Locking unmapped URLs results in creation of that resource now, as specified in http://www.webdav.org/specs/rfc4918.html#rfc.section.9.10.4

main/frontend-webdav/src/main/java/org/cryptomator/frontend/webdav/jackrabbitservlet/DavFile.java

@@ -21,6 +21,8 @@ import org.apache.jackrabbit.webdav.DavServletResponse;
 import org.apache.jackrabbit.webdav.DavSession;
 import org.apache.jackrabbit.webdav.io.InputContext;
 import org.apache.jackrabbit.webdav.io.OutputContext;
+import org.apache.jackrabbit.webdav.lock.ActiveLock;
+import org.apache.jackrabbit.webdav.lock.LockInfo;
 import org.apache.jackrabbit.webdav.lock.LockManager;
 import org.apache.jackrabbit.webdav.property.DavProperty;
 import org.apache.jackrabbit.webdav.property.DavPropertyName;
@@ -166,4 +168,13 @@ class DavFile extends DavNode<FileLocator> {
 		}
 	}
 
+	@Override
+	public ActiveLock lock(LockInfo reqLockInfo) throws DavException {
+		ActiveLock lock = super.lock(reqLockInfo);
+		if (!exists()) {
+			getCollection().addMember(this, new NullInputContext());
+		}
+		return lock;
+	}
+
 }

main/frontend-webdav/src/main/java/org/cryptomator/frontend/webdav/jackrabbitservlet/DavFolder.java

@@ -61,6 +61,7 @@ class DavFolder extends DavNode<FolderLocator> {
 		if (resource instanceof DavFolder) {
 			addMemberFolder((DavFolder) resource);
 		} else if (resource instanceof DavFile) {
+			assert inputContext.hasStream();
 			addMemberFile((DavFile) resource, inputContext.getInputStream());
 		} else {
 			throw new IllegalArgumentException("Unsupported resource type: " + resource.getClass().getName());

main/frontend-webdav/src/main/java/org/cryptomator/frontend/webdav/jackrabbitservlet/NullInputContext.java

@@ -0,0 +1,45 @@
+package org.cryptomator.frontend.webdav.jackrabbitservlet;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+
+import org.apache.jackrabbit.webdav.io.InputContext;
+
+public class NullInputContext implements InputContext {
+
+	@Override
+	public boolean hasStream() {
+		return true;
+	}
+
+	@Override
+	public InputStream getInputStream() {
+		return new ByteArrayInputStream(new byte[0]);
+	}
+
+	@Override
+	public long getModificationTime() {
+		return 0;
+	}
+
+	@Override
+	public String getContentLanguage() {
+		return null;
+	}
+
+	@Override
+	public long getContentLength() {
+		return 0;
+	}
+
+	@Override
+	public String getContentType() {
+		return null;
+	}
+
+	@Override
+	public String getProperty(String propertyName) {
+		return null;
+	}
+
+}

main/frontend-webdav/src/test/java/org/cryptomator/frontend/webdav/WebDavServerTest.java

@@ -45,9 +45,13 @@ import org.apache.jackrabbit.webdav.MultiStatus;
 import org.apache.jackrabbit.webdav.MultiStatusResponse;
 import org.apache.jackrabbit.webdav.client.methods.CopyMethod;
 import org.apache.jackrabbit.webdav.client.methods.DavMethodBase;
+import org.apache.jackrabbit.webdav.client.methods.LockMethod;
 import org.apache.jackrabbit.webdav.client.methods.MkColMethod;
 import org.apache.jackrabbit.webdav.client.methods.MoveMethod;
 import org.apache.jackrabbit.webdav.client.methods.PropFindMethod;
+import org.apache.jackrabbit.webdav.lock.LockInfo;
+import org.apache.jackrabbit.webdav.lock.Scope;
+import org.apache.jackrabbit.webdav.lock.Type;
 import org.cryptomator.filesystem.FileSystem;
 import org.cryptomator.filesystem.ReadableFile;
 import org.cryptomator.filesystem.WritableFile;
@@ -173,6 +177,40 @@ public class WebDavServerTest {
 		Assert.assertTrue(CollectionUtils.containsAll(hrefs, Arrays.asList(servletRoot + "/folder1/", servletRoot + "/folder2/", servletRoot + "/file1")));
 	}
 
+	/* LOCK */
+
+	@Test
+	public void testLockExisting() throws IOException, DavException {
+		final HttpClient client = new HttpClient();
+
+		// create file:
+		try (WritableFile writable = fs.file("foo.txt").openWritable()) {
+			writable.write(ByteBuffer.allocate(0));
+		}
+
+		// lock existing file:
+		LockInfo lockInfo = new LockInfo(Scope.EXCLUSIVE, Type.WRITE, "le me", 3600, false);
+		final DavMethodBase lockMethod = new LockMethod(servletRoot + "/foo.txt", lockInfo);
+		final int lockResponse = client.executeMethod(lockMethod);
+		Assert.assertEquals(200, lockResponse);
+
+		lockMethod.releaseConnection();
+	}
+
+	@Test
+	public void testLockNonExisting() throws IOException, DavException {
+		final HttpClient client = new HttpClient();
+
+		// lock nonexisting file:
+		LockInfo lockInfo = new LockInfo(Scope.EXCLUSIVE, Type.WRITE, "le me", 3600, false);
+		final DavMethodBase lockMethod = new LockMethod(servletRoot + "/foo.txt", lockInfo);
+		final int lockResponse = client.executeMethod(lockMethod);
+		Assert.assertEquals(201, lockResponse);
+		Assert.assertTrue(fs.file("foo.txt").exists());
+
+		lockMethod.releaseConnection();
+	}
+
 	/* MOVE */
 
 	@Test