Grape

Since Camel 2.16

Only producer is supported

Grape component allows you to fetch, load and manage additional jars when CamelContext is running. In practice with Camel Grape component you can add new components, data formats and beans to your CamelContext without the restart of the router.

Grape 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 as a type safe way of configuring endpoints.

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 Grape component supports 3 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.

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

patchesRepository (advanced)

Implementation of org.apache.camel.component.grape.PatchesRepository, by default: FilePatchesRepository.

PatchesRepository

Endpoint Options

The Grape endpoint is configured using URI syntax:

grape:defaultCoordinates

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

defaultCoordinates (producer)

Required Maven coordinates to use as default to grab if the message body is empty.

String

Query Parameters (1 parameters)

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.

boolean

Setting up class loader

Grape requires using Groovy class loader with the CamelContext. You can enable Groovy class loading on the existing Camel Context using the GrapeComponent#grapeCamelContext() method:

import static org.apache.camel.component.grape.GrapeComponent.grapeCamelContext;
...
CamelContext camelContext = grapeCamelContext(new DefaultCamelContext());

You can also set up the Groovy class loader used be Camel context by yourself:

camelContext.setApplicationContextClassLoader(new GroovyClassLoader(myClassLoader));

For example the following snippet loads Camel FTP component:

from("direct:loadCamelFTP").
  to("grape:org.apache.camel/camel-ftp/2.15.2");

You can also specify the Maven coordinates by sending them to the endpoint as the exchange body:

from("direct:loadCamelFTP").
  setBody().constant("org.apache.camel/camel-ftp/2.15.2").
  to("grape:defaultMavenCoordinates");

Adding the Grape component to the project

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

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

Default payload type

By default Camel Grape component operates on the String payloads:

producerTemplate.sendBody("grape:defaultMavenCoordinates", "org.apache.camel/camel-ftp/2.15.2");

But of course Camel build-in type conversion API can perform the automatic data type transformations for you. In the example below Camel automatically converts binary payload into the String:

producerTemplate.sendBody("grape:defaultMavenCoordinates", "org.apache.camel/camel-ftp/2.15.2".getBytes());

Headers

The following headers are recognized by the Grape component:

Header Java constant Endpoint type Value type Description

CamelGrapeCommand

GrapeConstants.GRAPE_COMMAND

Producer

org.apache.camel.component.grape.GrapeCommand

The command to be performed by the Grape endpoint. Default to grab.

Loading components at runtime

In order to load the new component at the router runtime, just grab the jar containing the given component:

ProducerTemplate template = camelContext.createProducerTemplate();
template.sendBody("grape:grape", "org.apache.camel/camel-stream/2.15.2");
template.sendBody("stream:out", "msg");

Loading processors bean at runtime

In order to load the new processor bean with your custom business login at the router runtime, just grab the jar containing the required bean:

ProducerTemplate template = camelContext.createProducerTemplate();
template.sendBody("grape:grape", "com.example/my-business-processors/1.0");
int productId = 1;
int price = template.requestBody("bean:com.example.PricingBean?method=currentProductPrice", productId, int.class)

Loading deployed jars after Camel context restart

After you download new jar, you usually would like to have it loaded by the Camel again after the restart of the CamelContext. It is certainly possible, as Grape component keeps track of the jar files you have installed. In order to load again the installed jars on the context startup, use the GrapeEndpoint.loadPatches() method in your route:

import static org.apache.camel.component.grape.GrapeEndpoint.loadPatches;

...
camelContext.addRoutes(
  new RouteBuilder() {
    @Override
    public void configure() throws Exception {
      loadPatches(camelContext);

      from("direct:loadCamelFTP").
        to("grape:org.apache.camel/camel-ftp/2.15.2");
    }
  });

Managing the installed jars

If you would like to check what jars have been installed into the given CamelContext, send message to the grape endpoint with the CamelGrapeCommand header set to GrapeCommand.listPatches:

from("netty-http:http://0.0.0.0:80/patches").
    setHeader(GrapeConstats.GRAPE_COMMAND, constant(CamelGrapeCommand.listPatches)).
    to("grape:list");

Connecting the to the route defined above using the HTTP client returns the list of the jars installed by Grape component:

$ curl http://my-router.com/patches
grape:org.apache.camel/camel-ftp/2.15.2
grape:org.apache.camel/camel-jms/2.15.2

If you would like to remove the installed jars, so these won’t be loaded again after the context restart, use the GrapeCommand.``clearPatches command:

from("netty-http:http://0.0.0.0:80/patches").
    setHeader(GrapeConstats.GRAPE_COMMAND, constant(CamelGrapeCommand.clearPatches)).
    setBody().constant("Installed patches have been deleted.");
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