JCache

Since Camel 2.17

Both producer and consumer are supported

The JCache component enables you to perform caching operations using JSR107/JCache as cache implementation.

URI Format

jcache:cacheName[?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 JCache component supports 8 options, which are listed below.

Name Description Default Type

cacheConfiguration (common)

A Configuration for the Cache.

Configuration

cacheConfigurationProperties (common)

Properties to configure jcache.

Map

cacheConfigurationPropertiesRef (common)

References to an existing Properties or Map to lookup in the registry to use for configuring jcache.

String

cachingProvider (common)

The fully qualified class name of the javax.cache.spi.CachingProvider.

String

configurationUri (common)

An implementation specific URI for the CacheManager.

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.

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

Endpoint Options

The JCache endpoint is configured using URI syntax:

jcache:cacheName

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

cacheName (common)

Required The name of the cache.

String

Query Parameters (23 parameters)

Name Description Default Type

cacheConfiguration (common)

A Configuration for the Cache.

Configuration

cacheConfigurationProperties (common)

The Properties for the javax.cache.spi.CachingProvider to create the CacheManager.

Properties

cachingProvider (common)

The fully qualified class name of the javax.cache.spi.CachingProvider.

String

configurationUri (common)

An implementation specific URI for the CacheManager.

String

managementEnabled (common)

Whether management gathering is enabled.

false

boolean

readThrough (common)

If read-through caching should be used.

false

boolean

statisticsEnabled (common)

Whether statistics gathering is enabled.

false

boolean

storeByValue (common)

If cache should use store-by-value or store-by-reference semantics.

true

boolean

writeThrough (common)

If write-through caching should be used.

false

boolean

filteredEvents (consumer)

Events a consumer should filter (multiple events can be separated by comma). If using filteredEvents option, then eventFilters one will be ignored.

Enum values:

  • CREATED

  • UPDATED

  • REMOVED

  • EXPIRED

String

oldValueRequired (consumer)

if the old value is required for events.

false

boolean

synchronous (consumer)

if the event listener should block the thread causing the event.

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

eventFilters (consumer (advanced))

The CacheEntryEventFilter. If using eventFilters option, then filteredEvents one will be ignored.

List

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

action (producer)

To configure using a cache operation by default. If an operation in the message header, then the operation from the header takes precedence.

String

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

cacheLoaderFactory (advanced)

The CacheLoader factory.

Factory

cacheWriterFactory (advanced)

The CacheWriter factory.

Factory

createCacheIfNotExists (advanced)

Configure if a cache need to be created if it does exist or can’t be pre-configured.

true

boolean

expiryPolicyFactory (advanced)

The ExpiryPolicy factory.

Factory

lookupProviders (advanced)

Configure if a camel-cache should try to find implementations of jcache api in runtimes like OSGi.

false

boolean

Message Headers

The JCache component supports 8 message header(s), which is/are listed below:

Name Description Default Type

CamelJCacheAction (producer)

Constant: ACTION

The cache operation to perform.

String

CamelJCacheResult (producer)

Constant: RESULT

The result of the cache operation.

boolean

CamelJCacheEventType (consumer)

Constant: EVENT_TYPE

The type of event received.

String

CamelJCacheKey (common)

Constant: KEY

The key of the cache entry.

Object

CamelJCacheKeys (producer)

Constant: KEYS

The collection of keys against which the action should be performed.

Set

CamelJCacheOldValue (consumer)

Constant: OLD_VALUE

The old value of the cache entry.

Object

CamelJCacheEntryProcessor (producer)

Constant: ENTRY_PROCESSOR

The EntryProcessor to invoke.

EntryProcessor

CamelJCacheEntryArgs (producer)

Constant: ARGUMENTS

The additional arguments to pass to the EntryProcessor.

Collection

JCache Policy

The JCachePolicy is an interceptor around a route that caches the "result of the route" - the message body - after the route is completed. If next time the route is called with a "similar" Exchange, the cached value is used on the Exchange instead of executing the route. The policy uses the JSR107/JCache API of a cache implementation, so it’s required to add one (e.g. Hazelcast, Ehcache) to the classpath.

The policy takes a key value from the received Exchange to get or store values in the cache. By default the key is the message body. For example if the route - having a JCachePolicy - receives an Exchange with a String body "fruit" and the body at the end of the route is "apple", it stores a key/value pair "fruit=apple" in the cache. If next time another Exchange arrives with a body "fruit", the value "apple" is taken from the cache instead of letting the route process the Exchange.

So by default the message body at the beginning of the route is the cache key and the body at the end is the stored value. It’s possible to use something else as key by setting a Camel Expression via .setKeyExpression() that will be used to determine the key.

The policy needs a JCache Cache. It can be set directly by .setCache() or the policy will try to get or create the Cache based on the other parameters set.

Similar caching solution is available for example in Spring using the @Cacheable annotation.

JCachePolicy Fields

Name Description Default Type

cache

The Cache to use to store the cached values. If this value is set, cacheManager, cacheName and cacheConfiguration is ignored.

Cache

cacheManager

The CacheManager to use to lookup or create the Cache. Used only if cache is not set.

Try to find a CacheManager in CamelContext registry or calls the standard JCache Caching.getCachingProvider().getCacheManager().

CacheManager

cacheName

Name of the cache. Get the Cache from cacheManager or create a new one if it doesn’t exist.

RouteId of the route.

String

cacheConfiguration

JCache cache configuration to use if a new Cache is created

Default new MutableConfiguration object.

CacheConfiguration

keyExpression

An Expression to evaluate to determine the cache key.

Exchange body

Expression

enabled

If policy is not enabled, no wrapper processor is added to the route. It has impact only during startup, not during runtime. For example it can be used to disable caching from properties.

true

boolean

How to determine cache to use?

Set cache

The cache used by the policy can be set directly. This means you have to configure the cache yourself and get a JCache Cache object, but this gives the most flexibility. For example it can be setup in the config xml of the cache provider (Hazelcast, EhCache, …​) and used here. Or it’s possible to use the standard Caching API as below:

MutableConfiguration configuration = new MutableConfiguration<>();
configuration.setTypes(String.class, Object.class);
configuration.setExpiryPolicyFactory(CreatedExpiryPolicy.factoryOf(new Duration(TimeUnit.MINUTES, 60)));
CacheManager cacheManager = Caching.getCachingProvider().getCacheManager();
Cache cache = cacheManager.createCache("orders",configuration);

JCachePolicy jcachePolicy = new JCachePolicy();
jcachePolicy.setCache(cache);

from("direct:get-orders")
    .policy(jcachePolicy)
    .log("Getting order with id: ${body}")
    .bean(OrderService.class,"findOrderById(${body})");

Set cacheManager

If the cache is not set, the policy will try to lookup or create the cache automatically. If the cacheManager is set on the policy, it will try to get cache with the set cacheName (routeId by default) from the CacheManager. If the cache does not exist it will create a new one using the cacheConfiguration (new MutableConfiguration by default).

//In a Spring environment for example the CacheManager may already exist as a bean
@Autowire
CacheManager cacheManager;
...

//Cache "items" is used or created if not exists
JCachePolicy jcachePolicy = new JCachePolicy();
jcachePolicy.setCacheManager(cacheManager);
jcachePolicy.setCacheName("items")

Find cacheManager

If cacheManager (and the cache) is not set, the policy will try to find a JCache CacheManager object:

  • Lookup a CacheManager in Camel registry - that falls back on JNDI or Spring context based on the environment

  • Use the standard api Caching.getCachingProvider().getCacheManager()

//A Cache "getorders" will be used (or created) from the found CacheManager
from("direct:get-orders").routeId("getorders")
    .policy(new JCachePolicy())
    .log("Getting order with id: ${body}")
    .bean(OrderService.class,"findOrderById(${body})");

Partially wrapped route

In the examples above the whole route was executed or skipped. A policy can be used to wrap only a segment of the route instead of all processors.

from("direct:get-orders")
    .log("Order requested: ${body}")
    .policy(new JCachePolicy())
        .log("Getting order with id: ${body}")
        .bean(OrderService.class,"findOrderById(${body})")
    .end()
    .log("Order found: ${body}");

The .log() at the beginning and at the end of the route is always called, but the section inside .policy() and .end() is executed based on the cache.

KeyExpression

By default the policy uses the received Exchange body as key, so the default expression is like simple("${body}). We can set a different Camel Expression as keyExpression which will be evaluated to determine the key. For example if we try to find an order by an orderId which is in the message headers, set header("orderId") (or simple("${header.orderId}) as keyExpression.

The expression is evaluated only once at the beginning of the route to determine the key. If nothing was found in cache, this key is used to store the value in cache at the end of the route.

MutableConfiguration configuration = new MutableConfiguration<>();
configuration.setTypes(String.class, Order.class);
configuration.setExpiryPolicyFactory(CreatedExpiryPolicy.factoryOf(new Duration(TimeUnit.MINUTES, 10)));

JCachePolicy jcachePolicy = new JCachePolicy();
jcachePolicy.setCacheConfiguration(configuration);
jcachePolicy.setCacheName("orders")
jcachePolicy.setKeyExpression(simple("${header.orderId}))

//The cache key is taken from "orderId" header.
from("direct:get-orders")
    .policy(jcachePolicy)
    .log("Getting order with id: ${header.orderId}")
    .bean(OrderService.class,"findOrderById(${header.orderId})");

Camel XML DSL examples

Use JCachePolicy in an XML route

In Camel XML DSL we need a named reference to the JCachePolicy instance (registered in CamelContext or simply in Spring). We have to wrap the route between <policy>…​</policy> tags after <from>.

<camelContext xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:get-order"/>
        <policy ref="jCachePolicy" >
            <setBody>
                <method ref="orderService" method="findOrderById(${body})"/>
            </setBody>
        </policy>
    </route>
</camelContext>

See this example when only a part of the route is wrapped:

<camelContext xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:get-order"/>
        <log message="Start - This is always called. body:${body}"/>
        <policy ref="jCachePolicy" >
            <log message="Executing route, not found in cache. body:${body}"/>
            <setBody>
                <method ref="orderService" method="findOrderById(${body})"/>
            </setBody>
        </policy>
        <log message="End - This is always called. body:${body}"/>
    </route>
</camelContext>

Define CachePolicy in Spring

It’s more convenient to create a JCachePolicy in Java especially within a RouteBuilder using the Camel DSL expressions, but see this example to define it in a Spring XML:

<bean id="jCachePolicy" class="org.apache.camel.component.jcache.policy.JCachePolicy">
    <property name="cacheName" value="spring"/>
    <property name="keyExpression">
        <bean class="org.apache.camel.model.language.SimpleExpression">
            <property name="expression" value="${header.mykey}"/>
        </bean>
    </property>
</bean>

Create Cache from XML

It’s not strictly speaking related to Camel XML DSL, but JCache providers usually have a way to configure the cache in an XML file. For example with Hazelcast you can add a hazelcast.xml to classpath to configure the cache "spring" used in the example above.

<hazelcast xmlns="http://www.hazelcast.com/schema/config"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.hazelcast.com/schema/config http://www.hazelcast.com/schema/config/hazelcast-config-4.0.xsd">

    <cache name="spring">
        <key-type class-name="java.lang.String"/>
        <value-type class-name="java.lang.String"/>
        <expiry-policy-factory>
            <timed-expiry-policy-factory expiry-policy-type="CREATED" duration-amount="60" time-unit="MINUTES"/>
        </expiry-policy-factory>
    </cache>

</hazelcast>

Special scenarios and error handling

If the Cache used by the policy is closed (can be done dynamically), the whole caching functionality is skipped, the route will be executed every time.

If the determined key is null, nothing is looked up or stored in cache.

In case of an exception during the route, the error handled is called as always. If the exception gets handled(), the policy stores the Exchange body, otherwise nothing is added to the cache. If an exception happens during evaluating the keyExpression, the routing fails, the error handler is called as normally.

Spring Boot Auto-Configuration

When using jcache 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-jcache-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 9 options, which are listed below.

Name Description Default Type

camel.component.jcache.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.jcache.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.jcache.cache-configuration

A Configuration for the Cache. The option is a javax.cache.configuration.Configuration type.

Configuration

camel.component.jcache.cache-configuration-properties

Properties to configure jcache.

Map

camel.component.jcache.cache-configuration-properties-ref

References to an existing Properties or Map to lookup in the registry to use for configuring jcache.

String

camel.component.jcache.caching-provider

The fully qualified class name of the javax.cache.spi.CachingProvider.

String

camel.component.jcache.configuration-uri

An implementation specific URI for the CacheManager.

String

camel.component.jcache.enabled

Whether to enable auto configuration of the jcache component. This is enabled by default.

Boolean

camel.component.jcache.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
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