#741: MyBeanComparator.java

Purpose

Generic reflection-based bean comparator with natural and alphanumeric sort support. 139 lines. Sorts any list of Java beans by one or two properties using runtime reflection — no compile-time type safety on the property name. This is the comparator used by Wicket's SortableDataProvider in every list page — when a user clicks a column header to sort, this comparator is instantiated with the column's property name and sort direction.

Sorting capabilities

• Primary + secondary sort: constructor accepts one property (single-key sort) or a primary + secondary property (secondary is used as tiebreaker when primary values are equal)
• Nested property access: uses BeanHelper.getNestedProperty(obj, "address.city") — dot notation traverses object graphs: user.getAddress().getCity()
• Null handling: null values sort before non-null in ascending mode (opposite in descending). Two nulls are equal
• Alphanumeric sort: if the property field is annotated @StringAlphanumericSort, uses se.sawano.java.text.AlphanumericComparator which correctly sorts "file2.txt" before "file10.txt" (natural sort order)
• Fallback to string: if the two values have incompatible types (e.g. one Integer, one String), falls back to String.valueOf() comparison — this handles mixed-type lists gracefully

Annotation-based sort type detection

The checkAnnotation() method checks if the property's getter/field has the @StringAlphanumericSort annotation. This annotation on a DO field means "sort this column alphanumerically, not lexicographically." Example: a field displaying document names like "Report1", "Report2", "Report10" — lexicographic sort gives "Report1", "Report10", "Report2"; alphanumeric gives "Report1", "Report2", "Report10". Both objects must have the annotation for alphanumeric sort to be used — otherwise falls back to standard String.compareTo().

Error resilience

If property access throws any exception (e.g. NoSuchMethodException for a misspelled property name), the error is logged and 0 is returned — the two objects are considered equal for sorting purposes. This prevents a single bad property name from breaking an entire list page. This is a fail-safe design — the user sees unsorted data rather than an error page.