Work on logical backups.
[lgpl/argeo-commons.git] / org.argeo.jcr / src / org / argeo / jcr / Jcr.java
index c3db4b604c71b1e8a955b45b2b5019de7a13dd14..20325cfe0bd30143ba1e9a8ac4d7f3a04dbd584c 100644 (file)
@@ -1,8 +1,10 @@
 package org.argeo.jcr;
 
 import java.math.BigDecimal;
+import java.text.MessageFormat;
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Calendar;
 import java.util.Collections;
 import java.util.Date;
@@ -22,6 +24,8 @@ import javax.jcr.Session;
 import javax.jcr.Value;
 import javax.jcr.Workspace;
 import javax.jcr.nodetype.NodeType;
+import javax.jcr.query.Query;
+import javax.jcr.query.QueryManager;
 import javax.jcr.security.Privilege;
 import javax.jcr.version.Version;
 import javax.jcr.version.VersionHistory;
@@ -36,65 +40,128 @@ import javax.jcr.version.VersionManager;
  * exceptions. Loosely inspired by Java's <code>Files</code> singleton.
  */
 public class Jcr {
+       /**
+        * The name of a node which will be serialized as XML text, as per section 7.3.1
+        * of the JCR 2.0 specifications.
+        */
+       public final static String JCR_XMLTEXT = "jcr:xmltext";
+       /**
+        * The name of a property which will be serialized as XML text, as per section
+        * 7.3.1 of the JCR 2.0 specifications.
+        */
+       public final static String JCR_XMLCHARACTERS = "jcr:xmlcharacters";
+       /**
+        * <code>jcr:name</code>, when used in another context than
+        * {@link Property#JCR_NAME}, typically to name a node rather than a property.
+        */
+       public final static String JCR_NAME = "jcr:name";
+       /**
+        * <code>jcr:path</code>, when used in another context than
+        * {@link Property#JCR_PATH}, typically to name a node rather than a property.
+        */
+       public final static String JCR_PATH = "jcr:path";
+       /**
+        * <code>jcr:primaryType</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_PRIMARY_TYPE}.
+        */
+       public final static String JCR_PRIMARY_TYPE = "jcr:primaryType";
+       /**
+        * <code>jcr:mixinTypes</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_MIXIN_TYPES}.
+        */
+       public final static String JCR_MIXIN_TYPES = "jcr:mixinTypes";
+       /**
+        * <code>jcr:uuid</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_UUID}.
+        */
+       public final static String JCR_UUID = "jcr:uuid";
+       /**
+        * <code>jcr:created</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_CREATED}.
+        */
+       public final static String JCR_CREATED = "jcr:created";
+       /**
+        * <code>jcr:createdBy</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_CREATED_BY}.
+        */
+       public final static String JCR_CREATED_BY = "jcr:createdBy";
+       /**
+        * <code>jcr:lastModified</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_LAST_MODIFIED}.
+        */
+       public final static String JCR_LAST_MODIFIED = "jcr:lastModified";
+       /**
+        * <code>jcr:lastModifiedBy</code> with prefix instead of namespace (as in
+        * {@link Property#JCR_LAST_MODIFIED_BY}.
+        */
+       public final static String JCR_LAST_MODIFIED_BY = "jcr:lastModifiedBy";
 
        /**
         * @see Node#isNodeType(String)
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static boolean isNodeType(Node node, String nodeTypeName) {
                try {
                        return node.isNodeType(nodeTypeName);
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get whether " + node + " is of type " + nodeTypeName, e);
+                       throw new JcrException("Cannot get whether " + node + " is of type " + nodeTypeName, e);
                }
        }
 
        /**
         * @see Node#hasNodes()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static boolean hasNodes(Node node) {
                try {
                        return node.hasNodes();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get whether " + node + " has children.", e);
+                       throw new JcrException("Cannot get whether " + node + " has children.", e);
                }
        }
 
        /**
         * @see Node#getParent()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static Node getParent(Node node) {
                try {
                        return isRoot(node) ? null : node.getParent();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get parent of " + node, e);
+                       throw new JcrException("Cannot get parent of " + node, e);
                }
        }
 
+       /**
+        * @see Node#getParent()
+        * @throws JcrException caused by {@link RepositoryException}
+        */
+       public static String getParentPath(Node node) {
+               return getPath(getParent(node));
+       }
+
        /**
         * Whether this node is the root node.
         * 
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static boolean isRoot(Node node) {
                try {
                        return node.getDepth() == 0;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get depth of " + node, e);
+                       throw new JcrException("Cannot get depth of " + node, e);
                }
        }
 
        /**
         * @see Node#getPath()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static String getPath(Node node) {
                try {
                        return node.getPath();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get path of " + node, e);
+                       throw new JcrException("Cannot get path of " + node, e);
                }
        }
 
@@ -109,25 +176,25 @@ public class Jcr {
 
        /**
         * @see Node#getIdentifier()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static String getIdentifier(Node node) {
                try {
                        return node.getIdentifier();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get identifier of " + node, e);
+                       throw new JcrException("Cannot get identifier of " + node, e);
                }
        }
 
        /**
         * @see Node#getName()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static String getName(Node node) {
                try {
                        return node.getName();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get name of " + node, e);
+                       throw new JcrException("Cannot get name of " + node, e);
                }
        }
 
@@ -157,20 +224,20 @@ public class Jcr {
        /**
         * @return the children as an {@link Iterable} for use in for-each llops.
         * @see Node#getNodes()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static Iterable<Node> nodes(Node node) {
                try {
                        return iterate(node.getNodes());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get children of " + node, e);
+                       throw new JcrException("Cannot get children of " + node, e);
                }
        }
 
        /**
         * @return the children as a (possibly empty) {@link List}.
         * @see Node#getNodes()
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static List<Node> getNodes(Node node) {
                List<Node> nodes = new ArrayList<>();
@@ -183,14 +250,14 @@ public class Jcr {
                        } else
                                return nodes;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get children of " + node, e);
+                       throw new JcrException("Cannot get children of " + node, e);
                }
        }
 
        /**
         * @return the child or <code>null</node> if not found
         * @see Node#getNode(String)
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static Node getNode(Node node, String child) {
                try {
@@ -199,14 +266,14 @@ public class Jcr {
                        else
                                return null;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get child of " + node, e);
+                       throw new JcrException("Cannot get child of " + node, e);
                }
        }
 
        /**
         * @return the node at this path or <code>null</node> if not found
         * @see Session#getNode(String)
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static Node getNode(Session session, String path) {
                try {
@@ -215,14 +282,93 @@ public class Jcr {
                        else
                                return null;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get node " + path, e);
+                       throw new JcrException("Cannot get node " + path, e);
+               }
+       }
+
+       /**
+        * Add a node to this parent, setting its primary type and its mixins.
+        * 
+        * @param parent      the parent node
+        * @param name        the name of the node, if <code>null</code>, the primary
+        *                    type will be used (typically for XML structures)
+        * @param primaryType the primary type, if <code>null</code>
+        *                    {@link NodeType#NT_UNSTRUCTURED} will be used.
+        * @param mixins      the mixins
+        * @return the created node
+        * @see Node#addNode(String, String)
+        * @see Node#addMixin(String)
+        */
+       public static Node addNode(Node parent, String name, String primaryType, String... mixins) {
+               if (name == null && primaryType == null)
+                       throw new IllegalArgumentException("Both node name and primary type cannot be null");
+               try {
+                       Node newNode = parent.addNode(name == null ? primaryType : name,
+                                       primaryType == null ? NodeType.NT_UNSTRUCTURED : primaryType);
+                       for (String mixin : mixins) {
+                               newNode.addMixin(mixin);
+                       }
+                       return newNode;
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot add node " + name + " to " + parent, e);
+               }
+       }
+
+       /**
+        * Add an {@link NodeType#NT_BASE} node to this parent.
+        * 
+        * @param parent the parent node
+        * @param name   the name of the node, cannot be <code>null</code>
+        * @return the created node
+        * 
+        * @see Node#addNode(String)
+        */
+       public static Node addNode(Node parent, String name) {
+               if (name == null)
+                       throw new IllegalArgumentException("Node name cannot be null");
+               try {
+                       Node newNode = parent.addNode(name);
+                       return newNode;
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot add node " + name + " to " + parent, e);
+               }
+       }
+
+       /**
+        * Add mixins to a node.
+        * 
+        * @param node   the node
+        * @param mixins the mixins
+        * @return the created node
+        * @see Node#addMixin(String)
+        */
+       public static void addMixin(Node node, String... mixins) {
+               try {
+                       for (String mixin : mixins) {
+                               node.addMixin(mixin);
+                       }
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot add mixins " + Arrays.asList(mixins) + " to " + node, e);
+               }
+       }
+
+       /**
+        * Removes this node.
+        * 
+        * @see Node#remove()
+        */
+       public static void remove(Node node) {
+               try {
+                       node.remove();
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot remove node " + node, e);
                }
        }
 
        /**
         * @return the node with htis id or <code>null</node> if not found
         * @see Session#getNodeByIdentifier(String)
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static Node getNodeById(Session session, String id) {
                try {
@@ -230,7 +376,7 @@ public class Jcr {
                } catch (ItemNotFoundException e) {
                        return null;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get node with id " + id, e);
+                       throw new JcrException("Cannot get node with id " + id, e);
                }
        }
 
@@ -238,12 +384,17 @@ public class Jcr {
         * Set a property to the given value, or remove it if the value is
         * <code>null</code>.
         * 
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static void set(Node node, String property, Object value) {
                try {
-                       if (!node.hasProperty(property))
-                               throw new IllegalArgumentException("No property " + property + " in " + node);
+                       if (!node.hasProperty(property)) {
+                               if (value != null)
+                                       node.setProperty(property, value.toString());
+                               return;
+                               // throw new IllegalArgumentException("No property " + property + " in " +
+                               // node);
+                       }
                        Property prop = node.getProperty(property);
                        if (value == null) {
                                prop.remove();
@@ -254,8 +405,12 @@ public class Jcr {
                                prop.setValue((String) value);
                        else if (value instanceof Long)
                                prop.setValue((Long) value);
+                       else if (value instanceof Integer)
+                               prop.setValue(((Integer) value).longValue());
                        else if (value instanceof Double)
                                prop.setValue((Double) value);
+                       else if (value instanceof Float)
+                               prop.setValue(((Float) value).doubleValue());
                        else if (value instanceof Calendar)
                                prop.setValue((Calendar) value);
                        else if (value instanceof BigDecimal)
@@ -272,7 +427,7 @@ public class Jcr {
                        } else // try with toString()
                                prop.setValue(value.toString());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot set property " + property + " of " + node + " to " + value, e);
+                       throw new JcrException("Cannot set property " + property + " of " + node + " to " + value, e);
                }
        }
 
@@ -282,28 +437,38 @@ public class Jcr {
         * @return the value of
         *         {@link Node#getProperty(String)}.{@link Property#getString()} or
         *         <code>null</code> if the property does not exist.
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static String get(Node node, String property) {
                return get(node, property, null);
        }
 
        /**
-        * Get property as a {@link String}.
+        * Get property as a {@link String}. If the property is multiple it returns the
+        * first value.
         * 
         * @return the value of
         *         {@link Node#getProperty(String)}.{@link Property#getString()} or
         *         <code>defaultValue</code> if the property does not exist.
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static String get(Node node, String property, String defaultValue) {
                try {
-                       if (node.hasProperty(property))
-                               return node.getProperty(property).getString();
-                       else
+                       if (node.hasProperty(property)) {
+                               Property p = node.getProperty(property);
+                               if (!p.isMultiple())
+                                       return p.getString();
+                               else {
+                                       Value[] values = p.getValues();
+                                       if (values.length == 0)
+                                               return defaultValue;
+                                       else
+                                               return values[0].getString();
+                               }
+                       } else
                                return defaultValue;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot retrieve property " + property + " from " + node);
+                       throw new JcrException("Cannot retrieve property " + property + " from " + node, e);
                }
        }
 
@@ -312,7 +477,7 @@ public class Jcr {
         * 
         * @return {@link Node#getProperty(String)} or <code>null</code> if the property
         *         does not exist.
-        * @throws IllegalStateException caused by {@link RepositoryException}
+        * @throws JcrException caused by {@link RepositoryException}
         */
        public static Value getValue(Node node, String property) {
                try {
@@ -321,7 +486,7 @@ public class Jcr {
                        else
                                return null;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot retrieve property " + property + " from " + node);
+                       throw new JcrException("Cannot retrieve property " + property + " from " + node, e);
                }
        }
 
@@ -331,12 +496,13 @@ public class Jcr {
         * @return the value of {@link Node#getProperty(String)} or
         *         <code>defaultValue</code> if the property does not exist.
         * @throws IllegalArgumentException if the value could not be cast
-        * @throws IllegalStateException    in case of unexpected
+        * @throws JcrException             in case of unexpected
         *                                  {@link RepositoryException}
         */
        @SuppressWarnings("unchecked")
        public static <T> T getAs(Node node, String property, T defaultValue) {
                try {
+                       // TODO deal with multiple
                        if (node.hasProperty(property)) {
                                Property p = node.getProperty(property);
                                try {
@@ -362,16 +528,44 @@ public class Jcr {
                                return defaultValue;
                        }
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot retrieve property " + property + " from " + node);
+                       throw new JcrException("Cannot retrieve property " + property + " from " + node, e);
                }
        }
 
-       /** Retrieves the {@link Session} related to this node. */
+       /**
+        * Retrieves the {@link Session} related to this node.
+        * 
+        * @deprecated Use {@link #getSession(Node)} instead.
+        */
+       @Deprecated
        public static Session session(Node node) {
+               return getSession(node);
+       }
+
+       /** Retrieves the {@link Session} related to this node. */
+       public static Session getSession(Node node) {
                try {
                        return node.getSession();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot retrieve session related to " + node, e);
+                       throw new JcrException("Cannot retrieve session related to " + node, e);
+               }
+       }
+
+       /** Retrieves the root node related to this session. */
+       public static Node getRootNode(Session session) {
+               try {
+                       return session.getRootNode();
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot get root node for " + session, e);
+               }
+       }
+
+       /** Whether this item exists. */
+       public static boolean itemExists(Session session, String path) {
+               try {
+                       return session.itemExists(path);
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot check whether " + path + " exists", e);
                }
        }
 
@@ -389,7 +583,7 @@ public class Jcr {
                        if (session.hasPendingChanges())
                                session.save();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot save session related to " + node + " in workspace "
+                       throw new JcrException("Cannot save session related to " + node + " in workspace "
                                        + session(node).getWorkspace().getName(), e);
                }
        }
@@ -414,6 +608,11 @@ public class Jcr {
                }
        }
 
+       /** Safely and silently logs out the underlying session. */
+       public static void logout(Node node) {
+               Jcr.logout(session(node));
+       }
+
        /*
         * SECURITY
         */
@@ -427,7 +626,7 @@ public class Jcr {
                        Session session = node.getSession();
                        JcrUtils.addPrivilege(session, node.getPath(), principal, privilege);
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot add privilege " + privilege + " to " + node, e);
+                       throw new JcrException("Cannot add privilege " + privilege + " to " + node, e);
                }
        }
 
@@ -439,7 +638,7 @@ public class Jcr {
                try {
                        return node.isCheckedOut();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot retrieve checked out status of " + node, e);
+                       throw new JcrException("Cannot retrieve checked out status of " + node, e);
                }
        }
 
@@ -448,7 +647,7 @@ public class Jcr {
                try {
                        versionManager(node).checkpoint(node.getPath());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot check in " + node, e);
+                       throw new JcrException("Cannot check in " + node, e);
                }
        }
 
@@ -457,7 +656,7 @@ public class Jcr {
                try {
                        versionManager(node).checkin(node.getPath());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot check in " + node, e);
+                       throw new JcrException("Cannot check in " + node, e);
                }
        }
 
@@ -466,7 +665,7 @@ public class Jcr {
                try {
                        versionManager(node).checkout(node.getPath());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot check out " + node, e);
+                       throw new JcrException("Cannot check out " + node, e);
                }
        }
 
@@ -475,7 +674,7 @@ public class Jcr {
                try {
                        return node.getSession().getWorkspace().getVersionManager();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get version manager from " + node, e);
+                       throw new JcrException("Cannot get version manager from " + node, e);
                }
        }
 
@@ -484,7 +683,7 @@ public class Jcr {
                try {
                        return versionManager(node).getVersionHistory(node.getPath());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get version history from " + node, e);
+                       throw new JcrException("Cannot get version history from " + node, e);
                }
        }
 
@@ -502,7 +701,7 @@ public class Jcr {
                        Collections.reverse(lst);
                        return lst;
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get linear versions from " + versionHistory, e);
+                       throw new JcrException("Cannot get linear versions from " + versionHistory, e);
                }
        }
 
@@ -511,7 +710,7 @@ public class Jcr {
                try {
                        return version.getFrozenNode();
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get frozen node from " + version, e);
+                       throw new JcrException("Cannot get frozen node from " + version, e);
                }
        }
 
@@ -520,7 +719,7 @@ public class Jcr {
                try {
                        return versionManager(node).getBaseVersion(node.getPath());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get base version from " + node, e);
+                       throw new JcrException("Cannot get base version from " + node, e);
                }
        }
 
@@ -538,7 +737,7 @@ public class Jcr {
                                throw new IllegalArgumentException(fileNode + " must be a file.");
                        return getBinarySize(fileNode.getNode(Node.JCR_CONTENT).getProperty(Property.JCR_DATA).getBinary());
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get file size of " + fileNode, e);
+                       throw new JcrException("Cannot get file size of " + fileNode, e);
                }
        }
 
@@ -549,8 +748,75 @@ public class Jcr {
                                return binary.getSize();
                        }
                } catch (RepositoryException e) {
-                       throw new IllegalStateException("Cannot get file size of binary " + binaryArg, e);
+                       throw new JcrException("Cannot get file size of binary " + binaryArg, e);
+               }
+       }
+
+       // QUERY
+       /** Creates a JCR-SQL2 query using {@link MessageFormat}. */
+       public static Query createQuery(QueryManager qm, String sql, Object... args) {
+               String query = MessageFormat.format(sql, args);
+               try {
+                       return qm.createQuery(query, Query.JCR_SQL2);
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot create JCR-SQL2 query from " + query, e);
+               }
+       }
+
+       /** Executes a JCR-SQL2 query using {@link MessageFormat}. */
+       public static NodeIterator executeQuery(QueryManager qm, String sql, Object... args) {
+               Query query = createQuery(qm, sql, args);
+               try {
+                       return query.execute().getNodes();
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot execute query " + sql + " with arguments " + Arrays.asList(args), e);
+               }
+       }
+
+       /** Executes a JCR-SQL2 query using {@link MessageFormat}. */
+       public static NodeIterator executeQuery(Session session, String sql, Object... args) {
+               QueryManager queryManager;
+               try {
+                       queryManager = session.getWorkspace().getQueryManager();
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot get query manager from session " + session, e);
+               }
+               return executeQuery(queryManager, sql, args);
+       }
+
+       /**
+        * Executes a JCR-SQL2 query using {@link MessageFormat}, which must return a
+        * single node at most.
+        * 
+        * @return the node or <code>null</code> if not found.
+        */
+       public static Node getNode(QueryManager qm, String sql, Object... args) {
+               NodeIterator nit = executeQuery(qm, sql, args);
+               if (nit.hasNext()) {
+                       Node node = nit.nextNode();
+                       if (nit.hasNext())
+                               throw new IllegalStateException(
+                                               "Query " + sql + " with arguments " + Arrays.asList(args) + " returned more than one node.");
+                       return node;
+               } else {
+                       return null;
+               }
+       }
+
+       /**
+        * Executes a JCR-SQL2 query using {@link MessageFormat}, which must return a
+        * single node at most.
+        * 
+        * @return the node or <code>null</code> if not found.
+        */
+       public static Node getNode(Session session, String sql, Object... args) {
+               QueryManager queryManager;
+               try {
+                       queryManager = session.getWorkspace().getQueryManager();
+               } catch (RepositoryException e) {
+                       throw new JcrException("Cannot get query manager from session " + session, e);
                }
+               return getNode(queryManager, sql, args);
        }
 
        /** Singleton. */