Chapter 32. JPA

32.1. Sending to the endpoint

You can store a Java entity bean in a database by sending it to a JPA producer endpoint. The body of the In message is assumed to be an entity bean (that is, a POJO with an @Entity annotation on it) or a collection or array of entity beans.

If the body is a List of entities, use entityType=java.util.List as a configuration passed to the producer endpoint.

If the body does not contain one of the previous listed types, put a Message Translator before the endpoint to perform the necessary conversion first.

You can use query, namedQuery or nativeQuery for the producer as well. For the value of the parameters, you can use the Simple expression which allows you to retrieve parameter values from Message body, header and etc. Those query can be used for retrieving a set of data with using SELECT JPQL/SQL statement as well as executing bulk update/delete with using UPDATE/DELETE JPQL/SQL statement. Please note that you need to specify useExecuteUpdate to true if you execute UPDATE/DELETE with namedQuery as camel doesn’t look into the named query unlike query and nativeQuery.

32.2. Consuming from the endpoint

Consuming messages from a JPA consumer endpoint removes (or updates) entity beans in the database. This allows you to use a database table as a logical queue: consumers take messages from the queue and then delete/update them to logically remove them from the queue.

If you do not wish to delete the entity bean when it has been processed (and when routing is done), you can specify consumeDelete=false on the URI. This will result in the entity being processed each poll.

If you would rather perform some update on the entity to mark it as processed (such as to exclude it from a future query) then you can annotate a method with @Consumed which will be invoked on your entity bean when the entity bean when it has been processed (and when routing is done).

You can use @PreConsumed which will be invoked on your entity bean before it has been processed (before routing).

If you are consuming a lot (100K+) of rows and experience OutOfMemory problems you should set the maximumResults to sensible value.

32.3. URI format

jpa:entityClassName[?options]

For sending to the endpoint, the entityClassName is optional. If specified, it helps the Type Converterto ensure the body is of the correct type.

For consuming, the entityClassName is mandatory.

32.4. Configuring Options

Camel components are configured on two separate levels:

component level
endpoint level

32.4.1. 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.

32.4.2. 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.

32.4.3. Component Options

The JPA component supports 9 options, which are listed below.

Name	Description	Default	Type
aliases (common)	Maps an alias to a JPA entity class. The alias can then be used in the endpoint URI (instead of the fully qualified class name).		Map
entityManagerFactory (common)	To use the EntityManagerFactory. This is strongly recommended to configure.		EntityManagerFactory
joinTransaction (common)	The camel-jpa component will join transaction by default. You can use this option to turn this off, for example if you use LOCAL_RESOURCE and join transaction doesn’t work with your JPA provider. This option can also be set globally on the JpaComponent, instead of having to set it on all endpoints.	true	boolean
sharedEntityManager (common)	Whether to use Spring’s SharedEntityManager for the consumer/producer. Note in most cases joinTransaction should be set to false as this is not an EXTENDED EntityManager.	false	boolean
transactionManager (common)	To use the PlatformTransactionManager for managing transactions.		PlatformTransactionManager
transactionStrategy (common)	To use the TransactionStrategy for running the operations in a transaction.		TransactionStrategy
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.	false	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.	false	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

32.4.4. Endpoint Options

The JPA endpoint is configured using URI syntax:

jpa:entityType

with the following path and query parameters:

32.4.4.1. Path Parameters (1 parameters)

Name	Description	Default	Type
entityType (common)	Required Entity class name.		Class

32.4.4.2. Query Parameters (44 parameters)

Name	Description	Default	Type
joinTransaction (common)	The camel-jpa component will join transaction by default. You can use this option to turn this off, for example if you use LOCAL_RESOURCE and join transaction doesn’t work with your JPA provider. This option can also be set globally on the JpaComponent, instead of having to set it on all endpoints.	true	boolean
maximumResults (common)	Set the maximum number of results to retrieve on the Query.	-1	int
namedQuery (common)	To use a named query.		String
nativeQuery (common)	To use a custom native query. You may want to use the option resultClass also when using native queries.		String
persistenceUnit (common)	Required The JPA persistence unit used by default.	camel	String
query (common)	To use a custom query.		String
resultClass (common)	Defines the type of the returned payload (we will call entityManager.createNativeQuery(nativeQuery, resultClass) instead of entityManager.createNativeQuery(nativeQuery)). Without this option, we will return an object array. Only has an affect when using in conjunction with native query when consuming data.		Class
consumeDelete (consumer)	If true, the entity is deleted after it is consumed; if false, the entity is not deleted.	true	boolean
consumeLockEntity (consumer)	Specifies whether or not to set an exclusive lock on each entity bean while processing the results from polling.	true	boolean
deleteHandler (consumer)	To use a custom DeleteHandler to delete the row after the consumer is done processing the exchange.		DeleteHandler
lockModeType (consumer)	To configure the lock mode on the consumer. Enum values: READ WRITE OPTIMISTIC OPTIMISTIC_FORCE_INCREMENT PESSIMISTIC_READ PESSIMISTIC_WRITE PESSIMISTIC_FORCE_INCREMENT NONE	PESSIMISTIC_WRITE	LockModeType
maxMessagesPerPoll (consumer)	An integer value to define the maximum number of messages to gather per poll. By default, no maximum is set. Can be used to avoid polling many thousands of messages when starting up the server. Set a value of 0 or negative to disable.		int
preDeleteHandler (consumer)	To use a custom Pre-DeleteHandler to delete the row after the consumer has read the entity.		DeleteHandler
sendEmptyMessageWhenIdle (consumer)	If the polling consumer did not poll any files, you can enable this option to send an empty message (no body) instead.	false	boolean
skipLockedEntity (consumer)	To configure whether to use NOWAIT on lock and silently skip the entity.	false	boolean
transacted (consumer)	Whether to run the consumer in transacted mode, by which all messages will either commit or rollback, when the entire batch has been processed. The default behavior (false) is to commit all the previously successfully processed messages, and only rollback the last failed message.	false	boolean
bridgeErrorHandler (consumer (advanced))	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
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
parameters (consumer (advanced))	This key/value mapping is used for building the query parameters. It is expected to be of the generic type java.util.Map where the keys are the named parameters of a given JPA query and the values are their corresponding effective values you want to select for. When it’s used for producer, Simple expression can be used as a parameter value. It allows you to retrieve parameter values from the message body, header and etc.		Map
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
findEntity (producer)	If enabled then the producer will find a single entity by using the message body as key and entityType as the class type. This can be used instead of a query to find a single entity.	false	boolean
flushOnSend (producer)	Flushes the EntityManager after the entity bean has been persisted.	true	boolean
remove (producer)	Indicates to use entityManager.remove(entity).	false	boolean
useExecuteUpdate (producer)	To configure whether to use executeUpdate() when producer executes a query. When you use INSERT, UPDATE or DELETE statement as a named query, you need to specify this option to 'true'.		Boolean
usePersist (producer)	Indicates to use entityManager.persist(entity) instead of entityManager.merge(entity). Note: entityManager.persist(entity) doesn’t work for detached entities (where the EntityManager has to execute an UPDATE instead of an INSERT query)!.	false	boolean
lazyStartProducer (producer (advanced))	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.	false	boolean
usePassedInEntityManager (producer (advanced))	If set to true, then Camel will use the EntityManager from the header JpaConstants.ENTITY_MANAGER instead of the configured entity manager on the component/endpoint. This allows end users to control which entity manager will be in use.	false	boolean
entityManagerProperties (advanced)	Additional properties for the entity manager to use.		Map
sharedEntityManager (advanced)	Whether to use Spring’s SharedEntityManager for the consumer/producer. Note in most cases joinTransaction should be set to false as this is not an EXTENDED EntityManager.	false	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.	false	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.	0	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

32.5. Message Headers

The JPA component supports 2 message header(s), which are listed below:

Name	Description	Default	Type
CamelEntityManager (common) Constant: ENTITY_MANAGER	The JPA EntityManager object.		EntityManager
CamelJpaParameters (producer) Constant: link: JPA_PARAMETERS_HEADER	Alternative way for passing query parameters as an Exchange header.		Map

Name

Description

Default

Type

CamelEntityManager (common)

Constant: ENTITY_MANAGER

The JPA EntityManager object.

EntityManager

CamelJpaParameters (producer)

Constant: link: JPA_PARAMETERS_HEADER

Alternative way for passing query parameters as an Exchange header.

Map

32.6. Configuring EntityManagerFactory

It is recommended to configure the JPA component to use a specific EntityManagerFactory instance. If failed to do so each JpaEndpoint will auto create their own instance of EntityManagerFactory which most often is not what you want.

For example, you can instantiate a JPA component that references the myEMFactory entity manager factory, as follows:

<bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent">
   <property name="entityManagerFactory" ref="myEMFactory"/>
</bean>

The JpaComponent automatically looks up the EntityManagerFactory from the Registry which means you do not need to configure this on the JpaComponent as shown above. You only need to do so if there is ambiguity, in which case Camel will log a WARN.

32.7. Configuring TransactionManager

The JpaComponent automatically looks up the TransactionManager from the Registry. If Camel won’t find any TransactionManager instance registered, it will also look up for the TransactionTemplate and try to extract TransactionManager from it.

If none TransactionTemplate is available in the registry, JpaEndpoint will auto create their own instance of TransactionManager which most often is not what you want.

If more than single instance of the TransactionManager is found, Camel will log a WARN. In such cases you might want to instantiate and explicitly configure a JPA component that references the myTransactionManager transaction manager, as follows:

<bean id="jpa" class="org.apache.camel.component.jpa.JpaComponent">
   <property name="entityManagerFactory" ref="myEMFactory"/>
   <property name="transactionManager" ref="myTransactionManager"/>
</bean>

32.8. Using a consumer with a named query

For consuming only selected entities, you can use the namedQuery URI query option. First, you have to define the named query in the JPA Entity class:

@Entity
@NamedQuery(name = "step1", query = "select x from MultiSteps x where x.step = 1")
public class MultiSteps {
   ...
}

After that you can define a consumer uri as shown below:

from("jpa://org.apache.camel.examples.MultiSteps?namedQuery=step1")
.to("bean:myBusinessLogic");

32.9. Using a consumer with a query

For consuming only selected entities, you can use the query URI query option. You only have to define the query option:

from("jpa://org.apache.camel.examples.MultiSteps?query=select o from org.apache.camel.examples.MultiSteps o where o.step = 1")
.to("bean:myBusinessLogic");

32.10. Using a consumer with a native query

For consuming only selected entities, you can use the nativeQuery URI query option. You only have to define the native query option:

from("jpa://org.apache.camel.examples.MultiSteps?nativeQuery=select * from MultiSteps where step = 1")
.to("bean:myBusinessLogic");

If you use the native query option, you will receive an object array in the message body.

32.11. Using a producer with a named query

For retrieving selected entities or execute bulk update/delete, you can use the namedQuery URI query option. First, you have to define the named query in the JPA Entity class:

@Entity
@NamedQuery(name = "step1", query = "select x from MultiSteps x where x.step = 1")
public class MultiSteps {
   ...
}

After that you can define a producer uri as shown below:

from("direct:namedQuery")
.to("jpa://org.apache.camel.examples.MultiSteps?namedQuery=step1");

Note that you need to specify useExecuteUpdate option to true to execute UPDATE/DELETE statement as a named query.

32.12. Using a producer with a query

For retrieving selected entities or execute bulk update/delete, you can use the query URI query option. You only have to define the query option:

from("direct:query")
.to("jpa://org.apache.camel.examples.MultiSteps?query=select o from org.apache.camel.examples.MultiSteps o where o.step = 1");

32.13. Using a producer with a native query

For retrieving selected entities or execute bulk update/delete, you can use the nativeQuery URI query option. You only have to define the native query option:

from("direct:nativeQuery")
.to("jpa://org.apache.camel.examples.MultiSteps?resultClass=org.apache.camel.examples.MultiSteps&nativeQuery=select * from MultiSteps where step = 1");

If you use the native query option without specifying resultClass, you will receive an object array in the message body.

32.14. Using the JPA-Based Idempotent Repository

The Idempotent Consumer from the EIP patterns is used to filter out duplicate messages. A JPA-based idempotent repository is provided.

To use the JPA based idempotent repository.

Procedure

Set up a persistence-unit in the persistence.xml file.
Set up a org.springframework.orm.jpa.JpaTemplate which is used by the org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository.
Configure the error formatting macro: snippet: java.lang.IndexOutOfBoundsException: Index: 20, Size: 20
Configure the idempotent repository as org.apache.camel.processor.idempotent.jpa.JpaMessageIdRepository.
Create the JPA idempotent repository in the Spring XML file as shown below:

<camelContext xmlns="http://camel.apache.org/schema/spring">
    <route id="JpaMessageIdRepositoryTest">
        <from uri="direct:start" />
        <idempotentConsumer idempotentRepository="jpaStore">
            <header>messageId</header>
            <to uri="mock:result" />
        </idempotentConsumer>
    </route>
</camelContext>

When running this Camel component tests inside your IDE

If you run the tests of this component directly inside your IDE, and not through Maven, then you could see exceptions like these:

org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is
<openjpa-2.2.1-r422266:1396819 nonfatal user error> org.apache.openjpa.persistence.ArgumentException: This configuration disallows runtime optimization,
but the following listed types were not enhanced at build time or at class load time with a javaagent: "org.apache.camel.examples.SendEmail".
    at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:427)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:127)
    at org.apache.camel.processor.jpa.JpaRouteTest.cleanupRepository(JpaRouteTest.java:96)
    at org.apache.camel.processor.jpa.JpaRouteTest.createCamelContext(JpaRouteTest.java:67)
    at org.apache.camel.test.junit5.CamelTestSupport.doSetUp(CamelTestSupport.java:238)
    at org.apache.camel.test.junit5.CamelTestSupport.setUp(CamelTestSupport.java:208)

The problem here is that the source has been compiled or recompiled through your IDE and not through Maven, which would enhance the byte-code at build time. To overcome this you need to enable dynamic byte-code enhancement of OpenJPA. For example, assuming the current OpenJPA version being used in Camel is 2.2.1, to run the tests inside your IDE you would need to pass the following argument to the JVM:

-javaagent:<path_to_your_local_m2_cache>/org/apache/openjpa/openjpa/2.2.1/openjpa-2.2.1.jar

32.15. Spring Boot Auto-Configuration

When using jpa 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-jpa-starter</artifactId>
</dependency>

The component supports 10 options, which are listed below.

Name	Description	Default	Type
camel.component.jpa.aliases	Maps an alias to a JPA entity class. The alias can then be used in the endpoint URI (instead of the fully qualified class name).		Map
camel.component.jpa.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.jpa.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.jpa.enabled	Whether to enable auto configuration of the jpa component. This is enabled by default.		Boolean
camel.component.jpa.entity-manager-factory	To use the EntityManagerFactory. This is strongly recommended to configure. The option is a javax.persistence.EntityManagerFactory type.		EntityManagerFactory
camel.component.jpa.join-transaction	The camel-jpa component will join transaction by default. You can use this option to turn this off, for example if you use LOCAL_RESOURCE and join transaction doesn’t work with your JPA provider. This option can also be set globally on the JpaComponent, instead of having to set it on all endpoints.	true	Boolean
camel.component.jpa.lazy-start-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.	false	Boolean
camel.component.jpa.shared-entity-manager	Whether to use Spring’s SharedEntityManager for the consumer/producer. Note in most cases joinTransaction should be set to false as this is not an EXTENDED EntityManager.	false	Boolean
camel.component.jpa.transaction-manager	To use the PlatformTransactionManager for managing transactions. The option is a org.springframework.transaction.PlatformTransactionManager type.		PlatformTransactionManager
camel.component.jpa.transaction-strategy	To use the TransactionStrategy for running the operations in a transaction. The option is a org.apache.camel.component.jpa.TransactionStrategy type.		TransactionStrategy