JSLT

Since Camel 3.1

Only producer is supported

The Jslt component allows you to process a JSON messages using an JSLT expression. This can be ideal when doing JSON to JSON transformation or querying data.

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

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

URI format

jslt:specName[?options]

Where specName is the classpath-local URI of the specification to invoke; or the complete URL of the remote specification (eg: file://folder/myfile.vm).

You can append query options to the URI in the following format, ?option=value&option=value&…​

Options

The JSLT component supports 5 options, which are listed below.

Name Description Default Type

allowTemplateFromHeader (producer)

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

boolean

lazyStartProducer (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

basicPropertyBinding (advanced)

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

false

boolean

functions (advanced)

JSLT can be extended by plugging in functions written in Java.

Collection

objectFilter (advanced)

JSLT can be extended by plugging in a custom jslt object filter

JsonFilter

The JSLT endpoint is configured using URI syntax:

jslt:resourceUri

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

resourceUri

Required Path to the resource. You can prefix with: classpath, file, http, ref, or bean. classpath, file and http loads the resource using these protocols (classpath is default). ref will lookup the resource in the registry. bean will call a method on a bean to be used as the resource. For bean you can specify the method name after dot, eg bean:myBean.myMethod.

String

Query Parameters (7 parameters):

Name Description Default Type

allowContextMapAll (producer)

Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API.

false

boolean

allowTemplateFromHeader (producer)

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

boolean

contentCache (producer)

Sets whether to use resource content cache or not

false

boolean

prettyPrint (common)

If true, JSON in output message is pretty printed.

false

boolean

lazyStartProducer (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

basicPropertyBinding (advanced)

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

false

boolean

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

Passing values to JSLT

Camel can supply exchange information as variables when applying a JSLT expression on the body. The available variables from the Exchange are:

name value

headers

The headers of the In message as a json object

exchange.properties

The Exchange properties as a json object. exchange is the name of the variable and properties is the path to the exchange properties. Available if allowContextMapAll option is true.

All the values that cannot be converted to json with Jackson are denied and will not be available in the jslt expression.

For example, the header named "type" and the exchange property "instance" can be accessed like

{
  "type": $headers.type,
  "instance": $exchange.properties.instance
}

Samples

For example you could use something like

from("activemq:My.Queue").
  to("jslt:com/acme/MyResponse.json");

And a file based resource:

from("activemq:My.Queue").
  to("jslt:file://myfolder/MyResponse.json?contentCache=true").
  to("activemq:Another.Queue");

You can also specify which JSLT expression the component should use dynamically via a header, so for example:

from("direct:in").
  setHeader("CamelJsltResourceUri").constant("path/to/my/spec.json").
  to("jslt:dummy");

Or send whole jslt expression via header: (suitable for querying)

from("direct:in").
  setHeader("CamelJsltResourceUri").constant(".published").
  to("jslt:dummy");

Passing exchange properties to the jslt expression can be done like this

from("direct:in").
  to("jslt:com/acme/MyResponse.json?allowContextMapAll=true");

Spring Boot Auto-Configuration

When using jslt with 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-jslt-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 6 options, which are listed below.

Name Description Default Type

camel.component.jslt.allow-template-from-header

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

Boolean

camel.component.jslt.enabled

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

Boolean

camel.component.jslt.functions

JSLT can be extended by plugging in functions written in Java.

Collection

camel.component.jslt.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.component.jslt.object-filter

JSLT can be extended by plugging in a custom jslt object filter. The option is a com.schibsted.spt.data.jslt.filters.JsonFilter type.

JsonFilter

camel.component.jslt.basic-property-binding

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

false

Boolean