Shell

Since Camel 4.21

Only consumer is supported

The Shell component provides an interactive terminal prompt using JLine. It allows Camel routes to read user input line-by-line (consumer) and write output back to the terminal.

Each line typed by the user becomes the body of a Camel Exchange that is routed normally. The response (exchange body after routing) is printed back to the terminal. Typing exit or sending EOF (Ctrl+D) shuts down the Camel context.

Dependencies

Maven users need to add the following dependency to their pom.xml:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-shell</artifactId>
    <version>${camel-version}</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

shell:prompt[?options]

Where prompt is the label displayed before the > cursor. For example, shell:myapp displays `myapp> `.

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 Shell component supports 4 options, which are listed below.

Name Description Default Type

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

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

bannerResource (advanced)

Classpath resource path to a custom banner text file.

camel-shell-banner.txt

String

showBanner (advanced)

Whether to print the Camel banner on startup.

true

boolean

Endpoint Options

The Shell endpoint is configured using URI syntax:

shell:prompt

With the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

prompt (consumer)

Required Shell prompt.

String

Query Parameters (4 parameters)

Name Description Default Type

color (consumer)

Prompt color: black, red, green, yellow, blue, magenta, cyan, white.

cyan

String

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

ExchangePattern

Usage

Consumer

The shell consumer starts an interactive terminal session. Each line typed by the user is set as the body of a new Exchange and sent through the route. The route result body is then printed back to the terminal.

Errors occurring in the route are displayed in red.

Examples

Chat with an LLM

from("shell:myapp?color=green")
    .to("huggingface:chat?modelId=Qwen/Qwen2.5-3B-Instruct");

Call a REST API

from("shell:myapp")
    .toD("http://api.example.com/chat?query=${body}");

Route to JMS (fire-and-forget)

from("shell:myapp")
    .setProperty("input", body())
    .to(ExchangePattern.InOnly, "activemq:queue:myqueue")
    .setBody(simple("Sent '${exchangeProperty.input}' to queue"));
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