Examples of org.apache.jackrabbit.oak.spi.state.NodeState

Package org.apache.jackrabbit.oak.spi.state

Examples of org.apache.jackrabbit.oak.spi.state.NodeState

org.apache.jackrabbit.oak.spi.state.NodeState
A node in a content tree consists of child nodes and properties, each of which evolves through different states during its lifecycle. This interface represents a specific, immutable state of a node. The state consists of an unordered set of name -> item mappings, where each item is either a property or a child node.
Depending on context, a NodeState instance can be interpreted as representing the state of just that node, of the subtree starting at that node, or of an entire tree in case it's a root node.
The crucial difference between this interface and the similarly named class in Jackrabbit 2.x is that this interface represents a specific, immutable state of a node, whereas the Jackrabbit 2.x class represented the current state of a node.
Immutability and thread-safety

As mentioned above, all node and property states are always immutable. Thus repeating a method call is always guaranteed to produce the same result as before unless some internal error occurs (see below). This immutability only applies to a specific state instance. Different states of a node can obviously be different, and in some cases even different instances of the same state may behave slightly differently. For example due to performance optimization or other similar changes the iteration order of properties or child nodes may be different for two instances of the same state.
In addition to being immutable, a specific state instance guaranteed to be fully thread-safe. Possible caching or other internal changes need to be properly synchronized so that any number of concurrent clients can safely access a state instance.
Persistence and error-handling

A node state can be (and often is) backed by local files or network resources. All IO operations or related concerns like caching should be handled transparently below this interface. Potential IO problems and recovery attempts like retrying a timed-out network access need to be handled below this interface, and only hard errors should be thrown up as {@link RuntimeException unchecked exceptions} that higher level codeis not expected to be able to recover from.
Since this interface exposes no higher level constructs like locking, node types or even path parsing, there's no way for content access to fail because of such concerns. Such functionality and related checked exceptions or other control flow constructs should be implemented on a higher level above this interface. On the other hand read access controls can be implemented below this interface, in which case some content that would otherwise be accessible might not show up through such an implementation.
Existence and iterability of node states

The {@link #getChildNode(String)} method is special in that itnever returns a {@code null} value, even if the named childnode does not exist. Instead a client should use the {@link #exists()}method on the returned child state to check whether that node exists. The purpose of this separation of concerns is to allow an implementation to lazily load content only when it's actually read instead of just traversed. It also simplifies client code by avoiding the need for many {@code null} checks when traversing paths.
The iterability of a node is a related concept to the above-mentioned existence. A node state is iterable if it is included in the return values of the {@link #getChildNodeCount(long)}, {@link #getChildNodeNames()} and {@link #getChildNodeEntries()} methods.An iterable node is guaranteed to exist, though not all existing nodes are necessarily iterable.
Furthermore, a non-existing node is guaranteed to contain no properties or iterable child nodes. It can, however contain non-iterable children. Such scenarios are typically the result of access control restrictions.
Decoration and virtual content

Not all content exposed by this interface needs to be backed by actual persisted data. An implementation may want to provide derived data, like for example the aggregate size of the entire subtree as an extra virtual property. A virtualization, sharding or caching layer could provide a composite view over multiple underlying trees. Or a an access control layer could decide to hide certain content based on specific rules. All such features need to be implemented according to the API contract of this interface. A separate higher level interface needs to be used if an implementation can't for example guarantee immutability of exposed content as discussed above.
Equality and hash codes

Two node states are considered equal if and only if their existence, properties and iterable child nodes match, regardless of ordering. The {@link Object#equals(Object)} method needs to be implemented so that itcomplies with this definition. And while node states are not meant for use as hash keys, the {@link Object#hashCode()} method should still beimplemented according to this equality contract.


    /**
     * Rebase this builder on top of the head of the underlying store
     */
    NodeState rebase() {
        NodeState head = getNodeState();
        NodeState inMemBase = super.getBaseState();


        // Rebase branch
        branch.rebase();


        // Rebase in memory changes on top of the head of the rebased branch

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     * Reset this builder by creating a new branch and setting the head
     * state of that branch as the new base state of this builder.
     */
    NodeState reset() {
        branch = store.createBranch(store.getRoot());
        NodeState head = branch.getHead();
        reset(head);
        return head;
    }

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            return names;
        }
    }


    private void addNodeType(NodeState types, String name) {
        NodeState type = types.getChildNode(name);


        for (String primary : type.getNames(REP_PRIMARY_SUBTYPES)) {
            primaryTypes = add(primaryTypes, primary);
        }


        if (type.getBoolean(JCR_ISMIXIN)) {
            mixinTypes = add(mixinTypes, name);


            // Only mixin types can have mixin descendants, so we
            // only fill the mixinTypes set in this branch of code.
            for (String mixin : type.getNames(REP_MIXIN_SUBTYPES)) {
                mixinTypes = add(mixinTypes, mixin);
            }
        } else {
            // No need to check whether the type actually exists, as if
            // it doesn't there should in any case be no matching content.

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            this.filter = filter;


            String path = filter.getPath();
            parentPath = null;
            currentPath = "/";
            NodeState parent = null;
            NodeState node = rootState;
            
            if (filter.isAlwaysFalse()) {
                // nothing can match this filter, leave nodes empty
                return;
            }


            if (!path.equals("/")) {
                for (String name : path.substring(1).split("/")) {
                    parentPath = currentPath;
                    currentPath = PathUtils.concat(parentPath, name);


                    parent = node;
                    node = parent.getChildNode(name);
                }
                if (!node.exists()) {
                    // nothing can match this filter, leave nodes empty
                    return;
                }
            }
            Filter.PathRestriction restriction = filter.getPathRestriction();
            switch (restriction) {
            case NO_RESTRICTION:
            case EXACT:
            case ALL_CHILDREN:
                nodeIterators.add(Iterators.singletonIterator(
                        new MemoryChildNodeEntry(currentPath, node)));
                parentPath = "";
                break;
            case PARENT:
                if (parent != null) {
                    nodeIterators.add(Iterators.singletonIterator(
                            new MemoryChildNodeEntry(parentPath, parent)));
                    parentPath = "";
                }
                break;
            case DIRECT_CHILDREN:
                nodeIterators.add(node.getChildNodeEntries().iterator());
                parentPath = currentPath;
                break;
            default:
                throw new IllegalArgumentException("Unknown restriction: " + restriction);
            }

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    @Override
    public boolean hasChildNode(String name) {
        assert base != null;
        checkNotNull(name);
        // checkArgument(!name.isEmpty()); TODO: should be caught earlier
        NodeState child = nodes.get(name);
        if (child != null) {
            return child.exists();
        } else {
            return base.hasChildNode(name);
        }
    }

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        return child;
    }


    @Override
    public NodeState getChildNode(String name) {
        NodeState child = nodes.get(name);
        if (child == null) {
            child = base.getChildNode(name);
        }
        return child;
    }

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                    readCount++;
                    if (readCount % 1000 == 0) {
                        LOG.warn("Traversed " + readCount + " nodes with filter " + filter + "; consider creating an index or changing the query");
                    }


                    NodeState node = entry.getNodeState();


                    String name = entry.getName();
                    if (NodeStateUtils.isHidden(name)) {
                        continue;
                    }
                    currentPath = PathUtils.concat(parentPath, name);


                    PathRestriction r = filter.getPathRestriction();
                    if (r == PathRestriction.ALL_CHILDREN || 
                            r == PathRestriction.NO_RESTRICTION) {
                        nodeIterators.addLast(node.getChildNodeEntries().iterator());
                        parentPath = currentPath;
                    }
                    return;
                } else {
                    nodeIterators.removeLast();

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    @Override
    public boolean apply(NodeState input) {
        if (!initialized) {
            // lazy initialization of the sets of matching type names
            NodeState types = checkNotNull(root)
                    .getChildNode(JCR_SYSTEM)
                    .getChildNode(JCR_NODE_TYPES);
            for (String name : checkNotNull(names)) {
                addNodeType(types, name);
            }

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    @Override
    public Editor getRootEditor(
            NodeState before, NodeState after, NodeBuilder builder)
            throws CommitFailedException {
        NodeState beforeTypes =
                before.getChildNode(JCR_SYSTEM).getChildNode(JCR_NODE_TYPES);
        NodeState afterTypes =
                after.getChildNode(JCR_SYSTEM).getChildNode(JCR_NODE_TYPES);


        Set<String> modifiedTypes = Collections.emptySet();
        TypeRegistration registration = new TypeRegistration();
        afterTypes.compareAgainstBaseState(beforeTypes, registration);
        if (registration.isModified()) {
            afterTypes = registration.apply(builder);
            modifiedTypes = registration.getModifiedTypes(beforeTypes);
        }


        String primary = after.getName(JCR_PRIMARYTYPE);
        Iterable<String> mixins = after.getNames(JCR_MIXINTYPES);


        if (primary == null && afterTypes.hasChildNode("rep:root")) {
            // no primary type on the root node, set the hardcoded default
            primary = "rep:root";
            builder.setProperty(JCR_PRIMARYTYPE, primary, NAME);
        }

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    }


    private static Query parseQuery(String statement, String language, 
            ExecutionContext context, NamePathMapper namePathMapper) throws ParseException {
        LOG.debug("Parsing {} statement: {}", language, statement);
        NodeState types = context.getBaseState()
                .getChildNode(JCR_SYSTEM)
                .getChildNode(JCR_NODE_TYPES);
        SQL2Parser parser = new SQL2Parser(namePathMapper, types);
        if (language.endsWith(NO_LITERALS)) {
            language = language.substring(0, language.length() - NO_LITERALS.length());

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org.apache.jackrabbit.oak.explorer.NodeStoreTree

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Examples of org.apache.jackrabbit.oak.spi.state.NodeState

Immutability and thread-safety

Persistence and error-handling

Existence and iterability of node states

Decoration and virtual content

Equality and hash codes

Related Classes of org.apache.jackrabbit.oak.spi.state.NodeState