Very useful technology for Java developers, and not only
Technology specification
http://jcp.org/en/jsr/detail?id=170
Implementations
It's similar to a File System we use everyday. But has more features and advantages.
You have to obtain a Repository instance to start. It's implementation specific and simple for most JCRs.
Each Repository presents a list of workspaces. Let us imagine it's drives in file system.
To begin the work with a content you have to login into Repository with selected Workspace.
After the login you have the Session. So, you have a tool which gives access to a content storage.
Add 'file'
You will use Property to read/write data.
Write
Node can include sub-nodes also. It's only managed by NodeType (like file type, but richer).
It's a good alternative to a databases in content-oriented applications and makes development process close to a task. A developer should know at least the specification, but it's simple than JDBC anyway.
http://jcp.org/en/jsr/detail?id=170
Implementations
- eXo Platform JCR http://wiki.exoplatform.org/xwiki/bin/view/JCR/
- Jackrabbit http://jackrabbit.apache.org/
- Alfresco JCR http://wiki.alfresco.com/wiki/Introducing_the_Alfresco_Java_Content_Repository_API
- Jeceira http://sourceforge.net/projects/jeceira/
It's similar to a File System we use everyday. But has more features and advantages.
You have to obtain a Repository instance to start. It's implementation specific and simple for most JCRs.
Each Repository presents a list of workspaces. Let us imagine it's drives in file system.
To begin the work with a content you have to login into Repository with selected Workspace.
InitialContext ctx = ...
Repository repository = (Repository)ctx.lookup("myrepo");
// Get a Credentials object
Credentials credentials = new SimpleCredentials("MyName", "MyPassword".toCharArray());
// Get a Session
Session mySession = repository.login(credentials, "MyWorkspace");
After the login you have the Session. So, you have a tool which gives access to a content storage.
Add 'file'
Node myFile = mySession.getRootNode().addNode("my-first-file");Node it's only object which handles 'file' entity... say handler. Node may contains Property(es). The Property it's a content. String, Integer, Float, Binary, Path etc.
You will use Property to read/write data.
Write
myFile.setProperty("creator_name", "John");Read
myFile.setProperty("create_date", Calendar.getInstance());
myFile.setProperty("file_content", source.getInputStream());
myFile.getProperty("creator_name").getSTring();So, not so complicated.
myFile.getProperty("create_date").getDate();
myFile.getProperty("file_content").getStream();
Node can include sub-nodes also. It's only managed by NodeType (like file type, but richer).
myFile.addNode("sub-file");You may get Node or Property by path, relative from other Node or Property or via Session.
// relativeSimple? I hope - yes.
Node ssFile = myFile.getNode("sub-file/sub-sub-file");
// or by abs path
Node ssFile = (Node) mySession.getItem("/my-first-file/sub-file/sub-sub-file");
It's a good alternative to a databases in content-oriented applications and makes development process close to a task. A developer should know at least the specification, but it's simple than JDBC anyway.
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