The Metastore project aims to provide a developer with a way of storing metadata, configuration information, settings and so on in a standardized way. To make this happen we choose a simple meta-model with the organization described below
The Metastore meta-model is organized as following:
So essentially, it's a key/value store with children allowing you to store just about any piece of metadata.
Common MetaModel Element Type definitions can be found on this page:
Standard MetaStore Element types
The Java project with the API and reference implementations is to be found over here:
There is a CI build process looking at the project over here:
This build process is pushing maven artifacts into the pentaho repository, ivy dependency line:
<dependency org="pentaho" name="metastore" rev="TRUNK-SNAPSHOT" />
Even though the organisation of the meta-model is kept simple (on purpose) it makes sense to cover the main Java interfaces a bit.
The IMetaStore interface is the top level interface describing all the possible operations which are available.
Self explanatory, to distinguish one Metastore from another.
You can ask the MetaStore to give you the methods for encoding, decoding and verifying passwords or you can set your own methods (right after instantiating) with the following methods:
For your convenience we provided you with a MetaStoreFactory to facilitate the specific use-case of serializing POJO.
Consider a class annotated with @MetaStoreElementType and where private members are annotated with @MetaStoreAttribute
MyElement me = new MyElement( NAME, ATTR, ANOTHER, INT, LONG, BOOL, DATE ); MetaStoreFactory<MyElement> factory = new MetaStoreFactory<MyElement>( MyElement.class, metaStore, "custom" );
Now we can save the element in the metastore simply by calling:
factory.saveElement( me );
Loading the element by name from the metastore simply becomes:
MyElement verify = factory.loadElement( NAME );
The unit test class which demos this behavior is: MetaStoreFactoryTest
The list of available methods in the factory is:
public void saveElement( T t ) throws MetaStoreException;
public List<T> getElements() throws MetaStoreException;
public void deleteElement( String name ) throws MetaStoreException;
public List<String> getElementNames() throws MetaStoreException;
public IMetaStoreElementType getElementType() throws MetaStoreException;
If you have one element referencing another by name we can pass a factory to another factory to handle automatic persistence.
See for example the following :
MetaStoreFactory<X> factoryX = new MetaStoreFactory<X>( X.class, metaStore, "pentaho" ); MetaStoreFactory<Y> factoryY = new MetaStoreFactory<Y>( Y.class, metaStore, "pentaho" ); factoryX.addNameFactory( X.FACTORY_Y, factoryY );
In this situation, if you call factoryX.saveElement() you will also persist any referenced elements of Y which are annotated as followed in class X:
@MetaStoreAttribute( factoryNameKey = FACTORY_Y, factoryNameReference = true ) private List<Y> ys; //and/or @MetaStoreAttribute( factoryNameKey = FACTORY_Y, factoryNameReference = true ) private Y y;
The factory is then also used when you are loading elements.
IMPORTANT NOTE: Do not rely on the referenced classes to be unique instances. If you want that goal, pass unique lists of elements to the factory using addNameList()
Since you don't always want elements to be shared and visible for the whole metastore to see, you can make an element optionally shared and as such, optionally 'embedded' in the parent element attributes.
To do this, you simply tell the factory what the name is of the boolean field which expresses the fact that the element is shared.
For example, if you have a "shared" flag in class B:
@MetaStoreAttribute private boolean shared;
In this case you can reference this in class A as follows:
@MetaStoreAttribute( factoryNameKey = FACTORY_B, factoryNameReference = true, factorySharedIndicatorName = "shared" ) private B b;
The factory will then automatically determine to either create or update an element for B or embed it in the attributes of the A element.