[#1803] better message in IllegalAnnotationsException

jaxb-ri/runtime/impl/src/main/java/org/glassfish/jaxb/runtime/v2/runtime/IllegalAnnotationsException.java

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 1997, 2022 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2025 Contributors to the Eclipse Foundation. All rights reserved.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0, which is available at
@@ -35,19 +36,19 @@ public class IllegalAnnotationsException extends JAXBException {
     private static final long serialVersionUID = 1L;
 
     public IllegalAnnotationsException(List<IllegalAnnotationException> errors) {
-        super(errors.size()+" counts of IllegalAnnotationExceptions");
-        assert !errors.isEmpty() : "there must be at least one error";
+        super(buildMessage(errors));
         this.errors = Collections.unmodifiableList(new ArrayList<>(errors));
     }
 
-    @Override
-    public String toString() {
-        StringBuilder sb = new StringBuilder(super.toString());
-        sb.append('\n');
-
-        for( IllegalAnnotationException error : errors )
-            sb.append(error.toString()).append('\n');
+    private static String buildMessage(List<IllegalAnnotationException> errors) {
+        assert !errors.isEmpty() : "there must be at least one error";
+
+        StringBuilder sb = new StringBuilder(errors.size() * 200);
+        sb.append(errors.size()).append(" counts of IllegalAnnotationExceptions").append('\n');
 
+        for (IllegalAnnotationException error : errors) {
+            sb.append("- ").append(error.toString()).append('\n');
+        }
         return sb.toString();
     }
 

jaxb-ri/runtime/impl/src/test/java/org/glassfish/jaxb/runtime/v2/runtime/IllegalAnnotationsExceptionDTO.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2025 Contributors to the Eclipse Foundation. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0, which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.glassfish.jaxb.runtime.v2.runtime;
+
+import jakarta.xml.bind.annotation.XmlAttribute;
+import jakarta.xml.bind.annotation.XmlRootElement;
+
+import java.util.Date;
+
+@XmlRootElement(name = "illegalAnnotationsExceptionDto")
+public class IllegalAnnotationsExceptionDTO {
+
+    @XmlAttribute(name = "field")
+    protected Date field;
+
+    public Date getField() {
+        return field;
+    }
+
+    public void setField(Date field) {
+        this.field = field;
+    }
+}

jaxb-ri/runtime/impl/src/test/java/org/glassfish/jaxb/runtime/v2/runtime/IllegalAnnotationsExceptionTest.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2025 Contributors to the Eclipse Foundation. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0, which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.glassfish.jaxb.runtime.v2.runtime;
+
+import jakarta.xml.bind.JAXBContext;
+import jakarta.xml.bind.JAXBException;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class IllegalAnnotationsExceptionTest {
+    @Test
+    public void test() {
+        try {
+            JAXBContext.newInstance(IllegalAnnotationsExceptionDTO.class);
+            Assert.fail("no exception thrown");
+        } catch (IllegalAnnotationsException e) {
+            // actual message (x counts of IllegalAnnotationExceptions)
+            Assert.assertTrue(e.getMessage().contains("1 counts of IllegalAnnotationExceptions"));
+            // new detailed message containing location of exception if present (here it is)
+            Assert.assertTrue(e.getMessage().contains("this problem is related to the following location:"));
+        } catch (JAXBException e) {
+            Assert.fail("unexpected JAXBException");
+        }
+    }
+}