What could be causing the error class java.lang.String cannot be cast to class java.util.Map?

[thammond]

Hello. I am new to Jasper reports and have a report running three queries that work in the SQL console. I have one parameter that I am mapping to with the queries. Here is an example query with parameter mapping at the bottom. When I try to populate the report with Jaspersoft Studio preview I get the following error: net.sf.jasperreports.engine.JRException: java.lang.ClassCastException: class java.lang.String cannot be cast to class java.util.Map (java.lang.String and java.util.Map are in module java.base of loader 'bootstrap') (see below). I have tried in vain to track down what is causing this. Could some one please help? Thanks in advance.

SELECT
    dfr._record_id,
    select_project,
    project_description,
    to_char(visit_date, 'Day') dayofweek,
    project_number,
    client, project_manager,
    to_char(visit_date, 'mm/dd/yyyy') visit_date,
    newfields_representative,
    ((case when pl_photo is null then 0 else pl_photo end))    count_photo,
    outfalls_free,
    outfall_obstruction_comment,
    outfall_obstruction_remedy,
    outfall_plugs_in_place,
    outfall_plugs_comment,
    outfall_plugs_remedy,
    east_pile_berm_inspection,
    east_pile_berm_comment,
    east_pile_berm_remedy

FROM public."AltEn Weekly Inspections" dfr
left join (Select _parent_id, count(take_photo) pl_photo from public."AltEn Weekly Inspections - photo_log" group by _parent_id) pl on pl._parent_id = dfr._record_id
where dfr. _record_id = $P{EventID};

Full error log:

net.sf.jasperreports.engine.JRException: java.lang.ClassCastException: class java.lang.String cannot be cast to class java.util.Map (java.lang.String and java.util.Map are in module java.base of loader 'bootstrap')
    at com.jaspersoft.studio.editor.preview.view.control.ReportController.fillReport(ReportController.java:553)
    at com.jaspersoft.studio.editor.preview.view.control.ReportController.access$18(ReportController.java:528)
    at com.jaspersoft.studio.editor.preview.view.control.ReportController$1.run(ReportController.java:446)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
Caused by: java.lang.ClassCastException: class java.lang.String cannot be cast to class java.util.Map (java.lang.String and java.util.Map are in module java.base of loader 'bootstrap')
    at net.sf.jasperreports.engine.fill.JRFillSubreport.getParameterValues(JRFillSubreport.java:716)
    at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateParameterValues(JRFillSubreport.java:559)
    at net.sf.jasperreports.components.table.fill.FillTableSubreport.evaluateParameterValues(FillTableSubreport.java:118)
    at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:534)
    at net.sf.jasperreports.components.table.fill.FillTableSubreport.evaluateSubreport(FillTableSubreport.java:112)
    at net.sf.jasperreports.components.table.fill.FillTable.evaluate(FillTable.java:136)
    at net.sf.jasperreports.engine.fill.JRFillComponentElement.evaluate(JRFillComponentElement.java:110)
    at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:383)
    at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:548)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:2613)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:836)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:275)
    at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:119)
    at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:622)
    at net.sf.jasperreports.engine.fill.BaseFillHandle$ReportFill.run(BaseFillHandle.java:135)
    at java.base/java.lang.Thread.run(Unknown Source)

[lucianc]

It looks like you have a parametersMapExpression in your report (under the dataset of a table) that evaluates to a String object instead of a java.util.Map.

You can check it in Jaspersoft Studio by selecting the table and then looking in the Properties view, Dataset tab, at Parameters Map.  That expression needs to evaluate to a java.util.Map instance.

Regards,

Lucian