessor(String expression) {
try {
this.expression = EXPRESSION_PARSER.parseExpression(expression);
this.expectedType = null;
}
catch (ParseException e) {
throw new IllegalArgumentException("Failed to parse expression.", e);
}
}
/**
* Construct {@link ExpressionEvaluatingMessageProcessor} for the provided
* SpEL expression and expected result type.
* @param expression a SpEL expression to evaluate.
* @param expectedType the expected result type.
* @since 5.0
*/
public ExpressionEvaluatingMessageProcessor(String expression, Class<T> expectedType) {
try {
this.expression = EXPRESSION_PARSER.parseExpression(expression);
this.expectedType = expectedType;
}
catch (ParseException e) {
throw new IllegalArgumentException("Failed to parse expression.", e);
}
}
/**
* Processes the Message by evaluating the expression with that Message as the
* root object. The expression evaluation result Object will be returned.
* @param message The message.
* @return The result of processing the message.
*/
@Override
public T processMessage(Message<?> message) {
return evaluateExpression(this.expression, message, this.expectedType);
}
@Override
public String toString() {
return "ExpressionEvaluatingMessageProcessor for: [" + this.expression.getExpressionString() + "]";
}
}