How can I get the ID of an object in a select multiple?

I have a system that registers proyectos and people who can have 1.n projects, and I need to send the id of a select multiple to a query GetMapping of java to warn that a persona You have a project assigned.

<el-form-item label="Asignar a:" prop="person">
                <el-select v-model="form.persons" multiple value-key="id"
                v-on:change="getData(person_id)" id="person_id placeholder="Seleccione personal" class="max-input" filterable>
                  <el-option v-for="person in orderedPersons"  
                            :label="person.name +' '+ person.last_name" 
                            :key="person.id" 
                            :value="person">
                  </el-option>
                </el-select>
              </el-form-item>

Computed

 computed: {
     orderedPersons: function () {
          return _.sortBy(this.persons, 'name')
      },

Method java Getmapping

@GetMapping("/person/hasproject/{id}")
public ResponseEntity getIfPersonHasProject(@PathVariable(value = "id") Long person_id) {
    try {
        HttpStatus status = HttpStatus.OK;
        if (!service.findByPersonId(person_id???).isEmpty()) {
            return ResponseEntity.status(status).body(new responseMessage(status.value(), null, getLocaleMessage("success.project.exist")));
        }
    }catch (Exception e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(new responseMessage(HttpStatus.INTERNAL_SERVER_ERROR.value(), e.getMessage(), getLocaleMessage("error.internal_error")));
    }
    return null;
}

Vue method that calls that query (Enhanced)

 methods: {
getData(el id de la persona que selecciono?) {
  this.$axios.get("/person/hasproject/" + person_id ???).then(response => {
               try {
                  notifications_success(response.data.userMessage);
                } catch (error) {
                 notifications_error('La persona no tiene proyectos');
                 }
  });
},

In summary, how can I pass to that query the id of the persona selected in select multiple