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2.3. Caching and Retrieving Data

Next, lets use the Cache API to access a Node in the cache and then do some simple reads and writes to that node. 
   // Let us get a hold of the root node.
   Node rootNode = cache.getRoot();

   // Remember, JBoss Cache stores data in a tree structure.
   // All nodes in the tree structure are identified by Fqn objects.
   Fqn peterGriffinFqn = Fqn.fromString("/griffin/peter");

   // Create a new Node
   Node peterGriffin = rootNode.addChild(peterGriffinFqn);

   // let us store some data in the node
   peterGriffin.put("isCartoonCharacter", Boolean.TRUE);
   peterGriffin.put("favoriteDrink", new Beer());

   // some tests (just assume this code is in a JUnit test case)
   assertTrue(peterGriffin.get("isCartoonCharacter"));
   assertEquals(peterGriffinFqn, peterGriffin.getFqn());
   assertTrue(rootNode.hasChild(peterGriffinFqn));

   Set keys = new HashSet();
   keys.add("isCartoonCharacter");
   keys.add("favoriteDrink");

   assertEquals(keys, peterGriffin.getKeys());

   // let us remove some data from the node
   peterGriffin.remove("favoriteDrink");

   assertNull(peterGriffin.get("favoriteDrink");

   // let us remove the node altogether
   rootNode.removeChild(peterGriffinFqn);

   assertFalse(rootNode.hasChild(peterGriffinFqn));
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The Cache interface also exposes put/get/remove operations that take an Section 2.4, “ The Fqn Class ” as an argument, for convenience: 
   Fqn peterGriffinFqn = Fqn.fromString("/griffin/peter");

   cache.put(peterGriffinFqn, "isCartoonCharacter", Boolean.TRUE);
   cache.put(peterGriffinFqn, "favoriteDrink", new Beer());

   assertTrue(peterGriffin.get(peterGriffinFqn, "isCartoonCharacter"));
   assertTrue(cache.getRootNode().hasChild(peterGriffinFqn));

   cache.remove(peterGriffinFqn, "favoriteDrink");

   assertNull(cache.get(peterGriffinFqn, "favoriteDrink");

   cache.removeNode(peterGriffinFqn);

   assertFalse(cache.getRootNode().hasChild(peterGriffinFqn));
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A Node should be viewed as a named logical grouping of data. A node should be used to contain data for a single data record, for example information about a particular person or account. It should be kept in mind that all aspects of the cache - locking, cache loading, replication and eviction - happen on a per-node basis. As such, anything grouped together by being stored in a single node will be treated as a single atomic unit.
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