Avro DataFormat

Since Camel 2.14

This component provides a dataformat for avro, which allows serialization and deserialization of messages using Apache Avro’s binary dataformat. Moreover, it provides support for Apache Avro’s rpc, by providing producers and consumers endpoint for using avro over netty or http.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-avro</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

Apache Avro Overview

Avro allows you to define message types and a protocol using a json like format and then generate java code for the specified types and messages. An example of how a schema looks like is below.

{"namespace": "org.apache.camel.avro.generated",
 "protocol": "KeyValueProtocol",

 "types": [
     {"name": "Key", "type": "record",
      "fields": [
          {"name": "key",   "type": "string"}
      ]
     },
     {"name": "Value", "type": "record",
      "fields": [
          {"name": "value",   "type": "string"}
      ]
     }
 ],

 "messages": {
     "put": {
         "request": [{"name": "key", "type": "Key"}, {"name": "value", "type": "Value"} ],
         "response": "null"
     },
     "get": {
         "request": [{"name": "key", "type": "Key"}],
         "response": "Value"
     }
 }
}

You can easily generate classes from a schema, using maven, ant etc. More details can be found at the Apache Avro documentation.

However, it doesn’t enforce a schema first approach and you can create schema for your existing classes. Since 2.12 you can use existing protocol interfaces to make RCP calls. You should use interface for the protocol itself and POJO beans or primitive/String classes for parameter and result types. Here is an example of the class that corresponds to schema above:

package org.apache.camel.avro.reflection;

public interface KeyValueProtocol {
    void put(String key, Value value);
    Value get(String key);
}

class Value {
    private String value;
    public String getValue() { return value; }
    public void setValue(String value) { this.value = value; }
}

Note: Existing classes can be used only for RPC (see below), not in data format.

Using the Avro data format

Using the avro data format is as easy as specifying that the class that you want to marshal or unmarshal in your route.

    <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
        <route>
            <from uri="direct:in"/>
            <marshal>
                <avro instanceClass="org.apache.camel.dataformat.avro.Message"/>
            </marshal>
            <to uri="log:out"/>
        </route>
    </camelContext>

An alternative can be to specify the dataformat inside the context and reference it from your route.

    <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
         <dataFormats>
            <avro id="avro" instanceClass="org.apache.camel.dataformat.avro.Message"/>
        </dataFormats>
        <route>
            <from uri="direct:in"/>
            <marshal><custom ref="avro"/></marshal>
            <to uri="log:out"/>
        </route>
    </camelContext>

In the same manner you can umarshal using the avro data format.

Avro Dataformat Options

The Avro dataformat supports 2 options, which are listed below.

Name Default Java Type Description

instanceClassName

String

Class name to use for marshal and unmarshalling

contentTypeHeader

false

Boolean

Whether the data format should set the Content-Type header with the type from the data format if the data format is capable of doing so. For example application/xml for data formats marshalling to XML, or application/json for data formats marshalling to JSon etc.

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-avro-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 17 options, which are listed below.

Name Description Default Type

camel.component.avro.basic-property-binding

Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

Boolean

camel.component.avro.bridge-error-handler

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

Boolean

camel.component.avro.configuration.host

Hostname to use

String

camel.component.avro.configuration.message-name

The name of the message to send.

String

camel.component.avro.configuration.port

Port number to use

Integer

camel.component.avro.configuration.protocol

Avro protocol to use

Protocol

camel.component.avro.configuration.protocol-class-name

Avro protocol to use defined by the FQN class name

String

camel.component.avro.configuration.protocol-location

Avro protocol location

String

camel.component.avro.configuration.reflection-protocol

If protocol object provided is reflection protocol. Should be used only with protocol parameter because for protocolClassName protocol type will be auto detected

false

Boolean

camel.component.avro.configuration.single-parameter

If true, consumer parameter won’t be wrapped into array. Will fail if protocol specifies more then 1 parameter for the message

false

Boolean

camel.component.avro.configuration.transport

Transport to use, can be either http or netty

AvroTransport

camel.component.avro.configuration.uri-authority

Authority to use (username and password)

String

camel.component.avro.enabled

Whether to enable auto configuration of the avro component. This is enabled by default.

Boolean

camel.component.avro.lazy-start-producer

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

Boolean

camel.dataformat.avro.content-type-header

Whether the data format should set the Content-Type header with the type from the data format if the data format is capable of doing so. For example application/xml for data formats marshalling to XML, or application/json for data formats marshalling to JSon etc.

false

Boolean

camel.dataformat.avro.enabled

Whether to enable auto configuration of the avro data format. This is enabled by default.

Boolean

camel.dataformat.avro.instance-class-name

Class name to use for marshal and unmarshalling

String

ND