Add Struts converters initialization to prevent GC issues

Bind custom converters to the ServletContext to ensure they are not garbage collected when "convertNull" is enabled. This includes handling null-safe conversions for types like BigDecimal, Boolean, and Integer. Also, deregisters and re-registers default converters accordingly.

src/main/java/org/tb/common/struts/DelegatingRequestProcessor.java

@@ -5,8 +5,24 @@
 import jakarta.servlet.http.HttpServletResponse;
 import jakarta.servlet.http.HttpSession;
 import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.HashMap;
+import java.util.Map;
 import lombok.SneakyThrows;
 import lombok.extern.slf4j.Slf4j;
+import org.apache.commons.beanutils.ConvertUtils;
+import org.apache.commons.beanutils.Converter;
+import org.apache.commons.beanutils.converters.BigDecimalConverter;
+import org.apache.commons.beanutils.converters.BigIntegerConverter;
+import org.apache.commons.beanutils.converters.BooleanConverter;
+import org.apache.commons.beanutils.converters.ByteConverter;
+import org.apache.commons.beanutils.converters.CharacterConverter;
+import org.apache.commons.beanutils.converters.DoubleConverter;
+import org.apache.commons.beanutils.converters.FloatConverter;
+import org.apache.commons.beanutils.converters.IntegerConverter;
+import org.apache.commons.beanutils.converters.LongConverter;
+import org.apache.commons.beanutils.converters.ShortConverter;
 import org.apache.struts.Globals;
 import org.apache.struts.action.Action;
 import org.apache.struts.action.ActionForm;
@@ -37,6 +53,31 @@ public void init(ActionServlet actionServlet, ModuleConfig moduleConfig) throws
   protected WebApplicationContext initWebApplicationContext(ActionServlet actionServlet) throws IllegalStateException {
     WebApplicationContext context = WebApplicationContextUtils.getRequiredWebApplicationContext(actionServlet.getServletContext());
     context.getServletContext().setAttribute("salatProperties", context.getBean(SalatProperties.class));
+
+    // ensure converters are bound to servlet context to not get garbage collected
+    String convertNull = actionServlet.getServletConfig().getInitParameter("convertNull");
+    if ("true".equalsIgnoreCase(convertNull) || "yes".equalsIgnoreCase(convertNull)
+        || "on".equalsIgnoreCase(convertNull) || "y".equalsIgnoreCase(convertNull)
+        || "1".equalsIgnoreCase(convertNull)) {
+
+      Map<Class<?>, Converter> converters = new HashMap<>();
+      converters.put(BigDecimal.class, new BigDecimalConverter(null));
+      converters.put(BigInteger.class, new BigIntegerConverter(null));
+      converters.put(Boolean.class, new BooleanConverter(null));
+      converters.put(Byte.class, new ByteConverter(null));
+      converters.put(Character.class, new CharacterConverter(null));
+      converters.put(Double.class, new DoubleConverter(null));
+      converters.put(Float.class, new FloatConverter(null));
+      converters.put(Integer.class, new IntegerConverter(null));
+      converters.put(Long.class, new LongConverter(null));
+      converters.put(Short.class, new ShortConverter(null));
+
+      context.getServletContext().setAttribute("struts.converters", converters);
+
+      ConvertUtils.deregister();
+      converters.forEach((clazz, converter) -> ConvertUtils.register(converter, clazz));
+    }
+
     return context;
   }