To use file watchers, the database Java virtual machine (JVM) component must be installed.

Check whether java is installed : 

    COMP_NAME                                          STATUS
    -------------------------------------------------- -----------
    Oracle Expression Filter                           VALID
    Oracle Enterprise Manager                          VALID
    Oracle Workspace Manager                           VALID
    Oracle Database Catalog Views                      VALID
    Oracle Database Packages and Types                 VALID
    JServer JAVA Virtual Machine                       VALID
    Oracle XDK                                         VALID
    Oracle Database Java Packages                      VALID

8 rows selected.

    SQL> l
      1* select comp_name, status from dba_registry