fix #1566 improve form.num in session

src/main/java/org/codelibs/fess/app/web/base/FessSearchAction.java

@@ -25,6 +25,7 @@ import java.util.Set;
 
 import javax.annotation.Resource;
 import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpSession;
 
 import org.apache.commons.text.StringEscapeUtils;
 import org.codelibs.core.lang.StringUtil;
@@ -144,6 +145,14 @@ public abstract class FessSearchAction extends FessBaseAction {
 
     protected void buildFormParams(final SearchForm form) {
 
+        final HttpSession session = request.getSession(false);
+        if (session != null) {
+            final Object resultsPerPage = session.getAttribute(Constants.RESULTS_PER_PAGE);
+            if (resultsPerPage instanceof Integer) {
+                form.num = (Integer) resultsPerPage;
+            }
+        }
+
         // label
         final List<Map<String, String>> labelTypeItems = labelTypeHelper.getLabelTypeItemList(SearchRequestType.SEARCH);
 

src/main/java/org/codelibs/fess/app/web/search/SearchAction.java

@@ -104,7 +104,7 @@ public class SearchAction extends FessSearchAction {
         if (viewHelper.isUseSession()) {
             LaRequestUtil.getOptionalRequest().ifPresent(request -> {
                 final HttpSession session = request.getSession(false);
-                if (session != null) {
+                if (session != null && form.num != null) {
                     session.setAttribute(Constants.RESULTS_PER_PAGE, form.num);
                 }
             });

src/main/webapp/WEB-INF/view/searchOptions.jsp

@@ -7,7 +7,7 @@
 		<label for="contentNum"><la:message key="labels.index_num" /></label>
 		<la:select property="num" styleId="numSearchOption"
 			styleClass="form-control">
-			<option value="">
+			<option value="10">
 				<la:message key="labels.search_result_select_num" />
 			</option>
 			<la:option value="10">10</la:option>