Show error message if no graph workspace exists

Author: mkemeter

src/main/java/org/sap/cytoscape/internal/tasks/CyLoadTask.java

@@ -71,7 +71,16 @@ public void run(TaskMonitor taskMonitor) throws Exception {
 
         // retrieve selected graph workspace
         String selectedWorkspaceKey = tunables.workspaceSelection.getSelectedValue();
-        HanaDbObject selectedWorkspace = tunables.graphWorkspaces.get(selectedWorkspaceKey);
+        HanaDbObject selectedWorkspace = tunables.graphWorkspaces == null ? null : tunables.graphWorkspaces.get(selectedWorkspaceKey);
+
+        if(selectedWorkspace == null){
+            taskMonitor.showMessage(
+                    TaskMonitor.Level.ERROR,
+                    "No valid graph workspaces found on this SAP HANA instance. Please create a graph workspace first."
+            );
+            taskMonitor.setProgress(1d);
+            return;
+        }
 
         taskMonitor.setStatusMessage("Downloading data from Graph Workspace " + selectedWorkspaceKey + " in SAP HANA");
 

src/test/java/CyLoadTaskTest.java

@@ -0,0 +1,131 @@
+import org.cytoscape.model.CyNetworkFactory;
+import org.cytoscape.model.CyNetworkManager;
+import org.cytoscape.work.TaskMonitor;
+import org.junit.Assert;
+import org.junit.Test;
+import org.sap.cytoscape.internal.hdb.HanaConnectionManager;
+import org.sap.cytoscape.internal.tasks.CyLoadTask;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Proxy;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Unit tests for CyLoadTask error handling.
+ */
+public class CyLoadTaskTest {
+
+    // -----------------------------------------------------------------------
+    // Stubs
+    // -----------------------------------------------------------------------
+
+    /** A TaskMonitor stub that records all showMessage calls. */
+    private static class RecordingTaskMonitor implements TaskMonitor {
+        final List<String> errors = new ArrayList<>();
+
+        @Override public void showMessage(Level level, String message) {
+            if (level == Level.ERROR) errors.add(message);
+        }
+        @Override public void setTitle(String title) {}
+        @Override public void setProgress(double progress) {}
+        @Override public void setStatusMessage(String statusMessage) {}
+    }
+
+    /**
+     * Builds a HanaConnectionManager stub that reports connected=true and returns
+     * an empty ResultSet for any query (simulating no graph workspaces).
+     */
+    private static HanaConnectionManager connectedManagerWithNoWorkspaces() throws Exception {
+        // Empty ResultSet stub
+        ResultSetMetaData emptyMeta = (ResultSetMetaData) Proxy.newProxyInstance(
+            ClassLoader.getSystemClassLoader(),
+            new Class[]{ResultSetMetaData.class},
+            (proxy, method, args) -> {
+                if (method.getName().equals("getColumnCount")) return 0;
+                return null;
+            }
+        );
+        ResultSet emptyRs = (ResultSet) Proxy.newProxyInstance(
+            ClassLoader.getSystemClassLoader(),
+            new Class[]{ResultSet.class},
+            (proxy, method, args) -> {
+                if (method.getName().equals("next")) return false;
+                if (method.getName().equals("getMetaData")) return emptyMeta;
+                return null;
+            }
+        );
+        PreparedStatement emptyStmt = (PreparedStatement) Proxy.newProxyInstance(
+            ClassLoader.getSystemClassLoader(),
+            new Class[]{PreparedStatement.class},
+            (proxy, method, args) -> {
+                if (method.getName().equals("executeQuery")) return emptyRs;
+                if (method.getName().equals("getResultSet")) return emptyRs;
+                return null;
+            }
+        );
+        Connection conn = (Connection) Proxy.newProxyInstance(
+            ClassLoader.getSystemClassLoader(),
+            new Class[]{Connection.class},
+            (proxy, method, args) -> {
+                switch (method.getName()) {
+                    case "isValid":             return true;
+                    case "isClosed":            return false;
+                    case "prepareStatement":    return emptyStmt;
+                    default:                    return null;
+                }
+            }
+        );
+
+        HanaConnectionManager manager = new HanaConnectionManager();
+        Field f = HanaConnectionManager.class.getDeclaredField("connection");
+        f.setAccessible(true);
+        f.set(manager, conn);
+        return manager;
+    }
+
+    private static CyNetworkFactory dummyNetworkFactory() {
+        return (CyNetworkFactory) Proxy.newProxyInstance(
+            ClassLoader.getSystemClassLoader(),
+            new Class[]{CyNetworkFactory.class},
+            (proxy, method, args) -> null
+        );
+    }
+
+    private static CyNetworkManager dummyNetworkManager() {
+        return (CyNetworkManager) Proxy.newProxyInstance(
+            ClassLoader.getSystemClassLoader(),
+            new Class[]{CyNetworkManager.class},
+            (proxy, method, args) -> null
+        );
+    }
+
+    // -----------------------------------------------------------------------
+    // Tests
+    // -----------------------------------------------------------------------
+
+    /**
+     * Regression test: when the connected HANA instance has no valid graph workspaces,
+     * run() must show a friendly error message and return — not throw a NullPointerException
+     * or a cryptic HanaConnectionManagerException.
+     */
+    @Test
+    public void testRunShowsErrorWhenNoWorkspacesExist() throws Exception {
+        HanaConnectionManager manager = connectedManagerWithNoWorkspaces();
+        CyLoadTask task = new CyLoadTask(dummyNetworkFactory(), dummyNetworkManager(), manager);
+
+        RecordingTaskMonitor monitor = new RecordingTaskMonitor();
+        task.run(monitor);
+
+        Assert.assertFalse("Expected at least one ERROR message", monitor.errors.isEmpty());
+        String errorMsg = monitor.errors.get(0).toLowerCase();
+        Assert.assertTrue(
+            "Error message should mention 'graph workspace'",
+            errorMsg.contains("graph workspace")
+        );
+    }
+}