2. Where to Start

This section tells you about the Cache interface and how it can be implemented to create your own cache.

2.1 Implementing the Cache interface

The Cache interface is the interface used by Report Server to manage Reports Cache. You can find the Cache Java API documentation here.

1. start(java.util.Properties cacheSystemProps, oracle.reports.utility.Trace trace)

This method Starts the Oracle9i Reports caching service. You can use this method to set all static information that you can load from the Reports Server configuration file. (server.conf file in the $ORACLE_HOME/reports/config directory). This method receives the properties object as a parameter, which contains the list of values in the configuration file. See the "Integration with Oracle9i Reports" Section.

In the Size Cache example, the start method is used to load the following information:

• maximum size of the cache
• maximum number of files in the cache
• cache directory

If the cache directory does not exist, it creates the directory.

2. newItem(Job job, String instanceKey)

This method creates a new item in cache system for the given job. The parameter job is the object that will own this cache item. The other parameter instanceKey is needed if the job will generate multiple instances of ouput for bursting reports. This parameter indicates which instance of the multiple outputs is being created. If it is null, it either means the item will be for the whole job, or that this job has only one set of output.

3. findItem(java.util.Properties jobProps)

This method gets the job properties like REPORT, DESTYPE, DESFORMAT, USERID, etc from the input parameter "props". These parameters are matched with the parameters used to submit earlier job requests whose results are stored in the cache directory. If the current parameters list matches with an earlier job request, the report output is picked up from cache instead of running the request again.

Note: If this is a single job run from the command line, the key will be used for comparison. If this is a distribution job, the group key will be used for comparison. If there is a match, the first item of the group is returned.

4. manage()

This method manages the cache, for example, how to keep the cache size within the limit specified in the server.conf file. In the default cache used with Oracle9i Reports, if the cache directory size exceeds the limit, this method deletes items based on the "first-in first-out" logic. In addition, it also checks for expired items and deletes them from cache.

In the Size Cache example, this method deletes top 5 items from the cache directory based on the "biggest file size" logic.

5. deleteItem(CacheItem item)

This method deletes the cache item referred to by the parameter item. This method can be invoked by other methods like manage and empty, for example, whenever items have to be deleted from the cache.

6. empty()

It invokes the method deleteItem repetitively to delete all items in the cache.

7. stop()

This method stops the Oracle9i Reports caching service. You can include some logic with this method to liberate resources like a connection pool to a database or an LDAP server.

8. getMaxCapacity(), setMaxCapacity()

As is clear from their names, these methods get and set the Maximum capacity of the cache - these values are loaded from the server.conf file in the method start().

9. getCurrentCapacity()

This method gets the current capacity of the cache.

10. getMaxNumberOfFiles(), setMaxNumberOfFiles()

As is clear from their names, these methods get and set the Maximum number of files allowed in the cache - these values are loaded from the server.conf file in the method start().

11. getCurrentNumberOfFiles()

This method gets the current number of files in the cache.