Add StatementGroup wrapper to control JSON serialization

extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementGroupExpr.java

@@ -28,6 +28,7 @@ import java.util.List;
 
 import org.jsoup.helper.Validate;
 import org.openrefine.wikidata.schema.exceptions.SkipSchemaExpressionException;
+import org.openrefine.wikidata.utils.StatementGroupJson;
 import org.wikidata.wdtk.datamodel.helpers.Datamodel;
 import org.wikidata.wdtk.datamodel.interfaces.ItemIdValue;
 import org.wikidata.wdtk.datamodel.interfaces.PropertyIdValue;

extensions/wikidata/src/org/openrefine/wikidata/updates/ItemUpdate.java

@@ -36,6 +36,8 @@ import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import org.jsoup.helper.Validate;
+import org.openrefine.wikidata.utils.StatementGroupJson;
+import org.wikidata.wdtk.datamodel.helpers.Datamodel;
 import org.wikidata.wdtk.datamodel.implementation.StatementGroupImpl;
 import org.wikidata.wdtk.datamodel.interfaces.EntityIdValue;
 import org.wikidata.wdtk.datamodel.interfaces.ItemIdValue;
@@ -176,7 +178,7 @@ public class ItemUpdate {
      * 
      * @return the list of all added statements
      */
-    @JsonProperty("addedStatements")
+    @JsonIgnore // exposed as statement groups below
     public List<Statement> getAddedStatements() {
         return addedStatements;
     }
@@ -295,6 +297,7 @@ public class ItemUpdate {
      * 
      * @return a grouped version of getAddedStatements()
      */
+    @JsonIgnore
     public List<StatementGroup> getAddedStatementGroups() {
         Map<PropertyIdValue, List<Statement>> map = new HashMap<>();
         for (Statement statement : getAddedStatements()) {
@@ -306,10 +309,22 @@ public class ItemUpdate {
         }
         List<StatementGroup> result = new ArrayList<>();
         for (Map.Entry<PropertyIdValue, List<Statement>> entry : map.entrySet()) {
+        	// We have to do this rather than use Datamodel in order to preserve the
+        	// custom entity id values which can link to new items.
             result.add(new StatementGroupImpl(entry.getValue()));
         }
         return result;
     }
+    
+    /**
+     * Json serialization for preview of item updates. Because StatementGroup
+     * is not designed for serialization (so its format is not specified by WDTK),
+     * we add a wrapper on top to specify it.
+     */
+    @JsonProperty("addedStatementGroups")
+    public List<StatementGroupJson> getAddedStatementGroupsJson() {
+    	return this.getAddedStatementGroups().stream().map(s -> new StatementGroupJson(s)).collect(Collectors.toList());
+    }
 
     /**
      * Group a list of ItemUpdates by subject: this is useful to make one single
@@ -339,6 +354,7 @@ public class ItemUpdate {
     /**
      * Is this update about a new item?
      */
+    @JsonProperty("new")
     public boolean isNew() {
         return EntityIdValue.SITE_LOCAL.equals(getItemId().getSiteIri());
     }

extensions/wikidata/src/org/openrefine/wikidata/utils/StatementGroupJson.java

@@ -0,0 +1,43 @@
+package org.openrefine.wikidata.utils;
+
+import java.util.List;
+
+import org.wikidata.wdtk.datamodel.helpers.Datamodel;
+import org.wikidata.wdtk.datamodel.interfaces.EntityIdValue;
+import org.wikidata.wdtk.datamodel.interfaces.PropertyIdValue;
+import org.wikidata.wdtk.datamodel.interfaces.Statement;
+import org.wikidata.wdtk.datamodel.interfaces.StatementGroup;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+/**
+ * Wikidata-Toolkit's StatementGroup class is not designed to be serialized,
+ * so its serialization via Jackson is not specified. This adds annotations
+ * to specify its behaviour.
+ * 
+ * @author Antonin Delpeuch
+ */
+public class StatementGroupJson {
+	
+	protected final StatementGroup statementGroup;
+
+	public StatementGroupJson(StatementGroup s) {
+		statementGroup = s;
+	}
+	
+	@JsonProperty("subject")
+	public EntityIdValue getSubject() {
+		return statementGroup.getSubject();
+	}
+	
+	@JsonProperty("property")
+	public PropertyIdValue getProperty() {
+		return statementGroup.getProperty();
+	}
+	
+	@JsonProperty("statements")
+	public List<Statement> getStatements() {
+		return statementGroup.getStatements();
+	}
+
+}

extensions/wikidata/tests/data/updates/statement_groups.json

@@ -68,34 +68,6 @@
       }
     }
   ],
-  "addedStatements": [
-    {
-      "mainsnak": {
-        "property": "P348",
-        "snaktype": "novalue"
-      },
-      "rank": "normal",
-      "type": "statement"
-    },
-    {
-      "mainsnak": {
-        "datatype": "wikibase-item",
-        "datavalue": {
-          "entityType": "http://www.wikidata.org/ontology#Item",
-          "id": "Q1234",
-          "iri": "http://localhost/entity/Q1234",
-          "label": "new item",
-          "reconInternalId": 1234,
-          "siteIri": "http://localhost/entity/",
-          "types": []
-        },
-        "property": "P52",
-        "snaktype": "value"
-      },
-      "rank": "normal",
-      "type": "statement"
-    }
-  ],
   "deletedStatements": [],
   "descriptions": [],
   "labels": [],