[CONF] Apache Camel: File (page edited)

Sun, 25 May 2008 07:00:37 -0700

Page Edited : CAMEL : File

File has been edited by Claus Ibsen (May 25, 2008).

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Content:

File Component

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

URI format

file:fileOrDirectoryName

or





file://fileOrDirectoryName





Where fileOrDirectoryName represents the underlying file name. Camel will determine if fileOrDirectoryName is a file or directory. 



Important Information


See the section "Common gotchas with folder and filenames" below.



URI Options






 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 
 if true, poll once after the initial delay




 recursive 
 true 
 if a directory, will look for changes in files in all the sub directories




 lock 
 true 
 if true will lock the file for the duration of the processing 




 regexPattern 
 null 
 will only fire a an exchange for a file that matches the regex pattern




 delete 
 false 
 If delete is true then the file will be deleted when it is processed (the default is to move it, see below) 




 noop 
 false 
 If true then the file is not moved or deleted in any way (see below). This option is good for read only data, or for ETL type requirements 




 moveNamePrefix 
 null 
 The prefix String perpended to the filename when moving it. For example to move processed files into the done directory, set this value to 'done/' 




 moveNamePostfix 
 null 
 The postfix String appended to the filename when moving it. For example to rename processed files from foo to foo.old set this value to '.old' 




 append 
 true 
 When writing do we append to the end of the file, or replace it? 




 autoCreate 
 true 
 If set to true Camel will create the directory to the file if the file path does not exists - Uses File#mkdirs()




 bufferSize 
 128kb 
 Write buffer sized in bytes. Camel uses a default of 128 * 1024 bytes. 




 ignoreFileNameHeader 
 false 
 If this flag is enabled then producers will ignore the 'org.apache.camel.file.name' header and generate a new dynamic filename 




 excludedNamePrefixes 
 "." 
 Is used to exclude files if filename is starting with any of the given prefixes. The parameter is a String[] 




 excludedNamePostfixes 
 ".camelLock" 
 Is used to exclude files if filename is ending with any of the given prefixes. The parameter is a String[] 




 generateEmptyExchangeWhenIdle 
 false 
 Option only for the FileConsumer. If this option is true and there was no files to process we simulate processing a single empty file, so an exchange is happening. In this situation the file parameter in FileExchange is null. 






By default the file is locked for the duration of the processing. Also when files are processed they are moved into the .camel directory; so that they appear to be deleted.



Message Headers



The following message headers can be used to affect the behavior of the component






 Header 
 Description 




 org.apache.camel.file.name 
 Specifies the output file name (relative to the endpoint directory) to be used for the output message when sending to the endpoint. If this is not present then a generated message ID is used instead 






Common gotchas with folder and filenames



When Camel is producing files (writing files) there are a few gotchas how to set a filename of your choice. By default 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. Such a filename is not desired and therefore best practice is to provide the filename in the message header "org.apache.camel.file.name".



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(FileComponent.HEADER_FILE_NAME, "report.txt").to( "file:target/reports");





Canel will default try to auto create the folder if it does not exists, and this is a bad combination with the UUID filename from above. So if you have:




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




And you want Camel to store in the file report.txt and autoCreate is true, then Camel will create the folder: target/reports/report.txt/. To fix this set the autoCreate=false and create the folder target/reports manually.




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




With auto create disabled Camel will store the report in the report.txt as expected.



Samples



Read from a directory and write to another directory





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.



Read from a directory and process the message in java 





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
  }
});





Body will be File object pointing to the file that was just dropped to the inputdir directory.



Read files from a directory and send the content to a jms queue





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





By default the file endpoint sends a FileMessage which contains a File as 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 to do.



Writing to files



Camel is of course also able to write files, eg. producing 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 {
    template.sendBody("seda:reports", "This is a great report");

    // give time for the file to be written before assertions
    Thread.sleep(1000);

    // assert the file exists
    File file = new File("target/test-reports/report.txt");
    assertTrue("The file should have been written", file.exists());
}

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("seda:reports").processRef("processReport").to("file://target/test-reports");
        }
    };
}

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(FileComponent.HEADER_FILE_NAME, "report.txt");
    }

}





FileProducer filename gotchas



This unit test demonstrates some of the gotchas with filenames for the File Producer.





public void testProducerWithMessageIdAsFileName() throws Exception {
    Endpoint endpoint = context.getEndpoint("direct:report");
    Exchange exchange = endpoint.createExchange();
    exchange.getIn().setBody("This is a good report");
    String id = exchange.getIn().getMessageId();

    template.send("direct:report", exchange);

    File file = new File("target/reports/report.txt/" + id);
    assertEquals("File should exists", true, file.exists());
}

public void testProducerWithConfiguedFileNameInEndpointURI() throws Exception {
    template.sendBody("direct:report2", "This is another good report");
    File file = new File("target/report2.txt");
    assertEquals("File should exists", true, file.exists());
}

public void testProducerWithHeaderFileName() throws Exception {
    template.sendBody("direct:report3", "This is super good report");
    File file = new File("target/report-super.txt");
    assertEquals("File should exists", true, file.exists());
}

protected RouteBuilder createRouteBuilder() throws Exception {
    return new RouteBuilder() {
        public void configure() throws Exception {
            from("direct:report").to( "file:target/reports/report.txt");

            from("direct:report2").to( "file:target/report2.txt?autoCreate=false");

            from("direct:report3").setHeader(FileComponent.HEADER_FILE_NAME, "report-super.txt").to( "file:target/");
        }
    };
}





See Also

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