[[Transformer-Transformer]]
== Transformer

*Available as of Camel 2.19*

Transformer performs declarative transformation of the message according
to the declared `Input Type` and/or `Output Type` on a route definition which declares
the expected message type.
The default camel Message implements `DataTypeAware`, which allows to hold the message type
represented by `DataType`.
If the input type and/or output type is declared by `Input Type` and/or `Output Type` in the route
definition, and it is different from actual message type at runtime, camel internal processor
looks for a Transformer which transforms from the current message type to the expected message
type and apply. Once transform succeed or message is already in expected type, then the message
 data type is updated.



[[Transformer-DataTypeFormat]]
=== Data type format
[source]
----
scheme:name
----
where *scheme* is the type of data model like `java`, `xml` or `json`, and *name* is the individual
data type name. If you only specify *scheme* then it hits all the data types which has that scheme like
a wildcard.



[[Transformer-SupportedTransformers]]
=== Supported Transformers

|===
| Transformer | Description

| Data Format Transformer | Transform with using Data Format

| Endpoint Transformer | Transform with using Endpoint

| Custom Transformer | Transform with using custom transformer class. Transformer must be a subclass of `org.apache.camel.spi.Transformer`
|===



[[Transformer-CommonOptions]]
==== Common Options
All transformers have following common options to specify which data type is supported by the transformer. `scheme` or both of `fromType` and `toType` must be specified.
|===
| Name | Description

| scheme | Type of data model like `xml` or `json`. For example if `xml` is specified, the transformer is applied for all java -&gt; xml and xml -&gt; java transformation.
 
| fromType | <<Transformer-DataTypeFormat,Data type>> to transform from.
 
| toType | <<Transformer-DataTypeFormat,Data type>> to transform to.
|===



[[Transformer-DataFormat]]
==== DataFormat Transformer Options
|===
| Name | Description

| type | Data Format type

| ref | reference to the Data Format ID
|===

Here is an example to specify bindy DataFormat type:

Java DSL:
[source,java]
----
BindyDataFormat bindy = new BindyDataFormat();
bindy.setType(BindyType.Csv);
bindy.setClassType(com.example.Order.class);
transformer()
    .fromType(com.example.Order.class)
    .toType("csv:CSVOrder")
    .withDataFormat(bindy);
----

XML DSL:
[source,xml]
----
<dataFormatTransformer fromType="java:com.example.Order" toType="csv:CSVOrder">
    <bindy id="csvdf" type="Csv" classType="com.example.Order"/>
</dataFormatTransformer>
----


[[Transformer-Endpoint]]
=== Endpoint Transformer Options
|===
| Name | Description

| ref | Reference to the Endpoint ID

| uri | Endpoint URI
|===

Here is an example to specify endpoint URI in Java DSL:

[source,java]
----
transformer()
    .fromType("xml")
    .toType("json")
    .withUri("dozer:myDozer?mappingFile=myMapping.xml...");
----

And here is an example to specify endpoint ref in XML DSL:
[source,xml]
----
<endpointTransformer ref="myDozerEndpoint" fromType="xml" toType="json"/>
----

[[Transformer-Custom]]
=== Custom Transformer Options
Note that Transformer must be a subclass of `org.apache.camel.spi.Transformer`
|===
| Name | Description

| ref | Reference to the custom Transformer bean ID

| className | Fully qualified class name of the custom Transformer class
|===

Here is an example to specify custom Transformer class:

Java DSL:
[source,java]
----
transformer()
    .fromType("xml")
    .toType("json")
    .withJava(com.example.MyCustomTransformer.class);
----

XML DSL:
[source,xml]
----
<customTransformer className="com.example.MyCustomTransformer" fromType="xml" toType="json"/>
----



[[Transformer-Examples]]
=== Examples

For example to declare the Endpoint Transformer which uses
xslt component to transform from `xml:ABCOrder` to `xml:XYZOrder`, we can do as follows:

Java DSL:
[source,java]
-------------------------------------------------------------------
transformer()
    .fromType("xml:ABCOrder")
    .toType("xml:XYZOrder")
    .withUri("xslt:transform.xsl");
-------------------------------------------------------------------

XML DSL:
[source,xml]
-------------------------------------------------------------------
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <transformers>
        <endpointTransformer uri="xslt:transform.xsl" fromType="xml:ABCOrder" toType="xml:XYZOrder"/>
    </transformers>
    ....
</camelContext>
-------------------------------------------------------------------

If you have following route definition, above transformer will be applied when `direct:abc` endpoint sends the message to `direct:xyz`:

Java DSL:
[source,java]
-------------------------------------------------------------------
from("direct:abc")
    .inputType("xml:ABCOrder")
    .to("direct:xyz");
from("direct:xyz")
    .inputType("xml:XYZOrder")
    .to("somewhere:else");
-------------------------------------------------------------------

XML DSL:
[source,xml]
-------------------------------------------------------------------
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:abc"/>
        <inputType urn="xml:ABCOrder"/>
        <to uri="direct:xyz"/>
    </route>
    <route>
        <from uri="direct:xyz"/>
        <inputType urn="xml:XYZOrder"/>
        <to uri="somewhere:else"/>
    </route>
</camelContext>
-------------------------------------------------------------------
