DistributedMap and DistributedObjectCache interfaces for the dynamic cache

 

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Before you begin

Enable the dynamic cache service.

 

Overview

The DistributedMap and DistributedObjectCache interfaces are simple interfaces for the dynamic cache. Using these interfaces, J2EE applications and system components can cache and share Java objects by storing a reference to the object in the cache. The default dynamic cache instance is created if the dynamic cache service is enabled in the administrative console. This default instance is bound to the global JNDI namespace using the name...

services/cache/distributedmap

Multiple instances of the DistributedMap and DistributedObjectCache interfaces on the same JVM enable applications to separately configure cache instances as needed. Each instance of the DistributedMap interface has its own properties that can be set using Object cache instance settings.

For more information about the DistributedMap and DistributedObjectCache interfaces, see the API documentation for the com.ibm.websphere.cache package.

If you are using custom object keys, place your classes in a shared library. We can define the shared library at cell, node, or server level. Then, in each server create a class loader and associate it with the shared library that you defined.

There are three methods for configuring and using cache instances.

 

Steps for this task (dependent on configuration)

• Method 1 - Administrative console

  We can create additional cache instances using the administrative console.

  1. In the administrative console, select...

     Resources | Object cache instances

     ...and create a new object cache instance.

  If you defined two object cache instances in the administrative console with JNDI names of services/cache/instance_one and services/cache/instance_two, use the following code to look up the cache instances

   InitialContext ic = new InitialContext();
  DistributedMap dm1 = (DistributedMap)ic.lookup("services/cache/instance_one");
  
  DistributedMap dm2 = (DistributedMap)ic.lookup("services/cache/instance_two");
  
  // or
  
  InitialContext ic = new InitialContext();
  DistributedObjectCache dm1 = (DistributedObjectCache)ic.lookup("services/cache/instance_one");
  
  DistributedObjectCache dm2 = (DistributedObjectCache)ic.lookup("services/cache/instance_two");
  
  

• Method 2 - Properties file

  We can create cache instances using the cacheinstances.properties file and package the file in your EAR file.

  Following is an example of how one can create additional cache instances using the cacheinstances.properties file

  cache.instance.0=/services/cache/instance_one
  cache.instance.0.cacheSize=1000
  cache.instance.0.enableDiskOffload=true
  cache.instance.0.diskOffloadLocation=${WAS_INSTALL_ROOT}/diskOffload
  cache.instance.0.flushToDiskOnStop=true
  cache.instance.0.useListenerContext=true
  cache.instance.0.enableCacheReplication=false
  cache.instance.0.disableDependencyId=false
  cache.instance.0.htodCleanupFrequency=60
  cache.instance.1=/services/cache/instance_two
  cache.instance.1.cacheSize=1500
  cache.instance.1.enableDiskOffload=false
  cache.instance.1.flushToDiskOnStop=false
  cache.instance.1.useListenerContext=false
  cache.instance.1.enableCacheReplication=true
  cache.instance.1.replicationDomain=DynaCacheCluster
  cache.instance.1.disableDependencyId=true
  

  The preceding example creates two cache instances named instance_one and instance_two. instance_one has a cache entry size of 1,000 and instance_two has a cache entry size of 1,500. Disk offload is enabled in instance_one and disabled in instance_two. Use listener context is enabled in instance_one and disabled in instance_two. Flush to disk on stop is enabled in instance_one and disabled in instance_two. Cache replication is enabled in instance_two and disabled in instance_one. The name of the data replication domain for instance_two is DynaCacheCluster. Dependency ID support is disabled in instance_two.

  You must place the cacheinstances.properties file in either your application server or application class path. For example, use your application WAR file,...

  WEB-INF\classes

  ...or...

  was_root\classes

  The first entry in the properties file (cache.instance.0) specifies the JNDI name for the cache instance in the global namespace. Use the following code to look up the cache instance:

       InitialContext ic = new InitialContext();
       DistributedMap dm1 = (DistributedMap)ic.lookup("services/cache/instance_one");
       DistributedMap dm2 = (DistributedMap)ic.lookup("services/cache/instance_two");
  

• Method 3 - Resource references

  Note: Method three is an extension to method one or method two, listed above. First use either method one or method two.

  Define a resource-ref in your module deployment descriptor (web.xml and ibm-web-bnd.xmi files) and look up the cache using the java:comp namespace

  Resource-ref example:
  File: web.xml
  <resource-ref id="ResourceRef_1">
    <res-ref-name>dmap/LayoutCache</res-ref-name>
    <res-type>com.ibm.websphere.cache.DistributedMap</res-type>
    <res-auth>Container</res-auth>
    <res-sharing-scope>Shareable</res-sharing-scope>
  </resource-ref>
  <resource-ref id="ResourceRef_2">
    <res-ref-name>dmap/UserCache</res-ref-name>
    <res-type>com.ibm.websphere.cache.DistributedMap</res-type>
    <res-auth>Container</res-auth>
    <res-sharing-scope>Shareable</res-sharing-scope>
  </resource-ref>
  
  File: ibm-web-bnd.xmi
  <?xml version="1.0" encoding="UTF-8"?>
  <webappbnd:WebAppBinding xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" 
  xmlns:webappbnd="webappbnd.xmi" 
  xmlns:webapplication="webapplication.xmi" xmlns:commonbnd="commonbnd.xmi" 
  xmlns:common="common.xmi" 
  xmi:id="WebApp_ID_Bnd" virtualHostName="default_host">
    <webapp href="WEB-INF/web.xml#WebApp_ID"/>
    <resRefBindings xmi:id="ResourceRefBinding_1" jndiName="services/cache/instance_one">
      <bindingResourceRef href="WEB-INF/web.xml#ResourceRef_1"/>
    </resRefBindings>
    <resRefBindings xmi:id="ResourceRefBinding_2" jndiName="services/cache/instance_two">
      <bindingResourceRef href="WEB-INF/web.xml#ResourceRef_2"/>
    </resRefBindings>
  </webappbnd:WebAppBinding>
  

  The following example shows how to look up the resource-ref

  InitialContext ic = new InitialContext();
    DistributedMap dm1a =(DistributedMap)ic.lookup("java:comp/env/dmap/LayoutCache");
    DistributedMap dm2a =(DistributedMap)ic.lookup("java:comp/env/dmap/UserCache");
  // or
    DistributedObjectCache dm1a =(DistributedObjectCache)ic.lookup("java:comp/env/dmap/LayoutCache");
    DistributedObjectCache dm2a =(DistributedObjectCache)ic.lookup("java:comp/env/dmap/UserCache");
  

  The previous resource-ref example maps java:comp/env/dmap/LayoutCache to /services/cache/instance_one and java:comp/env/dmap/UserCache to /services/cache/instance_two. In the examples, DistributedMap dm1 and dm1a are the same object. DistributedMap dm2 and dm2a are the same object.

   

  Restriction

  DistributedMap and DistributedObjectCache do not have authorization or access control associated with the cache entries.

 

What to do next

To learn how to share cached objects in a clustered environment, see Sharing cached objects in a clustered environment.

 

See also

Share cached objects in a clustered environment
Object cache instance settings
Object cache instance collection
Invalidation listeners
Cache instances
Enable the dynamic cache service
Configure dynamic cache disk offload
Use object cache instances
Manage cache entries stored on a disk

 

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