Megpróbálok hívni egy vezérlőben létrehozott szolgáltatást. Ez a szolgáltatás:
package matriculation
import grails.transaction.Transactional
import groovy.sql.Sql
@Transactional
class StudNamesService {
def getNameById(String id) {
return id
}
}
És ez a vezérlő része
package matriculation
import static org.springframework.http.HttpStatus.*
import grails.transaction.Transactional
@Transactional(readOnly = true)
class MatrEntryController {
static allowedMethods = [save: "POST", update: "PUT", delete: "DELETE"]
def studNamesService
def getNameById(String id){
return studNamesService.getNameById(id)
}
}
Amikor bármikor meghívom a vezérlőmben a szolgáltatást hívó metódust, a következő hibaüzenetet kapom:
Class: java.lang.NullPointerException
Message: Request processing failed; nested exception is org.grails.gsp.GroovyPagesException: Error evaluating expression [cont.getNameById(matrEntryInstance.peopleCodeId)] on line [61]: Cannot invoke method getNameById() on null object
Caused by:Cannot invoke method getNameById() on null object
Ennek a kérdésnek a kódjában minimális változtatásokat végeztem. Amint láthatja, a vezérlőben lévő hívásnak pontosan ugyanaz a neve, mint a szolgáltatás nevének, ahogy kell. A Grails 3.1.1-et futtatom
1. szerkesztés Ez annak a GSP-oldalnak a része, amely a metódust hívja:
<%@ page import="matriculation.MatrEntryController" %>
<%
def cont=grailsApplication.classLoader.loadClass("matriculation.MatrEntryController").newInstance()
%>
<!----------------------Skip a few lines----------------------------->
<table>
<thead>
<tr>
<th id="cols">Options</th>
<g:sortableColumn property="peopleCodeId" title="People Code ID" id="cols"/>
<g:sortableColumn property="cadetName" title="Cadet Name" id="cols"/>
<g:sortableColumn property="soff" title="SOFF" id="cols"/>
<g:sortableColumn property="infirmary" title="Infirmary" id="cols"/>
<g:sortableColumn property="hsRotc" title="HS ROTC" id="cols"/>
<g:sortableColumn property="idfy" title="IDFY" id="cols"/>
<g:sortableColumn property="pao" title="Public Affairs" id="cols"/>
<g:sortableColumn property="busOffice" title="Business Office" id="cols"/>
<g:sortableColumn property="telephone" title="Telephone" id="cols"/>
<g:sortableColumn property="computer" title="Computer" id="cols"/>
<g:sortableColumn property="athletics" title="Athletics" id="cols"/>
<g:sortableColumn property="financialAid" title="Financial Aid" id="cols"/>
<g:sortableColumn property="compass" title="Compass" id="cols"/>
<g:sortableColumn property="regFlag" title="Registration Flag" id="cols"/>
<g:sortableColumn property="busOfficeForm" title="${raw('Business<br/>Office Form')}" id="cols"/>
</tr>
</thead>
<tbody>
<g:each in="${matrEntryList}" status="i" var="matrEntryInstance">
<tr class="${(i % 2) == 0 ? 'even' : 'odd'}">
<td id="cols">
<g:form resource="${matrEntryInstance}" method="DELETE">
<a href="${createLink(controller:'matrEntry',action:'show')+'/'+matrEntryInstance.id}" class="btn btn-default">Show</a>
<a href="${createLink(controller:'matrEntry',action:'edit')+'/'+matrEntryInstance.id}" class="btn btn-default">Edit</a>
</g:form>
</td>
<td id="cols">${matrEntryInstance.peopleCodeId}</td>
<td id="cols">${cont.getNameById(matrEntryInstance.peopleCodeId)}</td>
<td id="cols">${matrEntryInstance.soff}</td>
<td id="cols">${matrEntryInstance.infirmary}</td>
<td id="cols">${matrEntryInstance.hsRotc}</td>
<td id="cols">${matrEntryInstance.idfy}</td>
<td id="cols">${matrEntryInstance.pao}</td>
<td id="cols">${matrEntryInstance.busOffice}</td>
<td id="cols">${matrEntryInstance.telephone}</td>
<td id="cols">${matrEntryInstance.computer}</td>
<td id="cols">${matrEntryInstance.athletics}</td>
<td id="cols">${matrEntryInstance.financialAid}</td>
<td id="cols">${matrEntryInstance.compass}</td>
<td id="cols"><g:formatDate date="${matrEntryInstance.regFlag}" format="dd MMM, yyyy"/></td>
<td id="cols">${matrEntryInstance.busOfficeForm}</td>
</tr>
</g:each>
</tbody>
</table>
