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Chapter 17. Groovy
Overview
Groovy is a Java-based scripting language that allows quick parsing of object. The Groovy support is part of the
camel-groovy module.
Adding the script module
To use Groovy in your routes you need to add a dependency on
camel-groovy to your project as shown in Example 17.1, “Adding the camel-groovy dependency”.
Example 17.1. Adding the camel-groovy dependency
<!-- Maven POM File -->
<properties>
<camel-version>2.17.0.redhat-630xxx</camel-version>
...
</properties>
<dependencies>
...
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-groovy</artifactId>
<version>${camel-version}</version>
</dependency>
</dependencies>Static import
To use the
groovy() static method in your application code, include the following import statement in your Java source files:
import static org.apache.camel.builder.script.ScriptBuilder.*;
Built-in attributes
Table 17.1, “Groovy attributes” lists the built-in attributes that are accessible when using Groovy.
| Attribute | Type | Value |
|---|---|---|
context | org.apache.camel.CamelContext | The Camel Context |
exchange | org.apache.camel.Exchange | The current Exchange |
request | org.apache.camel.Message | The IN message |
response | org.apache.camel.Message | The OUT message |
properties | org.apache.camel.builder.script.PropertiesFunction | Function with a resolve method to make it easier to use the properties component inside scripts. |
The attributes all set at
ENGINE_SCOPE.
Example
Example 17.2, “Routes using Groovy” shows two routes that use Groovy scripts.
Example 17.2. Routes using Groovy
<camelContext>
<route>
<from uri="direct:items" />
<filter>
<language language="groovy">request.lineItems.any { i -> i.value > 100 }</language>
<to uri="mock:mock1" />
</filter>
</route>
<route>
<from uri="direct:in"/>
<setHeader headerName="firstName">
<language language="groovy">$user.firstName $user.lastName</language>
</setHeader>
<to uri="seda:users"/>
</route>
</camelContext>Using the properties component
To access a property value from the properties component, invoke the
resolve method on the built-in properties attribute, as follows:
.setHeader("myHeader").groovy("properties.resolve(PropKey)")
Where PropKey is the key of the property you want to resolve, where the key value is of
String type.
For more details about the properties component, see Properties in the Apache Camel Component Reference Guide.
Customizing Groovy Shell
Sometimes, you might need to use the custom
GroovyShell instance, in your Groovy expressions. To provide custom GroovyShell, add an implementation of the org.apache.camel.language.groovy.GroovyShellFactory SPI interface to your Camel registry.
For example, when you add the following bean to your Spring context, Apache Camel will use the custom
GroovyShell instance that includes the custom static imports, instead of the default one.
public class CustomGroovyShellFactory implements GroovyShellFactory {
public GroovyShell createGroovyShell(Exchange exchange) {
ImportCustomizer importCustomizer = new ImportCustomizer();
importCustomizer.addStaticStars("com.example.Utils");
CompilerConfiguration configuration = new CompilerConfiguration();
configuration.addCompilationCustomizers(importCustomizer);
return new GroovyShell(configuration);
}
}
