/*
* Copyright 2006-2007 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.batch.repeat.interceptor;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.ProxyMethodInvocation;
import org.springframework.batch.repeat.RepeatStatus;
import org.springframework.batch.repeat.RepeatCallback;
import org.springframework.batch.repeat.RepeatContext;
import org.springframework.batch.repeat.RepeatException;
import org.springframework.batch.repeat.RepeatOperations;
import org.springframework.batch.repeat.support.RepeatTemplate;
import org.springframework.util.Assert;
/**
* A {@link MethodInterceptor} that can be used to automatically repeat calls to
* a method on a service. The injected {@link RepeatOperations} is used to
* control the completion of the loop. Independent of the completion policy in
* the {@link RepeatOperations} the loop will repeat until the target method
* returns null or false. Be careful when injecting a bespoke
* {@link RepeatOperations} that the loop will actually terminate, because the
* default policy for a vanilla {@link RepeatTemplate} will never complete if
* the return type of the target method is void (the value returned is always
* not-null, representing the {@link Void#TYPE}).
*
* @author Dave Syer
*/
public class RepeatOperationsInterceptor implements MethodInterceptor {
private RepeatOperations repeatOperations = new RepeatTemplate();
/**
* Setter for the {@link RepeatOperations}.
*
* @param batchTempate template to be used
* @throws IllegalArgumentException if the argument is null.
*/
public void setRepeatOperations(RepeatOperations batchTempate) {
Assert.notNull(batchTempate, "'repeatOperations' cannot be null.");
this.repeatOperations = batchTempate;
}
/**
* Invoke the proceeding method call repeatedly, according to the properties
* of the injected {@link RepeatOperations}.
*
* @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
*/
@Override
public Object invoke(final MethodInvocation invocation) throws Throwable {
final ResultHolder result = new ResultHolder();
// Cache void return value if intercepted method returns void
final boolean voidReturnType = Void.TYPE.equals(invocation.getMethod().getReturnType());
if (voidReturnType) {
// This will be ignored anyway, but we want it to be non-null for
// convenience of checking that there is a result.
result.setValue(new Object());
}
try {
repeatOperations.iterate(new RepeatCallback() {
@Override
public RepeatStatus doInIteration(RepeatContext context) throws Exception {
try {
MethodInvocation clone = invocation;
if (invocation instanceof ProxyMethodInvocation) {
clone = ((ProxyMethodInvocation) invocation).invocableClone();
}
else {
throw new IllegalStateException(
"MethodInvocation of the wrong type detected - this should not happen with Spring AOP, so please raise an issue if you see this exception");
}
Object value = clone.proceed();
if (voidReturnType) {
return RepeatStatus.CONTINUABLE;
}
if (!isComplete(value)) {
// Save the last result
result.setValue(value);
return RepeatStatus.CONTINUABLE;
}
else {
result.setFinalValue(value);
return RepeatStatus.FINISHED;
}
}
catch (Throwable e) {
if (e instanceof Exception) {
throw (Exception) e;
}
else {
throw new RepeatOperationsInterceptorException("Unexpected error in batch interceptor", e);
}
}
}
});
}
catch (Throwable t) {
// The repeat exception should be unwrapped by the template
throw t;
}
if (result.isReady()) {
return result.getValue();
}
// No result means something weird happened
throw new IllegalStateException("No result available for attempted repeat call to " + invocation
+ ". The invocation was never called, so maybe there is a problem with the completion policy?");
}
/**
* @param result
* @return
*/
private boolean isComplete(Object result) {
return result == null || (result instanceof Boolean) && !((Boolean) result).booleanValue();
}
/**
* Simple wrapper exception class to enable nasty errors to be passed out of
* the scope of the repeat operations and handled by the caller.
*
* @author Dave Syer
*
*/
@SuppressWarnings("serial")
private static class RepeatOperationsInterceptorException extends RepeatException {
/**
* @param message
* @param e
*/
public RepeatOperationsInterceptorException(String message, Throwable e) {
super(message, e);
}
}
/**
* Simple wrapper object for the result from a method invocation.
*
* @author Dave Syer
*
*/
private static class ResultHolder {
private Object value = null;
private boolean ready = false;
/**
* Public setter for the Object.
* @param value the value to set
*/
public void setValue(Object value) {
this.ready = true;
this.value = value;
}
/**
* @param value
*/
public void setFinalValue(Object value) {
if (ready) {
// Only set the value the last time if the last time was also
// the first time
return;
}
setValue(value);
}
/**
* Public getter for the Object.
* @return the value
*/
public Object getValue() {
return value;
}
/**
* @return true if a value has been set
*/
public boolean isReady() {
return ready;
}
}
}