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 the 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

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

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.

You can configure components using:

  • the Component DSL.

  • in a configuration file (application.properties, *.yaml files, etc).

  • directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or 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.

Property placeholders provide a few benefits:

  • They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.

  • They allow externalizing the configuration from the code.

  • They help the code to become more flexible and reusable.

The following two sections list 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.

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

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

Name Description Default Type

CamelGrapeCommand (producer)

Constant: GRAPE_COMMAND

The command to be performed by the Grape endpoint.

Enum values:

  • grab

  • listPatches

  • clearPatches

grab

GrapeCommand

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 by the 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, the Camel Grape component operates on the String payloads:

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

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());

Loading components at runtime

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

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. 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 a 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 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.");

Spring Boot Auto-Configuration

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

The component supports 4 options, which are listed below.

Name Description Default Type

camel.component.grape.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.grape.enabled

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

Boolean

camel.component.grape.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.grape.patches-repository

Implementation of org.apache.camel.component.grape.PatchesRepository, by default: FilePatchesRepository. The option is a org.apache.camel.component.grape.PatchesRepository type.

PatchesRepository
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