Chapter 320. Thrift DataFormat

Available as of Camel version 2.20

Camel provides a Data Format to serialize between Java and the Apache Thrift . The project’s site details why you may wish to https://thrift.apache.org/. Apache Thrift is language-neutral and platform-neutral, so messages produced by your Camel routes may be consumed by other language implementations.

Apache Thrift Implementation

320.1. Thrift Options

The Thrift dataformat supports 3 options which are listed below.

NameDefaultJava TypeDescription

instanceClass

 

String

Name of class to use when unarmshalling

contentTypeFormat

binary

String

Defines a content type format in which thrift message will be serialized/deserialized from(to) the Java been. The format can either be native or json for either native binary thrift, json or simple json fields representation. The default value is binary.

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.

320.2. Content type format

It’s possible to parse JSON message to convert it to the Thrift format and unparse it back using native util converter. To use this option, set contentTypeFormat value to 'json' or call thrift with second parameter. If default instance is not specified, always use native binary Thrift format. The simple JSON format is write-only (marshal) and produces a simple output format suitable for parsing by scripting languages. The sample code shows below:

from("direct:marshal")
    .unmarshal()
    .thrift("org.apache.camel.dataformat.thrift.generated.Work", "json")
    .to("mock:reverse");

320.3. Thrift overview

This quick overview of how to use Thrift. For more detail see the complete tutorial

320.4. Defining the thrift format

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

tutorial.thrift

namespace java org.apache.camel.dataformat.thrift.generated

enum Operation {
  ADD = 1,
  SUBTRACT = 2,
  MULTIPLY = 3,
  DIVIDE = 4
}

struct Work {
  1: i32 num1 = 0,
  2: i32 num2,
  3: Operation op,
  4: optional string comment,
}

320.5. Generating Java classes

The Apache Thrift provides a compiler which will generate the Java classes for the format we defined in our .thrift file.

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

thrift -r --gen java -out ../java/ ./tutorial-dataformat.thrift

This will generate separate Java class for each type defined in .thrift file, i.e. struct or enum. The generated classes implement org.apache.thrift.TBase 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 org.apache.thrift.TBase.

320.6. Java DSL

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

   ThriftDataFormat format = new ThriftDataFormat(new Work());

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

Or use the DSL thrift() passing the unmarshal default instance or default instance class name like this.

   // You don't need to specify the default instance for the thrift marshaling
   from("direct:marshal").marshal().thrift();
   from("direct:unmarshalA").unmarshal()
       .thrift("org.apache.camel.dataformat.thrift.generated.Work")
       .to("mock:reverse");

   from("direct:unmarshalB").unmarshal().thrift(new Work()).to("mock:reverse");

320.7. Spring DSL

The following example shows how to use Thrift to unmarshal using Spring configuring the thrift data type

<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="direct:start"/>
    <unmarshal>
      <thrift instanceClass="org.apache.camel.dataformat.thrift.generated.Work" />
    </unmarshal>
    <to uri="mock:result"/>
  </route>
</camelContext>

320.8. Dependencies

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

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