Continued work on DOIDataCiteIdentifier.

* Added a lot of functionality to DOIDataCiteIdentifierProvider.
 * Added a table Doi to the database.
 * Added use of Database table doi to DOIDataCiteIdentifierProvider.
 * Moved DOIDataCiteIdentifierProvider.DOIToExternalForm(String) to DOI.DOIToExterenalForm.

dspace-api/src/main/java/org/dspace/identifier/DOI.java

@@ -17,4 +17,37 @@ public class DOI
         implements Identifier
 {
     public static final String SCHEME = "doi:";
+    
+    
+    /**
+     * This method helps to convert a DOI into a URL. It takes DOIs in one of
+     * the following formats  and returns it as URL (f.e. 
+     * http://dx.doi.org/10.123/456). Allowed formats are:
+     * <ul>
+     *   <li>doi:10.123/456</li>
+     *   <li>10.123/456</li>
+     *   <li>http://dx.doi.org/10.123/456</li>
+     * </ul>
+     * 
+     * @param identifier  A DOI that should be returned in external form.
+     * @return A String containing a URL to the official DOI resolver.
+     * @throws IllegalArgumentException If identifier is null or an empty String.
+     * @throws IdentifierException If identifier could not be recognized as valid DOI.
+     */
+    public static String DOIToExternalForm(String identifier)
+            throws IdentifierException
+    {
+        if (null == identifier) 
+            throw new IllegalArgumentException("Identifier is null.", new NullPointerException());
+        if (identifier.isEmpty())
+            throw new IllegalArgumentException("Cannot format an empty identifier.");
+        if (identifier.startsWith(SCHEME))
+            return "http://dx.doi.org/" + identifier.substring(SCHEME.length());
+        if (identifier.startsWith("10.") && identifier.contains("/"))
+            return "http://dx.doi.org/" + identifier;
+        if (identifier.startsWith("http://dx.doi.org/10."))
+            return identifier;
+        
+        throw new IdentifierException(identifier + "does not seem to be a DOI.");
+    }
 }

dspace-api/src/main/java/org/dspace/identifier/DOIDataCiteIdentifierProvider.java

@@ -12,13 +12,22 @@ import java.io.IOException;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.logging.Level;
 import org.dspace.authorize.AuthorizeException;
+import org.dspace.authorize.AuthorizeManager;
+import org.dspace.content.Bitstream;
 import org.dspace.content.DCValue;
 import org.dspace.content.DSpaceObject;
+import org.dspace.content.FormatIdentifier;
 import org.dspace.content.Item;
 import org.dspace.content.ItemIterator;
+import org.dspace.content.crosswalk.DisseminationCrosswalk;
+import org.dspace.core.Constants;
 import org.dspace.core.Context;
+import org.dspace.core.PluginManager;
 import org.dspace.identifier.doi.RegistrationAgency;
+import org.dspace.storage.rdbms.DatabaseManager;
+import org.dspace.storage.rdbms.TableRow;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -51,6 +60,121 @@ public class DOIDataCiteIdentifierProvider
     
     private static final String DOI_SCHEME = DOI.SCHEME;
     
+    /**
+     * Stores the scheme used to connect to the DataCite server. It will be set
+     * by spring dependency injection.
+     */
+    private String DATACITE_SCHEME;
+    /**
+     * Stores the hostname of the DataCite server. Set by spring dependency
+     * injection.
+     */
+    private String DATACITE_HOST;
+    /**
+     * Path on the DataCite server used to generate DOIs. Set by spring
+     * dependency injection.
+     */
+    private String DATACITE_DOI_PATH;
+    /**
+     * Path on the DataCite server used to register metadata. Set by spring
+     * dependency injection.
+     */
+    private String DATACITE_METADATA_PATH;
+    /**
+     * Name of crosswalk to convert metadata into DataCite Metadata Scheme. Set 
+     * by spring dependency injection.
+     */
+    protected String CROSSWALK_NAME;
+    
+    /**
+     * Prefix of DOI namespace. Set in dspace.cfg.
+     */
+    protected String PREFIX;
+    /**
+     * Part of DOI to seperate several applications that generate DOIs. F.e. it
+     * could be 'dspace/' if DOIs generated by DSpace should have the form
+     * prefix/dspace/uniqueString. Set it to the empty String if DSpace should
+     * generate DOIs directly after the DOI Prefix. Set in dspace.cfg.
+     */
+    protected String NAMESPACE_SEPARATOR;
+    
+    // TODO: document how exception while initializing the crosswalks will be
+    // handeled.
+    /** 
+     * DisseminationCrosswalk to map local metadata into DataCite metadata.
+     * The name of the crosswalk is set by spring dependency injection using
+     * {@link setDisseminationCrosswalk(String) setDisseminationCrosswalk} which
+     * instantiate the crosswalk.
+     */
+    protected DisseminationCrosswalk crosswalk;
+    
+    /**
+     * Used to set the scheme to connect the DataCite server. Used by spring
+     * dependency injection.
+     * @param DATACITE_SCHEME Probably https or http.
+     */
+    @Required
+    public void setDATACITE_SCHEME(String DATACITE_SCHEME) {
+        this.DATACITE_SCHEME = DATACITE_SCHEME;
+    }
+
+    /**
+     * Set the hostname of the DataCite server. Used by spring dependency
+     * injection.
+     * @param DATACITE_HOST Hostname to connect to register DOIs (f.e. test.datacite.org).
+     */
+    @Required
+    public void setDATACITE_HOST(String DATACITE_HOST) {
+        this.DATACITE_HOST = DATACITE_HOST;
+    }
+    
+    /**
+     * Set the path on the DataCite server to register DOIs. Used by spring
+     * dependency injection.
+     * @param DATACITE_DOI_PATH Path to register DOIs, f.e. /doi.
+     */
+    @Required
+    public void setDATACITE_DOI_PATH(String DATACITE_DOI_PATH) {
+        this.DATACITE_DOI_PATH = DATACITE_DOI_PATH;
+    }
+    
+    /**
+     * Set the path to register metadata on DataCite server. Used by spring
+     * dependency injection.
+     * @param DATACITE_METADATA_PATH Path to register metadata, f.e. /mds.
+     */
+    @Required
+    public void setDATACITE_METADATA_PATH(String DATACITE_METADATA_PATH) {
+        this.DATACITE_METADATA_PATH = DATACITE_METADATA_PATH;
+    }
+    
+    // TODO: document how exception while initializing the crosswalks will be
+    // handeled.
+    /**
+     * Set the name of the dissemination crosswalk used to convert the metadata
+     * into DataCite Metadata Schema. This method tries to initialize the named
+     * crosswalk. Used by spring dependency injection.
+     * @param CROSSWALK_NAME The name of the dissemination crosswalk to use. This
+     *                       crosswalk must be configured in dspace.cfg.
+     */
+    @Required
+    public void setDisseminationCrosswalk(String CROSSWALK_NAME) {
+        this.CROSSWALK_NAME= CROSSWALK_NAME;
+
+    	// FIXME add some caching here
+    	this.crosswalk = (DisseminationCrosswalk) PluginManager.getNamedPlugin(DisseminationCrosswalk.class, CROSSWALK_NAME);
+        // FIXME handle the case if the crosswalk can't be found
+        if (this.crosswalk == null) {
+            throw new IllegalArgumentException("Can't find crosswalk '" + CROSSWALK_NAME + "'!");
+        }
+    }
+    
+    public DOIDataCiteIdentifierProvider() {
+        // FIXME
+        PREFIX = "10.0123";
+        NAMESPACE_SEPARATOR = "DSpace/";
+    }
+    
     /**
      * This identifier provider supports identifiers of type
      * {@link org.dspace.identifier.DOI}.
@@ -90,7 +214,8 @@ public class DOIDataCiteIdentifierProvider
             throws IdentifierException
     {
         String doi = mint(context, dso);
-        if (null != doi)
+        // register tries to reserve doi if it's not already.
+        // So we don't have to reserve it here.
         this.register(context, dso, doi);
         return doi;
     }
@@ -100,10 +225,17 @@ public class DOIDataCiteIdentifierProvider
             throws IdentifierException
     {
         String doi = formatIdentifier(identifier);
-        if (!isDOIReservedForObject(dso, doi))
+        if (isDOIRegistered(dso, doi))
+            return;
+
+        if (isDOIRegistered(doi))
+            throw new IllegalArgumentException("Trying to register a DOI that is registered for another object.");
+        
+        if (!isDOIReserved(dso, doi))
         {
             if (isDOIReserved(doi))
-                throw new IllegalStateException("Trying to register a DOI that is reserved for another object.");
+                throw new IllegalArgumentException("Trying to register a DOI that is reserved for another object.");
+            
             if(!reserveDOI(dso, doi))
                 throw new IdentifierException("It was impossible to reserve the DOI "
                         + doi + ". Take a look into the logs for further details.");
@@ -111,9 +243,7 @@ public class DOIDataCiteIdentifierProvider
         
         try
         {
-            if (registerDOI(dso, doi))
+            if (!registerDOI(context, dso, doi))
-                saveDOIToObject(context, dso, doi);
-            else
                 throw new IdentifierException("It was impossible to register the DOI "
                         + doi + ". Take a look into the logs for further details.");
         }
@@ -124,15 +254,23 @@ public class DOIDataCiteIdentifierProvider
         }
     }
 
+    /**
+     * @param context
+     * @param dso DSpaceObject the DOI should be reserved for. Some metadata of this object will be send to the registration agency.
+     * @param identifier DOI to register in a format that {@link FormatIdentifier(String)} accepts.
+     * @throws IdentifierException If the format of {@code identifier} was unrecognized or if it was impossible to reserve the DOI (registration agency denied for some reason, see logs).
+     * @throws IllegalArgumentException If {@code identifier} is a DOI already registered for another DSpaceObject then {@code dso}.
+     * @see IdentifierProvider.reserve(Context, DSpaceObject, String)
+     */
     @Override
     public void reserve(Context context, DSpaceObject dso, String identifier)
-            throws IdentifierException
+            throws IdentifierException, IllegalArgumentException
     {
         String doi = formatIdentifier(identifier);
-        if (!isDOIReservedForObject(dso, doi))
+        if (!isDOIReserved(dso, doi))
         {
             if (isDOIReserved(doi))
-                throw new IllegalStateException("Trying to register a DOI that is reserved for another object.");
+                throw new IllegalArgumentException("Trying to register a DOI that is reserved for another object.");
             if(!reserveDOI(dso, doi))
                 throw new IdentifierException("It was impossible to reserve the DOI "
                         + doi + ". Take a look into the logs for further details.");
@@ -143,8 +281,27 @@ public class DOIDataCiteIdentifierProvider
     public String mint(Context context, DSpaceObject dso)
             throws IdentifierException
     {
-        //TODO
+        String doi = null;
-        return null;
+        try
+        {
+            doi = getDOIByObject(context, dso);
+        }
+        catch (SQLException e)
+        {
+            log.error("Error while attemping to retrieve information about a DOI for " + dso.getTypeText() + " with ID " + dso.getID() + ".");
+            throw new RuntimeException("Error while attemping to retrieve information about a DOI for " + dso.getTypeText() + " with ID " + dso.getID() + ".", e);
+        }
+        if (null == doi) {
+            try {
+                doi = createNewIdentifier(context, dso, null);
+            }
+            catch (SQLException e)
+            {
+                log.error("Error while creating new DOI for Object of ResourceType {} with id {}.", dso.getType(), dso.getID());
+                throw new RuntimeException("Error while attemping to create a new DOI for " + dso.getTypeText() + " with ID " + dso.getID() + ".", e);
+            }
+        }
+        return doi;
     }
 
     @Override
@@ -152,80 +309,62 @@ public class DOIDataCiteIdentifierProvider
             String... attributes)
             throws IdentifierNotFoundException, IdentifierNotResolvableException
     {
-        // TODO check
+        String doi = null;
-        log.debug("resolve {}", identifier);
         try {
-            identifier = formatIdentifier(identifier);
+            doi = formatIdentifier(identifier);
         } catch (IdentifierException e) {
-            throw new IdentifierNotFoundException(e.getMessage());
+            throw new IdentifierNotResolvableException(e.getMessage());
         }
-        log.debug("formated identifier as {}", identifier);
+        try
-
+        {
-        ItemIterator found;
+            return getObjectByDOI(context, doi);
-        try {
-            found = Item.findByMetadataField(context,
-                    MD_SCHEMA, DOI_ELEMENT, DOI_QUALIFIER,
-                    identifier);
-        } catch (SQLException ex) {
-            log.error(ex.getMessage());
-            throw new IdentifierNotResolvableException(ex);
-        } catch (AuthorizeException ex) {
-            log.error(ex.getMessage());
-            throw new IdentifierNotResolvableException(ex);
-        } catch (IOException ex) {
-            log.error(ex.getMessage());
-            throw new IdentifierNotResolvableException(ex);
         }
-        try {
+        catch (SQLException e)
-            if (!found.hasNext())
+        {
-                throw new IdentifierNotFoundException("No object bound to " + identifier);
+            throw new RuntimeException("Unable to retrieve information about a DOI out of database.", e);
-            Item found1 = found.next();
+        }
-            if (found.hasNext())
+        catch (IdentifierException e)
-                log.error("More than one object bound to {}!", identifier);
+        {
-            log.debug("Resolved to {}", found1);
+            throw new IdentifierNotResolvableException(e);
-            return found1;
-        } catch (SQLException ex) {
-            log.error(ex.getMessage());
-            throw new IdentifierNotResolvableException(ex);
         }
     }
 
     @Override
-    public String lookup(Context context, DSpaceObject object)
+    public String lookup(Context context, DSpaceObject dso)
             throws IdentifierNotFoundException, IdentifierNotResolvableException
     {
-        // TODO: check
+        String doi = null;
-        log.debug("lookup {}", object);
+        try
-
-        if (!(object instanceof Item))
-            throw new IllegalArgumentException("Unsupported type " + object.getTypeText());
-
-        Item item = (Item)object;
-        DCValue found = null;
-        for (DCValue candidate : item.getMetadata(MD_SCHEMA, DOI_ELEMENT, DOI_QUALIFIER, null))
-            if (candidate.value.startsWith(DOI_SCHEME))
         {
-                found = candidate;
+            doi = getDOIByObject(context, dso);
-                break;
         }
-        if (null != found)
+        catch (SQLException e)
         {
-            log.debug("Found {}", found.value);
+            throw new RuntimeException("Error retrieving DOI out of database.", e);
-            return found.value;
         }
-        else
+        
-            throw new IdentifierNotFoundException(object.getTypeText() + " "
+        if (null == doi)
-                    + object.getID() + " has no DOI");
+            throw new IdentifierNotFoundException("No DOI for DSpaceObject of type "
+                    + dso.getTypeText() + " with ID " + dso.getID() + " found.");
+        
+        return doi;
     }
 
     @Override
     public void delete(Context context, DSpaceObject dso)
             throws IdentifierException
     {
-        String[] DOIs = getDOIsByObject(dso);
+        String doi = null;
-        for (String doi : DOIs) {
+        try {
-            this.delete(context, dso, doi);
+            doi = getDOIByObject(context, dso);
         }
+        catch (SQLException e)
+        {
+            log.error("Error while attemping to retrieve information about a DOI for " + dso.getTypeText() + " with ID " + dso.getID() + ".");
+            log.error(e.getMessage());
+            throw new RuntimeException("Error while attemping to retrieve information about a DOI for " + dso.getTypeText() + " with ID " + dso.getID() + ".", e);
+        }
+        this.delete(context, dso, doi);
     }
 
     @Override
@@ -236,54 +375,70 @@ public class DOIDataCiteIdentifierProvider
         String doi = formatIdentifier(identifier);
         log.debug("formated identifier as {}", doi);
         
-        if (!deleteDOI(dso, doi))
+        if (isDOIRegistered(doi))
             throw new IdentifierException("Unable to delete DOI " + doi +
-                    ". Was it already registered? Take a look into the logs for further details.");
+                    ". It is already registered.");
 
+        try {
+            removeDOIFromObject(context, dso, doi);
+        }
+        catch (AuthorizeException ex)
+        {
+            log.error("Not authorized to delete a DOI out of an Item.");
+            throw new IdentifierException("Not authorized to delete DOI.", ex);
+        }
+        catch (SQLException ex)
+        {
+            log.error("SQLException occured while deleting a DOI out of an item: " + ex.getMessage());
+            throw new RuntimeException("Error while deleting a DOI out of the metadata of an Item " + dso.getID(), ex);
+        }
+        
+        if (!deleteDOI(context, dso, doi))
+        {
+            // It was not possible to delete a DOI at the registry agency. We
+            // already removed the DOI out of the metadata of the object,
+            // so we should restore these information.
             try
             {
-            deleteDOIFromObject(context, dso, doi);
+                saveDOIToObject(context, dso, doi);
             }
-        // TODO: better Exception handling.
+            catch (AuthorizeException e)
-        catch (Exception e)
             {
-            throw new IdentifierException(e);
+                log.error("We were authorized to delete a DOI out of an Item, but we can't restore these informations?!");
+                log.error("DSO-Type: " + dso.getTypeText() + ", ID: " + dso.getID() +
+                        ", DOI: " + doi + ".");
+                throw new IllegalStateException("We were authorized to delete a DOI out of an Item, but we can't restore these informations?!", e);
+            }
+            catch (SQLException ex)
+            {
+                log.error("SQLError while restoring DOI " + doi +
+                        " for Object of Type " + dso.getTypeText() + " with ID "
+                        + dso.getID() + ".");
+                log.error("Exception message: " + ex.getMessage());
+                throw new RuntimeException("Error while restoring a DOI as metadata of an Item " + dso.getID(), ex);
+            }
+            throw new IdentifierException("Unable to delete DOI " + doi +
+                    ". Take a look into the logs for further details.");
         }
-        
         log.info("Deleted {}", doi);
     }
 
-    /**
-     * This method helps to convert a DOI into a URL. It takes DOIs with or
-     * without leading DOI scheme (f.e. doi:10.123/456 as well as 10.123/456)
-     * and returns it as URL (f.e. http://dx.doi.org/10.123/456).
-     * 
-     * @param id A DOI that should be returned in external form.
-     * @return A String containing a URL to the official DOI resolver.
-     * @throws IdentifierException 
-     */
-    public static String DOIToExternalForm(String id) throws IdentifierException{
-        if (id.startsWith("http://dx.doi.org/10.")) {
-            return id;
-        }
-        String doi = formatIdentifier(id);
-        return "http://dx.doi.org/" + doi.substring(DOI_SCHEME.length());
-    }
     
     /**
-     * Format any accepted identifier with DOI scheme.
+     * Recognize format of DOI and return it with leading doi-Scheme.
      * @param identifier Identifier to format, following format are accepted: f.e. 10.123/456, doi:10.123/456, http://dx.doi.org/10.123/456.
      * @return Given Identifier with DOI-Scheme, f.e. doi:10.123/456.
-     * @throws IdentifierException 
+     * @throws IllegalArgumentException If identifier is empty or null.
+     * @throws IdentifierException If DOI could not be recognized.
      */
     public static String formatIdentifier(String identifier) throws IdentifierException
     {
         if (null == identifier) 
-            throw new IdentifierException("Identifier is null.", new NullPointerException());
+            throw new IllegalArgumentException("Identifier is null.", new NullPointerException());
-        if (identifier.isEmpty())
-            throw new IdentifierException("Cannot format an empty identifier.");
         if (identifier.startsWith("doi:"))
             return identifier;
+        if (identifier.isEmpty())
+            throw new IllegalArgumentException("Cannot format an empty identifier.");
         if (identifier.startsWith("10.") && identifier.contains("/"))
             return DOI_SCHEME + identifier;
         if (identifier.startsWith("http://dx.doi.org/10."))
@@ -293,36 +448,231 @@ public class DOIDataCiteIdentifierProvider
     
     protected boolean reserveDOI(DSpaceObject dso, String doi)
     {
+        // send metadata as post to mds/metadata
+        // 400 -> invalid XML
+        // 401 -> no login
+        // 403 -> wrong credentials or datasets belong to another party
+        // 201 -> created / ok
+        // 500 -> try again later / internal server error
         return false;
     }
     
     protected boolean isDOIReserved(String doi)
     {
-        return true;
+        return isDOIReserved(null, doi);
     }
     
-    protected boolean isDOIReservedForObject(DSpaceObject dso, String doi)
+    protected boolean isDOIReserved(DSpaceObject dso, String doi)
     {
+        // get mds/metadata/<doi>
+        // 410 GONE -> inactive (not clear if ever registered or reserved and deleted)
+        // 404 Not Found -> not reserved
+        // 401 -> no login
+        // 403 -> wrong credential or doi belongs to another party.
+        // 400 -> Bad Content -> f.e. non existing prefix
+        // 500 -> try again later or doi belongs to another registry agency
+        // 200 -> registered and reserved
+        // 204 no content -> reserved but not registered
+        // if (204 && dso != null) -> get mds/doi/<doi> and compare xml->alternative identifier
+        // if (200 && dso != null) -> compare url (out of response-content) with dso
         return false;
     }
     
-    protected boolean registerDOI(DSpaceObject dso, String doi)
+    protected boolean isDOIRegistered(String doi)
     {
+        return isDOIRegistered(null, doi);
+    }
+    
+        protected boolean isDOIRegistered(DSpaceObject dso, String doi)
+    {
+        // get mds/doi/<doi>
+        // 404 -> not reservered, not registered
+        // 204 -> reserved, not registered
+        // 200 -> reserved, registered
+        // if dso != null && response-code == 200 -> compare url and response
         return false;
     }
 
-    protected boolean deleteDOI(DSpaceObject dso, String doi)
+    
+    protected boolean registerDOI(Context context, DSpaceObject dso, String doi)
+            throws SQLException
     {
+        // send doi=<doi>\nurl=<url> to mds/doi
+        // 412 -> prediction failed -> not reserved
+        // 403 -> wrong credential, quota exceeded
+        // 401 -> no login
+        // 400 -> wrong domain, wrong prefix, wrong request body
+        // 201 -> created/updated
+        // 500 -> try again later / internal server error
+        
+        // saveDOIToObject(context, dso, doi);
         return false;
     }
     
-    protected String[] getDOIsByObject(DSpaceObject dso)
+    protected boolean deleteDOI(Context context, DSpaceObject dso, String doi)
-            throws IdentifierException
     {
-        // TODO
+        if (isDOIRegistered(doi))
-        return (new String[0]);
+            return false;
+
+        // look for doi in DB
+        // if it exists compare resource type and id
+        // if not okay throw exception
+        
+        // delete mds/metadata/<doi>
+        // 200 -> ok
+        // 401 -> no login
+        // 403 -> wrong credential or doi belongs another party
+        // 404 -> doi neither reserved nor registered
+        // 500 -> internal server error
+        
+        // delete doi from database
+        
+        return false;
     }
     
+    /**
+     * Returns a DSpaceObject depending on its DOI.
+     * @param context the context
+     * @param identifier The DOI in a format that is accepted by
+     *                   {@link formatIdentifier(String)}.
+     * @return Null if the DOI couldn't be found or the associated DSpaceObject.
+     * @throws SQLException
+     * @throws IdentifierException If {@code identifier} is null or an empty string.
+     * @throws IllegalArgumentException If the identifier couldn't be recognized as DOI.
+     */
+    public static DSpaceObject getObjectByDOI(Context context, String identifier)
+            throws SQLException, IdentifierException, IllegalArgumentException
+    {
+        String doi = formatIdentifier(identifier);
+        TableRow doiRow = DatabaseManager.findByUnique(context, "Doi", "doi", doi);
+        
+        if (null == doiRow)
+            return null;
+        
+        if (doiRow.isColumnNull("resource_type_id") ||
+                doiRow.isColumnNull("resource_id"))
+        {
+            throw new IllegalStateException("Found DOI " + doi +
+                    " in database, but no assigned Object could be found.");
+        }
+        
+        return DSpaceObject.find(context,
+                doiRow.getIntColumn("resource_type_id"),
+                doiRow.getIntColumn("resource_id"));
+    }
+    
+    /**
+     * Search the database for a DOI, using the type and id of an DSpaceObject.
+     * 
+     * @param context
+     * @param dso DSpaceObject to find doi for.
+     * @return The DOI as String or null if DOI was not found.
+     * @throws SQLException 
+     */
+    public static String getDOIByObject(Context context, DSpaceObject dso)
+            throws SQLException
+    {
+        String sql = "SELECT * FROM Doi WHERE resource_type_id = ? " +
+                "AND resource_id = ?";
+
+        TableRow doiRow = DatabaseManager.querySingleTable(context, "Doi", sql, dso.getType(), dso.getID());
+        if (null == doiRow)
+            return null;
+
+        if (doiRow.isColumnNull("doi"))
+        {
+            log.error("A DOI with an empty doi column was found in the database. DSO-Type: "
+                    + dso.getTypeText() + ", ID: " + dso.getID() + ".");
+            throw new IllegalStateException("A DOI with an empty doi column was found in the database. DSO-Type: "
+                    + dso.getTypeText() + ", ID: " + dso.getID() + ".");
+        }
+        
+        return DOI_SCHEME + doiRow.getStringColumn("doi");
+    }
+    
+    /**
+     * Creates a new DOI and saves it into the database.
+     * 
+     * @param context
+     * @param dso The DSpaceObject the DOI should be created for.
+     * @param doi A DOI or null if DOI should be generated.
+     * @return The generated DOI or @doi if it was saved into the database.
+     * @throws SQLException In case of an error using the database.
+     * @throws IllegalArgumentException If the given DOI already exists for an other object.
+     */
+    protected String createNewIdentifier(Context context, DSpaceObject dso, String doi)
+            throws SQLException, IllegalArgumentException
+    {
+        TableRow doiRow = null;
+        if (null != doi)
+        {
+            // check if DOI is already in Database, remove DOI_SCHEME before searching in DB.
+            doiRow = DatabaseManager.findByUnique(context, "Doi", "doi", doi.substring(DOI_SCHEME.length()));
+            if (null != doiRow)
+            {
+                // check if DOI already belongs to dso
+                if (doiRow.getIntColumn("resource_id") == dso.getID() &&
+                        doiRow.getIntColumn("resource_type_id") == dso.getType())
+                {
+                    return doi;
+                }
+                else
+                {
+                    throw new IllegalArgumentException("Trying to save a DOI that is already reserved for another object.");
+                }
+            }
+            else
+            {
+                // doi is not null but was not found in db
+                // check if it registered online
+                if (isDOIRegistered(doi) || isDOIReserved(doi))
+                    throw new IllegalArgumentException("Trying to save a DOI that is already reserved for another object.");
+                // safe it to db (see below)
+            }
+        }
+        
+        doiRow = DatabaseManager.create(context, "Doi");
+        if (null != doi)
+        {
+            doi = doi.substring(DOI_SCHEME.length());
+            if (!doi.startsWith(PREFIX + "/"))
+                throw new IllegalArgumentException("Trying to create a DOI that's not part of our Namespace!");
+        }
+        else
+            doi = PREFIX + "/" + NAMESPACE_SEPARATOR + doiRow.getIntColumn("doi_id");
+        doiRow.setColumn("doi", doi);
+        doiRow.setColumn("resource_type_id", dso.getType());
+        doiRow.setColumn("resource_id", dso.getID());
+        DatabaseManager.update(context, doiRow);
+
+        return DOI_SCHEME + doi;
+    }
+    
+    protected String getDOIOutOfObject(DSpaceObject dso) {
+        // FIXME
+        if (!(dso instanceof Item))
+            throw new IllegalArgumentException("Unsupported type " + dso.getTypeText());
+
+        Item item = (Item)dso;
+
+        DCValue[] metadata = item.getMetadata(MD_SCHEMA, DOI_ELEMENT, DOI_QUALIFIER, null);
+        for (DCValue id : metadata)
+        {
+            if (!id.value.startsWith(DOI_SCHEME))
+                return id.value;
+        }
+        return null;
+    }
+    
+    /**
+     * Adds a DOI to the Metadata of an item.
+     * 
+     * @param context
+     * @param dso DSpaceObject the DOI should be added to.
+     * @param doi The DOI that should be added as metadata.
+     * @throws SQLException
+     * @throws AuthorizeException 
+     */
     protected void saveDOIToObject(Context context, DSpaceObject dso, String doi)
             throws SQLException, AuthorizeException
     {
@@ -344,7 +694,16 @@ public class DOIDataCiteIdentifierProvider
         }
     }
     
-    protected void deleteDOIFromObject(Context context, DSpaceObject dso, String doi)
+    /**
+     * Removes a DOI out of the metadata of a DSpaceObject.
+     * 
+     * @param context
+     * @param dso The DSpaceObject the DOI should be removed from.
+     * @param doi The DOI to remove out of the metadata.
+     * @throws AuthorizeException
+     * @throws SQLException 
+     */
+    protected void removeDOIFromObject(Context context, DSpaceObject dso, String doi)
             throws AuthorizeException, SQLException
     {
         // FIXME

dspace/etc/clean-database.sql

@@ -64,6 +64,7 @@ DROP TABLE TasklistItem;
 DROP TABLE WorkflowItem;
 DROP TABLE WorkspaceItem;
 DROP TABLE Handle;
+DROP TABLE Doi;
 DROP TABLE EPersonGroup2EPerson;
 DROP TABLE ResourcePolicy;
 DROP TABLE Collection2Item;
@@ -114,6 +115,7 @@ DROP SEQUENCE collection2item_seq;
 DROP SEQUENCE resourcepolicy_seq;
 DROP SEQUENCE epersongroup2eperson_seq;
 DROP SEQUENCE handle_seq;
+DROP SEQUENCE doi_seq;
 DROP SEQUENCE workspaceitem_seq;
 DROP SEQUENCE workflowitem_seq;
 DROP SEQUENCE tasklistitem_seq;

dspace/etc/h2/database_schema.sql

@@ -102,6 +102,7 @@ CREATE SEQUENCE collection2item_seq;
 CREATE SEQUENCE resourcepolicy_seq;
 CREATE SEQUENCE epersongroup2eperson_seq;
 CREATE SEQUENCE handle_seq;
+CREATE SEQUENCE doi_seq;
 CREATE SEQUENCE workspaceitem_seq;
 CREATE SEQUENCE workflowitem_seq;
 CREATE SEQUENCE tasklistitem_seq;
@@ -492,6 +493,22 @@ CREATE INDEX handle_handle_idx ON Handle(handle);
 -- index by resource id and resource type id
 CREATE INDEX handle_resource_id_and_type_idx ON handle(resource_id, resource_type_id);
 
+-------------------------------------------------------
+-- Doi table
+-------------------------------------------------------
+CREATE TABLE Doi
+(
+  doi_id           INTEGER PRIMARY KEY,
+  doi              VARCHAR(256),
+  resource_type_id INTEGER,
+  resource_id      INTEGER
+);
+
+-- index by handle, commonly looked up
+CREATE INDEX doi_doi_idx ON Doi(doi);
+-- index by resource id and resource type id
+CREATE INDEX doi_resource_id_and_type_idx ON Doi(resource_id, resource_type_id);
+
 -------------------------------------------------------
 --  WorkspaceItem table
 -------------------------------------------------------

dspace/etc/oracle/database_schema.sql

@@ -55,6 +55,7 @@ CREATE SEQUENCE collection2item_seq;
 CREATE SEQUENCE resourcepolicy_seq;
 CREATE SEQUENCE epersongroup2eperson_seq;
 CREATE SEQUENCE handle_seq;
+CREATE SEQUENCE doi_seq;
 CREATE SEQUENCE workspaceitem_seq;
 CREATE SEQUENCE workflowitem_seq;
 CREATE SEQUENCE tasklistitem_seq;
@@ -444,6 +445,20 @@ CREATE TABLE Handle
 -- index by resource id and resource type id
 CREATE INDEX handle_resource_id_type_idx ON handle(resource_id, resource_type_id);
 
+-------------------------------------------------------
+-- Doi table
+-------------------------------------------------------
+CREATE TABLE Doi
+(
+  doi_id           INTEGER PRIMARY KEY,
+  doi              VARCHAR2(256) UNIQUE,
+  resource_type_id INTEGER,
+  resource_id      INTEGER
+);
+
+-- index by resource id and resource type id
+CREATE INDEX doi_resource_id_type_idx ON doi(resource_id, resource_type_id);
+
 -------------------------------------------------------
 --  WorkspaceItem table
 -------------------------------------------------------

dspace/etc/postgres/database_schema.sql

@@ -93,6 +93,7 @@ CREATE SEQUENCE collection2item_seq;
 CREATE SEQUENCE resourcepolicy_seq;
 CREATE SEQUENCE epersongroup2eperson_seq;
 CREATE SEQUENCE handle_seq;
+CREATE SEQUENCE doi_seq;
 CREATE SEQUENCE workspaceitem_seq;
 CREATE SEQUENCE workflowitem_seq;
 CREATE SEQUENCE tasklistitem_seq;
@@ -485,6 +486,22 @@ CREATE INDEX handle_handle_idx ON Handle(handle);
 -- index by resource id and resource type id
 CREATE INDEX handle_resource_id_and_type_idx ON handle(resource_id, resource_type_id);
 
+-------------------------------------------------------
+-- Doi table
+-------------------------------------------------------
+CREATE TABLE Doi
+(
+  doi_id           INTEGER PRIMARY KEY,
+  doi              VARCHAR(256) UNIQUE,
+  resource_type_id INTEGER,
+  resource_id      INTEGER
+);
+
+-- index by handle, commonly looked up
+CREATE INDEX doi_doi_idx ON Doi(doi);
+-- index by resource id and resource type id
+CREATE INDEX doi_resource_id_and_type_idx ON Doi(resource_id, resource_type_id);
+
 -------------------------------------------------------
 --  WorkspaceItem table
 -------------------------------------------------------