Red Hat SummitChapter 77. Language
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.
This component is provided out of the box in camel-core and hence no additional JARs is needed. You only have to include additional Camel components if the language of choice mandates it, such as using Groovy or JavaScript languages.
77.1. Dependencies
When using language 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-language-starter</artifactId> </dependency>
<dependency>
<groupId>org.apache.camel.springboot</groupId>
<artifactId>camel-language-starter</artifactId>
</dependency>77.2. URI format
language://languageName[:script][?options]
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]
language://languageName:resource:scheme:location][?options]77.3. Configuring Options
Camel components are configured on two levels:
- Component level
- Endpoint level
77.3.1. 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.
77.3.2. 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.
77.4. 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 |
77.5. Endpoint Options
The Language endpoint is configured using URI syntax:
language:languageName:resourceUri
language:languageName:resourceUriwith the following path and query parameters:
77.5.1. Path Parameters (2 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| languageName (producer) | Required Sets the name of the language to use. Enum values:
| String | |
| resourceUri (producer) | Path to the resource, or a reference to lookup a bean in the Registry to use as the resource. | String |
77.5.2. 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 |
| 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 |
| 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 |
| 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 |
77.6. Message Headers
The following message headers can be used to affect the behavior of the component
| Header | Description |
|---|---|
|
| The script to execute provided in the header. Takes precedence over script configured on the endpoint. |
77.7. Examples
For example you can use the Simple language to Message Translator a message.
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);
Object out = producer.requestBodyAndHeader("language:xpath", "<foo>Hello World</foo>", Exchange.LANGUAGE_SCRIPT, "/foo/text()");
assertEquals("Hello World", out);77.8. 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:
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:
You can refer to the resource similar to the other Languages in Camel by prefixing with "resource:" as shown below.
77.9. Spring Boot Auto-Configuration
The component supports 3 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| camel.component.language.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.language.enabled | Whether to enable auto configuration of the language component. This is enabled by default. | Boolean | |
| camel.component.language.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 |
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