Language

Since Camel 2.5

Only producer is supported

The Language component allows you to send Exchange to an endpoint which executes a script by any of the supported Languages in Camel.

By having a component to execute language scripts, it allows more dynamic routing capabilities. For example by using the Routing Slip or Dynamic Router EIPs you can send messages to language endpoints where the script is dynamic defined as well.

You only have to include additional Camel components if the language of choice mandates it, such as using Groovy or JavaScript languages.

URI format

language://languageName[:script][?options]

You can refer to an external resource for the script using same notation as supported by the other Languages in Camel

language://languageName:resource:scheme:location][?options]

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

The following two sections lists all the options, firstly for the component followed by the endpoint.

Component Options

The Language component supports 2 options, which are listed below.

Name Description Default Type

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

Endpoint Options

The Language endpoint is configured using URI syntax:

language:languageName:resourceUri

with the following path and query parameters:

Path Parameters (2 parameters)

Name Description Default Type

languageName (producer)

Required Sets the name of the language to use.

Enum values:

  • bean

  • constant

  • csimple

  • datasonnet

  • exchangeProperty

  • file

  • groovy

  • header

  • hl7terser

  • java

  • joor

  • jq

  • jsonpath

  • mvel

  • ognl

  • ref

  • simple

  • spel

  • sql

  • tokenize

  • xpath

  • xquery

  • xtokenize

String

resourceUri (producer)

Path to the resource, or a reference to lookup a bean in the Registry to use as the resource.

String

Query Parameters (8 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

binary (producer)

Whether the script is binary content or text content. By default the script is read as text content (eg java.lang.String).

false

boolean

cacheScript (producer)

Whether to cache the compiled script and reuse Notice reusing the script can cause side effects from processing one Camel org.apache.camel.Exchange to the next org.apache.camel.Exchange.

false

boolean

contentCache (producer)

Sets whether to use resource content cache or not.

true

boolean

resultType (producer)

Sets the class of the result type (type from output).

String

script (producer)

Sets the script to execute.

String

transform (producer)

Whether or not the result of the script should be used as message body. This options is default true.

true

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

Message Headers

The Language component supports 1 message header(s), which is/are listed below:

Name Description Default Type

CamelLanguageScript (producer)

Constant: LANGUAGE_SCRIPT

The script to execute provided in the header. Takes precedence over script configured on the endpoint.

String or Expression

Examples

For example, you can use the Simple language as Message Translator EIP:

from("direct:hello")
    .to("language:simple:Hello ${body}")

In case you want to convert the message body type you can do this as well (however it is better to use Convert Body To):

from("direct:toString")
    .to("language:simple:${bodyAs(String.class)}")

You can also use the Groovy language, such as this example where the input message will be multiplied with 2:

from("direct:double")
    .to("language:groovy:${body} * 2}")

You can also provide the script as a header as shown below. Here we use XPath language to extract the text from the <foo> tag.

Object out = producer.requestBodyAndHeader("language:xpath", "<foo>Hello World</foo>", Exchange.LANGUAGE_SCRIPT, "/foo/text()");
assertEquals("Hello World", out);

Loading scripts from resources

You can specify a resource uri for a script to load in either the endpoint uri, or in the Exchange.LANGUAGE_SCRIPT header. The uri must start with one of the following schemes: file:, classpath:, or http:

from("direct:start")
        // load the script from the classpath
        .to("language:simple:resource:classpath:org/apache/camel/component/language/mysimplescript.txt")
        .to("mock:result");

By default, the script is loaded once and cached. However, you can disable the contentCache option and have the script loaded on each evaluation. For example if the file myscript.txt is changed on disk, then the updated script is used:

from("direct:start")
        // the script will be loaded on each message, as we disabled cache
        .to("language:simple:myscript.txt?contentCache=false")
        .to("mock:result");

You can also refer to the script as a resource similar to how all the other Languages in Camel functions, by prefixing with resource: as shown below:

from("direct:start")
    .to("language:constant:resource:classpath:org/apache/camel/component/language/hello.txt")
    .to("mock:result");