I'm trying to initialize an Object with the @ModelAttribute Annontation on a Method. When calling the URL "/p/PPP/scope" strange things happen. The ProjectService seems not to be instantiated when calling the @ModelAttribute method, but it is there when calling the show() method. Has anybody an idea whats wrong in this?
Here are the log statements:
12:32:19 [DEBUG] ScopeController - getProject() - loading project for 'PPP'
12:32:19 [DEBUG] ScopeController - getProject() - projectService initialized? null
12:32:21 [DEBUG] ScopeController - show() - projectService initialized? ...project.ProjectService@20f2442e
and the source:
@Controller
@RequestMapping("/p/{abbr}/scope")
@SessionAttributes("project")
public class ScopeController {
public static final String SHOW_PROJECT_PAGE = "/projects/scope/show";
private static final Logger log = LoggerFactory.getLogger(ScopeController.class);
@Autowired
private ProjectService projectService;
@ModelAttribute("project")
private Project getProject(@PathVariable(value = "abbr") String abbr) {
log.debug("getProject() - loading project for '{}'", abbr);
log.debug("getProject() - projectService initialized? {}", projectService);
// should call this method:
// return projectService.find(abbr);
return new Project();
}
@RequestMapping(method = RequestMethod.GET)
@Transactional
public String show() throws BindException {
log.debug("show() - projectService initialized? {}", projectService);
return SHOW_PROJECT_PAGE;
}
}
All methods with ModelAttibute annotation must be be public.
So when method getProject is public - it will work properly:
@ModelAttribute("project")
public Project getProject( ...
Perhaps try a few things.
So it would look something like:
@Controller
@RequestMapping("/p/{abbr}/scope")
@SessionAttributes("project")
public class ScopeController {
public static final String SHOW_PROJECT_PAGE = "/projects/scope/show";
private static final Logger log = LoggerFactory.getLogger(ScopeController.class);
@Autowired
private ProjectService projectService;
@RequestMapping(value = "/<yourUri for getProject>", method = RequestMethod.GET)
public @ResponseBody Project get(@PathVariable(value = "abbr") String abbr) {
return getProject(abbr);
}
private Project getProject(String abbr) {
log.debug("getProject() - loading project for '{}'", abbr);
log.debug("getProject() - projectService initialized? {}", projectService);
// should call this method:
// return projectService.find(abbr);
return new Project();
}
@RequestMapping(method = RequestMethod.GET)
@Transactional
public String show() throws BindException {
log.debug("show() - projectService initialized? {}", projectService);
return SHOW_PROJECT_PAGE;
}
}
//In your Project class
@ModelAttribute("project")
public class Project {
//your class stuff
}
For one thing, I would put the @Transactional
annotation in the Repository/data access layer as that is the norm of good layered Spring MVC-annotation based applications. In addition, your @PathVariable
annotation is used to retrieve values passed in the URI after the controller's base URI. So having this annotation in a private helper method that does not intercept a URI pattern makes little sense.
So after playing around I found the solution. The problem was the name in the @ModelAttribute. After removing the "project" the method works as expectet. Because of the confusion regarding the "getProject()"-method, I did a little refactoring to make the intention of the method more clear. Here is the complete class with additional comments:
@Controller
@RequestMapping("/p/{abbr}/scope")
public class ScopeController {
private static final String SHOW_PROJECT_PAGE = "/projects/scope/show";
private static final Logger log = LoggerFactory.getLogger(ScopeController.class);
@Autowired
private ProjectService projectService;
// method is called before show() and update()
@ModelAttribute
private void initProject(@PathVariable(value = "abbr") String abbr, Model model) {
log.debug("loading project for '{}'", abbr);
// load the project JPA entity from the database, will be merged with the
// updated form values in the POST request. By doing this, I can asure
// that the primary key (the ID) and the related objects are present as
// needed for the em.saveOrUpdate() in the projectService.save() method.
model.addAttribute("project", projectService.find(abbr));
}
@RequestMapping(method = RequestMethod.GET)
public String show() throws BindException {
// shows the project scope form with the project
// added in 'initProject()'
return SHOW_PROJECT_PAGE;
}
@RequestMapping(method = RequestMethod.POST)
public String update(
// the project with the updated form values and the JPA ID and JPA
// relations as loaded in the initProject()
@Valid @ModelAttribute Project project, BindingResult result,
RedirectAttributes redirectAttrs)
throws MethodArgumentNotValidException {
redirectAttrs.addFlashAttribute(project);
try {
if (!result.hasErrors()) {
projectService.save(project);
}
}
catch (Exception e) {
log.error(e.toString());
throw new MethodArgumentNotValidException(null, result);
}
log.debug("project '{}' updated", project.getAbbreviation());
return SHOW_PROJECT_PAGE;
}
}
Thanks all for your answers.
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