[[protobuf-dataformat]]
= Protobuf DataFormat
:docTitle: Protobuf
:artifactId: camel-protobuf
:description: Serialize and deserialize Java objects using Google's Protocol buffers.
:since: 2.2
:supportLevel: Stable

*Since Camel {since}*

Protobuf - Protocol Buffers
---------------------------

"Protocol Buffers - Google's data interchange format"

Camel provides a Data Format to serialize between
Java and the Protocol Buffer protocol. The project's site details why
you may wish to
https://developers.google.com/protocol-buffers/docs/overview[choose this format over xml].
Protocol Buffer is language-neutral and
platform-neutral, so messages produced by your Camel routes may be
consumed by other language implementations.

https://developers.google.com/protocol-buffers/docs/reference/java/[API Site] +
https://github.com/google/protobuf[Protobuf Implementation] +

https://developers.google.com/protocol-buffers/docs/javatutorial[Protobuf Java Tutorial]

== Protobuf Options

// dataformat options: START
The Protobuf dataformat supports 3 options, which are listed below.



[width="100%",cols="2s,1m,1m,6",options="header"]
|===
| Name | Default | Java Type | Description
| instanceClass |  | String | Name of class to use when unmarshalling
| contentTypeFormat | native | String | Defines a content type format in which protobuf message will be serialized/deserialized from(to) the Java been. The format can either be native or json for either native protobuf or json fields representation. The default value is native. The value can be one of: json, native
| 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.
|===
// dataformat options: END


== Content type format

It's possible to parse JSON message to convert it to the protobuf format and unparse it back using native util converter.
To use this option, set contentTypeFormat value to 'json' or call protobuf with second parameter.
If default instance is not specified, always use native protobuf format.
The sample code shows below:

[source,java]
--------------------------------------------------------------------------------------------------
from("direct:marshal")
    .unmarshal()
    .protobuf("org.apache.camel.dataformat.protobuf.generated.AddressBookProtos$Person", "json")
    .to("mock:reverse");
--------------------------------------------------------------------------------------------------

== Input data type
This dataformat supports marshaling input data either as protobuf `Message` type or `Map` data type. In case of input data as `Map` type, first it will try to retrieve the data as `Map` using built-in type converters, if it fails to
do so, it will fall back to retrieve it as proto `Message`.

== Output data type
As mentioned above, you can define the content type format to choose from JSON or native to serialize/deserialize data from/to. In addition, you can also obtain the data as `Map` and let this component to do the heavy lifting to parse the
data from proto `Message` to `Map`, you will just need to set the `contentTypeFormat` to *native* and explicitly define the data type `Map` when you obtain body of the exchange, e.g: `exchange.getMessage().getBody(Map.class)`.

== Protobuf overview

This quick overview of how to use Protobuf. For more detail see the
http://code.google.com/apis/protocolbuffers/docs/javatutorial.html[complete tutorial]

== Defining the proto format

The first step is to define the format for the body of your exchange.
This is defined in a .proto file as so:

*addressbook.proto*

[source,java]
------------------------------------------------------------
syntax = "proto2";

package org.apache.camel.component.protobuf;

option java_package = "org.apache.camel.component.protobuf";
option java_outer_classname = "AddressBookProtos";

message Person {
  required string name = 1;
  required int32 id = 2;
  optional string email = 3;

  enum PhoneType {
    MOBILE = 0;
    HOME = 1;
    WORK = 2;
  }

  message PhoneNumber {
    required string number = 1;
    optional PhoneType type = 2 [default = HOME];
  }

  repeated PhoneNumber phone = 4;
}

message AddressBook {
  repeated Person person = 1;
}
------------------------------------------------------------

== Generating Java classes

The Protobuf SDK provides a compiler which will generate the Java
classes for the format we defined in our .proto file.
If your operating system is supporting by https://www.xolstice.org/protobuf-maven-plugin[Protobuf Java code generator maven plugin],
you can automate protobuf Java code generating by adding following configurations to your pom.xml:

Insert operating system and CPU architecture detection extension inside **<build>** tag of the project pom.xml or set \${os.detected.classifier} parameter manually 
[source,xml]
-------------------------------------------------------------------------
<extensions>
  <extension>
    <groupId>kr.motd.maven</groupId>
    <artifactId>os-maven-plugin</artifactId>
    <version>1.4.1.Final</version>
  </extension>
</extensions>
-------------------------------------------------------------------------
Insert gRPC and protobuf Java code generator plugin **<plugins>** tag of the project pom.xml
[source,xml]
-------------------------------------------------------------------------
<plugin>
  <groupId>org.xolstice.maven.plugins</groupId>
  <artifactId>protobuf-maven-plugin</artifactId>
  <version>0.5.0</version>
  <extensions>true</extensions>
  <executions>
    <execution>
      <goals>
        <goal>test-compile</goal>
        <goal>compile</goal>
      </goals>
      <configuration>
        <protocArtifact>com.google.protobuf:protoc:${protobuf-version}:exe:${os.detected.classifier}</protocArtifact>
      </configuration>
    </execution>
  </executions>
</plugin>
-------------------------------------------------------------------------

You can also run the compiler for any additional supported languages you require manually.

`protoc --java_out=. ./proto/addressbook.proto`

This will generate a single Java class named AddressBookProtos which
contains inner classes for Person and AddressBook. Builders are also
implemented for you. The generated classes implement
com.google.protobuf.Message which is required by the serialization
mechanism. For this reason it important that only these classes are used
in the body of your exchanges. Camel will throw an exception on route
creation if you attempt to tell the Data Format
to use a class that does not implement com.google.protobuf.Message. Use
the generated builders to translate the data from any of your existing
domain classes.

== Java DSL

You can use create the ProtobufDataFormat instance and pass it to Camel
DataFormat marshal and unmarshal API like this.

[source,java]
-----------------------------------------------------------------------------------
   ProtobufDataFormat format = new ProtobufDataFormat(Person.getDefaultInstance());

   from("direct:in").marshal(format);
   from("direct:back").unmarshal(format).to("mock:reverse");
-----------------------------------------------------------------------------------

Or use the DSL protobuf() passing the unmarshal default instance or
default instance class name like this. However, if you have input data as `Map` type, you will need to **specify** the ProtobufDataFormat otherwise it will throw an error.

[source,java]
--------------------------------------------------------------------------------------------------
   // You don't need to specify the default instance for protobuf marshaling, but you will need in case your input data is a Map type
   from("direct:marshal").marshal().protobuf();
   from("direct:unmarshalA").unmarshal()
       .protobuf("org.apache.camel.dataformat.protobuf.generated.AddressBookProtos$Person")
       .to("mock:reverse");
                
   from("direct:unmarshalB").unmarshal().protobuf(Person.getDefaultInstance()).to("mock:reverse");
--------------------------------------------------------------------------------------------------

== Spring DSL

The following example shows how to use Protobuf to unmarshal using Spring
configuring the protobuf data type

[source,java]
----------------------------------------------------------------------------------------------------------
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="direct:start"/>
    <unmarshal>
      <protobuf instanceClass="org.apache.camel.dataformat.protobuf.generated.AddressBookProtos$Person" />
    </unmarshal>
    <to uri="mock:result"/>
  </route>
</camelContext>
----------------------------------------------------------------------------------------------------------

== Dependencies

To use Protobuf in your camel routes you need to add the a dependency on
*camel-protobuf* which implements this data format.

[source,xml]
-----------------------------------------
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-protobuf</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>
-----------------------------------------

include::camel-spring-boot::page$protobuf-starter.adoc[]
