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Get the default branch of a remote repository with JGit

I am working on a Git client, and right now I am trying to implement the checkout of a specific branch. I have a combo box that I populate with branch names, and I would like to find out which branch is the default, so that I can set it as the preselected item in the combo box when connecting to a valid Git repository.
I am listing all the remote branches as you can see below, but I cannot figure out which is the default one.
Map<String, Ref> callAsMap = Git.lsRemoteRepository()
.setRemote("https://github.com/example")
.setCredentialsProvider(credentialsProvider)
.callAsMap();
So, is there a way (standard or "hacky") to detect which Ref object represents the default branch? And how can I get its name?

Repository::getFullBranch returns the current branch of the local repository.
To get the default branch of a remote repository, you need to ask for its HEAD ref. The map that is returned by the snippet that you posted should contain an entry with key HEAD and (if I'm not mistaken) a value that denotes the name of the default branch.
If HEAD refers to an object id, you could obtain a list of all remote refs with repository.getRefDatabase().getRefs(Constants.R_REMOTES) to look up the HEAD id. This approach may be inaccurate as multiple refs could point to the same object id.
Note that it is not required for a remote repository to advertise a default branch.
See also these posts for how C-Git finds the default branch: git - how to get default branch? and What determines default branch after "git clone"?)

After the chain with .get("HEAD"), if it is a symbolic link, you can chain it with .getTarget().getName() to "extract" its name e.g.
Map<String, Ref> callAsMap = Git.lsRemoteRepository()
.setRemote("https://github.com/example")
.setCredentialsProvider(credentialsProvider)
.callAsMap().get("HEAD").getTarget().getName()
Source: https://www.eclipse.org/lists/jgit-dev/msg03320.html

How to Copy AEM node one place to another location?

I need to copy an AEM JCR node source to destination. The following code is working but if that node already exists in the destination I'm getting an error:
String sourcePath="/content/dam/assets/content";
String destinationPath="/content/dam/Marketing/content";
Session session = resourceResolver.adaptTo(Session.class);
Workspace workspace = session.getWorkspace();
workspace.copy(sourcePath, destinationPath);
session.logout();
But the problem is that the content node already exists inside the folder "Marketing" so that it's only working on the first time. Once the content node is created I'm not able to copy/update the node but I need to replace each time without deleting the source node.

If you want to operate on a whole node you can always use workspace move/copy operations (workspace.copy(String srcAbsPath, String destAbsPath) to the destination path, where the destination node should not be present/exist in JCR, if it present/exist you will end up with
javax.jcr.ItemExistsException: /jcr/repository/path/nodepresent
and for the workspace clone (workspace.clone(String srcWorkspace, String srcAbsPath, String destAbsPath, boolean removeExisting) usage you need to operate with two different workspaces, if you use the clone operation with the same workspace you will end up with
javax.jcr.RepositoryException: crx.default: illegal workspace (same as
current)
As i can see your requirement is to verify the destination path and update operation, you need to handle it with custom code which can verify destpath and have the NodeIterations and perform update operation.
Also have a look at copy-aem-node-tree-in-jcr which might help for your use case.

Use clone instead of copy.because clone has a removexisting boolean argument. Refer https://docs.adobe.com/docs/en/spec/jsr170/javadocs/jcr-1.0/javax/jcr/Workspace.html#clone

How to give connection details for cassandra in properties file using datastax java driver

Initializer myInitializer = ... // your implementation
Cluster cluster = Cluster.buildFrom(myInitializer);
Im trying to connect to Cassandracluster with several node details mentioning in addcontactpoints("192.1.1.1","192.2.2.2").build().
Now I want to connect to Cassandra cluster with out mentioning the in that method. I want to mention my node details in separate properties file and want to connect to my cluster using that properties file. I have got one method in Java driver called getcontactpoint().
I'm not getting how to use that and implement it. Please help me to improve my code

put all nodes ip like below
nodes=192.1.1.1,192.2.2.2
In java Resource interface is there by using that you can get your properties file
Like ResourceBundle resource=ResourceBundle.getBundle("cassandra")
then by getProperty method you can get nodes and split it by comma(,) so it will gives you Array of String mean all IP .
Like
nodes=resource.getString("nodes")
then in method addContactPoints() just give nodes variable .
Like addContactPoints(nodes)

How can I get the number of nodes of a Neo4j graph database from java and can we store and reuse graphdb from disk?

I just started looking at neo4j to use it for my social-network related project. During this I came across the following code:
https://github.com/neo4j/neo4j/blob/1.9.M04/community/embedded-examples/src/main/java/org/neo4j/examples/EmbeddedNeo4jWithIndexing.java
While going through it (please refer to above link for code), I was struggling to know, how to get the total number of nodes added to a given graphDb. Is there any way to find it (total number of nodes) using graphDb or nodeIndex or referenceIndex or anything else? If yes, How?
I also need help to know, how to store the graphdb to any given path on disk? How to load this stored graphdb and perform operations on it like searching for a node/relationship etc?
(There are several files like *.db, *.id, *.keys etc.. created at given DB_PATH when above code is executed. What are all those files useful for? Does any of those files contain nodes created? if yes, how can we use them?)
How can we access this graphDb from web-interfaces like, Dashboard at http://localhost:7474/webadmin/ or data at http://localhost:7474/db/data/ ?
Please let me know in case you need any specific information to help me..
Thanks, Nitin.

For getting started with Neo4j Embedded and the Java API see:
http://docs.neo4j.org/chunked/milestone/tutorials-java-embedded.html
Getting correct counts of nodes and relationships:
IteratorUtil.count(GlobalGraphOperations.at(gdb).getAllNodes())
IteratorUtil.count(GlobalGraphOperations.at(gdb).getAllRelationships())
For accessing an embedded graph database with an integrated neo4j server, see
http://docs.neo4j.org/chunked/milestone/server-embedded.html

Phewww! Those are a lot of questions for one entry...
To get the total number of nodes and relationships in your DB, use:
NodeManager nodeManager = ((GraphDatabaseAPI) graphDb).getDependencyResolver().resolveDependency(
NodeManager.class);
long currentRelationships = nodeManager.getNumberOfIdsInUse(Relationship.class);
long currentNodes = nodeManager.getNumberOfIdsInUse(Node.class);
To change the path of the graph DB, simply pass the path to the GraphDatabaseFactory().newEmbeddedDatabase method. In the example you mentioned, you could simply set DB_PATH e.g. to /home/youruser/neo4j.
To access your DB with the webadmin, download neo4j, change the org.neo4j.server.database.location property in the file conf/neo4j-server.properties and point it to the path of your DB and launch the server.

Migration of blobs from database to the file system in jackrabbit

As being proposed in the previous discussion Using file system instead of database to store pdf files in jackrabbit
we can use FileDataStore to store blob files in the file system instead of database (i my case have stored ~ 100 kb size pdfs).
The following problem I have faced is dealing with files that have been previously stored in blobstore and I want them to be accessible after switching to FileDataStore.
After adding FileDataStore support to the repository.xml
when using JcrUtils method getOrAddNode i get ItemExistsException:
public static Node getOrAddNode(Node parent, String name)
throws RepositoryException {
if (parent.hasNode(name)) {
return parent.getNode(name);
} else {
return parent.addNode(name);
}
}
e.g. parent.hasNode(name) returns false (it seems the item doesn't exist)
but then we fall in to the code parent.addNode(name) which consequently throws ItemExistsException.
Any help?
Is it necessary to proceed the migration of blobs to the FileDataStore or there is kind of configuration that jackrabbit could search for blobs in different locations at the same time: in my case mysql database and filesystem.
Some comments:
I have found at least several ways that could help do the migration job:
spec http://wiki.apache.org/jackrabbit/BackupAndMigration
tells about using JCR API (Session.exportSystemView(..) and then Session.importXML(..) ), using RepositoryCopier API etc.
jackrabbit-jcr-import-export-tool (see http://svn.apache.org/repos/asf/jackrabbit/sandbox/jackrabbit-jcr-import-export-tool/README.txt)
using jackrabbit standalone server (http://jackrabbit.apache.org/standalone-server.html)

It might be possible that there is a repository corruption. That is, the node contains a child node entry for the given name (the node you want to add), but the child node itself doesn't exist. Specially in older version of Jackrabbit you could get into this situation if multiple sessions concurrently tried to change the same nodes.
To fix such corruption problems, the bundle db persistence managers support a consistency check & fix feature. You would need to set those options in the repository.xml and workspace.xml files, and restart Jackrabbit. Once fixed, you can disable those options again.
There is also a way to fix such problems at runtime, by setting the system property org.apache.jackrabbit.autoFixCorruptions to true, and then traverse over all nodes in the repository.