Cache Component
Warning |
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This component is deprecated. As of Camel 2.18.0 You should use Ehcache. |
Available as of Camel 2.1
The cache component enables you to perform caching operations using EHCache as the Cache Implementation. The cache itself is created on demand or if a cache of that name already exists then it is simply utilized with its original settings.
This component supports producer and event based consumer endpoints.
The Cache consumer is an event based consumer and can be used to listen and respond to specific cache activities. If you need to perform selections from a pre-existing cache, use the processors defined for the cache component.
Maven users will need to add the following dependency to their pom.xml
for this component:
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h2. Cache Component *Available as of Camel 2.1* The *cache* component enables you to perform caching operations using EHCache as the Cache Implementation. The cache itself is created on demand or if a cache of that name already exists then it is simply utilized with its original settings. This component supports producer and event based consumer endpoints. The Cache consumer is an event based consumer and can be used to listen and respond to specific cache activities. If you need to perform selections from a pre-existing cache, used the processors defined for the cache component. Maven users will need to add the following dependency to their {{pom.xml}} for this component: {code:xml} <dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-cache</artifactId> <version>x.x.x</version> <!-- use the same version as your Camel core version --> </dependency> {code} h3. URI format {code} |
URI format
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cache://cacheName[?options]
{code}
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You
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can
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append
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query
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options
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to
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the
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URI
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in
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the
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following
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format,
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?option=value&option=#beanRef&...
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Options
Name | Default Value | Description |
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| The number of elements that may be stored in the defined cache |
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| The number of elements that may be stored in the defined cache. Options include
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| Specifies whether cache may overflow to disk |
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| Sets whether elements are eternal. If eternal, timeouts are ignored and the |
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| The maximum time between creation time and when an element expires. |
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| The maximum amount of time between accesses before an element expires |
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| Whether the disk store persists between restarts of the Virtual Machine. |
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| The number of seconds between runs of the disk expiry thread. |
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| Camel 2.8: If you want to use a custom factory which instantiates and creates the EHCache |
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list |
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of |
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EHCache |
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for |
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all |
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new |
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caches- |
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no |
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need |
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to |
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define |
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it |
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per |
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cache |
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in |
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EHCache |
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xml |
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config |
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anymore. |
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org.apache.camel.component.cache.CacheEventListenerRegistry |
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Sets |
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a |
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list |
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of |
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that |
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extends |
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EHCache |
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for |
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all |
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new |
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caches- |
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no |
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need |
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to |
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define |
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it |
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per |
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cache |
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in |
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EHCache |
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xml |
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config |
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anymore. |
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org.apache.camel.component.cache.CacheLoaderRegistry |
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| Camel 2.10: To configure using a cache key by default. If a key is provided in the message header, then the key from the header takes precedence. |
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| Camel 2.10: To configure using an cache operation by default. If an operation in the message header, then the operation from the header takes precedence. |
objectCache | false | Camel 2.15: Whether to turn on allowing to store non serializable objects in the cache. If this option is enabled then overflow to disk cannot be enabled as well. |
Cache Component options
Name | Default Value | Description |
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| To use a custom |
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| To use a custom |
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| Camel 2.13/2.12.3: To configure the location of the |
Sending/Receiving Messages to/from the cache
Message Headers up to Camel 2.7
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Message Headers Camel 2.8+
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The header names and supported values have changed to be prefixed with 'CamelCache' and use mixed case. This makes them easier to identify and keep separate from other headers. The CacheConstants variable names remain unchanged, just their values have been changed. Also, these headers are now removed from the exchange after the cache operation is performed. |
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The CamelCacheAdd
and CamelCacheUpdate
operations support additional headers:
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Cache Producer
Sending data to the cache involves the ability to direct payloads in exchanges to be stored in a pre-existing or created-on-demand cache. The mechanics of doing this involve
- setting the Message Exchange Headers shown above.
- ensuring that the Message Exchange Body contains the message directed to the cache
Cache Consumer
Receiving data from the cache involves the ability of the CacheConsumer to listen on a pre-existing or created-on-demand Cache using an event Listener and receive automatic notifications when any cache activity take place (i.e CamelCacheGet/CamelCacheUpdate/CamelCacheDelete/CamelCacheDeleteAll).
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Upon
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such
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an
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activity
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taking place
- an exchange containing Message Exchange Headers and a Message Exchange Body containing the just added/updated payload is placed and sent.
- in case of a CamelCacheDeleteAll operation, the Message Exchange Header CamelCacheKey and the Message Exchange Body are not populated.
Cache Processors
There are a set of nice processors with the ability to perform cache lookups and selectively replace payload content at the
- body
- token
- xpath level
Cache Usage Samples
Example 1: Configuring the cache
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place - an exchange containing Message Exchange Headers and a Message Exchange Body containing the just added/updated payload is placed and sent. - in case of a CamelCacheDeleteAll operation, the Message Exchange Header CamelCacheKey and the Message Exchange Body are not populated. h4. Cache Processors There are a set of nice processors with the ability to perform cache lookups and selectively replace payload content at the - body - token - xpath level h3. Cache Usage Samples h4. Example 1: Configuring the cache {code} from("cache://MyApplicationCache" + "?maxElementsInMemory=1000" + "&memoryStoreEvictionPolicy=" + "MemoryStoreEvictionPolicy.LFU" + "&overflowToDisk=true" + "&eternal=true" + "&timeToLiveSeconds=300" + "&timeToIdleSeconds=true" + "&diskPersistent=true" + "&diskExpiryThreadIntervalSeconds=300") {code} h4. Example |
Example 2:
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Adding
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keys
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to
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the
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cache
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{code} RouteBuilder builder = new RouteBuilder() { public void configure() { from("direct:start") .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_OPERATION_ADD)) .setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")) .to("cache://TestCache1") } }; {code} h4. Example |
Example 2:
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Updating
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existing
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keys
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in
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a cache
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cache {code} RouteBuilder builder = new RouteBuilder() { public void configure() { from("direct:start") .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_OPERATION_UPDATE)) .setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")) .to("cache://TestCache1") } }; {code} h4. Example |
Example 3:
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Deleting
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existing
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keys
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in
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a
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cache
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{code} RouteBuilder builder = new RouteBuilder() { public void configure() { from("direct:start") .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_DELETE)) .setHeader(CacheConstants.CACHE_KEY", constant("Ralph_Waldo_Emerson")) .to("cache://TestCache1") } }; {code} h4. Example |
Example 4:
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Deleting
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all
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existing
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keys
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in
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a
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cache
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{code} RouteBuilder builder = new RouteBuilder() { public void configure() { from("direct:start") .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_DELETEALL)) .to("cache://TestCache1"); } }; {code} h4. Example |
Example 5:
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Notifying
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any
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changes
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registering
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in
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a
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Cache
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to
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Processors
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and
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other
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Producers
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} RouteBuilder builder = new RouteBuilder() { public void configure() { from("cache://TestCache1") .process(new Processor() { public void process(Exchange exchange) throws Exception { String operation = (String) exchange.getIn().getHeader(CacheConstants.CACHE_OPERATION); String key = (String) exchange.getIn().getHeader(CacheConstants.CACHE_KEY); Object body = exchange.getIn().getBody(); // Do something } }) } }; {code} h4. Example |
Example 6:
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Using
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Processors
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to
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selectively
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replace
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payload
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with
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cache
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values
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} RouteBuilder builder = new RouteBuilder() { public void configure() { //Message Body Replacer from("cache://TestCache1") .filter(header(CacheConstants.CACHE_KEY).isEqualTo("greeting")) .process(new CacheBasedMessageBodyReplacer("cache://TestCache1","farewell")) .to("direct:next"); //Message Token replacer from("cache://TestCache1") .filter(header(CacheConstants.CACHE_KEY).isEqualTo("quote")) .process(new CacheBasedTokenReplacer("cache://TestCache1","novel","#novel#")) .process(new CacheBasedTokenReplacer("cache://TestCache1","author","#author#")) .process(new CacheBasedTokenReplacer("cache://TestCache1","number","#number#")) .to("direct:next"); //Message XPath replacer from("cache://TestCache1"). .filter(header(CacheConstants.CACHE_KEY).isEqualTo("XML_FRAGMENT")) .process(new CacheBasedXPathReplacer("cache://TestCache1","book1","/books/book1")) .process (new CacheBasedXPathReplacer("cache://TestCache1","book2","/books/book2")) .to("direct:next"); } }; {code} h4. Example |
Example 7:
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Getting
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an
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entry
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from
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the
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Cache
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} from("direct:start") // Prepare headers .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_OPERATION_GET)) .setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")). .to("cache://TestCache1"). // Check if entry was not found .choice().when(header(CacheConstants.CACHE_ELEMENT_WAS_FOUND).isNull()). // If not found, get the payload and put it to cache .to("cxf:bean:someHeavyweightOperation"). .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_OPERATION_ADD)) .setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")) .to("cache://TestCache1") .end() .to("direct:nextPhase"); {code} h4. Example |
Example 8:
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Checking
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for
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an
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entry
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in
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the
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Cache
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Note:
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The CHECK
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command
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tests
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existence
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of
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an entry
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in
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the
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cache
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but
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doesn't
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place
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a message
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in the
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body.
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} from("direct:start") // Prepare headers .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_OPERATION_CHECK)) .setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")). .to("cache://TestCache1"). // Check if entry was not found .choice().when(header(CacheConstants.CACHE_ELEMENT_WAS_FOUND).isNull()). // If not found, get the payload and put it to cache .to("cxf:bean:someHeavyweightOperation"). .setHeader(CacheConstants.CACHE_OPERATION, constant(CacheConstants.CACHE_OPERATION_ADD)) .setHeader(CacheConstants.CACHE_KEY, constant("Ralph_Waldo_Emerson")) .to("cache://TestCache1") .end(); {code} h3. Management of EHCache EHCache has its own statistics and management from [JMX|Camel JMX]. Here's a snippet on how to expose them via JMX in a Spring application context: {code:xml} |
Management of EHCache
EHCache has its own statistics and management from JMX.
Here's a snippet on how to expose them via JMX in a Spring application context:
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<bean id="ehCacheManagementService" class="net.sf.ehcache.management.ManagementService" init-method="init" lazy-init="false">
<constructor-arg>
<bean class="net.sf.ehcache.CacheManager" factory-method="getInstance"/>
</constructor-arg>
<constructor-arg>
<bean class="org.springframework.jmx.support.JmxUtils" factory-method="locateMBeanServer"/>
</constructor-arg>
<constructor-arg value="true"/>
<constructor-arg value="true"/>
<constructor-arg value="true"/>
<constructor-arg value="true"/>
</bean>
{code}
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Of
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course you can do the same thing in straight Java:
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ManagementService.registerMBeans(CacheManager.getInstance(), mbeanServer, true, true, true, true);
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You can get cache hits, misses, in-memory hits, disk hits, size stats this way. You can also change CacheConfiguration parameters on the fly.
Cache replication Camel 2.8+
The Camel Cache component is able to distribute a cache across server nodes using several different replication mechanisms including: RMI, JGroups, JMS and Cache Server.
There are two different ways to make it work:
1. You can configure ehcache.xml
manually
OR
2. You can configure these three options:
- cacheManagerFactory
- eventListenerRegistry
- cacheLoaderRegistry
Configuring Camel Cache replication using the first option is a bit of hard work as you have to configure all caches separately. So in a situation when the all names of caches are not known, using ehcache.xml
is not a good idea.
The second option is much better when you want to use many different caches as you do not need to define options per cache. This is because replication options are set per CacheManager
and per CacheEndpoint
. Also it is the only way when cache names are not know at the development phase.
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It might be useful to read the EHCache manual to get a better understanding of the Camel Cache replication mechanism. |
Example: JMS cache replication
JMS replication is the most powerful and secured replication method. Used together with Camel Cache replication makes it also rather simple.
An example is available on a separate page.