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6.6.8.0.18: Assembly properties for servlet caching configurations
6.6.8.0.18: Assembly properties for servlet caching configurations
Dynamic caching can be used to improve the performance of servlet and
JavaServer Pages (JSP) files by serving requests from an in-memory
cache. Cache entries contain the servlet's output, results of the
servlet's execution, and metadata.
The properties on the General tab define a cache group and govern how long
an entry remains in the cache. The properties on the ID Generation tab
define how cache IDs are built and the criteria used to cache or invalidate
entries. The properties on the Advanced tab define external cache
groups and specify custom interfaces for handling servlet caching.
- Caching group name (Required, String)
- Specifies a name for the group of servlets or JSP files to be
cached.
- Priority
- An integer that defines the default priority for servlets that are
cached. The default value is 1. Priority is an extension of the
Least Recently Used (LRU) caching algorithm. It represents the number
of cycles through the LRU algorithm that an entry is guaranteed to stay in the
cache. The priority represents the length of time that an entry remains
in the cache before being eligible for removal. On each cycle of the
algorithm, the priority of an entry is decremented. When the priority
reaches zero, the entry is eligible for invalidation. If an entry is
requested while in the cache, its priority is reset to the priority
value. Regardless of the priority value and the number of requests, an
entry is invalidated when its timeout occurs. Consider increasing the
priority of a servlet or JSP file when it is difficult to calculate the output
of the servlet or JSP file or when the servlet or JSP file is executed more
often than average. Priority values should be low. Higher values
do not yield much improvement but use extra LRU cycles. Use timeout to
guarantee the validity of an entry. Use priority to rank the relative
importance of one entry to other entries. Giving all entries equal
priority results in a standard LRU cache that increases performance
significantly.
- Timeout
- Specifies the length of time, in seconds, that a cache entry is to remain
in the cache after it has been created. When this time elapses, the
entry is removed from the cache. If the timeout is zero or a negative
number, the entry does not time out. It is removed when the cache is
full or programmatically, from within an application.
- Invalidate only
- Specifies that invalidations for a servlet are to take place, but that no
caching is to be performed for the servlet. For example, this property
can be used to prevent caching of control servlets. Control servlets
treat HTTP requests as commands and execute those commands. By default,
this checkbox is not selected.
- Caching group members
- Specifies the names of the servlets or JSP files to be cached. The
URIs are determined from the servlet mappings.
- Use URIs for cache ID building
- Specifies whether or not the URI of the requested servlet is to be used to
create a cache ID. By default, URIs are used.
- Use specified string
- Specifies a string representing a combination of request and session
variables that are to be used to create cache IDs. (This property
defines request and session variables, and the cache uses the values of these
variables to create IDs for the entries.)
- Variables - ID
- The name of a request parameter, request attribute, session parameter, or
cookie.
- Variables - Type
- Indicates the type of variable specified in the ID field. The valid
values are Request parameter, Request attribute, Session parameter, or
Cookie.
- Variables - Method
- The name of a method in the request attribute or session parameter.
The output of this method is used to generate cache entry IDs. If this
value is not specified, the toString method is used by default.
- Variables - Data ID
- Specifies a string that, combined with the value of the variable,
generates a group name for the cache entry. The cache entry is placed
in this group. This group can later be invalidated.
- Variables - Invalidate ID
- Specifies a string that is combined with the value of the variable on the
request or session to form a group name. The cache invalidates the
group name.
- Required
- Indicates whether a value must be present in the request. If this
checkbox is selected, and either the request parameter, request attribute, or
session parameter is not specified, or the method is not specified, the
request is not cached.
- External cache groups - Group name
- Specifies the name of the external cache group to which this servlet will
be published.
- ID generator
- Specifies a user-written interface for handling parameters, attributes,
and sessions. The value must be a full package and class name of a
class extending
com.ibm.websphere.servlet.cache.IdGenerator.
The properties specified in the Application Assembly Tool will still be used
and passed to the IdGenerator in the initialize method inside a
com.ibm.websphere.servlet.cache.CacheConfig
object.
- Meta data generator
- Specifies a user-written interface for handling invalidation, priority
levels, and external cache groups. The value must be the full package
and class name of a class extending
com.ibm.websphere.servlet.cache.MetaDataGenerator.
The properties specified in the Application Assembly Tool will still be used
and passed to the MetaDataGenerator in the initialize method inside a
com.ibm.websphere.servlet.cache.CacheConfig
object.
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