针对 .js 优化 isJsp

src/main/java/com/jfinal/core/JFinalFilter.java

@@ -137,10 +137,10 @@ public class JFinalFilter implements Filter {
     boolean isJsp(String target) {
         int lastIndexOf = target.lastIndexOf('.');
         if (lastIndexOf > -1) {
-            String t = target.substring(lastIndexOf + 1);
-            if (t.length() < 3) {
+            if (lastIndexOf + 3 >= target.length()) {
                 return false;
             }
+            String t = target.substring(lastIndexOf + 1);
             int len = t.length();
             int i = 0;
             char c;