QQQ-37 adding pre & post run to ETL transform & load; minor QOL

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/actions/reporting/RecordPipe.java

@@ -41,6 +41,9 @@ public class RecordPipe
 {
    private static final Logger LOG = LogManager.getLogger(RecordPipe.class);
 
+   private static final long BLOCKING_SLEEP_MILLIS = 100;
+   private static final long MAX_SLEEP_LOOP_MILLIS = 300_000; // 5 minutes
+
    private ArrayBlockingQueue<QRecord> queue = new ArrayBlockingQueue<>(1_000);
 
    private boolean isTerminated = false;
@@ -53,6 +56,7 @@ public class RecordPipe
    private List<QRecord> singleRecordListForPostRecordActions = new ArrayList<>();
 
 
+
    /*******************************************************************************
     ** Turn off the pipe.  Stop accepting new records (just ignore them in the add
     ** method).  Clear the existing queue.  Don't return any more records.  Note that
@@ -103,11 +107,22 @@ public class RecordPipe
    {
       boolean offerResult = queue.offer(record);
 
-      while(!offerResult && !isTerminated)
+      if(!offerResult && !isTerminated)
       {
-         LOG.debug("Record pipe.add failed (due to full pipe).  Blocking.");
+         long sleepLoopStartTime = System.currentTimeMillis();
-         SleepUtils.sleep(100, TimeUnit.MILLISECONDS);
+         long now                = System.currentTimeMillis();
-         offerResult = queue.offer(record);
+         while(!offerResult && !isTerminated)
+         {
+            if(now - sleepLoopStartTime > MAX_SLEEP_LOOP_MILLIS)
+            {
+               LOG.warn("Giving up adding record to pipe, due to pipe being full for more than {} millis", MAX_SLEEP_LOOP_MILLIS);
+               throw (new IllegalStateException("Giving up adding record to pipe, due to pipe staying full too long."));
+            }
+            LOG.debug("Record pipe.add failed (due to full pipe).  Blocking.");
+            SleepUtils.sleep(BLOCKING_SLEEP_MILLIS, TimeUnit.MILLISECONDS);
+            offerResult = queue.offer(record);
+            now = System.currentTimeMillis();
+         }
       }
    }
 

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/actions/values/QPossibleValueTranslator.java

@@ -89,7 +89,7 @@ public class QPossibleValueTranslator
     *******************************************************************************/
    public void translatePossibleValuesInRecords(QTableMetaData table, List<QRecord> records)
    {
-      if(records == null)
+      if(records == null || table == null)
       {
          return;
       }

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/instances/QInstanceEnricher.java

@@ -307,8 +307,8 @@ public class QInstanceEnricher
          .withFormField(new QFieldMetaData("theFile", QFieldType.BLOB).withIsRequired(true))
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
-            // .withValue("text", "Upload a CSV or XLSX file with the following columns: " + fieldsForHelpText));
+            .withValue("text", "Upload a CSV file with the following columns: " + fieldsForHelpText))
-            .withValue("text", "Upload a CSV file with the following columns: " + fieldsForHelpText));
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.EDIT_FORM));
 
       QBackendStepMetaData receiveFileStep = new QBackendStepMetaData()
          .withName("receiveFile")
@@ -322,7 +322,9 @@ public class QInstanceEnricher
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
             .withValue("text", "The records below were parsed from your file, and will be inserted if you click Submit."))
-         .withViewField(new QFieldMetaData("noOfFileRows", QFieldType.INTEGER).withLabel("# of file rows"));
+         .withViewField(new QFieldMetaData("noOfFileRows", QFieldType.INTEGER).withLabel("# of file rows"))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.VIEW_FORM))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.RECORD_LIST));
 
       QBackendStepMetaData storeStep = new QBackendStepMetaData()
          .withName("storeRecords")
@@ -336,7 +338,9 @@ public class QInstanceEnricher
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
             .withValue("text", "The records below have been inserted."))
-         .withViewField(new QFieldMetaData("noOfFileRows", QFieldType.INTEGER).withLabel("# of file rows"));
+         .withViewField(new QFieldMetaData("noOfFileRows", QFieldType.INTEGER).withLabel("# of file rows"))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.VIEW_FORM))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.RECORD_LIST));
 
       qInstance.addProcess(
          new QProcessMetaData()
@@ -375,9 +379,7 @@ public class QInstanceEnricher
                The values you supply here will be updated in all of the records you are bulk editing.
                You can clear out the value in a field by flipping the switch on for that field and leaving the input field blank.
                Fields whose switches are off will not be updated."""))
-         .withComponent(new QFrontendComponentMetaData()
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.BULK_EDIT_FORM));
-            .withType(QComponentType.BULK_EDIT_FORM)
-         );
 
       QBackendStepMetaData receiveValuesStep = new QBackendStepMetaData()
          .withName("receiveValues")
@@ -393,7 +395,9 @@ public class QInstanceEnricher
          .withViewField(new QFieldMetaData(BulkEditReceiveValuesStep.FIELD_VALUES_BEING_UPDATED, QFieldType.STRING))
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
-            .withValue("text", "The records below will be updated if you click Submit."));
+            .withValue("text", "The records below will be updated if you click Submit."))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.VIEW_FORM))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.RECORD_LIST));
 
       QBackendStepMetaData storeStep = new QBackendStepMetaData()
          .withName("storeRecords")
@@ -407,7 +411,9 @@ public class QInstanceEnricher
          .withViewField(new QFieldMetaData(BulkEditReceiveValuesStep.FIELD_VALUES_BEING_UPDATED, QFieldType.STRING))
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
-            .withValue("text", "The records below have been updated."));
+            .withValue("text", "The records below have been updated."))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.VIEW_FORM))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.RECORD_LIST));
 
       qInstance.addProcess(
          new QProcessMetaData()
@@ -437,7 +443,8 @@ public class QInstanceEnricher
          .withRecordListFields(new ArrayList<>(table.getFields().values()))
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
-            .withValue("text", "The records below will be deleted if you click Submit."));
+            .withValue("text", "The records below will be deleted if you click Submit."))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.RECORD_LIST));
 
       QBackendStepMetaData storeStep = new QBackendStepMetaData()
          .withName("delete")
@@ -448,7 +455,8 @@ public class QInstanceEnricher
          .withRecordListFields(new ArrayList<>(table.getFields().values()))
          .withComponent(new QFrontendComponentMetaData()
             .withType(QComponentType.HELP_TEXT)
-            .withValue("text", "The records below have been deleted."));
+            .withValue("text", "The records below have been deleted."))
+         .withComponent(new QFrontendComponentMetaData().withType(QComponentType.RECORD_LIST));
 
       qInstance.addProcess(
          new QProcessMetaData()
@@ -569,6 +577,7 @@ public class QInstanceEnricher
    }
 
 
+
    /*******************************************************************************
     ** If a table didn't have any sections, generate "sensible defaults"
     *******************************************************************************/

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/model/metadata/fields/QFieldMetaData.java

@@ -76,6 +76,17 @@ public class QFieldMetaData
 
 
 
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Override
+   public String toString()
+   {
+      return ("QFieldMetaData[" + name + "]");
+   }
+
+
+
    /*******************************************************************************
     ** Initialize a fieldMetaData from a reference to a getter on an entity.
     ** e.g., new QFieldMetaData(Order::getOrderNo).

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/model/metadata/processes/QProcessMetaData.java

@@ -51,6 +51,17 @@ public class QProcessMetaData implements QAppChildMetaData
 
 
 
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   @Override
+   public String toString()
+   {
+      return ("QProcessMetaData[" + name + "]");
+   }
+
+
+
    /*******************************************************************************
     ** Getter for name
     **

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/AbstractLoadStep.java

@@ -8,6 +8,7 @@ import com.kingsrook.qqq.backend.core.actions.QBackendTransaction;
 import com.kingsrook.qqq.backend.core.actions.processes.BackendStep;
 import com.kingsrook.qqq.backend.core.exceptions.QException;
 import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepInput;
+import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepOutput;
 import com.kingsrook.qqq.backend.core.model.data.QRecord;
 
 
@@ -29,6 +30,32 @@ public abstract class AbstractLoadStep implements BackendStep
 
 
 
+   /*******************************************************************************
+    ** Allow subclasses to do an action before the run is complete - before any
+    ** pages of records are passed in.
+    *******************************************************************************/
+   public void preRun(RunBackendStepInput runBackendStepInput, RunBackendStepOutput runBackendStepOutput) throws QException
+   {
+      ////////////////////////
+      // noop in base class //
+      ////////////////////////
+   }
+
+
+
+   /*******************************************************************************
+    ** Allow subclasses to do an action after the run is complete - after the last
+    ** page of records is passed in.
+    *******************************************************************************/
+   public void postRun(RunBackendStepInput runBackendStepInput, RunBackendStepOutput runBackendStepOutput) throws QException
+   {
+      ////////////////////////
+      // noop in base class //
+      ////////////////////////
+   }
+
+
+
    /*******************************************************************************
     **
     *******************************************************************************/

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/AbstractTransformStep.java

@@ -4,6 +4,9 @@ package com.kingsrook.qqq.backend.core.processes.implementations.etl.streamedwit
 import java.util.ArrayList;
 import java.util.List;
 import com.kingsrook.qqq.backend.core.actions.processes.BackendStep;
+import com.kingsrook.qqq.backend.core.exceptions.QException;
+import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepInput;
+import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepOutput;
 import com.kingsrook.qqq.backend.core.model.data.QRecord;
 
 
@@ -16,11 +19,37 @@ import com.kingsrook.qqq.backend.core.model.data.QRecord;
  *******************************************************************************/
 public abstract class AbstractTransformStep implements BackendStep
 {
-   private List<QRecord> inputRecordPage = new ArrayList<>();
+   private List<QRecord> inputRecordPage  = new ArrayList<>();
    private List<QRecord> outputRecordPage = new ArrayList<>();
 
 
 
+   /*******************************************************************************
+    ** Allow subclasses to do an action before the run is complete - before any
+    ** pages of records are passed in.
+    *******************************************************************************/
+   public void preRun(RunBackendStepInput runBackendStepInput, RunBackendStepOutput runBackendStepOutput) throws QException
+   {
+      ////////////////////////
+      // noop in base class //
+      ////////////////////////
+   }
+
+
+
+   /*******************************************************************************
+    ** Allow subclasses to do an action after the run is complete - after the last
+    ** page of records is passed in.
+    *******************************************************************************/
+   public void postRun(RunBackendStepInput runBackendStepInput, RunBackendStepOutput runBackendStepOutput) throws QException
+   {
+      ////////////////////////
+      // noop in base class //
+      ////////////////////////
+   }
+
+
+
    /*******************************************************************************
     ** Getter for recordPage
     **

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/BaseStreamedETLStep.java

@@ -1,9 +1,14 @@
 package com.kingsrook.qqq.backend.core.processes.implementations.etl.streamedwithfrontend;
 
 
+import java.util.List;
 import com.kingsrook.qqq.backend.core.actions.customizers.QCodeLoader;
+import com.kingsrook.qqq.backend.core.actions.values.QPossibleValueTranslator;
+import com.kingsrook.qqq.backend.core.actions.values.QValueFormatter;
 import com.kingsrook.qqq.backend.core.model.actions.processes.RunBackendStepInput;
+import com.kingsrook.qqq.backend.core.model.data.QRecord;
 import com.kingsrook.qqq.backend.core.model.metadata.code.QCodeReference;
+import com.kingsrook.qqq.backend.core.model.metadata.tables.QTableMetaData;
 
 
 /*******************************************************************************
@@ -46,4 +51,23 @@ public class BaseStreamedETLStep
       return (QCodeLoader.getBackendStep(AbstractLoadStep.class, codeReference));
    }
 
+
+
+   /*******************************************************************************
+    **
+    *******************************************************************************/
+   protected void updateRecordsWithDisplayValuesAndPossibleValues(RunBackendStepInput input, List<QRecord> list)
+   {
+      String destinationTable = input.getValueString(StreamedETLWithFrontendProcess.FIELD_DESTINATION_TABLE);
+      QTableMetaData table    = input.getInstance().getTable(destinationTable);
+
+      if(table != null && list != null)
+      {
+         QValueFormatter qValueFormatter = new QValueFormatter();
+         qValueFormatter.setDisplayValuesInRecords(table, list);
+
+         QPossibleValueTranslator qPossibleValueTranslator = new QPossibleValueTranslator(input.getInstance(), input.getSession());
+         qPossibleValueTranslator.translatePossibleValuesInRecords(input.getTable(), list);
+      }
+   }
 }

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/StreamedETLExecuteStep.java

@@ -67,6 +67,8 @@ public class StreamedETLExecuteStep extends BaseStreamedETLStep implements Backe
          AbstractTransformStep transformStep = getTransformStep(runBackendStepInput);
          AbstractLoadStep      loadStep      = getLoadStep(runBackendStepInput);
 
+         transformStep.preRun(runBackendStepInput, runBackendStepOutput);
+
          transaction = loadStep.openTransaction(runBackendStepInput);
          loadStep.setTransaction(transaction);
 
@@ -80,15 +82,9 @@ public class StreamedETLExecuteStep extends BaseStreamedETLStep implements Backe
          );
 
          runBackendStepOutput.addValue(StreamedETLWithFrontendProcess.FIELD_RECORD_COUNT, recordCount);
-         runBackendStepOutput.setRecords(loadedRecordList);
 
-         /////////////////////
+         updateRecordsWithDisplayValuesAndPossibleValues(runBackendStepInput, loadedRecordList);
-         // commit the work //
+         runBackendStepOutput.setRecords(loadedRecordList);
-         /////////////////////
-         if(transaction.isPresent())
-         {
-            transaction.get().commit();
-         }
 
          if(transformStep instanceof ProcessSummaryProviderInterface processSummaryProvider)
          {
@@ -98,6 +94,17 @@ public class StreamedETLExecuteStep extends BaseStreamedETLStep implements Backe
             //////////////////////////////////////////////////////////////////////////////////////////////
             runBackendStepOutput.addValue(StreamedETLWithFrontendProcess.FIELD_PROCESS_SUMMARY, processSummaryProvider.getProcessSummary(true));
          }
+
+         transformStep.postRun(runBackendStepInput, runBackendStepOutput);
+         loadStep.postRun(runBackendStepInput, runBackendStepOutput);
+
+         /////////////////////
+         // commit the work //
+         /////////////////////
+         if(transaction.isPresent())
+         {
+            transaction.get().commit();
+         }
       }
       catch(Exception e)
       {

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/StreamedETLPreviewStep.java

@@ -90,6 +90,7 @@ public class StreamedETLPreviewStep extends BaseStreamedETLStep implements Backe
       extractStep.setRecordPipe(recordPipe);
 
       AbstractTransformStep transformStep = getTransformStep(runBackendStepInput);
+      transformStep.preRun(runBackendStepInput, runBackendStepOutput);
 
       List<QRecord> previewRecordList = new ArrayList<>();
       new AsyncRecordPipeLoop().run("StreamedETL>Preview>ExtractStep", PROCESS_OUTPUT_RECORD_LIST_LIMIT, recordPipe, (status) ->
@@ -100,7 +101,10 @@ public class StreamedETLPreviewStep extends BaseStreamedETLStep implements Backe
          () -> (consumeRecordsFromPipe(recordPipe, transformStep, runBackendStepInput, runBackendStepOutput, previewRecordList))
       );
 
+      updateRecordsWithDisplayValuesAndPossibleValues(runBackendStepInput, previewRecordList);
       runBackendStepOutput.setRecords(previewRecordList);
+
+      transformStep.postRun(runBackendStepInput, runBackendStepOutput);
    }
 
 

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/StreamedETLValidateStep.java

@@ -94,11 +94,13 @@ public class StreamedETLValidateStep extends BaseStreamedETLStep implements Back
       AbstractTransformStep transformStep = getTransformStep(runBackendStepInput);
       if(!(transformStep instanceof ProcessSummaryProviderInterface processSummaryProvider))
       {
+         // todo - really?  if this is required, then put it on the AbstractTransformStep class
          throw (new QException("Transform Step " + transformStep.getClass().getName() + " does not implement ProcessSummaryProviderInterface."));
       }
+      transformStep.preRun(runBackendStepInput, runBackendStepOutput);
 
       List<QRecord> previewRecordList = new ArrayList<>();
-      int recordCount = new AsyncRecordPipeLoop().run("StreamedETL>Preview>ValidateStep", PROCESS_OUTPUT_RECORD_LIST_LIMIT, recordPipe, (status) ->
+      int recordCount = new AsyncRecordPipeLoop().run("StreamedETL>Preview>ValidateStep", null, recordPipe, (status) ->
          {
             extractStep.run(runBackendStepInput, runBackendStepOutput);
             return (runBackendStepOutput);
@@ -106,6 +108,7 @@ public class StreamedETLValidateStep extends BaseStreamedETLStep implements Back
          () -> (consumeRecordsFromPipe(recordPipe, transformStep, runBackendStepInput, runBackendStepOutput, previewRecordList))
       );
 
+      updateRecordsWithDisplayValuesAndPossibleValues(runBackendStepInput, previewRecordList);
       runBackendStepOutput.setRecords(previewRecordList);
       runBackendStepOutput.addValue(StreamedETLWithFrontendProcess.FIELD_RECORD_COUNT, recordCount);
 
@@ -113,6 +116,8 @@ public class StreamedETLValidateStep extends BaseStreamedETLStep implements Back
       // get the process summary from the validation step //
       //////////////////////////////////////////////////////
       runBackendStepOutput.addValue(StreamedETLWithFrontendProcess.FIELD_VALIDATION_SUMMARY, processSummaryProvider.getProcessSummary(false));
+
+      transformStep.postRun(runBackendStepInput, runBackendStepOutput);
    }
 
 

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/processes/implementations/etl/streamedwithfrontend/StreamedETLWithFrontendProcess.java

@@ -78,6 +78,10 @@ public class StreamedETLWithFrontendProcess
    public static final String FIELD_VALIDATION_SUMMARY       = "validationSummary"; // List<ProcessSummaryLine>
    public static final String FIELD_PROCESS_SUMMARY          = "processResults"; // List<ProcessSummaryLine>
 
+   public static final String DEFAULT_PREVIEW_MESSAGE_FOR_INSERT = "This is a preview of the records that will be created.";
+   public static final String DEFAULT_PREVIEW_MESSAGE_FOR_UPDATE = "This is a preview of the records that will be updated.";
+   public static final String FIELD_PREVIEW_MESSAGE              = "previewMessage";
+
 
 
    /*******************************************************************************
@@ -106,6 +110,7 @@ public class StreamedETLWithFrontendProcess
     ** - FIELD_SUPPORTS_FULL_VALIDATION
     ** - FIELD_DEFAULT_QUERY_FILTER
     ** - FIELD_DO_FULL_VALIDATION
+    ** - FIELD_PREVIEW_MESSAGE
     *******************************************************************************/
    public static QProcessMetaData defineProcessMetaData(
       Class<? extends AbstractExtractStep> extractStepClass,
@@ -119,10 +124,12 @@ public class StreamedETLWithFrontendProcess
          .withCode(new QCodeReference(StreamedETLPreviewStep.class))
          .withInputData(new QFunctionInputMetaData()
             .withField(new QFieldMetaData(FIELD_SOURCE_TABLE, QFieldType.STRING).withDefaultValue(defaultFieldValues.get(FIELD_SOURCE_TABLE)))
+            .withField(new QFieldMetaData(FIELD_DESTINATION_TABLE, QFieldType.STRING).withDefaultValue(defaultFieldValues.get(FIELD_DESTINATION_TABLE)))
             .withField(new QFieldMetaData(FIELD_SUPPORTS_FULL_VALIDATION, QFieldType.BOOLEAN).withDefaultValue(defaultFieldValues.getOrDefault(FIELD_SUPPORTS_FULL_VALIDATION, false)))
             .withField(new QFieldMetaData(FIELD_DEFAULT_QUERY_FILTER, QFieldType.STRING).withDefaultValue(defaultFieldValues.get(FIELD_DEFAULT_QUERY_FILTER)))
             .withField(new QFieldMetaData(FIELD_EXTRACT_CODE, QFieldType.STRING).withDefaultValue(new QCodeReference(extractStepClass)))
             .withField(new QFieldMetaData(FIELD_TRANSFORM_CODE, QFieldType.STRING).withDefaultValue(new QCodeReference(transformStepClass)))
+            .withField(new QFieldMetaData(FIELD_PREVIEW_MESSAGE, QFieldType.STRING).withDefaultValue(defaultFieldValues.getOrDefault(FIELD_PREVIEW_MESSAGE, DEFAULT_PREVIEW_MESSAGE_FOR_INSERT)))
          );
 
       QFrontendStepMetaData reviewStep = new QFrontendStepMetaData()
@@ -142,7 +149,6 @@ public class StreamedETLWithFrontendProcess
          .withName(STEP_NAME_EXECUTE)
          .withCode(new QCodeReference(StreamedETLExecuteStep.class))
          .withInputData(new QFunctionInputMetaData()
-            .withField(new QFieldMetaData(FIELD_DESTINATION_TABLE, QFieldType.STRING).withDefaultValue(defaultFieldValues.get(FIELD_DESTINATION_TABLE)))
             .withField(new QFieldMetaData(FIELD_LOAD_CODE, QFieldType.STRING).withDefaultValue(new QCodeReference(loadStepClass))))
          .withOutputMetaData(new QFunctionOutputMetaData()
             .withField(new QFieldMetaData(FIELD_PROCESS_SUMMARY, QFieldType.STRING))

qqq-middleware-javalin/src/main/java/com/kingsrook/qqq/backend/javalin/QJavalinProcessHandler.java

@@ -24,6 +24,7 @@ package com.kingsrook.qqq.backend.javalin;
 
 import java.io.IOException;
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
@@ -443,16 +444,21 @@ public class QJavalinProcessHandler
          }
          ProcessState processState = optionalProcessState.get();
 
-         List<QRecord> records = processState.getRecords();
+         List<QRecord>       records         = processState.getRecords();
-         if(CollectionUtils.nullSafeIsEmpty(records))
+         Map<String, Object> resultForCaller = new HashMap<>();
+
+         if(records == null)
          {
-            throw (new Exception("No records were found for the process."));
+            resultForCaller.put("records", new ArrayList<>());
+            resultForCaller.put("totalRecords", 0);
+         }
+         else
+         {
+            List<QRecord> recordPage = CollectionUtils.safelyGetPage(records, skip, limit);
+            resultForCaller.put("records", recordPage);
+            resultForCaller.put("totalRecords", records.size());
          }
 
-         Map<String, Object> resultForCaller = new HashMap<>();
-         List<QRecord>       recordPage      = CollectionUtils.safelyGetPage(records, skip, limit);
-         resultForCaller.put("records", recordPage);
-         resultForCaller.put("totalRecords", records.size());
          context.result(JsonUtils.toJson(resultForCaller));
       }
       catch(Exception e)

qqq-sample-project/src/main/java/com/kingsrook/sampleapp/SampleMetaDataProvider.java

@@ -402,6 +402,7 @@ public class SampleMetaDataProvider
       values.put(StreamedETLWithFrontendProcess.FIELD_SOURCE_TABLE, TABLE_NAME_PERSON);
       values.put(StreamedETLWithFrontendProcess.FIELD_DESTINATION_TABLE, TABLE_NAME_PERSON);
       values.put(StreamedETLWithFrontendProcess.FIELD_SUPPORTS_FULL_VALIDATION, true);
+      values.put(StreamedETLWithFrontendProcess.FIELD_PREVIEW_MESSAGE, "This is a preview of what the clones will look like.");
 
       QProcessMetaData process = StreamedETLWithFrontendProcess.defineProcessMetaData(
          ExtractViaQueryStep.class,