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Chapter 21. File2

The File component provides access to file systems, allowing files to be processed by any other Apache Camel Components or messages from other components to be saved to disk.

file:directoryName[?options]

or

file://directoryName[?options]

Where directoryName represents the underlying file directory.

You can append query options to the URI in the following format, ?option=value&option=value&...

[Tip]Only directories

Apache Camel 2.0 only support endpoints configured with a starting directory. So the directoryName must be a directory. If you want to consume a single file only, you can use the fileName option, e.g. by setting fileName=thefilename. Also, the starting directory must not contain dynamic expressions with ${ } placeholders. Again use the fileName option to specify the dynamic part of the filename.

In Apache Camel 1.x you could also configure a file and this caused more harm than good as it could lead to confusing situations.

[Warning]Avoid reading files currently being written by another application

Beware the JDK File IO API is a bit limited in detecting whether another application is currently writing/copying a file. And the implementation can be different depending on OS platform as well. This could lead to that Apache Camel thinks the file is not locked by another process and start consuming it. Therefore you have to do you own investigation as to what suits your environment. To help with this, Apache Camel provides different readLock options that you can use. See also the section Consuming files from folders where others drop files directly.

Name Default Value Description
autoCreate true Automatically create missing directories in the file's pathname. For the file consumer, that means creating the starting directory. For the file producer, it means the directory to where the files should be written.
bufferSize 128kb Write buffer sized in bytes.
fileName null Use Expression such as File Language to dynamically set the filename. For consumers, it's used as a filename filter. For producers, it's used to evaluate the filename to write. If an expression is set, it take precedence over the CamelFileName header. (Note: The header itself can also be an Expression). The expression options support both String and Expression types. If the expression is a String type, it is always evaluated using the File Language. If the expression is an Expression type, the specified Expression type is used - this allows you, for instance, to use OGNL expressions. For the consumer, you can use it to filter filenames, so you can for instance consume today's file using the File Language syntax: mydata-${date:now:yyyyMMdd}.txt.
flatten false Flatten is used to flatten the file name path to strip any leading paths, so it's just the file name. This allows you to consume recursively into sub-directories, but when you eg write the files to another directory they will be written in a single directory. Setting this to true on the producer enforces that any file name recived in CamelFileName header will be stripped for any leading paths.
Name Default Value Description
initialDelay 1000 Milliseconds before polling the file/directory starts.
delay 500 Milliseconds before the next poll of the file/directory.
useFixedDelay false Set to true to use fixed delay between pools, otherwise fixed rate is used. See ScheduledExecutorService in JDK for details.
recursive false If a directory, will look for files in all the sub-directories as well.
delete false If true, the file will be deleted after it is processed
noop false If true, the file is not moved or deleted in any way. This option is good for readonly data, or for ETL type requirements. If noop=true, Apache Camel will set idempotent=true as well, to avoid consuming the same files over and over again.
preMove null Use Expression such as File Language to dynamically set the filename when moving it before processing. For example to move in-progress files into the order directory set this value to order.
move .camel Use Expression such as File Language to dynamically set the filename when moving it after processing. To move files into a .done subdirectory just enter .done.
moveFailed null Use Expression such as File Language to dynamically set the filename when moving failed files after processing. To move files into a error subdirectory just enter error. Note: When moving the files to another location it can/will handle the error when you move it to another location so Apache Camel cannot pick up the file again.
include null Is used to include files, if filename matches the regex pattern.
exclude null Is used to exclude files, if filename matches the regex pattern.
idempotent false Option to use the Idempotent Consumer EIP pattern to let Apache Camel skip already processed files. Will by default use a memory based LRUCache that holds 1000 entries. If noop=true then idempotent will be enabled as well to avoid consuming the same files over and over again.
idempotentRepository null Pluggable repository as a org.apache.camel.processor.idempotent.MessageIdRepository class. Will by default use MemoryMessageIdRepository if none is specified and idempotent is true.
inProgressRepository memory Pluggable in-progress repository as a org.apache.camel.processor.idempotent.MessageIdRepository class. The in-progress repository is used to account the current in progress files being consumed. By default a memory based repository is used.
filter null Pluggable filter as a org.apache.camel.component.file.GenericFileFilter class. Will skip files if filter returns false in its accept() method. Apache Camel also ships with an ANT path matcher filter in the camel-spring component. More details in section below.
sorter null Pluggable sorter as a java.util.Comparator<org.apache.camel.component.file.GenericFile> class.
sortBy null Built-in sort using the File Language. Supports nested sorts, so you can have a sort by file name and as a 2nd group sort by modified date. See sorting section below for details.
readLock markerFile

Used by consumer, to only poll the files if it has exclusive read-lock on the file (i.e. the file is not in-progress or being written). Apache Camel will wait until the file lock is granted.

The readLock option supports the following built-in strategies:

  • markerFile is the behaviour from Apache Camel 1.x, where Apache Camel will create a marker file and hold a lock on the marker file. This option is not available for the FTP component.

  • changed uses a length/modification timestamp to detect whether the file is currently being copied or not. Will wait at least 1 second to determine this, so this option cannot consume files as fast as the others, but can be more reliable as the JDK IO API cannot always determine whether a file is currently being used by another process. This option is not available for the FTP component.

  • fileLock uses java.nio.channels.FileLock. This option is not available for the FTP component.

  • rename attempts to rename the file, in order to test whether we can get an exclusive read-lock.

  • none is for no read locks at all.

readLockTimeout 0 Optional timeout in milliseconds for the read-lock, if supported by the read-lock. If the read-lock could not be granted and the timeout triggered, then Apache Camel will skip the file. At next poll Apache Camel, will try the file again, and this time maybe the read-lock could be granted. Currently fileLock, changed and rename support the timeout.
exclusiveReadLockStrategy null Pluggable read-lock as a org.apache.camel.component.file.GenericFileExclusiveReadLockStrategy implementation.
processStrategy null A pluggable org.apache.camel.component.file.GenericFileProcessStrategy allowing you to implement your own readLock option or similar. Can also be used when special conditions must be met before a file can be consumed, such as a special ready file exists. If this option is set then the readLock option does not apply.
maxMessagesPerPoll 0 An integer that defines the maximum number of messages to gather per poll. By default, no maximum is set. Can be used to set a limit of e.g. 1000 to avoid having the server read thousands of files as it starts up. Set a value of 0 or negative to disabled it.
Name Default Value Description
fileExist Override What to do if a file already exists with the same name. The following values can be specified: Override, Append, Fail and Ignore. Override, which is the default, replaces the existing file. Append adds content to the existing file. Fail throws a GenericFileOperationException, indicating that there is already an existing file. Ignore silently ignores the problem and does not override the existing file, but assumes everything is okay.
tempPrefix null This option is used to write the file using a temporary name and then, after the write is complete, rename it to the real name. Can be used to identify files being written and also avoid consumers (not using exclusive read locks) reading in progress files. Is often used by FTP when uploading big files.
tempFileName null Camel 2.1: The same as tempPrefix option but offering a more fine grained control on the naming of the temporary filename as it uses the File Language.
keepLastModified false Camel 2.2: Will keep the last modified timestamp from the source file (if any). Will use the Exchange.FILE_LAST_MODIFIED header to located the timestamp. This header can contain either a java.util.Date or long with the timestamp. If the timestamp exists and the option is enabled it will set this timestamp on the written file. Note: This option only applies to the file producer. You cannot use this option with any of the ftp producers.
eagerDeleteTargetFile true Camel 2.3: Whether or not to eagerly delete any existing target file. This option only applies when you use fileExists=Override and the tempFileName option as well. You can use this to disable (set it to false) deleting the target file before the temp file is written. For example you may write big files and want the target file to exists during the temp file is being written. This ensure the target file is only deleted until the very last moment, just before the temp file is being renamed to the target filename.

Any move or delete operations is executed after (post command) the routing has completed; so during processing of the Exchange the file is still located in the inbox folder.

Lets illustrate this with an example:

    from("file://inbox?move=.done").to("bean:handleOrder");

When a file is dropped in the inbox folder, the file consumer notices this and creates a new FileExchange that is routed to the handleOrder bean. The bean then processes the File object. At this point in time the file is still located in the inbox folder. After the bean completes, and thus the route is completed, the file consumer will perform the move operation and move the file to the .done sub-folder.

The move and preMove options should be a directory name, which can be either relative or absolute. If relative, the directory is created as a sub-folder from within the folder where the file was consumed.

By default, Apache Camel will move consumed files to the .camel sub-folder relative to the directory where the file was consumed.

If you want to delete the file after processing, the route should be:

    from("file://inobox?delete=true").to("bean:handleOrder");

We have introduced a pre move operation to move files before they are processed. This allows you to mark which files have been scanned as they are moved to this sub folder before being processed.

    from("file://inbox?preMove=inprogress").to("bean:handleOrder");

You can combine the pre move and the regular move:

    from("file://inbox?preMove=inprogress&move=.done").to("bean:handleOrder");

So in this situation, the file is in the inprogress folder when being processed and after it's processed, it's moved to the .done folder.

The move and preMove option is Expression-based, so we have the full power of the File Language to do advanced configuration of the directory and name pattern. Apache Camel will, in fact, internally convert the directory name you enter into a File Language expression. So when we enter move=.done Apache Camel will convert this into: ${file:parent}/.done/${file:onlyname}. This is only done if Apache Camel detects that you have not provided a ${ } in the option value yourself. So when you enter an expression containing ${ }, the expression is interpreted as a File Language expression.

So if we want to move the file into a backup folder with today's date as the pattern, we can do:

move=backup/${date:now:yyyyMMdd}/${file:name}

The moveFailed option allows you to move files that could not be processed succesfully to another location such as a error folder of your choice. For example to move the files in an error folder with a timestamp you can use moveFailed=/error/${file:name.noext}-${date:now:yyyyMMddHHmmssSSS}.${file:name.ext}.

See more examples at File Language.

The following headers are supported by this component:

Header Description
CamelFileName Specifies the name of the file to write (relative to the endpoint directory). The name can be a String; a String with a File Language or Simple expression; or an Expression object. If it's null then Apache Camel will auto-generate a filename based on the message unique ID.
Header Description
CamelFileName Name of the consumed file as a relative file path with offset from the starting directory configured on the endpoint.
CamelFileNameOnly Only the file name (the name with no leading paths).
CamelFileNameProduced The actual absolute filepath (path + name) for the output file that was written. This header is set by Apache Camel and its purpose is providing end-users with the name of the file that was written.
CamelFileAbsolute A boolean option specifying whether the consumed file denotes an absolute path or not. Should normally be false for relative paths. Absolute paths should normally not be used but we added to the move option to allow moving files to absolute paths. But can be used elsewhere as well.
CamelFileAbsolutePath The absolute path to the file. For relative files this path holds the relative path instead.
CamelFilePath The file path. For relative files this is the starting directory + the relative filename. For absolute files this is the absolute path.
CamelFileRelativePath The relative path.
CamelFileParent The parent path.
CamelFileLength A long value containing the file size.
CamelFileLastModified A Date value containing the last modified timestamp of the file.

This component implements the Batch Consumer.

As the file consumer is BatchConsumer it supports batching the files it polls. By batching it means that Apache Camel will add some properties to the Exchange so you know the number of files polled the current index in that order.

Property Description
CamelBatchSize The total number of files that was polled in this batch.
CamelBatchIndex The current index of the batch. Starts from 0.
CamelBatchComplete A boolean value indicating the last Exchange in the batch. Is only true for the last entry.

This allows you for instance to know how many files exists in this batch and for instance let the Aggregator aggregate this number of files.

When Apache Camel is producing files (writing files) there are a few gotchas affecting how to set a filename of your choice. By default, Apache Camel will use the message ID as the filename, and since the message ID is normally a unique generated ID, you will end up with filenames such as: ID-MACHINENAME-2443-1211718892437-1-0. If such a filename is not desired, then you must provide a filename in the CamelFileName message header. The constant, Exchange.FILE_NAME, can also be used.

The sample code below produces files using the message ID as the filename:

from("direct:report").to("file:target/reports");

To use report.txt as the filename you have to do:

from("direct:report").setHeader(Exchange.FILE_NAME, constant("report.txt")).to( "file:target/reports");

Or the same as above, but with CamelFileName:

from("direct:report").setHeader("CamelFileName", constant("report.txt")).to( "file:target/reports");

And a syntax where we set the filename on the endpoint with the fileName URI option.

from("direct:report").to("file:target/reports/?fileName=report.txt");

Filename can be set either using the expression option or as a string-based File Language expression in the CamelFileName header. See the File Language for syntax and samples.

Beware if you consume files from a folder where other applications write files directly. Take a look at the different readLock options to see what suits your use cases. The best approach is however to write to another folder and after the write move the file in the drop folder. However if you write files directly to the drop folder then the option changed could better detect whether a file is currently being written/copied as it uses a file changed algorithm to see whether the file size / modification changes over a period of time. The other read lock options rely on Java File API that sadly is not always very good at detecting this.

from("file://inputdir/?delete=true").to("file://outputdir")

Listen on a directory and create a message for each file dropped there. Copy the contents to the outputdir and delete the file in the inputdir.

from("file://inputdir/?recursive=true&delete=true").to("file://outputdir")

Listen on a directory and create a message for each file dropped there. Copy the contents to the outputdir and delete the file in the inputdir. Will scan recursively into sub-directories. Will lay out the files in the same directory structure in the outputdir as the inputdir, including any sub-directories.

inputdir/foo.txt
inputdir/sub/bar.txt

Will result in the following output layout:

outputdir/foo.txt
outputdir/sub/bar.txt

If you want to store the files in the outputdir directory in the same directory, disregarding the source directory layout (e.g. to flatten out the path), you just add the flatten=true option on the file producer side:

from("file://inputdir/?recursive=true&delete=true").to("file://outputdir?flatten=true")

Will result in the following output layout:

outputdir/foo.txt
outputdir/bar.txt

Apache Camel will by default move any processed file into a .camel subdirectory in the directory the file was consumed from.

from("file://inputdir/?recursive=true&delete=true").to("file://outputdir")

Affects the layout as follows: before

inputdir/foo.txt
inputdir/sub/bar.txt

after

inputdir/.camel/foo.txt
inputdir/sub/.camel/bar.txt
outputdir/foo.txt
outputdir/sub/bar.txt
from("file://inputdir/").process(new Processor() {
  public void process(Exchange exchange) throws Exception {
    Object body = exchange.getIn().getBody();
    // do some business logic with the input body
  }
});

The body will be a File object that points to the file that was just dropped into the inputdir directory.

from("file://inputdir/").convertBodyTo(String.class).to("jms:test.queue")

By default the file endpoint sends a FileMessage which contains a File object as the body. If you send this directly to the JMS component the JMS message will only contain the File object but not the content. By converting the File to a String, the message will contain the file contents what is probably what you want.

The route above using Spring DSL:

   <route>
      <from uri="file://inputdir/"/>
      <convertBodyTo type="java.lang.String"/>
      <to uri="jms:test.queue"/>
   </route>

Apache Camel is of course also able to write files, i.e. produce files. In the sample below we receive some reports on the SEDA queue that we processes before they are written to a directory.

public void testToFile() throws Exception {
    MockEndpoint mock = getMockEndpoint("mock:result");
    mock.expectedMessageCount(1);
    mock.expectedFileExists("target/test-reports/report.txt");

    template.sendBody("direct:reports", "This is a great report");

    assertMockEndpointsSatisfied();
}

protected JndiRegistry createRegistry() throws Exception {
    // bind our processor in the registry with the given id
    JndiRegistry reg = super.createRegistry();
    reg.bind("processReport", new ProcessReport());
    return reg;
}

protected RouteBuilder createRouteBuilder() throws Exception {
    return new RouteBuilder() {
        public void configure() throws Exception {
            // the reports from the seda queue is processed by our processor
            // before they are written to files in the target/reports directory
            from("direct:reports").processRef("processReport").to("file://target/test-reports", "mock:result");
        }
    };
}

private class ProcessReport implements Processor {

    public void process(Exchange exchange) throws Exception {
        String body = exchange.getIn().getBody(String.class);
        // do some business logic here

        // set the output to the file
        exchange.getOut().setBody(body);

        // set the output filename using java code logic, notice that this is done by setting
        // a special header property of the out exchange
        exchange.getOut().setHeader(Exchange.FILE_NAME, "report.txt");
    }

}

Using a single route, it is possible to write a file to any number of subdirectories. If you have a route setup as such:

  <route>
    <from uri="bean:myBean"/>
    <to uri="file:/rootDirectory"/>
  </route> 

You can have myBean set the header Exchange.FILE_NAME to values such as:

Exchange.FILE_NAME = hello.txt => /rootDirectory/hello.txt
Exchange.FILE_NAME = foo/bye.txt => /rootDirectory/foo/bye.txt 

This allows you to have a single route to write files to multiple destinations.

In this sample we want to move consumed files to a backup folder using today's date as a sub-folder name:

from("file://inbox?move=backup/${date:now:yyyyMMdd}/${file:name}").to("...");

See File Language for more samples.

Apache Camel supports Idempotent Consumer directly within the component so it will skip already processed files. This feature can be enabled by setting the idempotent=true option.

from("file://inbox?idempotent=true").to("...");

By default Apache Camel uses a in memory based store for keeping track of consumed files, it uses a least recently used cache storing holding up to 1000 entries. You can plugin your own implementation of this store by using the idempotentRepository option using the # sign in the value to indicate it's a referring to a bean in the Registry with the specified id.

   <!-- define our store as a plain spring bean -->
   <bean id="myStore" class="com.mycompany.MyIdempotentStore"/>

  <route>
    <from uri="file://inbox?idempotent=true&dempotentRepository=#myStore"/>
    <to uri="bean:processInbox"/>
  </route>

Apache Camel will log at DEBUG level if it skips a file because it has been consumed before:

DEBUG FileConsumer is idempotent and the file has been consumed before. Will skip this file: target\idempotent\report.txt

In this section we will use the file based idempotent repository org.apache.camel.processor.idempotent.FileIdempotentRepository instead of the in-memory based that is used as default. This repository uses a 1st level cache to avoid reading the file repository. It will only use the file repository to store the content of the 1st level cache. Thereby the repository can survive server restarts. It will load the content of the file into the 1st level cache upon startup. The file structure is very simple as it store the key in separate lines in the file. By default, the file store has a size limit of 1mb when the file grew larger Apache Camel will truncate the file store be rebuilding the content by flushing the 1st level cache in a fresh empty file.

We configure our repository using Spring XML creating our file idempotent repository and define our file consumer to use our repository with the idempotentRepository using \# sign to indicate Registry lookup:

<!-- this is our file based idempotent store configured to use the .filestore.dat as file -->
<bean id="fileStore" class="org.apache.camel.processor.idempotent.FileIdempotentRepository">
    <!-- the filename for the store -->
    <property name="fileStore" value="target/fileidempotent/.filestore.dat"/>
    <!-- the max filesize in bytes for the file. Apache Camel will trunk and flush the cache
         if the file gets bigger -->
    <property name="maxFileStoreSize" value="512000"/>
    <!-- the number of elements in our store -->
    <property name="cacheSize" value="250"/>
</bean>

<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="file://target/fileidempotent/?idempotent=true&dempotentRepository=#fileStore&ove=done/${file:name}"/>
        <to uri="mock:result"/>
    </route>
</camelContext>

In this section we will use the JPA based idempotent repository instead of the in-memory based that is used as default.

First we need a persistence-unit in META-INF/persistence.xml where we need to use the class org.apache.camel.processor.idempotent.jpa.MessageProcessed as model.

<persistence-unit name="idempotentDb" transaction-type="RESOURCE_LOCAL">
  <class>org.apache.camel.processor.idempotent.jpa.MessageProcessed</class>

  <properties>
    <property name="openjpa.ConnectionURL" value="jdbc:derby:target/idempotentTest;create=true"/>
    <property name="openjpa.ConnectionDriverName" value="org.apache.derby.jdbc.EmbeddedDriver"/>
    <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema"/>
    <property name="openjpa.Log" value="DefaultLevel=WARN, Tool=INFO"/>
  </properties>
</persistence-unit>

Then we need to setup a Spring jpaTemplate in the spring XML file:

<!-- this is standard spring JPA configuration -->
<bean id="jpaTemplate" class="org.springframework.orm.jpa.JpaTemplate">
    <property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
    <!-- we use idempotentDB as the persitence unit name defined in the persistence.xml file -->
    <property name="persistenceUnitName" value="idempotentDb"/>
</bean>

And finally we can create our JPA idempotent repository in the spring XML file as well:

<!-- we define our jpa based idempotent repository we want to use in the file consumer -->
<bean id="jpaStore" class="org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository">
    <!-- Here we refer to the spring jpaTemplate -->
    <constructor-arg index="0" ref="jpaTemplate"/>
    <!-- This 2nd parameter is the name  (= a cateogry name).
         You can have different repositories with different names -->
    <constructor-arg index="1" value="FileConsumer"/>
</bean>

And then we just need to reference the jpaStore bean in the file consumer endpoint, using the idempotentRepository option and the # syntax:

  <route>
    <from uri="file://inbox?idempotent=true&dempotentRepository=#jpaStore"/>
    <to uri="bean:processInbox"/>
  </route>

Apache Camel supports pluggable filtering strategies. You can then configure the endpoint with such a filter to skip certain files being processed.

In the sample we have build our own filter that skips files starting with skip in the filename:

public class MyFileFilter implements GenericFileFilter {
    public boolean accept(GenericFile pathname) {
        // we dont accept any files starting with skip in the name
        return !pathname.getFileName().startsWith("skip");
    }
}

And then we can configure our route using the filter attribute to reference our filter (using # notation) that we have defined in the spring XML file:

   <!-- define our sorter as a plain spring bean -->
   <bean id="myFilter" class="com.mycompany.MyFileSorter"/>

  <route>
    <from uri="file://inbox?filter=#myFilter"/>
    <to uri="bean:processInbox"/>
  </route>

The ANT path matcher is shipped out-of-the-box in the camel-spring jar. So you need to depend on camel-spring if you are using Maven. The reasons is that we leverage Spring's AntPathMatcher to do the actual matching.

The file paths is matched with the following rules:

  • ? matches one character

  • * matches zero or more characters

  • ** matches zero or more directories in a path

The sample below demonstrates how to use it:

<camelContext xmlns="http://camel.apache.org/schema/spring">
    <template id="camelTemplate"/>

    <!-- use myFilter as filter to allow setting ANT paths for which files to scan for -->
    <endpoint id="myFileEndpoint" uri="file://target/antpathmatcher?recursive=true&ilter=#myAntFilter"/>

    <route>
        <from ref="myFileEndpoint"/>
        <to uri="mock:result"/>
    </route>
</camelContext>

<!-- we use the antpath file filter to use ant paths for includes and exlucde -->
<bean id="myAntFilter" class="org.apache.camel.component.file.AntPathMatcherGenericFileFilter">
    <!-- include and file in the subfolder that has day in the name -->
    <property name="includes" value="**/subfolder/**/*day*"/>
    <!-- exclude all files with bad in name or .xml files. Use comma to seperate multiple excludes -->
    <property name="excludes" value="**/*bad*,**/*.xml"/>
</bean>

Apache Camel supports pluggable sorting strategies. This strategy it to use the build in java.util.Comparator in Java. You can then configure the endpoint with such a comparator and have Apache Camel sort the files before being processed.

In the sample we have built our own comparator that just sorts by file name:

public class MyFileSorter implements Comparator<GenericFile> {
    public int compare(GenericFile o1, GenericFile o2) {
        return o1.getFileName().compareToIgnoreCase(o2.getFileName());
    }
}

And then we can configure our route using the sorter option to reference to our sorter (mySorter) we have defined in the spring XML file:

   <!-- define our sorter as a plain spring bean -->
   <bean id="mySorter" class="com.mycompany.MyFileSorter"/>

  <route>
    <from uri="file://inbox?sorter=#mySorter"/>
    <to uri="bean:processInbox"/>
  </route>
[Tip]URI options can reference beans using the # syntax

In the Spring DSL route about notice that we can reference beans in the Registry by prefixing the id with #. So writing sorter=#mySorter, will instruct Apache Camel to go look in the Registry for a bean with the ID, mySorter.

Apache Camel supports pluggable sorting strategies. This strategy it to use the File Language to configure the sorting. The sortBy option is configured as follows:

sortBy=group 1;group 2;group 3;...

Where each group is separated with semi colon. In the simple situations you just use one group, so a simple example could be:

sortBy=file:name

This will sort by file name, you can reverse the order by prefixing reverse: to the group, so the sorting is now Z..A:

sortBy=reverse:file:name

As we have the full power of File Language we can use some of the other parameters, so if we want to sort by file size we do:

sortBy=file:size

You can configure to ignore the case, using ignoreCase: for string comparison, so if you want to use file name sorting but to ignore the case then we do:

sortBy=ignoreCase:file:name

You can combine ignore case and reverse, however reverse must be specified first:

sortBy=reverse:ignoreCase:file:name

In the sample below we want to sort by last modified file, so we do:

sortBy=file:modifed

And then we want to group by name as a 2nd option so files with same modifcation is sorted by name:

sortBy=file:modifed;file:name

Now there is an issue here, can you spot it? Well the modified timestamp of the file is too fine as it will be in milliseconds, but what if we want to sort by date only and then subgroup by name? Well as we have the true power of File Language we can use the its date command that supports patterns. So this can be solved as:

sortBy=date:file:yyyyMMdd;file:name

Yeah, that is pretty powerful, oh by the way you can also use reverse per group, so we could reverse the file names:

sortBy=date:file:yyyyMMdd;reverse:file:name

The option processStrategy can be used to use a custom GenericFileProcessStrategy that allows you to implement your own begin, commit and rollback logic. For instance lets assume a system writes a file in a folder you should consume. But you should not start consuming the file before another ready file have been written as well.

So by implementing our own GenericFileProcessStrategy we can implement this as:

This component has log level TRACE that can be helpful if you have problems.

See also: