Jaspersoft Reports, how to check if a file exists or not in IF-ELSE clause? - jasper-reports

Question

For a Jaspersoft Report I have an HTML file(very simple string content, no HTML marks) which I load into a Text Field, the loading path is dynamic, so it depends on a given parameter. Loading the HTML file works fine, I used this code:
new String(net.sf.jasperreports.repo.RepositoryUtil.getInstance($P{JASPER_REPORTS_CONTEXT}).getBytesFromLocation("repo:/home/res/html/file_" + $P{PARAM_HTML} + ".html"), java.nio.charset.StandardCharsets.UTF_8)
If i try it with a file who doesnt exists, i get the following error message:
net.sf.jasperreports.engine.JRException: net.sf.jasperreports.engine.fill.JRExpressionEvalException: Error evaluating expression for source text: new String(net.sf.jasperreports.repo.RepositoryUtil.getInstance($P{JASPER_REPORTS_CONTEXT}).getBytesFromLocation("repo:/home/res/html/file_" + $P{PARAM_HTML} + ".html"), java.nio.charset.StandardCharsets.UTF_8)
at com.jaspersoft.studio.editor.preview.view.control.ReportController.fillReport(ReportController.java:551)
at com.jaspersoft.studio.editor.preview.view.control.ReportController.access$18(ReportController.java:526)
at com.jaspersoft.studio.editor.preview.view.control.ReportController$1.run(ReportController.java:444)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
Caused by: net.sf.jasperreports.engine.fill.JRExpressionEvalException: Error evaluating expression for source text: new String(net.sf.jasperreports.repo.RepositoryUtil.getInstance($P{JASPER_REPORTS_CONTEXT}).getBytesFromLocation("repo:/home/res/html/file_" + $P{PARAM_HTML} + ".html"), java.nio.charset.StandardCharsets.UTF_8)
at net.sf.jasperreports.engine.fill.JREvaluator.handleEvaluationException(JREvaluator.java:294)
at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:328)
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:673)
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:641)
at net.sf.jasperreports.engine.fill.JRFillElement.evaluateExpression(JRFillElement.java:1173)
at net.sf.jasperreports.engine.fill.JRFillTextField.evaluateText(JRFillTextField.java:555)
at net.sf.jasperreports.engine.fill.JRFillTextField.evaluate(JRFillTextField.java:540)
at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:383)
at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:548)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillTitle(JRVerticalFiller.java:325)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:258)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:110)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:621)
at net.sf.jasperreports.engine.fill.BaseFillHandle$ReportFill.run(BaseFillHandle.java:135)
at java.lang.Thread.run(Thread.java:748)
Caused by: net.sf.jasperreports.engine.JRException: Byte data not found at: repo:/home/res/html/file_12.html.
at net.sf.jasperreports.repo.RepositoryUtil.getBytesFromLocation(RepositoryUtil.java:215)
at Blank_A4_1636094714772_424965.evaluate(Blank_A4_1636094714772_424965:96)
at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:313)
... 13 more
The Problem is, that it is not clear if the file exists or not, so I use a IF-ELSE clause to check if the HTML file exists or not. If the file exists, the content should be loaded into the Text Field, if not, a default HTML file should be used instead. What I've tried so far are the following conditions in the Text Field expression.
(new File("repo:/home/res/html/file_" + $P{PARAM_HTML} + ".html").isFile()) ? "LOAD FILE" : "LOAD DEFAULT FILE"
(new File("repo:/home/res/html/file_" + $P{PARAM_HTML} + ".html").exists()) ? "LOAD FILE" : "LOAD DEFAULT FILE"
I also tried the same conditions to use in a variable, and use the variable in the Text Field. Always it uses the ELSE condition, even if the file exists or not.
I am not sure where my mistake is, or what I did wrong.