File Expression Language

Available as of Camel 1.5

File language is now merged with Simple language
From Camel 2.2 onwards, the file language is now merged with Simple language which means you can use all the file syntax directly within the simple language.

The File Expression Language is an extension to the Simple language, adding file related capabilities. These capabilities are related to common use cases working with file path and names. The goal is to allow expressions to be used with the File and FTP components for setting dynamic file patterns for both consumer and producer.

Syntax

This language is an extension to the Simple language so the Simple syntax applies also. So the table below only lists the additional.
As opposed to Simple language File Language also supports Constant expressions so you can enter a fixed filename.

All the file tokens use the same expression name as the method on the java.io.File object, for instance file:absolute refers to the java.io.File.getAbsolute() method. Notice that not all expressions are supported by the current Exchange. For instance the FTP component supports some of the options, where as the File component supports all of them.

Expression Type File Consumer File Producer FTP Consumer FTP Producer Description
file:name String yes no yes no refers to the file name (is relative to the starting directory, see note below)
file:name.ext String yes no yes no Camel 2.3: refers to the file extension only
file:name.noext String yes no yes no refers to the file name with no extension (is relative to the starting directory, see note below)
file:onlyname String yes no yes no Camel 2.0: refers to the file name only with no leading paths.
file:onlyname.noext String yes no yes no Camel 2.0: refers to the file name only with no extension and with no leading paths.
file:ext String yes no yes no Camel 1.6.1/Camel 2.0: refers to the file extension only
file:parent String yes no yes no refers to the file parent
file:path String yes no yes no refers to the file path
file:absolute Boolean yes no no no Camel 2.0: refers to whether the file is regarded as absolute or relative
file:absolute.path String yes no no no refers to the absolute file path
file:length Long yes no yes no refers to the file length returned as a Long type
file:size Long yes no yes no Camel 2.5: refers to the file length returned as a Long type
file:modified Date yes no yes no Camel 2.0: refers to the file last modified returned as a Date type
date:command:pattern String yes yes yes yes for date formatting using the java.text.SimepleDataFormat patterns. Is an extension to the Simple language. Additional command is: file (consumers only) for the last modified timestamp of the file. Notice: all the commands from the Simple language can also be used.

File token example

Relative paths

We have a java.io.File handle for the file hello.txt in the following relative directory: .\filelanguage\test. And we configure our endpoint to use this starting directory .\filelanguage. The file tokens will return as:

Expression Returns
file:name test\hello.txt
file:name.ext txt
file:name.noext test\hello
file:onlyname hello.txt
file:onlyname.noext hello
file:ext txt
file:parent filelanguage\test
file:path filelanguage\test\hello.txt
file:absolute false
file:absolute.path \workspace\camel\camel-core\target\filelanguage\test\hello.txt

Absolute paths

We have a java.io.File handle for the file hello.txt in the following absolute directory: \workspace\camel\camel-core\target\filelanguage\test. And we configure out endpoint to use the absolute starting directory \workspace\camel\camel-core\target\filelanguage. The file tokens will return as:

Expression Returns
file:name test\hello.txt
file:name.ext txt
file:name.noext test\hello
file:onlyname hello.txt
file:onlyname.noext hello
file:ext txt
file:parent \workspace\camel\camel-core\target\filelanguage\test
file:path \workspace\camel\camel-core\target\filelanguage\test\hello.txt
file:absolute true
file:absolute.path \workspace\camel\camel-core\target\filelanguage\test\hello.txt

Samples

You can enter a fixed Constant expression such as myfile.txt:

fileName="myfile.txt"

Lets assume we use the file consumer to read files and want to move the read files to backup folder with the current date as a sub folder. This can be archieved using an expression like:

fileName="backup/${date:now:yyyyMMdd}/${file:name.noext}.bak"

relative folder names are also supported so suppose the backup folder should be a sibling folder then you can append .. as:

fileName="../backup/${date:now:yyyyMMdd}/${file:name.noext}.bak"

As this is an extension to the Simple language we have access to all the goodies from this language also, so in this use case we want to use the in.header.type as a parameter in the dynamic expression:

fileName="../backup/${date:now:yyyyMMdd}/type-${in.header.type}/backup-of-${file:name.noext}.bak"

If you have a custom Date you want to use in the expression then Camel supports retrieving dates from the message header.

fileName="orders/order-${in.header.customerId}-${date:in.header.orderDate:yyyyMMdd}.xml"

And finally we can also use a bean expression to invoke a POJO class that generates some String output (or convertible to String) to be used:

fileName="uniquefile-${bean:myguidgenerator.generateid}.txt"

And of course all this can be combined in one expression where you can use the File Language, Simple and the Bean language in one combined expression. This is pretty powerful for those common file path patterns.

Using Spring PropertyPlaceholderConfigurer together with the File component

In Camel you can use the File Language directly from the Simple language which makes a Content Based Router easier to do in Spring XML, where we can route based on file extensions as shown below:

  <from uri="file://input/orders"/>
     <choice>
       <when>
           <simple>${file:ext} == 'txt'</simple>
           <to uri="bean:orderService?method=handleTextFiles"/>
       </when>
       <when>
           <simple>${file:ext} == 'xml'</simple>
           <to uri="bean:orderService?method=handleXmlFiles"/>
       </when>
       <otherwise>
           <to uri="bean:orderService?method=handleOtherFiles"/>
       </otherwise>
    </choice>

If you use the fileName option on the File endpoint to set a dynamic filename using the File Language then make sure you
use the alternative syntax (available from Camel 2.5 onwards) to avoid clashing with Springs PropertyPlaceholderConfigurer.

bundle-context.xml
<bean id="propertyPlaceholder" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location" value="classpath:bundle-context.cfg" />
</bean>

<bean id="sampleRoute" class="SampleRoute">
    <property name="fromEndpoint" value="${fromEndpoint}" />
    <property name="toEndpoint" value="${toEndpoint}" />
</bean>
bundle-context.cfg
fromEndpoint=activemq:queue:test
toEndpoint=file://fileRoute/out?fileName=test-$simple{date:now:yyyyMMdd}.txt

Notice how we use the $simple{ } syntax in the toEndpoint above.
If you don't do this, there is a clash and Spring will throw an exception like

org.springframework.beans.factory.BeanDefinitionStoreException:
Invalid bean definition with name 'sampleRoute' defined in class path resource [bundle-context.xml]:
Could not resolve placeholder 'date:now:yyyyMMdd'

Dependencies

The File language is part of camel-core.
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