File Watch

Since Camel 3.0

Only consumer is supported

This component can be used to watch file modification events in folder. It is based on gmethvin/directory-watcher.

URI Options

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

The following two sections lists all the options, firstly for the component followed by the endpoint.

Component Options

The File Watch component supports 7 options, which are listed below.

Name Description Default Type

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

useFileHashing (consumer)

Enables or disables file hashing to detect duplicate events. If you disable this, you can get some events multiple times on some platforms and JDKs. Check java.nio.file.WatchService limitations for your target platform.

true

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

concurrentConsumers (advanced)

The number of concurrent consumers. Increase this value, if your route is slow to prevent buffering in queue.

1

int

fileHasher (advanced)

Reference to io.methvin.watcher.hashing.FileHasher. This prevents emitting duplicate events on some platforms. For working with large files and if you dont need detect multiple modifications per second per file, use #lastModifiedTimeFileHasher. You can also provide custom implementation in registry.

#murmur3FFileHasher

FileHasher

pollThreads (advanced)

The number of threads polling WatchService. Increase this value, if you see OVERFLOW messages in log.

1

int

queueSize (advanced)

Maximum size of queue between WatchService and consumer. Unbounded by default.

2147483647

int

Endpoint Options

The File Watch endpoint is configured using URI syntax:

file-watch:path

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

path (consumer)

Required Path of directory to consume events from.

String

Query Parameters (12 parameters)

Name Description Default Type

antInclude (consumer)

ANT style pattern to match files. The file is matched against path relative to endpoint path. Pattern must be also relative (not starting with slash).

**

String

autoCreate (consumer)

Auto create directory if does not exist.

true

boolean

events (consumer)

Comma separated list of events to watch. Possible values: CREATE,MODIFY,DELETE.

CREATE,MODIFY,DELETE

String

recursive (consumer)

Watch recursive in current and child directories (including newly created directories).

true

boolean

useFileHashing (consumer)

Enables or disables file hashing to detect duplicate events. If you disable this, you can get some events multiple times on some platforms and JDKs. Check java.nio.file.WatchService limitations for your target platform.

true

boolean

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

ExchangePattern

concurrentConsumers (advanced)

The number of concurrent consumers. Increase this value, if your route is slow to prevent buffering in queue.

1

int

fileHasher (advanced)

Reference to io.methvin.watcher.hashing.FileHasher. This prevents emitting duplicate events on some platforms. For working with large files and if you dont need detect multiple modifications per second per file, use #lastModifiedTimeFileHasher. You can also provide custom implementation in registry.

#murmur3FFileHasher

FileHasher

pollThreads (advanced)

The number of threads polling WatchService. Increase this value, if you see OVERFLOW messages in log.

1

int

queueSize (advanced)

Maximum size of queue between WatchService and consumer. Unbounded by default.

2147483647

int

Message Headers

The File Watch component supports 10 message header(s), which is/are listed below:

Name Description Default Type

CamelFileEventType (consumer)

Constant: EVENT_TYPE_HEADER

Type of event. Possible values: CREATE, DELETE, MODIFY.

String

CamelFileNameOnly (consumer)

Constant: FILE_NAME_ONLY

Only the file name (the name with no leading paths).

String

CamelFileAbsolute (consumer)

Constant: FILE_ABSOLUTE

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.

Boolean

CamelFileAbsolutePath (consumer)

Constant: FILE_ABSOLUTE_PATH

The absolute path to the file. For relative files this path holds the relative path instead.

String

CamelFilePath (consumer)

Constant: FILE_PATH

The file path. For relative files this is the starting directory the relative filename. For absolute files this is the absolute path.

String

CamelFileName (consumer)

Constant: FILE_NAME

Name of the consumed file as a relative file path with offset from the starting directory configured on the endpoint.

String

CamelFileRelativePath (consumer)

Constant: FILE_RELATIVE_PATH

The relative path.

String

CamelFileNameConsumed (consumer)

Constant: FILE_NAME_CONSUMED

The name of the file that has been consumed.

String

CamelFileParent (consumer)

Constant: FILE_PARENT

The parent path.

String

CamelFileLastModified (consumer)

Constant: FILE_LAST_MODIFIED

A Long value containing the last modified timestamp of the file.

long

Examples:

Recursive watch all events (file creation, file deletion, file modification):

from("file-watch://some-directory")
    .log("File event: ${header.CamelFileEventType} occurred on file ${header.CamelFileName} at ${header.CamelFileLastModified}");

Recursive watch for creation and deletion of txt files:

from("file-watch://some-directory?events=DELETE,CREATE&antInclude=**/*.txt")
    .log("File event: ${header.CamelFileEventType} occurred on file ${header.CamelFileName} at ${header.CamelFileLastModified}");

Create snapshot of file when modified:

from("file-watch://some-directory?events=MODIFY&recursive=false")
    .setHeader(Exchange.FILE_NAME, simple("${header.CamelFileName}.${header.CamelFileLastModified}"))
    .to("file:some-directory/snapshots");