Spring Boot Erreur : Cannot invoke XXX because "th par MattSender - page 1

Bonjour,

Je dois coder une Web app en utilisant SpringBoot pour un projet perso, mais je ne comprends rien XD

En outre, plusieurs problèmes apparaissent et je les règle en général, mais celui-ci est récurant. (Si quelqu'un peut m'aider, ce serait vraiment cool ^^).

Le but de ma web app est de pouvoir se connecter sur son compte, rentrer nos propres recettes et finalement, les enregistrer (puis pourvoir les modifier ou supprimer).

Mon code :

- RecetteController :

```

@Controller

public class RecetteController {

private RecetteService recetteService;

@GetMapping("/showNewRecetteForm")

public String showNewRecetteForm(Model model) {

Recette recette = new Recette();

model.addAttribute("recette", recette);

return "new_recette";

}

@PostMapping("/saveRecette")

public String saveRecette(@ModelAttribute("recette") Recette recette) {

recetteService.saveRecette(recette);

return "redirect:/";

}

@GetMapping("/showFormForUpdate/{id}")

public String showFormForUpdate(@PathVariable ( value = "id") long id, Model model) {

Recette recette = recetteService.getRecetteById(id);

model.addAttribute("recette", recette);

return "update_recette";

}

@GetMapping("/deleteRecette/{id}")

public String deleteRecette(@PathVariable (value = "id") long id) {

this.recetteService.deleteRecetteById(id);

return "redirect:/";

}

```

- RecetteService

```

public interface RecetteService {

List<Recette> getAllRecette();

void saveRecette(Recette recette);

Recette getRecetteById(long id);

void deleteRecetteById(long id);

Page<Recette> findPaginated(int pageNo, int pageSize, String sortField, String sortDirection);

}

```

- Code Html

```

<!DOCTYPE html>

<html lang="en"

xmlns:th="http://www.thymeleaf.org">

<head>

<title>CooknLife | Nouveau</title>

href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"

integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO"

crossorigin="anonymous">

</head>

<body>

<h1>CooknLife</h1>

<hr>

<h2>Nouvelle Recette :</h2>

<form action="#" th:action="@{/saveRecette}" th:object="${recette}"

method="POST">

<input type="text" field="*{nameof}" name="nameof"

placeholder="Donnez un nom a votre Recette" class="form-control mb-4 col-4">

<input type="text" field="*{ingredients}" name="ingredients"

placeholder="Quelles sont les ingredients necessaires ?" class="form-control mb-4 col-4">

<input type="text" field="*{preparation}" name="preparation"

placeholder="Ecrivez votre recette" class="form-control mb-4 col-4">

<button type="submit" class="btn btn-info col-2">Enregistrer</button>

</form>

<hr>

<a th:href = "@{/}">Retour a vos Recettes</a>

</div>

</body>

</html>

```

- Erreur

```

java.lang.NullPointerException: Cannot invoke "net.javaguides.springboot.service.RecetteService.saveRecette(net.javaguides.springboot.model.Recette)" because "this.recetteService" is null

at net.javaguides.springboot.controller.RecetteController.saveRecette(RecetteController.java:28) ~[classes/:na]

at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[na:na]

at java.base/java.lang.reflect.Method.invoke(Method.java:577) ~[na:na]

at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.35.jar:9.0.35]

at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]

at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.35.jar:9.0.35]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.35.jar:9.0.35]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.35.jar:9.0.35]

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.35.jar:9.0.35]

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:320) ~[spring-security-web-5.3.2.RELEASE.jar:5.3.2.RELEASE]

at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126) ~[spring-security-web-5.3.2.RELEASE.jar:5.3.2.RELEASE]

at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90) ~[spring-security-web-5.3.2.RELEASE.jar:5.3.2.RELEASE]