how to check if the record exists in the table

I'm using jdbctemplate.update to insert a record in the database.

public void write(List<? extends Person> persons) throws Exception {
            LOGGER.debug("Entering<---");
            personList.addAll((Collection<? extends Person>) persons.get(0));
            for(Person person:personList) {
                  jdbcTemplate.update(INSERT_PERSON_INFO, new Object[] {Integer.parseInt(person.getID()),person.getPassword(),person.getUserName());}
            LOGGER.debug("Exit  --->");
      }


So I want to modify the code to not allow any duplicate entry into the database and instead update the existing record.

Any help would be appreciated?