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SkyVault 2.0 » Developer guide » Platform extensions » Platform extension points

Patches

A patch is a piece of Java code that executes once when SkyVault is started. Custom patches can be implemented.
Information Patch
Support Status Full Support
Architecture Information Platform Architecture
Description

A patch executes a piece of Java code when SkyVault starts up, and logs the result in the ALF_APPLIED_PATCHES database table. A patch is only executed once and can be targeted at a certain SkyVault version range. Patches are used a lot by SkyVault internally to do things like database schema updates and content bootstrapping.

Developing a patch involves a number of steps of which the first one is to implement the Java class that does the actual work during the bootstrapping of the repository. As an example, a patch that creates a folder under the Company Home folder is examined:

public class ContentCreationPatch extends AbstractPatch {
   private static Log logger = LogFactory.getLog(ContentCreationPatch.class);
   private static final String PATCH_ID = "org.alfresco.tutorial.patch.contentCreationPatch";
   private static final String MSG_SUCCESS = PATCH_ID + ".result";
   private static final String MSG_ERROR = PATCH_ID + ".error";
   
   /**
     * The SkyVault Service Registry that gives access to all public content services in SkyVault.
     */
   private ServiceRegistry serviceRegistry;
   
   public void setServiceRegistry(ServiceRegistry serviceRegistry) {
      this.serviceRegistry = serviceRegistry;
   }
   
   @Override
   protected String applyInternal() throws Exception {
      logger.info("Starting execution of patch: " + I18NUtil.getMessage(PATCH_ID));
      
      // Get the store reference for the Repository store that contains live content
      StoreRef store = StoreRef.STORE_REF_WORKSPACE_SPACESSTORE;
      
      // Get root node for store
      NodeRef rootRef = serviceRegistry.getNodeService().getRootNode(store);
      
      // Do the patch work
      createFolder(getCompanyHomeNodeRef(rootRef));
      
      logger.info("Finished execution of patch: " + I18NUtil.getMessage(PATCH_ID));
      
      return I18NUtil.getMessage(MSG_SUCCESS);
    }

All patches should extend the org.alfresco.repo.admin.patch.AbstractPatch base class, which among other things has functionality to register the patch with the server so it is executed. When the patch is executed it will be run in a new transaction and any content created will have the System User as creator.

It is good practice to define a patch ID that distinguishes it from other patches, such as out-of-the-box patches and patches installed by other extension modules. So in this case org.alfresco.tutorial.patch.contentCreationPatch is used as the patch ID.

As with all other Java extensions the ServiceRegistry is used to get to the Java APIs, such as the NodeService. This patch gets the root node for the live content store (that is workspace://SpacesStore) and then calls a method to get the Company Home node reference:

private NodeRef getCompanyHomeNodeRef(NodeRef rootNodeRef) {
    String companyHomeXPath = "/app:company_home";

    List<NodeRef> refs = searchService.selectNodes(rootNodeRef, companyHomeXPath, null,
      serviceRegistry.getNamespaceService(), false);
    if (refs.size() != 1) {
      throw new SkyVaultRuntimeException(I18NUtil.getMessage(MSG_ERROR,
         "Company home could not be found, XPATH query " + companyHomeXPath +
         " returned " + refs.size() + " nodes."));
    }

    return refs.get(0);
}

When the Company Home node reference is looked up, an XPATH expression is used. This is because the Apache Solr search functionality might not be fully initialized during bootstrapping so an XPATH based search is used instead, which does not use the Lucene index. Once you have obtained the node reference for Company Home the folder is created with the NodeService:

private void createFolder(NodeRef rootRef) {
    String folderName = "FolderCreatedByPatch";
    NodeRef parentFolderNodeRef = rootRef;

    // Create Node
    QName associationType = ContentModel.ASSOC_CONTAINS;
    QName associationQName = QName.createQName(NamespaceService.CONTENT_MODEL_1_0_URI,
            QName.createValidLocalName(folderName));
    QName nodeType = ContentModel.TYPE_FOLDER;
    Map<QName, Serializable> nodeProperties = new HashMap<QName, Serializable>();
    nodeProperties.put(ContentModel.PROP_NAME, folderName);
    ChildAssociationRef parentChildAssocRef = nodeService.createNode(
            parentFolderNodeRef, associationType, associationQName, nodeType, nodeProperties);

    NodeRef newFolderNodeRef = parentChildAssocRef.getChildRef();

    // Add an aspect to the node
    Map<QName, Serializable> aspectProperties = new HashMap<QName, Serializable>();
    aspectProperties.put(ContentModel.PROP_TITLE, "My Patch Folder");
    aspectProperties.put(ContentModel.PROP_DESCRIPTION, "This is a folder that has been created by a patch");
    nodeService.addAspect(newFolderNodeRef, ContentModel.ASPECT_TITLED, aspectProperties);
}

When the patch class is completed a Spring bean needs to be defined for it. The bean needs to indicate to the server the version of SkyVault for which it should be run. In the bootstrap-context.xml file define a bean as follows: 

<bean id="patch.contentCreationPatch" class="org.alfresco.tutorial.patch.ContentCreationPatch" parent="basePatch">
   <property name="id">
      <value>org.alfresco.tutorial.patch.contentCreationPatch</value>
   </property>
   <property name="description">
      <value>org.alfresco.tutorial.patch.contentCreationPatch.description</value>
   </property>
   <property name="fixesFromSchema">
      <value>0</value>
   </property>
   <property name="fixesToSchema">
      <value>${version.schema}</value>
   </property>
   <property name="targetSchema">
      <value>10000</value>
   </property>
   <property name="serviceRegistry">
      <ref bean="ServiceRegistry"/>
   </property>
</bean>

The bean needs to extend the basePatch bean so the patch gets automatically registered with the server. Patches will be applied to the store only once. This patch should always be run once for every new installation, regardless of SkyVault version, so setting the fixesToSchema value to ${version.schema}. Note that patches are sorted according to targetSchema, and lowest will be executed first.

The last thing to do is define the i18n properties for the patch, this is done as follows in a property file:

org.alfresco.tutorial.patch.contentCreationPatch=Create Content
org.alfresco.tutorial.patch.contentCreationPatch.description=Creating a folder under Company Home
org.alfresco.tutorial.patch.contentCreationPatch.result=Created a folder under Company Home
org.alfresco.tutorial.patch.contentCreationPatch.error=Could not create folder under Company Home: {0}

When this patch is executed you will see something like the following in the log file if everything went OK:

2016-02-07 17:31:47,700 INFO [admin.patch.PatchExecuter] [localhost-startStop-1] Checking for patches to apply ... 
2016-02-07 17:31:48,207 INFO [admin.patch.PatchExecuter] [localhost-startStop-1] Applying patch 'org.alfresco.tutorial.patch.contentCreationPatch' (Creating a folder under Company Home). 
2016-02-07 17:31:48,550 INFO [admin.patch.PatchExecuter] [localhost-startStop-1] 
=== Applied patch === 
ID: org.alfresco.tutorial.patch.contentCreationPatch RESULT: 
Created a folder under Company Home 
=====================================

When working with patches there will be times when you will want to re-run a patch after an update to its implementation. Restarting SkyVault will not re-run the patch as it only runs once. You can check the status of a patch with the following SQL query:

select * from alf_applied_patch where id='org.alfresco.tutorial.patch.contentCreationPatch'

This will return information about if the patch was successfully applied, when it was run, to what SkyVault version it was applied, etc. If the patch failed then an error message is available. To reset this database record issue the following update:

update alf_applied_patch set was_executed = 0, succeeded = 0 where id='org.alfresco.tutorial.patch.contentCreationPatch'

The patch will now be executed again if SkyVault is restarted. However, note that you would have to delete any content this patch has created before doing this update, otherwise the patch will fail as the content already exists.
Deployment - App Server As patches are implemented in Java it is better to use an SDK project for deployment than deploying directly to an application server.
Deployment SDK Project
  • repo-amp/src/main/java/ - Java patch implementation classes
  • repo-amp/src/main/amp/config/alfresco/module/repo-amp/context/bootstrap-context.xml - Spring beans
More Information
  • See the Bootstrap content extension point for out-of-the-box patch implementations that import content.
Sample Code
Tutorials None
SkyVault Developer Blogs None
Parent topic: Platform extension points

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