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https://github.com/meliorartefacts/service-harness-amqp-rabbitmq

An easy to use, auto-configuring RabbitMQ client with connection pooling and automatic object mapping. Plus, an easy to use, auto-configuring RabbitMQ listener for messages. Plus, an easy to use RabbitMQ service harness with transaction correlation.
https://github.com/meliorartefacts/service-harness-amqp-rabbitmq

connection-pool rabbit-mq spring-boot spring-client

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An easy to use, auto-configuring RabbitMQ client with connection pooling and automatic object mapping. Plus, an easy to use, auto-configuring RabbitMQ listener for messages. Plus, an easy to use RabbitMQ service harness with transaction correlation.

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README 

        
# Melior Service Harness :: AMQP : RabbitMQ












## Artefact

Get the artefact and the POM file in the *artefact* folder.

```



    org.melior

    melior-harness-amqp-rabbitmq

    2.3



```



## Client

Create a bean to instantiate the RabbitMQ client.  The RabbitMQ client uses connection pooling to improve performance.

```

@Bean("myclient")

@ConfigurationProperties("myclient")

public RabbitMQClient client() {

    return RabbitMQClientBuilder.create().build();

}

```



The RabbitMQ client is auto-configured from the application properties.

```

myclient.url=amqp://some.service:5672/environment

myclient.username=user

myclient.password=password

myclient.exchange=myExchange

myclient.routing-key=myQueue

myclient.request-timeout=30

myclient.inactivity-timeout=300

```



Map the attributes in the JSON message to the fields in the JAVA class.

```

public class Message {

    @JsonProperty("category")

    private String category;



    @JsonProperty("type")

    private String type;



    @JsonProperty("description")

    private String description;



    @JsonProperty("volume")

    private double volume;



    @JsonProperty("balance")

    private double balance;



    ...

}

```



Wire in and use the RabbitMQ client.  There is no need to convert the JAVA object to JSON before using the RabbitMQ client to send the message.  The RabbitMQ client performs the object mapping automatically.

```

@Autowired

private RabbitMQClient client;



public void foo(Message message) throws RemotingException {

    client.send(message)

}

```



The RabbitMQ client may be configured using these application properties.



|Name|Default|Description|

|:---|:---|:---|

|`url`||The URL of the RabbitMQ server|

|`username`||The user name required by the RabbitMQ server|

|`password`||The password required by the RabbitMQ server|

|`exchange`||The message exchange to bind to in the RabbitMQ server|

|`routing-key`||The routing key to use when sending messages to the RabbitMQ server|

|`queue`||An alternative name for the routing-key parameter, if the queue name and routing key are configured the same in the RabbitMQ server|

|`minimum-connections`|0|The minimum number of connections to open to the RabbitMQ server|

|`maximum-connections`|1000|The maximum number of connections to open to the RabbitMQ server|

|`connection-timeout`|30 s|The amount of time to allow for a new connection to open to the RabbitMQ server|

|`request-timeout`|60 s|The amount of time to allow for a request to the RabbitMQ server to complete|

|`backoff-period`|1 s|The amount of time to back off when the circuit breaker trips|

|`backoff-multiplier`|1|The factor with which to increase the backoff period when the circuit breaker trips repeatedly|

|`backoff-limit`||The maximum amount of time to back off when the circuit breaker trips repeatedly|

|`inactivity-timeout`|300 s|The amount of time to allow before surplus connections to the RabbitMQ server are pruned|

|`maximum-lifetime`|unlimited|The maximum lifetime of a connection to the RabbitMQ server|

|`prune-interval`|60 s|The interval at which surplus connections to the RabbitMQ server are pruned|



 

## Listener

Create a bean to instantiate the RabbitMQ listener.  The RabbitMQ listener listens to the registered queue and executes the registered application code when new items arrive in the queue.

```

@Bean("myListener")

@ConfigurationProperties("myListener")

public RabbitMQListener listener() {

    return RabbitMQListenerBuilder.create(Person.class).client(client()).build();

}

```



The RabbitMQ listener is auto-configured from the application properties.

```

myListener.queue=myQueue

myListener.consumers=5

myListener.prefetch=1

```



Wire in the RabbitMQ listener and register the queue and application code.

```

@Autowired

@Qualifier("myListener")

private RabbitMQListener listener;



public void foo() {

    listener.register("people")

        .single(person -> processPerson(person))

        .start();

}



private void processPeople(List people) {

...

}



private void processPerson(Person person) {

...

}

```



The RabbitMQ listener may be configured using these application properties.



|Name|Default|Description|

|:---|:---|:---|

|`consumers`|1|The number of RabbitMQ consumers to create|

|`prefetch`|1|The maximum number of messages to fetch from the RabbitMQ server each time|



 

## Service

Use the RabbitMQ service harness to get a service with the standard Melior logging system and a configuration object that may be used to access the application properties anywhere and at any time in the application code, even in the constructor.

```

public class MyApplication extends RabbitMQService



public MyApplication(ServiceContext serviceContext, RabbitMQListener listener) throws ApplicationException {

    super(serviceContext);



    registerQueue(listener, "people")

        .single(person -> processPerson(person))

        .start();

}

```



The RabbitMQ service harness automatically generates a unique correlation id for each transaction that originates from the RabbitMQ listener, and makes the correlation id available in the transaction context for other components to access.  For example, if the REST client is used to communicate with another service then the **X-Request-Id** HTTP header is automatically populated with the correlation id.



   

## References

Refer to the [**Melior Service Harness :: Core**](https://github.com/MeliorArtefacts/service-harness-core) module for detail on the Melior logging system and available utilities.