I have a requirement to cache xml bean java objects by reading xml’s from database . I am using a HashMap in memory to maintain my java objects. I am using spring for DI and Weblogic 11g app server.
Can you please suggest me a mechanism to reload cache when there is an update in xml files.
You can make use of weblogic p13n cache for this purpose, instead of using your own HashMap to cache the java objects. You will have to configure p13n-cache-config.xml file, which contains, TTL, max value etc. for your cache.
Coming to the first point, the cache will be automatically reloaded after the TTL time is done with. For manually clearing cache, You can implement a Servlet kind of thing, which you can hit directly from your browser (can restrict it for a particular URL). In that servlet clear the cache which you want to reload.
weblogic p13n cache provides you method for cluster aware cache clear as well, in case you need it, in case you want to use your own HashMap for caching, provide a update method for that HashMap and clear the java objects that you want to be reloaded and then call the cache creation method.
Related
I have some static configurations that will not be changed for each environment, for example, the mapping between client names and their id. In this case, should I store them in a Spring yml property file or in a database, eg. mongoDB, so that they can be easily accessed via Java code?
From the one side, consider that when you are adding a database component, you are adding additional potential point of failure to your app. What will happen if DB will not be accessible, for any reason ? ( crashed, under maintenance, network issues ) ?
From the second side, it depends how exactly your implementation will be using files. For example, if you will be adding items in your mapping between clients/ids, will you need to restart/rebuild/redeploy your app? How many running instances of your app will you have?
So, there are no one exact answer for all cases
It better keep in spring yaml instead of storing in any Database. Because calling the IO operations little expensive . Keeping static code in yaml or properties file will faster to access.
I am unable to configure/change the Map(declared as part of hazelcast config in spring) properties after hazelcast instance start up. I am using hazelcast integrated with spring as hibernate second level cache. I am trying to configure the properties of map (like TTL) in an init method (PostConstruct annotated) which is called during spring bean initialization.
There is not enough Documentation , if there is please guide me to it.
Mean while i went through this post and found this Hazelcast MapStoreConfig ignored
But how does the management center changes the config, will it recreate a new instance again ?
Is hazelcast Instance light weight unlike session factory ? i assume not,
please share your thoughts
This is not yet supported. JCache is the only on-the-fly configuration data structure at the moment.
However you'll most probably be able to destroy a proxy (DistributedObject like IMap, IQueue, ...), reconfigure it and recreate it. Anyhow at the time of recreation you must make sure that every node sees the same configuration, for example by storing the configuration itself inside an IMap or something like that. You'll have to do some wrapping on your own.
PS: This is not officially supported and an implementation detail that might change at later versions!
PPS: This feature is on the roadmap for quite some time but didn't made it into a release version yet, it however is still expected to have full support at some time in the future.
I want to load the data from database into cache memory using Spring ehCache when the application starts i.e when the server starts before any other method is called. I dont want to use a constructor. Please help me.
One option for this is to use a Spring BeanPostProcessor and have it work on the CacheManager bean, get the Cache and load it.
Another option is to have a BootstrapCacheLoader configured for doing this. You can also consider extending from MemoryLimitedCacheLoader to help you stop loading once you have reached cache capacity.
Scenario: Project consists of reference data which is updated once a week. Hence constantly querying this reference data for every transaction from the database is not efficient. Hence the motivation to cache this data.
Question: If secondary level caching and query caching in Hibernate is activated and the cache element in the hibernate configuration is set to read-only, how will hibernate know when to update the cache if a change is made to the database via another program. Is this automatically handled by Hibernate or do we have to clear the cache using some trigger?
If this is handled by Hibernate could someone shed light on how this is handled?
The JBoss documentation was not very clear about the management of the cache.
I am currently using Hibernate 3.6 with Spring 3.1 and do not wish to upgrade to Hibernate 4 if its not necessary.
It wont.
The second level cache expects all access to the data to happen via the ORM framework so if you have another actor in the db your cache will become stale.
You can clear the cache though - see this
code snippet
So you could expose a service that allows the 3rd party to clear the cache on your app when the database gets updated.
I have a web-application running on Google AppEngine.
I have a single PRODUCTION environment, a STAGING env and multiple development & QA envs. There are many configuration parameters that should differ between PRODUCTION and other environments - such as API keys for services we integrate with (GoogleAnalytics for example). Some of those parameters are defined in code, other are defined in web.xml (inside init-param tag for Filters, for example), and others cases as well.
I know that there are a couple of approaches to do so:
Saving all parameters in the datastore (and possible caching them in each running instance / Memcached)
Deploying the applications with different system-properties / environment-variables in the web.xml
Other options...?
Anyway, I'm interested to hear your best-practices for resloving this issue.
My favorite approach is to store them all in datastore and having only one master record in it with all the different properties and making a good use of the memcache. By doing that you don't need to have different configuration files or polluting your code with different configuration settings. Instead you can deploy and change this values from an administrative form that you will have to create in order to update this master record.
Also if you are storing tokens and secret keys then you are aware of the fact that is definitely not a good idea to have them in the web.xml or anywhere else in the code, but rather having it per application on something more secure, like datastore.
Once you have that, then you can have one global function that will retrieve properties by name and if you want to get the Google Analytics ID from anywhere in your app you should use it by having something like this:
getProperty('googleAnalyticsID')
where this global getProperty() function will try to find this value with these steps:
Check if it exist in memcache and return
If not in memcache, update memcache from master entity from datastore and return
If not in datastore create an entity with a default values, update memcache and return
Of course there are different approaches on how to retrieve data from that Model but the idea is the same: Store in one record and use the memcache.
You must have separate app ids for your production/staging/qa envs. This must be hardcorded into your web.xml (or you have a script of some sort that updates your web.xml)
After that you can code in your settings based on appid. I assume there's a java equivalent to this:
https://developers.google.com/appengine/docs/python/appidentity/functions#get_application_id
You could put it in the datastore if they're settings that change dynamically, but if they are static to the environment, it doesn't make sense to keep fetching from datastore.