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The Core Camel Java DSL based router
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.camel.model;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementRef;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import org.apache.camel.Expression;
import org.apache.camel.Processor;
import org.apache.camel.model.loadbalancer.CircuitBreakerLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.CustomLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.FailoverLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.RandomLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.RoundRobinLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.StickyLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.TopicLoadBalancerDefinition;
import org.apache.camel.model.loadbalancer.WeightedLoadBalancerDefinition;
import org.apache.camel.processor.loadbalancer.LoadBalancer;
import org.apache.camel.spi.Metadata;
import org.apache.camel.spi.RouteContext;
import org.apache.camel.util.CollectionStringBuffer;
/**
* Balances message processing among a number of nodes
*/
@Metadata(label = "eip,routing")
@XmlRootElement(name = "loadBalance")
@XmlAccessorType(XmlAccessType.FIELD)
public class LoadBalanceDefinition extends ProcessorDefinition {
@XmlElements({
@XmlElement(required = false, name = "failover", type = FailoverLoadBalancerDefinition.class),
@XmlElement(required = false, name = "random", type = RandomLoadBalancerDefinition.class),
// TODO: Camel 3.0 - Should be named customLoadBalancer to avoid naming clash with custom dataformat
@XmlElement(required = false, name = "custom", type = CustomLoadBalancerDefinition.class),
@XmlElement(required = false, name = "roundRobin", type = RoundRobinLoadBalancerDefinition.class),
@XmlElement(required = false, name = "sticky", type = StickyLoadBalancerDefinition.class),
@XmlElement(required = false, name = "topic", type = TopicLoadBalancerDefinition.class),
@XmlElement(required = false, name = "weighted", type = WeightedLoadBalancerDefinition.class),
@XmlElement(required = false, name = "circuitBreaker", type = CircuitBreakerLoadBalancerDefinition.class)}
)
private LoadBalancerDefinition loadBalancerType;
@XmlElementRef
private List> outputs = new ArrayList>();
public LoadBalanceDefinition() {
}
@Override
public List> getOutputs() {
return outputs;
}
public void setOutputs(List> outputs) {
this.outputs = outputs;
if (outputs != null) {
for (ProcessorDefinition output : outputs) {
configureChild(output);
}
}
}
public boolean isOutputSupported() {
return true;
}
public LoadBalancerDefinition getLoadBalancerType() {
return loadBalancerType;
}
/**
* The load balancer to be used
*/
public void setLoadBalancerType(LoadBalancerDefinition loadbalancer) {
if (loadBalancerType != null) {
throw new IllegalArgumentException("Loadbalancer already configured to: " + loadBalancerType + ". Cannot set it to: " + loadbalancer);
}
loadBalancerType = loadbalancer;
}
@Override
public Processor createProcessor(RouteContext routeContext) throws Exception {
// the load balancer is stateful so we should only create it once in case its used from a context scoped error handler
LoadBalancer loadBalancer = loadBalancerType.getLoadBalancer(routeContext);
if (loadBalancer == null) {
// then create it and reuse it
loadBalancer = loadBalancerType.createLoadBalancer(routeContext);
loadBalancerType.setLoadBalancer(loadBalancer);
// some load balancer can only support a fixed number of outputs
int max = loadBalancerType.getMaximumNumberOfOutputs();
int size = getOutputs().size();
if (size > max) {
throw new IllegalArgumentException("To many outputs configured on " + loadBalancerType + ": " + size + " > " + max);
}
for (ProcessorDefinition processorType : getOutputs()) {
// output must not be another load balancer
// check for instanceof as the code below as there is compilation errors on earlier versions of JDK6
// on Windows boxes or with IBM JDKs etc.
if (LoadBalanceDefinition.class.isInstance(processorType)) {
throw new IllegalArgumentException("Loadbalancer already configured to: " + loadBalancerType + ". Cannot set it to: " + processorType);
}
Processor processor = createProcessor(routeContext, processorType);
processor = wrapChannel(routeContext, processor, processorType);
loadBalancer.addProcessor(processor);
}
}
Boolean inherit = inheritErrorHandler;
if (loadBalancerType instanceof FailoverLoadBalancerDefinition) {
// special for failover load balancer where you can configure it to not inherit error handler for its children
// but the load balancer itself should inherit so Camels error handler can react afterwards
inherit = true;
}
Processor target = wrapChannel(routeContext, loadBalancer, this, inherit);
return target;
}
// Fluent API
// -------------------------------------------------------------------------
/**
* Uses a custom load balancer
*
* @param loadBalancer the load balancer
* @return the builder
*/
public LoadBalanceDefinition loadBalance(LoadBalancer loadBalancer) {
CustomLoadBalancerDefinition def = new CustomLoadBalancerDefinition();
def.setLoadBalancer(loadBalancer);
setLoadBalancerType(def);
return this;
}
/**
* Uses fail over load balancer
*
* Will not round robin and inherit the error handler.
*
* @return the builder
*/
public LoadBalanceDefinition failover() {
return failover(-1, true, false);
}
/**
* Uses fail over load balancer
*
* Will not round robin and inherit the error handler.
*
* @param exceptions exception classes which we want to failover if one of them was thrown
* @return the builder
*/
public LoadBalanceDefinition failover(Class... exceptions) {
return failover(-1, true, false, exceptions);
}
/**
* Uses fail over load balancer
*
* @param maximumFailoverAttempts maximum number of failover attempts before exhausting.
* Use -1 to newer exhaust when round robin is also enabled.
* If round robin is disabled then it will exhaust when there are no more endpoints to failover
* @param inheritErrorHandler whether or not to inherit error handler.
* If false then it will failover immediately in case of an exception
* @param roundRobin whether or not to use round robin (which keeps state)
* @param exceptions exception classes which we want to failover if one of them was thrown
* @return the builder
*/
public LoadBalanceDefinition failover(int maximumFailoverAttempts, boolean inheritErrorHandler, boolean roundRobin, Class... exceptions) {
return failover(maximumFailoverAttempts, inheritErrorHandler, roundRobin, false, exceptions);
}
/**
* Uses fail over load balancer
*
* @param maximumFailoverAttempts maximum number of failover attempts before exhausting.
* Use -1 to newer exhaust when round robin is also enabled.
* If round robin is disabled then it will exhaust when there are no more endpoints to failover
* @param inheritErrorHandler whether or not to inherit error handler.
* If false then it will failover immediately in case of an exception
* @param roundRobin whether or not to use round robin (which keeps state)
* @param sticky whether or not to use sticky (which keeps state)
* @param exceptions exception classes which we want to failover if one of them was thrown
* @return the builder
*/
public LoadBalanceDefinition failover(int maximumFailoverAttempts, boolean inheritErrorHandler, boolean roundRobin, boolean sticky, Class... exceptions) {
FailoverLoadBalancerDefinition def = new FailoverLoadBalancerDefinition();
def.setExceptionTypes(Arrays.asList(exceptions));
def.setMaximumFailoverAttempts(maximumFailoverAttempts);
def.setRoundRobin(roundRobin);
def.setSticky(sticky);
setLoadBalancerType(def);
this.setInheritErrorHandler(inheritErrorHandler);
return this;
}
/**
* Uses weighted load balancer
*
* @param roundRobin used to set the processor selection algorithm.
* @param distributionRatio String of weighted ratios for distribution of messages.
* @return the builder
*/
public LoadBalanceDefinition weighted(boolean roundRobin, String distributionRatio) {
return weighted(roundRobin, distributionRatio, ",");
}
/**
* Uses circuitBreaker load balancer
*
* @param threshold number of errors before failure.
* @param halfOpenAfter time interval in milliseconds for half open state.
* @param exceptions exception classes which we want to break if one of them was thrown
* @return the builder
* @deprecated use Hystrix EIP instead which is the popular Netflix implementation of circuit breaker
*/
@Deprecated
public LoadBalanceDefinition circuitBreaker(int threshold, long halfOpenAfter, Class... exceptions) {
CircuitBreakerLoadBalancerDefinition def = new CircuitBreakerLoadBalancerDefinition();
def.setExceptionTypes(Arrays.asList(exceptions));
def.setThreshold(threshold);
def.setHalfOpenAfter(halfOpenAfter);
setLoadBalancerType(def);
return this;
}
/**
* Uses weighted load balancer
*
* @param roundRobin used to set the processor selection algorithm.
* @param distributionRatio String of weighted ratios for distribution of messages.
* @param distributionRatioDelimiter String containing delimiter to be used for ratios
* @return the builder
*/
public LoadBalanceDefinition weighted(boolean roundRobin, String distributionRatio, String distributionRatioDelimiter) {
WeightedLoadBalancerDefinition def = new WeightedLoadBalancerDefinition();
def.setRoundRobin(roundRobin);
def.setDistributionRatio(distributionRatio);
def.setDistributionRatioDelimiter(distributionRatioDelimiter);
setLoadBalancerType(def);
return this;
}
/**
* Uses round robin load balancer
*
* @return the builder
*/
public LoadBalanceDefinition roundRobin() {
setLoadBalancerType(new RoundRobinLoadBalancerDefinition());
return this;
}
/**
* Uses random load balancer
*
* @return the builder
*/
public LoadBalanceDefinition random() {
setLoadBalancerType(new RandomLoadBalancerDefinition());
return this;
}
/**
* Uses the custom load balancer
*
* @param ref reference to lookup a custom load balancer from the {@link org.apache.camel.spi.Registry} to be used.
* @return the builder
*/
public LoadBalanceDefinition custom(String ref) {
CustomLoadBalancerDefinition balancer = new CustomLoadBalancerDefinition();
balancer.setRef(ref);
setLoadBalancerType(balancer);
return this;
}
/**
* Uses sticky load balancer
*
* @param correlationExpression the expression for correlation
* @return the builder
*/
public LoadBalanceDefinition sticky(Expression correlationExpression) {
StickyLoadBalancerDefinition def = new StickyLoadBalancerDefinition();
def.setCorrelationExpression(correlationExpression);
setLoadBalancerType(def);
return this;
}
/**
* Uses topic load balancer
*
* @return the builder
*/
public LoadBalanceDefinition topic() {
setLoadBalancerType(new TopicLoadBalancerDefinition());
return this;
}
@Override
public String getLabel() {
CollectionStringBuffer buffer = new CollectionStringBuffer("loadBalance[");
List> list = getOutputs();
for (ProcessorDefinition processorType : list) {
buffer.append(processorType.getLabel());
}
buffer.append("]");
return buffer.toString();
}
@Override
public String toString() {
return "LoadBalanceType[" + loadBalancerType + ", " + getOutputs() + "]";
}
}