Retain unknown VCard properties, ez-vcard update, handle stale connections

* store unknown VCard properties in an extra column and load them when generating a new VCard (closes #118)
* upgrade to ez-vcard/0.9.3 (fixes sync error reported via Play Store)
* (re-)enable stale collection check, RetryHandler to retry idempotent CalDAV/CardDAV requests (hopefully fixes #225)
* always set FN/display name (take organization if no structured name is available) (hopefully fixes #227)

src/at/bitfire/davdroid/resource/Contact.java

@@ -35,6 +35,7 @@ import ezvcard.property.Birthday;
 import ezvcard.property.Email;
 import ezvcard.property.FormattedName;
 import ezvcard.property.Impp;
+import ezvcard.property.Logo;
 import ezvcard.property.Nickname;
 import ezvcard.property.Note;
 import ezvcard.property.Organization;
@@ -42,12 +43,15 @@ import ezvcard.property.Photo;
 import ezvcard.property.RawProperty;
 import ezvcard.property.Revision;
 import ezvcard.property.Role;
+import ezvcard.property.Sound;
+import ezvcard.property.Source;
 import ezvcard.property.StructuredName;
 import ezvcard.property.Telephone;
 import ezvcard.property.Title;
 import ezvcard.property.Uid;
 import ezvcard.property.Url;
 
+
 @ToString(callSuper = true)
 public class Contact extends Resource {
 	private final static String TAG = "davdroid.Contact";
@@ -68,7 +72,9 @@ public class Contact extends Resource {
 		PHONE_TYPE_ASSISTANT = TelephoneType.get("X-ASSISTANT"),
 		PHONE_TYPE_MMS = TelephoneType.get("X-MMS");
 	
-	@Getter @Setter boolean starred;
+	@Getter @Setter private String unknownProperties;
+	
+	@Getter @Setter private boolean starred;
 	
 	@Getter @Setter private String displayName, nickName;
 	@Getter @Setter private String prefix, givenName, middleName, familyName, suffix;
@@ -98,16 +104,16 @@ public class Contact extends Resource {
 	public Contact(long localID, String resourceName, String eTag) {
 		super(localID, resourceName, eTag);
 	}
-
+	
 	
 	@Override
-	public void generateUID() {
+	public void initialize() {
-		uid = UUID.randomUUID().toString();
+		generateUID();
+		name = uid + ".vcf";
 	}
 	
-	@Override
+	protected void generateUID() {
-	public void generateName() {
+		uid = UUID.randomUUID().toString();
-		name = uid + ".vcf";
 	}
 
 	
@@ -119,20 +125,37 @@ public class Contact extends Resource {
 		if (vcard == null)
 			return;
 		
-		Uid uid = vcard.getUid();
+		// now work through all supported properties
-		if (uid == null) {
+		// supported properties are removed from the VCard after parsing
-			Log.w(TAG, "Received VCard without UID, generating new one");
+		// so that only unknown properties are left and can be stored separately
-			uid = new Uid(UUID.randomUUID().toString());
-		}
-		this.uid = uid.getValue();
-
-		RawProperty starred = vcard.getExtendedProperty(PROPERTY_STARRED);
-		this.starred = starred != null && starred.getValue().equals("1");
 		
-		FormattedName fn = vcard.getFormattedName();
+		// UID
-		if (fn != null)
+		Uid uid = vcard.getUid();
-			displayName = fn.getValue();
+		if (uid != null) {
+			this.uid = uid.getValue();
+			vcard.removeProperties(Uid.class);
+		} else {
+			Log.w(TAG, "Received VCard without UID, generating new one");
+			generateUID();
+		}
 
+		// X-DAVDROID-STARRED
+		RawProperty starred = vcard.getExtendedProperty(PROPERTY_STARRED);
+		if (starred != null && starred.getValue() != null) {
+			this.starred = starred.getValue().equals("1");
+			vcard.removeExtendedProperty(PROPERTY_STARRED);
+		} else
+			this.starred = false;
+		
+		// FN
+		FormattedName fn = vcard.getFormattedName();
+		if (fn != null) {
+			displayName = fn.getValue();
+			vcard.removeProperties(FormattedName.class);
+		} else
+			Log.w(TAG, "Received invalid VCard without FN (formatted name) property");
+
+		// N
 		StructuredName n = vcard.getStructuredName();
 		if (n != null) {
 			prefix = StringUtils.join(n.getPrefixes(), " ");
@@ -140,77 +163,141 @@ public class Contact extends Resource {
 			middleName = StringUtils.join(n.getAdditional(), " ");
 			familyName = n.getFamily();
 			suffix = StringUtils.join(n.getSuffixes(), " ");
+			vcard.removeProperties(StructuredName.class);
 		}
 		
+		// phonetic names
 		RawProperty
 			phoneticFirstName = vcard.getExtendedProperty(PROPERTY_PHONETIC_FIRST_NAME),
 			phoneticMiddleName = vcard.getExtendedProperty(PROPERTY_PHONETIC_MIDDLE_NAME),
 			phoneticLastName = vcard.getExtendedProperty(PROPERTY_PHONETIC_LAST_NAME);
-		if (phoneticFirstName != null)
+		if (phoneticFirstName != null) {
 			phoneticGivenName = phoneticFirstName.getValue();
-		if (phoneticMiddleName != null)
+			vcard.removeExtendedProperty(PROPERTY_PHONETIC_FIRST_NAME);
+		}
+		if (phoneticMiddleName != null) {
 			this.phoneticMiddleName = phoneticMiddleName.getValue();
-		if (phoneticLastName != null)
+			vcard.removeExtendedProperty(PROPERTY_PHONETIC_MIDDLE_NAME);
+		}
+		if (phoneticLastName != null) {
 			phoneticFamilyName = phoneticLastName.getValue();
+			vcard.removeExtendedProperty(PROPERTY_PHONETIC_LAST_NAME);
+		}
 		
+		// TEL
 		phoneNumbers = vcard.getTelephoneNumbers();
-		emails = vcard.getEmails();
+		vcard.removeProperties(Telephone.class);
 		
+		// EMAIL
+		emails = vcard.getEmails();
+		vcard.removeProperties(Email.class);
+		
+		// PHOTO
 		for (Photo photo : vcard.getPhotos()) {
 			this.photo = photo.getData();
+			vcard.removeProperties(Photo.class);
 			break;
 		}
 
+		// ORG
 		organization = vcard.getOrganization();
+		vcard.removeProperties(Organization.class);
+		// TITLE
 		for (Title title : vcard.getTitles()) {
 			jobTitle = title.getValue();
+			vcard.removeProperties(Title.class);
 			break;
 		}
+		// ROLE
 		for (Role role : vcard.getRoles()) {
 			this.jobDescription = role.getValue();
+			vcard.removeProperties(Role.class);
 			break;
 		}
 	
+		// IMPP
 		impps = vcard.getImpps();
+		vcard.removeProperties(Impp.class);
 		
+		// NICKNAME
 		Nickname nicknames = vcard.getNickname();
-		if (nicknames != null && nicknames.getValues() != null)
+		if (nicknames != null) {
-			nickName = StringUtils.join(nicknames.getValues(), ", ");
+			if (nicknames.getValues() != null)
+				nickName = StringUtils.join(nicknames.getValues(), ", ");
+			vcard.removeProperties(Nickname.class);
+		}
 		
+		// NOTE
 		List<String> notes = new LinkedList<String>();
 		for (Note note : vcard.getNotes())
 			notes.add(note.getValue());
 		if (!notes.isEmpty())
 			note = StringUtils.join(notes, "\n---\n");
+		vcard.removeProperties(Note.class);
 
+		// ADR
 		addresses = vcard.getAddresses();
+		vcard.removeProperties(Address.class);
 		
+		// URL
 		for (Url url : vcard.getUrls())
 			URLs.add(url.getValue());
+		vcard.removeProperties(Url.class);
 
+		// BDAY
 		birthDay = vcard.getBirthday();
+		vcard.removeProperties(Birthday.class);
+		// ANNIVERSARY
 		anniversary = vcard.getAnniversary();
+		vcard.removeProperties(Anniversary.class);
 		
-		// get X-SIP and import as IMPP
+		// X-SIP
 		for (RawProperty sip : vcard.getExtendedProperties(PROPERTY_SIP))
 			impps.add(new Impp("sip", sip.getValue()));
+		vcard.removeExtendedProperty(PROPERTY_SIP);
+
+		// remove binary properties because of potential OutOfMemory / TransactionTooLarge exceptions
+		vcard.removeProperties(Logo.class);
+		vcard.removeProperties(Sound.class);
+		// remove properties that don't apply anymore
+		vcard.removeProperties(Revision.class);
+		vcard.removeProperties(Source.class);
+		// store all remaining properties into unknownProperties
+		if (!vcard.getProperties().isEmpty() || !vcard.getExtendedProperties().isEmpty())
+			unknownProperties = vcard.write();
+		else
+			unknownProperties = null;
 	}
 
 	
 	@Override
 	public ByteArrayOutputStream toEntity() throws IOException {
-		VCard vcard = new VCard();
+		VCard vcard = null;
-		vcard.setProdId("DAVdroid/" + Constants.APP_VERSION + " (ez-vcard/" + Ezvcard.VERSION + ")");
+		try {
+			if (unknownProperties != null)
+				vcard = Ezvcard.parse(unknownProperties).first();
+		} catch (Exception e) {
+			Log.w(TAG, "Couldn't parse original property set, beginning from scratch");
+		}
+		if (vcard == null)
+			vcard = new VCard();
 		
 		if (uid != null)
 			vcard.setUid(new Uid(uid));
+		else
+			Log.wtf(TAG, "Generating VCard without UID");
 		
 		if (starred)
 			vcard.setExtendedProperty(PROPERTY_STARRED, "1");
 		
 		if (displayName != null)
 			vcard.setFormattedName(displayName);
+		else if (organization != null && organization.getValues() != null && organization.getValues().get(0) != null)
+			vcard.setFormattedName(organization.getValues().get(0));
+		else
+			Log.w(TAG, "No FN (formatted name) available to generate VCard");
 
+		// N
 		if (familyName != null || middleName != null || givenName != null) {
 			StructuredName n = new StructuredName();
 			if (prefix != null)
@@ -227,6 +314,7 @@ public class Contact extends Resource {
 			vcard.setStructuredName(n);
 		}
 		
+		// phonetic names
 		if (phoneticGivenName != null)
 			vcard.addExtendedProperty(PROPERTY_PHONETIC_FIRST_NAME, phoneticGivenName);
 		if (phoneticMiddleName != null)
@@ -234,42 +322,55 @@ public class Contact extends Resource {
 		if (phoneticFamilyName != null)
 			vcard.addExtendedProperty(PROPERTY_PHONETIC_LAST_NAME, phoneticFamilyName);
 		
+		// TEL
 		for (Telephone phoneNumber : phoneNumbers)
 			vcard.addTelephoneNumber(phoneNumber);
 		
+		// EMAIL
 		for (Email email : emails)
 			vcard.addEmail(email);
 
+		// ORG, TITLE, ROLE
 		if (organization != null)
-			vcard.addOrganization(organization);
+			vcard.setOrganization(organization);
 		if (jobTitle != null)
 			vcard.addTitle(jobTitle);
 		if (jobDescription != null)
 			vcard.addRole(jobDescription);
 		
+		// IMPP
 		for (Impp impp : impps)
 			vcard.addImpp(impp);
 
-		if (nickName != null && !nickName.isEmpty())
+		// NICKNAME
+		if (!StringUtils.isBlank(nickName))
 			vcard.setNickname(nickName);
 		
-		if (note != null && !note.isEmpty())
+		// NOTE
+		if (!StringUtils.isBlank(note))
 			vcard.addNote(note);
 		
+		// ADR
 		for (Address address : addresses)
 			vcard.addAddress(address);
 		
+		// URL
 		for (String url : URLs)
 			vcard.addUrl(url);
-		
+
+		// ANNIVERSARY
 		if (anniversary != null)
 			vcard.setAnniversary(anniversary);
+		// BDAY
 		if (birthDay != null)
 			vcard.setBirthday(birthDay);
 		
+		// PHOTO
 		if (photo != null)
 			vcard.addPhoto(new Photo(photo, ImageType.JPEG));
 		
+		// PRODID, REV
+		vcard.setProdId("DAVdroid/" + Constants.APP_VERSION + " (ez-vcard/" + Ezvcard.VERSION + ")");
 		vcard.setRevision(Revision.now());
 		
 		ByteArrayOutputStream os = new ByteArrayOutputStream();

src/at/bitfire/davdroid/resource/Event.java

@@ -109,14 +109,14 @@ public class Event extends Resource {
 
 	
 	@Override
-	public void generateUID() {
+	public void initialize() {
-		UidGenerator generator = new UidGenerator(new SimpleHostInfo(DavSyncAdapter.getAndroidID()), String.valueOf(android.os.Process.myPid()));
+		generateUID();
-		uid = generator.generateUid().getValue();
+		name = uid.replace("@", "_") + ".ics";
 	}
 	
-	@Override
+	protected void generateUID() {
-	public void generateName() {
+		UidGenerator generator = new UidGenerator(new SimpleHostInfo(DavSyncAdapter.getAndroidID()), String.valueOf(android.os.Process.myPid()));
-		name = uid.replace("@", "_") + ".ics";
+		uid = generator.generateUid().getValue();
 	}
 
 

src/at/bitfire/davdroid/resource/LocalAddressBook.java

@@ -20,10 +20,6 @@ import java.util.Set;
 
 import lombok.Cleanup;
 
-import org.apache.commons.io.IOUtils;
-import org.apache.commons.lang.StringUtils;
-import org.apache.commons.lang.WordUtils;
-
 import android.accounts.Account;
 import android.content.ContentProviderClient;
 import android.content.ContentProviderOperation;
@@ -49,7 +45,11 @@ import android.provider.ContactsContract.CommonDataKinds.Website;
 import android.provider.ContactsContract.Data;
 import android.provider.ContactsContract.RawContacts;
 import android.util.Log;
-import at.bitfire.davdroid.syncadapter.AccountSettings;
+
+import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang.StringUtils;
+import org.apache.commons.lang.WordUtils;
+
 import ezvcard.parameter.AddressType;
 import ezvcard.parameter.EmailType;
 import ezvcard.parameter.ImppType;
@@ -61,10 +61,15 @@ import ezvcard.property.DateOrTimeProperty;
 import ezvcard.property.Impp;
 import ezvcard.property.Telephone;
 
+import at.bitfire.davdroid.syncadapter.AccountSettings;
+
 
 public class LocalAddressBook extends LocalCollection<Contact> {
 	private final static String TAG = "davdroid.LocalAddressBook";
 	
+	protected final static String COLUMN_UNKNOWN_PROPERTIES = RawContacts.SYNC3;
+
+	
 	protected AccountSettings accountSettings;
 	
 	
@@ -146,10 +151,11 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 		
 		try {
 			@Cleanup Cursor cursor = providerClient.query(ContentUris.withAppendedId(entriesURI(), c.getLocalID()),
-				new String[] { entryColumnUID(), RawContacts.STARRED }, null, null, null);
+				new String[] { entryColumnUID(), COLUMN_UNKNOWN_PROPERTIES, RawContacts.STARRED }, null, null, null);
 			if (cursor != null && cursor.moveToNext()) {
 				c.setUid(cursor.getString(0));
-				c.setStarred(cursor.getInt(1) != 0);
+				c.setUnknownProperties(cursor.getString(1));
+				c.setStarred(cursor.getInt(2) != 0);
 			} else
 				throw new RecordNotFoundException();
 		
@@ -177,6 +183,7 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 				/* 6 */ StructuredName.PHONETIC_GIVEN_NAME, StructuredName.PHONETIC_MIDDLE_NAME, StructuredName.PHONETIC_FAMILY_NAME
 			}, StructuredName.RAW_CONTACT_ID + "=? AND " + Data.MIMETYPE + "=?",
 			new String[] { String.valueOf(c.getLocalID()), StructuredName.CONTENT_ITEM_TYPE }, null);
+		
 		if (cursor != null && cursor.moveToNext()) {
 			c.setDisplayName(cursor.getString(0));
 			
@@ -512,6 +519,7 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 			.withValue(entryColumnRemoteName(), contact.getName())
 			.withValue(entryColumnUID(), contact.getUid())
 			.withValue(entryColumnETag(), contact.getETag())
+			.withValue(COLUMN_UNKNOWN_PROPERTIES, contact.getUnknownProperties())
 			.withValue(RawContacts.STARRED, contact.isStarred());
 	}
 	
@@ -519,8 +527,8 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 	@Override
 	protected void addDataRows(Resource resource, long localID, int backrefIdx) {
 		Contact contact = (Contact)resource;
-		
+
-		pendingOperations.add(buildStructuredName(newDataInsertBuilder(localID, backrefIdx), contact).build());
+		queueOperation(buildStructuredName(newDataInsertBuilder(localID, backrefIdx), contact));
 		
 		for (Telephone number : contact.getPhoneNumbers())
 			queueOperation(buildPhoneNumber(newDataInsertBuilder(localID, backrefIdx), number));
@@ -531,9 +539,7 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 		if (contact.getPhoto() != null)
 			queueOperation(buildPhoto(newDataInsertBuilder(localID, backrefIdx), contact.getPhoto()));
 		
-		if (contact.getOrganization() != null || contact.getJobTitle() != null || contact.getJobDescription() != null)
+		queueOperation(buildOrganization(newDataInsertBuilder(localID, backrefIdx), contact));
-			queueOperation(buildOrganization(newDataInsertBuilder(localID, backrefIdx),
-				contact.getOrganization(), contact.getJobTitle(), contact.getJobDescription()));
 			
 		for (Impp impp : contact.getImpps())
 			queueOperation(buildIMPP(newDataInsertBuilder(localID, backrefIdx), impp));
@@ -560,7 +566,7 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 		
 		// TODO relations
 		
-		// SIP addresses built by buildIMPP
+		// SIP addresses are built by buildIMPP
 	}
 	
 	@Override
@@ -695,9 +701,12 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 			.withValue(Photo.PHOTO, photo);
 	}
 	
-	protected Builder buildOrganization(Builder builder, ezvcard.property.Organization organization, String jobTitle, String jobDescription) {
+	protected Builder buildOrganization(Builder builder, Contact contact) {
+		if (contact.getOrganization() == null && contact.getJobTitle() == null && contact.getJobDescription() == null)
+			return null;
+
+		ezvcard.property.Organization organization = contact.getOrganization();
 		String company = null, department = null;
-		
 		if (organization != null) {
 			Iterator<String> org = organization.getValues().iterator();
 			if (org.hasNext())
@@ -710,8 +719,8 @@ public class LocalAddressBook extends LocalCollection<Contact> {
 				.withValue(Data.MIMETYPE, Organization.CONTENT_ITEM_TYPE)
 				.withValue(Organization.COMPANY, company)
 				.withValue(Organization.DEPARTMENT, department)
-				.withValue(Organization.TITLE, jobTitle)
+				.withValue(Organization.TITLE, contact.getJobTitle())
-				.withValue(Organization.JOB_DESCRIPTION, jobDescription);
+				.withValue(Organization.JOB_DESCRIPTION, contact.getJobDescription());
 	}
 
 	protected Builder buildIMPP(Builder builder, Impp impp) {

src/at/bitfire/davdroid/resource/LocalCollection.java

@@ -40,7 +40,7 @@ public abstract class LocalCollection<T extends Resource> {
 
 	abstract protected String entryColumnAccountType();
 	abstract protected String entryColumnAccountName();
-
+	
 	abstract protected String entryColumnParentID();
 	abstract protected String entryColumnID();
 	abstract protected String entryColumnRemoteName();
@@ -85,8 +85,7 @@ public abstract class LocalCollection<T extends Resource> {
 				
 				// new record: generate UID + remote file name so that we can upload
 				T resource = findById(id, false);
-				resource.generateUID();
+				resource.initialize();
-				resource.generateName();
 				// write generated UID + remote file name into database
 				ContentValues values = new ContentValues(2);
 				values.put(entryColumnUID(), resource.getUid());

src/at/bitfire/davdroid/resource/Resource.java

@@ -23,7 +23,7 @@ public abstract class Resource {
 	@Getter protected String name, ETag;
 	@Getter @Setter protected String uid;
 	@Getter protected long localID;
-	
+
 	
 	public Resource(String name, String ETag) {
 		this.name = name;
@@ -36,8 +36,7 @@ public abstract class Resource {
 	}
 	
 	// sets UID and resource name (= remote file name)
-	public abstract void generateUID();
+	public abstract void initialize();
-	public abstract void generateName();
 	
 	public abstract void parseEntity(InputStream entity) throws IOException, InvalidResourceException;
 	public abstract ByteArrayOutputStream toEntity() throws IOException;

src/at/bitfire/davdroid/syncadapter/CalendarsSyncAdapterService.java

@@ -14,7 +14,6 @@ import java.net.URISyntaxException;
 import java.util.HashMap;
 import java.util.Map;
 
-import lombok.Synchronized;
 import android.accounts.Account;
 import android.app.Service;
 import android.content.ContentProviderClient;
@@ -32,13 +31,13 @@ public class CalendarsSyncAdapterService extends Service {
 	private static SyncAdapter syncAdapter;
 	
 	
-	@Override @Synchronized
+	@Override
 	public void onCreate() {
 		if (syncAdapter == null)
 			syncAdapter = new SyncAdapter(getApplicationContext());
 	}
 
-	@Override @Synchronized
+	@Override
 	public void onDestroy() {
 		syncAdapter.close();
 		syncAdapter = null;

src/at/bitfire/davdroid/syncadapter/ContactsSyncAdapterService.java

@@ -14,7 +14,6 @@ import java.net.URISyntaxException;
 import java.util.HashMap;
 import java.util.Map;
 
-import lombok.Synchronized;
 import android.accounts.Account;
 import android.app.Service;
 import android.content.ContentProviderClient;
@@ -29,9 +28,9 @@ import at.bitfire.davdroid.resource.RemoteCollection;
 
 public class ContactsSyncAdapterService extends Service {
 	private static ContactsSyncAdapter syncAdapter;
-	
 
-	@Override @Synchronized
+	
+	@Override
 	public void onCreate() {
 		if (syncAdapter == null)
 			syncAdapter = new ContactsSyncAdapter(getApplicationContext());
@@ -55,7 +54,6 @@ public class ContactsSyncAdapterService extends Service {
 		
 		private ContactsSyncAdapter(Context context) {
 			super(context);
-			Log.i(TAG, "httpClient = " + httpClient);
 		}
 
 		@Override
@@ -71,7 +69,6 @@ public class ContactsSyncAdapterService extends Service {
 			
 			try {
 				LocalCollection<?> database = new LocalAddressBook(account, provider, settings);
-				Log.i(TAG, "httpClient 2 = " + httpClient);
 				RemoteCollection<?> dav = new CardDavAddressBook(httpClient, addressBookURL, userName, password, preemptive);
 				
 				Map<LocalCollection<?>, RemoteCollection<?>> map = new HashMap<LocalCollection<?>, RemoteCollection<?>>();

src/at/bitfire/davdroid/syncadapter/DavSyncAdapter.java

@@ -57,7 +57,8 @@ public abstract class DavSyncAdapter extends AbstractThreadedSyncAdapter impleme
 		httpClient = DavHttpClient.create();
 	}
 	
-	@Override public void close() {
+	@Override
+	public void close() {
 		// apparently may be called from a GUI thread
 		new AsyncTask<Void, Void, Void>() {
 			@Override
@@ -104,7 +105,7 @@ public abstract class DavSyncAdapter extends AbstractThreadedSyncAdapter impleme
 					Log.e(TAG, "Hard HTTP error " + ex.getCode(), ex);
 					syncResult.stats.numParseExceptions++;
 				} else {
-					Log.w(TAG, "Soft HTTP error" + ex.getCode(), ex);
+					Log.w(TAG, "Soft HTTP error " + ex.getCode() + " (Android will try again later)", ex);
 					syncResult.stats.numIoExceptions++;
 				}
 				
@@ -113,7 +114,7 @@ public abstract class DavSyncAdapter extends AbstractThreadedSyncAdapter impleme
 				Log.e(TAG, "Local storage (content provider) exception", ex);
 			} catch (IOException ex) {
 				syncResult.stats.numIoExceptions++;
-				Log.e(TAG, "I/O error", ex);
+				Log.e(TAG, "I/O error (Android will try again later)", ex);
 			}
 	}
 }

src/at/bitfire/davdroid/webdav/DavHttpClient.java

@@ -36,7 +36,7 @@ public class DavHttpClient {
 		defaultRqConfig = RequestConfig.copy(RequestConfig.DEFAULT)
 				.setConnectTimeout(20*1000)
 				.setSocketTimeout(20*1000)
-				.setStaleConnectionCheckEnabled(false)
+				.setStaleConnectionCheckEnabled(true)
 				.build();
 		
 		// enable logging
@@ -56,6 +56,7 @@ public class DavHttpClient {
 				.useSystemProperties()
 				.setConnectionManager(connectionManager)
 				.setDefaultRequestConfig(defaultRqConfig)
+				.setRetryHandler(DavHttpRequestRetryHandler.INSTANCE)
 				.setUserAgent("DAVdroid/" + Constants.APP_VERSION)
 				.disableCookieManagement()
 				.build();

src/at/bitfire/davdroid/webdav/DavHttpRequestRetryHandler.java

@@ -0,0 +1,28 @@
+package at.bitfire.davdroid.webdav;
+
+import java.util.Locale;
+
+import org.apache.commons.lang.ArrayUtils;
+
+import ch.boye.httpclientandroidlib.HttpRequest;
+import ch.boye.httpclientandroidlib.impl.client.DefaultHttpRequestRetryHandler;
+
+public class DavHttpRequestRetryHandler extends DefaultHttpRequestRetryHandler {
+	final static DavHttpRequestRetryHandler INSTANCE = new DavHttpRequestRetryHandler();
+	
+	// see http://www.iana.org/assignments/http-methods/http-methods.xhtml
+	private final static String idempotentMethods[] = {
+		"DELETE", "GET", "HEAD", "MKCALENDAR", "MKCOL", "OPTIONS", "PROPFIND", "PROPPATCH",
+		"PUT", "REPORT", "SEARCH", "TRACE"
+	};
+
+    public DavHttpRequestRetryHandler() {
+        super(/* retry count */ 3, /* retry already sent requests? */ false);
+    }
+
+    @Override
+    protected boolean handleAsIdempotent(final HttpRequest request) {
+        final String method = request.getRequestLine().getMethod().toUpperCase(Locale.ROOT);
+        return ArrayUtils.contains(idempotentMethods, method);
+    }
+}

test/src/at/bitfire/davdroid/webdav/test/WebDavResourceTest.java

@@ -14,9 +14,7 @@ import lombok.Cleanup;
 import org.apache.commons.io.IOUtils;
 
 import android.content.res.AssetManager;
-import android.os.Build;
 import android.test.InstrumentationTestCase;
-import android.util.Log;
 import at.bitfire.davdroid.webdav.DavException;
 import at.bitfire.davdroid.webdav.DavHttpClient;
 import at.bitfire.davdroid.webdav.DavMultiget;
@@ -31,8 +29,6 @@ import ch.boye.httpclientandroidlib.impl.client.CloseableHttpClient;
 // tests require running robohydra!
 
 public class WebDavResourceTest extends InstrumentationTestCase {
-	private static final String TAG = "davdroidTest.WebDavResourceTest";
-	
 	static final String ROBOHYDRA_BASE = "http://10.0.0.11:3000/";
 	static byte[] SAMPLE_CONTENT = new byte[] { 1, 2, 3, 4, 5 };