How to create and announce a Camel release.

File Expression Language

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File Expression Language

File language is now merged with Simple language

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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.

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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.

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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.

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Syntax

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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.

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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.

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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	refers to the file name only with no leading paths.
file:onlyname.noext	String	yes	no	yes	no	refers to the file name only with no extension and with no leading paths.
file:ext	String	yes	no	yes	no	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	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	efers 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.

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File token example

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Relative paths

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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:

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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

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Absolute paths

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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:

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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

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Samples

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

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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:

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

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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:

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

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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:

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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.

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Using Spring PropertyPlaceholderConfigurer together with the File component

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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:

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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.

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bundle-context.xml

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bundle-context.cfg

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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

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Dependencies

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The File language is part of camel-core.

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Unmarshalling a CSV message into a Java List

File Expression Language

File Expression Language

Syntax

File token example

Relative paths

Absolute paths

Samples

Using Spring PropertyPlaceholderConfigurer together with the File component

Dependencies

Dependencies

How to create and announce a Camel release.

Maven 2 Setup

How to create and announce a Camel release.

Maven 2 Setup