Historically, Jawr regenerate all defined bundles at server startup. Depending on the bundle definition, the start-up time could be long. To fix this issue, Jawr introduces since Jawr 3.9 a new feature called “smart bundling” which allow Jawr analyze the bundle which have changed, and only rebuild these bundles. The smart bundling feature extends existing features to help to speed up the bundling process. This tutorial will explain you how to setup Jawr to use this feature.
The property jawr.use.bundle.mapping introduced in Jawr 3.0, when set to true, force Jawr to create files which contains the result of the bundle process.
Once generated, Jawr was not rebuilding the bundles. This was a good improvement to speed up start up time, but unfortunately when the bundles were modified the bundles were not rebuild.
Now Jawr is able to determine if the bundles have changed since the last bundle processing, in every case (server started or stopped).
The property jawr.config.reload.interval was previously used to determine the interval between Jawr configuration file reload to check if there were changes in Jawr configuration. Now Jawr checks also if the content of the files associated to the bundles have changed. This means that if a file content changed Jawr will rebuild the bundles.
By default, the smart bundling feature is deactivated. The property jawr.use.smart.bundling can be used to unable or disable it.
jawr.use.smart.bundling=true #This will enable the smart bundling feature
Note : It is important to note that if you enable the smart bundling feature, the use bundle mapping property will be enable by default, because it’s a prerequisite to use the smart bundling feature
If you want to use the automatic bundle processing when your application is started, you have update your Jawr configuration file like below :
jawr.config.reload.interval=10 #Here we configured Jawr to check for update every 10 sec
Using this configuration, if a change is detected on a bundle when the server is started, the bundle will be rebuild.
If you want to use the automatic bundle processing when your application is started, and also being able to force the refresh using JMX, you have update your Jawr configuration file like below :
jawr.use.smart.bundling=true #This will enable the smart bundling feature
To force bundle processing using JMX, you need to execute the method refreshConfig(). You’ll be able to refresh the configuration for one resource type, or for all resources by selecting the right JawrConfigManagerMBean or the JawrApplicationConfigManagerMBean. Please refer to the JMX documentation for more detail.
Note : The recommended way to force rebuild is to use JMX. It’s a more secure way to handle this use case. In some cases, JMX could not be an option, in these cases, you can use the refreshKey URL parameter. (see below)
If you want to use the automatic bundle processing when your application is started, and also being able to force the refresh using a key, you have update your Jawr configuration file like below :
jawr.use.smart.bundling=true #This will enable the smart bundling feature
jawr.config.reload.interval=3600 #Here we configured Jawr to check for update every hour
jawr.config.reload.refreshKey=mySecretKey #To force a refresh of bundles which needs to be rebuild, hit any bundle URL and add ?refreshKey=mySecretKey to reload the bundles.
Using this configuration, if a change on a bundle is detected when Jawr checks the configuration or if the refresh is forced using the refresh key parameter, the bundle will be rebuild. The information are stored in the bundle mapping files.
If you want to use the smart bundling feature only on server restart, you only have to set the jawr.use.bundle.mapping property to true, in your Jawr configuration file like below :
jawr.use.smart.bundling=true #This will enable the smart bundling feature
Using this configuration, if a change is detected on a bundle when the server is started, the bundle will not be rebuild until next server restart.
Jawr watches resources on server to detect resource creation, modification or deletion using WatchService API. When there are a lot of events, to ensure that all events have been processed before starting the bundling process, Jawr uses a delay after the last event to make sure that there no more event to process before starting the bundling process.
This delay is configurable using the property jawr.smart.bundling.delay.after.last.event :
| Property name | Type | Purpose | Default value |
|---|---|---|---|
| jawr.smart.bundling.delay.after.last.event | Integer | Defines the delay after the last event before starting the bundle processing (in second) | 2 |
Jawr allows the user to defines processor which can process all the bundles at once. An example of these kind of processors is the smartsprite global preprocessor, which will retrieve information about CSS sprite defines in every bundle and which will update sprite reference in all the bundles.
By nature, it is not possible to avoid the processing of all bundle for these global processors, but Jawr will try to find the impacted bundles after the global preprocessing phase, to only process those bundles.
To make sure that change are detected, you need to put ${md5} property in the image of the sprite-ref, like below :
/** sprite: mysprite; sprite-image: url('../../img/mysprite-${md5}.png'); sprite-layout: vertical */
.header {
background-image: url("../../../img/logo.png"); /** sprite-ref: mysprite; */
background-repeat: no-repeat;
height : 74px;
}
There are two way to force the complete rebuild (ignoring the information in cache) :
Clean the web application working directory where the files for cache are stored
Modify your Jawr configuration file
For the time being, this feature only works with modification on the file resources associated to bundle like : - modifying a resource - creating or deleting a resource on a bundle which has a mapping defines with wildcards For example, if you have a bundle mapping like ‘/css/**’, adding a resource to ‘/css’ or deleting one will be handle as a bundle modification
If you modify your configuration, Jawr will consider this as a complete modification and will rebuild all the bundles. So a modification in your configuration will trigger a full bundling process.
Jawr doesn’t detect modification on Processor or Generator class. So if a Processor or a Generator has been modified, you’ll have to clean your cache so Jawr will rebuild the bundles with this modification.