Package com.zfabrik.impl.components.processing

Class Jexl3ComponentDescriptorProcessor

java.lang.Object

com.zfabrik.impl.components.processing.Jexl3ComponentDescriptorProcessor

All Implemented Interfaces:

com.zfabrik.components.provider.IComponentDescriptorProcessor

public class Jexl3ComponentDescriptorProcessor
extends java.lang.Object
implements com.zfabrik.components.provider.IComponentDescriptorProcessor

A jexl3 component descriptor processor. This processor is based on the Apache Commons JEXL library version 3.0 (see https://commons.apache.org/proper/commons-jexl).

All values of properties tagged as of JEXL3 processing style in the original component descriptor source will be considered JEXL expressions. If evaluating to a non-null value, the expression evaluation result will be set as resulting property value of the same property name. If the expression evaluates to null, the corresponding property will not be set.

The following implicit variables are made available by this processor:

Variable name	Definition	Example
system	System.getProperties()	`user dir is ${system["user.dir"]}`
env	System.getenv()	"JAVA_HOME is ${env.JAVA_HOME}"
this	The actual property set in its evaluated form. This may be used to resolve properties that are again computed by some processor. Note that a max evaluation depth of 50 is enforced when resolving properties defined in the property set.	this['com.zfabrik.component.type']
components	IComponentsManager.INSTANCE	components.getComponent("mymodule/mycomponent").getProperty("myProp")

Using the this variable, re-use of definitions within a single descriptor is possible. For example, assuming some other processor ext is involved, a property set

 hostName\:JEXl3=env.hostName
 database\:ext=_THE_DB_
 ds.prop.url\:JEXl3=`jdbc:derby://${this.hostName}/${this.database};create=true`
 

would be evaluated resolving across processors.

Note that a JEXL expression does not necessarily evaluate to a string object. Neither is the input property value to be processed considered a JEXL string. For example, the expression

 `Hallo this is ${system["user.name"]}`
 

does indeed evaluate to a string. As does

 "Hallo this is ${system[\"user.name\"]}"
 

(without processing the ${} expression) and more advanced

 system["os.name"].startsWith("Linux")? "We are running on a Linux OS" : "We are running on something else"
 

but not

 500+10
 

which is indeed an integer.

See also https://commons.apache.org/proper/commons-jexl/reference/syntax.html for more syntax information.

Author:

hb

Field Summary

Fields

Modifier and Type	Field	Description
static java.lang.String	JEXL3_STYLE	Style processed by this processor

Fields inherited from interface com.zfabrik.components.provider.IComponentDescriptorProcessor

EXTENSION_POINT, STYLE_PROCESSED

Constructor Summary

Constructors

Constructor	Description
Jexl3ComponentDescriptorProcessor()

Method Summary

Modifier and Type	Method	Description
com.zfabrik.components.provider.props.Evaluator	createEvaluator()	Provide an evaluator instance.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

JEXL3_STYLE

public static final java.lang.String JEXL3_STYLE

Style processed by this processor

See Also:

Constant Field Values

Constructor Detail

Jexl3ComponentDescriptorProcessor

public Jexl3ComponentDescriptorProcessor()

Method Detail

createEvaluator

public com.zfabrik.components.provider.props.Evaluator createEvaluator()

Description copied from interface: com.zfabrik.components.provider.IComponentDescriptorProcessor

Provide an evaluator instance. The evaluator will be used during the processing of on component descriptor property map.

Specified by:

createEvaluator in interface com.zfabrik.components.provider.IComponentDescriptorProcessor