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 as a type safe way of configuring endpoints.

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 occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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.

boolean

concurrentConsumers (consumer)

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

int

fileHasher (consumer)

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.

FileHasher

pollThreads (consumer)

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

int

queueSize (consumer)

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

int

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.

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.

boolean

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 exists.

boolean

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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.

boolean

concurrentConsumers (consumer)

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

int

events (consumer)

Comma separated list of events to watch.

Enum values:

  • CREATE

  • MODIFY

  • DELETE

Set

fileHasher (consumer)

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.

FileHasher

pollThreads (consumer)

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

int

queueSize (consumer)

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

int

recursive (consumer)

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

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.

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

  • InOptionalOut

ExchangePattern

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");

Message Headers

The following headers are supported by this component:

File Watch consumer only

Header Description

CamelFileEventType

Type of event. Possible values: CREATE, DELETE, MODIFY. The java type of this header is String

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).

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.

CamelFileLastModified

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

Spring Boot Auto-Configuration

When using file-watch with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-file-watch-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 8 options, which are listed below.

Name Description Default Type

camel.component.file-watch.autowired-enabled

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

camel.component.file-watch.bridge-error-handler

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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

camel.component.file-watch.concurrent-consumers

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

1

Integer

camel.component.file-watch.enabled

Whether to enable auto configuration of the file-watch component. This is enabled by default.

Boolean

camel.component.file-watch.file-hasher

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. The option is a io.methvin.watcher.hashing.FileHasher type.

FileHasher

camel.component.file-watch.poll-threads

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

1

Integer

camel.component.file-watch.queue-size

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

2147483647

Integer

camel.component.file-watch.use-file-hashing

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