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https://issues.apache.org/jira/browse/STRATOS-110?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nirmal Fernando resolved STRATOS-110.
-------------------------------------
Resolution: Fixed
> Topology Event Message Processors should follow 'chain of responsibility'
> design pattern
> ----------------------------------------------------------------------------------------
>
> Key: STRATOS-110
> URL: https://issues.apache.org/jira/browse/STRATOS-110
> Project: Stratos
> Issue Type: Improvement
> Affects Versions: 4.0.0 M1
> Reporter: Nirmal Fernando
> Assignee: Nirmal Fernando
> Priority: Critical
> Fix For: 4.0.0 M1
>
>
> Following is the MessageProcessor interface with this change.
> package org.apache.stratos.messaging.message.processor;
> import org.apache.stratos.messaging.domain.topology.Topology;
> /**
> * Message processor interface. Every Message Processor should implement this.
> */
> public interface MessageProcessor {
>
> /**
> * Link a message processor and its successor, if there's any.
> * @param nextProcessor
> */
> public abstract void setNext(MessageProcessor nextProcessor);
> /**
> * Message processing and delegating logic.
> * @param type type of the message.
> * @param message real message body.
> * @param topology Topology that will get updated.
> * @return whether the processing was successful or not.
> */
> public abstract boolean process(String type, String message, Topology
> topology);
> }
> I've implemented initial Message Processors:
> ├── ClusterCreatedEventProcessor.java
> ├── ClusterRemovedEventProcessor.java
> ├── CompleteTopologyEventProcessor.java
> ├── MemberActivatedEventProcessor.java
> ├── MemberStartedEventProcessor.java
> ├── MemberSuspendedEventProcessor.java
> ├── MemberTerminatedEventProcessor.java
> ├── ServiceCreatedEventProcessor.java
> └── ServiceRemovedEventProcessor.java
> Now, it is up to the Message Processor Delegator to build the Message
> processor chain.
> // instantiate all the relevant processors
> ServiceCreatedEventProcessor processor1 = new
> ServiceCreatedEventProcessor();
> ServiceRemovedEventProcessor processor2 = new
> ServiceRemovedEventProcessor();
> ClusterCreatedEventProcessor processor3 = new
> ClusterCreatedEventProcessor();
>
>
> // link all the relevant processors in the required order
> processor1.setNext(processor2);
> processor2.setNext(processor3);
> processor3.setNext(processor4);
> and also it's a duty of the deligator to start the flow:
> boolean hasProcessed = processor1.process(type, json,
> TopologyManager.getTopology());
> After the flow started, Processor who is capable of handling the message
> would eventually receive it and will process the message and other Processors
> will simply delegate the message to its successor.
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