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Chapter 54. 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.
54.1. Dependencies
When using jslt with Red Hat build of Camel 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> </dependency>
54.2. 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).
54.3. Configuring Options
Camel components are configured on two levels:
- Component level
- Endpoint level
54.3.1. Component Level Options
The component level is the highest level. The configurations you define at this level are inherited by all the endpoints. For example, a component can have security settings, credentials for authentication, urls for network connection, and so on.
Since components typically have pre-configured defaults for the most common cases, you may need to only configure a few component options, or maybe none at all.
You can configure components with Component DSL in a configuration file (application.properties|yaml), or directly with Java code.
54.3.2. Endpoint Level Options
At the Endpoint level you have many options, which you can use to configure what you want the endpoint to do. The options are categorized according to whether the endpoint is used as a consumer (from) or as a producer (to) or used for both.
You can configure endpoints directly in the endpoint URI as path and query parameters. You can also use Endpoint DSL and DataFormat DSL as type safe ways of configuring endpoints and data formats in Java.
When configuring options, use Property Placeholders for urls, port numbers, sensitive information, and other settings.
Placeholders allows you to externalize the configuration from your code, giving you more flexible and reusable code.
54.4. Component 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 |
| autowiredEnabled (advanced) | Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. | true | 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 |
54.4.1. Endpoint Options
The JSLT endpoint is configured using URI syntax:
jslt:resourceUri
with the following path and query parameters:
54.4.1.1. Path Parameters (1 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| resourceUri (producer) | 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 |
54.4.1.2. 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 |
| mapBigDecimalAsFloats (producer) | If true, the mapper will use the USE_BIG_DECIMAL_FOR_FLOATS in serialization features. | false | boolean |
| objectMapper (producer) | Setting a custom JSON Object Mapper to be used. | ObjectMapper | |
| prettyPrint (common) | If true, JSON in output message is pretty printed. | false | boolean |
| lazyStartProducer (producer (advanced)) | 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 |
54.5. Message Headers
The JSLT component supports 2 message header(s), which is/are listed below:
| Name | Description | Default | Type |
|---|---|---|---|
| CamelJsltString (producer) Constant: HEADER_JSLT_STRING | The JSLT Template as String. | String | |
| CamelJsltResourceUri (producer) Constant: HEADER_JSLT_RESOURCE_URI | The resource URI. | String |
54.6. 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 |
| exchange.properties |
The Exchange properties as a json object. |
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
}54.7. Samples
The sample example is as given below.
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?allowTemplateFromHeader=true");Or send whole jslt expression via header: (suitable for querying)
from("direct:in").
setHeader("CamelJsltString").constant(".published").
to("jslt:dummy?allowTemplateFromHeader=true");Passing exchange properties to the jslt expression can be done like this
from("direct:in").
to("jslt:com/acme/MyResponse.json?allowContextMapAll=true");54.8. Spring Boot Auto-Configuration
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.autowired-enabled | Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. | true | 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 |
