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:

<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>


URI format


cache://cacheName[?options]



You can append query options to the URI in the following format, ?option=value&option=value&...

Options




 Name 
 Default Value 
 Description 


 maxElementsInMemory 
 1000 
 The numer of elements that may be stored in the defined cache 


 memoryStoreEvictionPolicy 
 MemoryStoreEvictionPolicy.LFU 
 The number of elements that may be stored in the defined cache. Options include

	MemoryStoreEvictionPolicy.LFU - Least frequently used
	MemoryStoreEvictionPolicy.LRU - Least recently used
	MemoryStoreEvictionPolicy.FIFO - first in first out, the oldest element by creation time




 overflowToDisk 
 true 
 Specifies whether cache may overflow to disk


 eternal 
 false 
 Sets whether elements are eternal. If eternal, timeouts are ignored and the

element is never expired. 


 timeToLiveSeconds 
 300 
 The maximum time between creation time and when an element expires.

Is only used if the element is not eternal 


 timeToIdleSeconds 
 300 
 The maximum amount of time between accesses before an element expires 


 diskPersistent 
 true 
 Whether the disk store persists between restarts of the Virtual Machine.

The default value is false. 


 diskExpiryThreadIntervalSeconds 
 120 
 The number of seconds between runs of the disk expiry thread. The default value

is 120 seconds 


 cacheManagerFactory 
 null 
 Camel 2.3: If you want to use a custom factory which instantiates and creates the EHCache net.sf.ehcache.CacheManager. 





Sending/Receiving Messages to/from the cache

Message Headers




 Header 
 Description 


 CACHE_OPERATION 
 The operation to be performed on the cache. The valid options are

	GET
	CHECK
	ADD
	UPDATE
	DELETE
	DELETEALL

The GET and CHECK requires Camel 2.3 onwards. 




 CACHE_KEY 
 The cache key used to store the Message in the cache. The cache key is optional if the CACHE_OPERATION is DELETEALL 




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 ADD/UPDATE/DELETE/DELETEALL). Upon such an activity 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 DELETEALL operation, the Message Exchange Header CACHE_KEY 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

from("cache://MyApplicationCache" +
          "?maxElementsInMemory=1000" + 
          "&memoryStoreEvictionPolicy=" +
              "MemoryStoreEvictionPolicy.LFU" +
          "&overflowToDisk=true" +
          "&eternal=true" +
          "&timeToLiveSeconds=300" + 
          "&timeToIdleSeconds=true" +
          "&diskPersistent=true" +
          "&diskExpiryThreadIntervalSeconds=300")



Example 2: Adding keys to the cache 

RouteBuilder builder = new RouteBuilder() {
    public void configure() {
     from("direct:start")
     .setHeader("CACHE_OPERATION", constant("ADD"))
     .setHeader("CACHE_KEY", constant("Ralph_Waldo_Emerson"))
     .to("cache://TestCache1")
   }
};



Example 2: Updating existing keys in a cache 

RouteBuilder builder = new RouteBuilder() {
    public void configure() {
     from("direct:start")
     .setHeader("CACHE_OPERATION", constant("UPDATE"))
     .setHeader("CACHE_KEY", constant("Ralph_Waldo_Emerson"))
     .to("cache://TestCache1")
   }
};



Example 3: Deleting existing keys in a cache 

RouteBuilder builder = new RouteBuilder() {
    public void configure() {
     from("direct:start")
     .setHeader("CACHE_OPERATION", constant("DELETE"))
     .setHeader("CACHE_KEY", constant("Ralph_Waldo_Emerson"))
     .to("cache://TestCache1")
   }
};



Example 4: Deleting all existing keys in a cache 

RouteBuilder builder = new RouteBuilder() {
    public void configure() {
     from("direct:start")
     .setHeader("CACHE_OPERATION", constant("DELETEALL"))
     .to("cache://TestCache1");
    }
};



Example 5: Notifying any changes registering in a Cache to Processors and other Producers

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("CACHE_OPERATION");
           String key = (String) exchange.getIn().getHeader("CACHE_KEY");
           Object body = exchange.getIn().getBody();
           // Do something
        } 
     })
   } 
};



Example 6: Using Processors to selectively replace payload with cache values

RouteBuilder builder = new RouteBuilder() {
   public void configure() {
     //Message Body Replacer
     from("cache://TestCache1")
     .filter(header("CACHE_KEY").isEqualTo("greeting"))
     .process(new CacheBasedMessageBodyReplacer("cache://TestCache1","farewell"))
     .to("direct:next");  

    //Message Token replacer
    from("cache://TestCache1")
    .filter(header("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("CACHE_KEY").isEqualTo("XML_FRAGMENT"))
    .process(new CacheBasedXPathReplacer("cache://TestCache1","book1","/books/book1"))
    .process (new CacheBasedXPathReplacer("cache://TestCache1","book2","/books/book2"))
    .to("direct:next");
   }
};

Change Notification Preferences

View Online | View Changes | Add Comment

[CONF] Apache Camel > Cache

Cache

Page edited by Claus Ibsen

Changes (3)

Full Content

Cache Component

URI format

Options

Sending/Receiving Messages to/from the cache

Message Headers

Cache Producer

Cache Consumer

Cache Processors

Cache Usage Samples

Example 1: Configuring the cache

Example 2: Adding keys to the cache

Example 2: Updating existing keys in a cache

Example 3: Deleting existing keys in a cache

Example 4: Deleting all existing keys in a cache

Example 5: Notifying any changes registering in a Cache to Processors and other Producers

Example 6: Using Processors to selectively replace payload with cache values

Reply via email to