OAI-PMH

Since Camel 3.5

Both producer and consumer are supported

The oaipmh component is used for harvest OAI-PMH data providers. It allows do request to OAI-PMH endpoint using all verbs supported by the protocol.

Maven users will need to add the following dependency to their pom.xml for this component:

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

URI format

oaipmh:url[?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 OAI-PMH component supports 3 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
lazyStartProducer (producer)	Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.		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

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

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

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

Endpoint Options

The OAI-PMH endpoint is configured using URI syntax:

oaipmh:baseUrl

with the following path and query parameters:

Path Parameters (1 parameters)

Name	Description	Default	Type
baseUrl (common)	Required Base URL of the repository to which the request is made through the OAI-PMH protocol.		String

Name

Description

Default

Type

baseUrl (common)

Required Base URL of the repository to which the request is made through the OAI-PMH protocol.

String

Query Parameters (29 parameters)

Name	Description	Default	Type
from (common)	Specifies a lower bound for datestamp-based selective harvesting. UTC DateTime value.		String
identifier (common)	Identifier of the requested resources. Applicable only with certain verbs.		String
metadataPrefix (common)	Specifies the metadataPrefix of the format that should be included in the metadata part of the returned records.	oai_dc	String
set (common)	Specifies membership as a criteria for set-based selective harvesting.		String
until (common)	Specifies an upper bound for datestamp-based selective harvesting. UTC DateTime value.		String
verb (common)	Request name supported by OAI-PMh protocol.	ListRecords	String
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
sendEmptyMessageWhenIdle (consumer)	If the polling consumer did not poll any files, you can enable this option to send an empty message (no body) instead.		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
pollStrategy (consumer (advanced))	A pluggable org.apache.camel.PollingConsumerPollingStrategy allowing you to provide your custom implementation to control error handling usually occurred during the poll operation before an Exchange have been created and being routed in Camel.		PollingConsumerPollStrategy
lazyStartProducer (producer)	Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.		boolean
onlyFirst (producer)	Returns the response of a single request. Otherwise it will make requests until there is no more data to return.		boolean
backoffErrorThreshold (scheduler)	The number of subsequent error polls (failed due some error) that should happen before the backoffMultipler should kick-in.		int
backoffIdleThreshold (scheduler)	The number of subsequent idle polls that should happen before the backoffMultipler should kick-in.		int
backoffMultiplier (scheduler)	To let the scheduled polling consumer backoff if there has been a number of subsequent idles/errors in a row. The multiplier is then the number of polls that will be skipped before the next actual attempt is happening again. When this option is in use then backoffIdleThreshold and/or backoffErrorThreshold must also be configured.		int
delay (scheduler)	Milliseconds before the next poll.	500	long
greedy (scheduler)	If greedy is enabled, then the ScheduledPollConsumer will run immediately again, if the previous run polled 1 or more messages.		boolean
initialDelay (scheduler)	Milliseconds before the first poll starts.	1000	long
repeatCount (scheduler)	Specifies a maximum limit of number of fires. So if you set it to 1, the scheduler will only fire once. If you set it to 5, it will only fire five times. A value of zero or negative means fire forever.		long
runLoggingLevel (scheduler)	The consumer logs a start/complete log line when it polls. This option allows you to configure the logging level for that. Enum values: TRACE DEBUG INFO WARN ERROR OFF	TRACE	LoggingLevel
scheduledExecutorService (scheduler)	Allows for configuring a custom/shared thread pool to use for the consumer. By default each consumer has its own single threaded thread pool.		ScheduledExecutorService
scheduler (scheduler)	To use a cron scheduler from either camel-spring or camel-quartz component. Use value spring or quartz for built in scheduler.	none	Object
schedulerProperties (scheduler)	To configure additional properties when using a custom scheduler or any of the Quartz, Spring based scheduler.		Map
startScheduler (scheduler)	Whether the scheduler should be auto started.	true	boolean
timeUnit (scheduler)	Time unit for initialDelay and delay options. Enum values: NANOSECONDS MICROSECONDS MILLISECONDS SECONDS MINUTES HOURS DAYS	MILLISECONDS	TimeUnit
useFixedDelay (scheduler)	Controls if fixed delay or fixed rate is used. See ScheduledExecutorService in JDK for details.	true	boolean
ignoreSSLWarnings (security)	Ignore SSL certificate warnings.		boolean
ssl (security)	Causes the defined url to make an https request.		boolean

Name

Description

Default

Type

from (common)

Specifies a lower bound for datestamp-based selective harvesting. UTC DateTime value.

String

identifier (common)

Identifier of the requested resources. Applicable only with certain verbs.

String

metadataPrefix (common)

Specifies the metadataPrefix of the format that should be included in the metadata part of the returned records.

oai_dc

String

set (common)

Specifies membership as a criteria for set-based selective harvesting.

String

until (common)

Specifies an upper bound for datestamp-based selective harvesting. UTC DateTime value.

String

verb (common)

Request name supported by OAI-PMh protocol.

ListRecords

String

bridgeErrorHandler (consumer)

boolean

sendEmptyMessageWhenIdle (consumer)

If the polling consumer did not poll any files, you can enable this option to send an empty message (no body) instead.

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

pollStrategy (consumer (advanced))

A pluggable org.apache.camel.PollingConsumerPollingStrategy allowing you to provide your custom implementation to control error handling usually occurred during the poll operation before an Exchange have been created and being routed in Camel.

PollingConsumerPollStrategy

lazyStartProducer (producer)

boolean

onlyFirst (producer)

Returns the response of a single request. Otherwise it will make requests until there is no more data to return.

boolean

backoffErrorThreshold (scheduler)

The number of subsequent error polls (failed due some error) that should happen before the backoffMultipler should kick-in.

int

backoffIdleThreshold (scheduler)

The number of subsequent idle polls that should happen before the backoffMultipler should kick-in.

int

backoffMultiplier (scheduler)

To let the scheduled polling consumer backoff if there has been a number of subsequent idles/errors in a row. The multiplier is then the number of polls that will be skipped before the next actual attempt is happening again. When this option is in use then backoffIdleThreshold and/or backoffErrorThreshold must also be configured.

int

delay (scheduler)

Milliseconds before the next poll.

500

long

greedy (scheduler)

If greedy is enabled, then the ScheduledPollConsumer will run immediately again, if the previous run polled 1 or more messages.

boolean

initialDelay (scheduler)

Milliseconds before the first poll starts.

1000

long

repeatCount (scheduler)

Specifies a maximum limit of number of fires. So if you set it to 1, the scheduler will only fire once. If you set it to 5, it will only fire five times. A value of zero or negative means fire forever.

long

runLoggingLevel (scheduler)

The consumer logs a start/complete log line when it polls. This option allows you to configure the logging level for that.

Enum values:

TRACE
DEBUG
INFO
WARN
ERROR
OFF

TRACE

LoggingLevel

scheduledExecutorService (scheduler)

Allows for configuring a custom/shared thread pool to use for the consumer. By default each consumer has its own single threaded thread pool.

ScheduledExecutorService

scheduler (scheduler)

To use a cron scheduler from either camel-spring or camel-quartz component. Use value spring or quartz for built in scheduler.

none

Object

schedulerProperties (scheduler)

To configure additional properties when using a custom scheduler or any of the Quartz, Spring based scheduler.

Map

startScheduler (scheduler)

Whether the scheduler should be auto started.

true

boolean

timeUnit (scheduler)

Time unit for initialDelay and delay options.

Enum values:

NANOSECONDS
MICROSECONDS
MILLISECONDS
SECONDS
MINUTES
HOURS
DAYS

MILLISECONDS

TimeUnit

useFixedDelay (scheduler)

Controls if fixed delay or fixed rate is used. See ScheduledExecutorService in JDK for details.

true

boolean

ignoreSSLWarnings (security)

Ignore SSL certificate warnings.

boolean

ssl (security)

Causes the defined url to make an https request.

boolean

Message Headers

Name Description

Name	Description
`CamelOaimphResumptionToken`	This header is obtained when onlyFirst option is enable. Return resumptiontoken of the request when data is still available.

CamelOaimphResumptionToken

This header is obtained when onlyFirst option is enable. Return resumptiontoken of the request when data is still available.

Usage

The OAIPMH component supports both consumer and producer endpoints.

Producer Example

The following is a basic example of how to send a request to a OAIPMH Server.

in Java DSL

from("direct:start").to("oaipmh:baseUrlRepository/oai/request");

The result is a set of pages in XML format with all the records of the consulted repository.

Consumer Example

The following is a basic example of how to receive all messages from a OAIPMH Server. In Java DSL

from("oaipmh:baseUrlRepository/oai/request")
.to(mock:result)

More Information

For more details about OAI-PMH see the documentation: http://www.openarchives.org/pmh/