I'm new to Spring MVC Framework. I'm doing some self study to extend my knowledge in Java.
This is how I understand the getProducts() code definition from a tutorial I'm following but please correct me if I'm wrong.
Controller requests something from the Data Access Object >
Data Access Object gets the data from a Database or a Model through the getProductList() method > Stores the information to list > Then binds the list to the model.
So I got two question about this.
Is the inclusion of model as parameter in public String getProducts(Model model) considered the dependency injection
Is products (within quotes) in model.addAttribute("products",products); just a name which I can change to whatever I like or should it match something?
public class HomeController {
private ProductDao productDao = new ProductDao();
#RequestMapping("/")
public String home(){
return "home";
}
#RequestMapping("/productList")
public String getProducts(Model model){
List<Product> products = productDao.getProductList();
model.addAttribute("products",products);
return "productList"; //productList string is the productList.jsp which is a view
}
#RequestMapping("/productList/viewProduct")
public String viewProduct(){
return "viewProduct";
}
}
I'd appreciate any explanation or comment.
Thank you.
Yes,
model is instantiated by spring and injected to your method, means if any of model attribute matches anything in request it will be filled. and it should be the last param in the method
model.addAttribute("products",products);
"products" is just a name which you can use it in your view get the value with ${products}
My code. this is sample.
#Autowired
private ProductService productService;
#RequestMapping(value = "/settings/product")
public ModelAndView showProduct(ModelAndView mav, HttpServletRequest req, Authentication auth) {
CustomUserDetail customUserDetail = (CustomUserDetail) auth.getPrincipal();
int associationIdx = customUserDetail.getAccount().getAssociation().getIdx();
String language = CookieUtil.getCookieValue(req, "lang");
Association association = associationService.findAssociationByIdx(associationIdx);
List<AssociationProductColumnDefine> columns = associationService.findByAssociationAndLanguage(association,
language);
List<AssociationProductColumnDefine> source = associationService.findByAssociationAndLanguage(association,
"ko-kr");
mav.addObject("association", association);
mav.addObject("source", source);
mav.addObject("columns", columns);
mav.setViewName("/association/association_settings_product");
return mav;
}
Yes, you choice model and ModelAndView.
Yes, simple.
Related
I have a controller annotated with #RestController and it implements an interface:
public interface ContratEndpoint {
String ROOT = "/api/contrats";
String GET_CONTRAT = "";
String GET_CONTRAT_PER_PK = "/{idContrat}";
#RequestMapping(value = GET_CONTRAT)
Contrat getContrat(#RequestParam(value = "contratId")Long contratId);
#RequestMapping(value = GET_CONTRAT_PER_ID)
ExtContrat getContratById(#PathVariable("idContrat") Long idContrat);
}
The controller:
#RestController
#RequestMapping(value = ContratEndpoint.ROOT)
public class ContratController implements ContratEndpoint {
//Injecting Services....
#Resource
private Mapper mapper;
#Override
public Contrat getContrat(Long contratId) {
return mapper.map(contratService.get(contratId),Contrat.class);
}
#Override
public ExtContrat getContratById(#PathVariable("idContrat") Long idContrat){
Preconditions.checkArgument(idContrat !=null);
return mapper.map(contratService.get(idContrat),ExtContrat.class);
}
.The above Code works just fine.
. But For the first inherited method , I didn't have to annotate arguments with #RequestParam and it worked just fine.
As for the second method I tried at first :
#Override
public ExtContrat getContratById(Long idContrat){
Preconditions.checkArgument(idContrat !=null);
return mapper.map(contratService.get(idContrat),ExtContrat.class);
}
. I expected the same behaviour Like the first Method, But i was wrong and the code ended up firing an IllegalArgumentException because of the check in ligne Preconditions.checkArgument(idContrat!=null).
My question is what is so specific about #PathVariable that i've missed ?
Or is it just something is wrong with my approach?
Thanks.
There is difference between Request param and path variable,seee below post that you can confirm with your uri the cause for the exception :
#PathVariable is to obtain some placeholder from the uri (Spring call it an URI Template) — see Spring Reference Chapter 16.3.2.2 URI Template Patterns
#RequestParam is to obtain an parameter — see Spring Reference Chapter 16.3.3.3 Binding request parameters to method parameters with #RequestParam
Assume this Url http://localhost:8080/SomeApp/user/1234/invoices?date=12-05-2013 (to get the invoices for user 1234 for today)
#RequestMapping(value="/user/{userId}/invoices", method = RequestMethod.GET)
public List<Invoice> listUsersInvoices(
#PathVariable("userId") int user,
#RequestParam(value = "date", required = false) Date dateOrNull) {
...
}
I have a Spring web app (Spring 3.2) and I have used following scenario to handle edit pages:
#Controller
#SessionAttributes(value = { "packet" })
public class PacketController {
#RequestMapping(value = "/edit-packet/{packet_id}", method = RequestMethod.GET)
public String editPacketForm(#PathVariable(value = "packet_id") Long packet_id, Model model)
{
model.addAttribute("packet", packetService.findById(packet_id));
return "packets/packetEdit";
}
POST method:
#RequestMapping(value = "/edit-packet/{packet_id}", method = RequestMethod.POST)
public String packetEditAction(Model model, #Valid #ModelAttribute(value = "packet")
Packet packet, BindingResult result, SessionStatus status)
{
if (result.hasErrors())
{
return "packets/packetEdit";
}
packetService.update(packet);
status.setComplete();
return "redirect:/";
}
Now the problem is what if someone tries to open multiple tabs for /edit-packet/{id} with different ids. With every new open tab the session 'packet' object will be overwritten. Then after trying to submit forms on multiple tabs, first tab will be submitted but it actually change the second packet because in session is second object and second tab will cause error because setComplete has been invoked so there is no 'packet' object in session.
(This is known issue https://jira.spring.io/browse/SPR-4160).
I am trying to implement this solution http://duckranger.com/2012/11/add-conversation-support-to-spring-mvc/ to solve this problem. I copied ConversationalSessionAttributeStore.java
ConversationIdRequestProcessor.java classes and in my servlet-config.xml I made this:
<mvc:annotation-driven />
<bean id="conversationalSessionAttributeStore"
class="com.xx.session.ConversationalSessionAttributeStore">
</bean>
<bean name="requestDataValueProcessor" class="com.xx.session.ConversationIdRequestProcessor" />
But it doesn't work, in my POST methods I don't see any new parameters, did I miss something?
UPDATE: Actually, it started working, but maybe someone has a better idea to solve this issue?
My other idea is to force a new session on every new tab, but it's not a nice solution.
Don't use session attributes, make your controller stateless and simply use the path variable to retrieve the correct model attribute.
#Controller
public class PacketController {
#ModelAttribute
public Packet packet(#PathVariable(value = "packet_id") Long packet_id) {
return packetService.findById(packet_id);
}
#RequestMapping(value = "/edit-packet/{packet_id}", method = RequestMethod.GET)
public String editPacketForm() {
return "packets/packetEdit";
}
#RequestMapping(value = "/edit-packet/{packet_id}", method = RequestMethod.POST)
public String packetEditAction(Model model, #Valid #ModelAttribute(value = "packet")
Packet packet, BindingResult result) {
if (result.hasErrors()) {
return "packets/packetEdit";
}
packetService.update(packet);
return "redirect:/";
}
}
Something like that should do the trick.
I have been looking for a way to somehow reduce the amount of code that is duplicated with subtle variance in my Spring MVC controllers, but searching through the SO questions so far has only yielded some questions without any satisfactory answers.
One example of duplication that I want to remove is this, where the user creation page and the role creation page share similarities:
#RequestMapping(value = "user/create", method = RequestMethod.GET)
public String create(#ModelAttribute("user") User user, BindingResult errors) {
LOG.debug("Displaying user creation page.");
return "user/create";
}
#RequestMapping(value = "role/create", method = RequestMethod.GET)
public String create(#ModelAttribute("role") Role role, BindingResult errors) {
LOG.debug("Displaying role creation page.");
return "role/create";
}
A slightly more involved variant of duplication that I would like to remove is the one for posting the create form:
#RequestMapping(value = "user/create", method = RequestMethod.POST)
public String save(#ModelAttribute("user") User user, BindingResult errors) {
LOG.debug("Entering save ({})", user);
validator.validate(user, errors);
validator.validatePassword(user, errors);
validator.validateUsernameAvailable(user, errors);
String encodedPassword = encoder.encode(user.getPassword());
user.setPassword(encodedPassword);
if (errors.hasErrors()) {
return create(user, errors);
} else {
service.save(user);
}
return "redirect:/user/index/1";
}
#RequestMapping(value = "role/create", method = RequestMethod.POST)
public String save(#ModelAttribute("role") Role role, BindingResult errors) {
LOG.debug("Entering save({})", role);
validator.validate(role, errors);
if (errors.hasErrors()) {
return create(role, errors);
} else {
service.save(role);
}
return "redirect:/index";
}
This example includes a validate then save if correct and a redirect to the error page if things don't go as planned.
How to remove this duplication?
Spring uses your handler method parameter types to create class instances from the request parameters or body. As such, there is no way to create a handler (#RequestMapping) method that could take an Object and check if it is either a Role or a User. (Technically you could have both parameters and just check which one isn't null, but that is terrible design).
Consequently, you need a handler method for each. This makes sense since, even through the logic is similar, it is still specific to the exact type of model object you are trying to create. You perform different validation, call a different service method, and return a different view name.
I say your code is fine.
Thought I would provide the solution that I settled on in the hope that it might help someone. My gf suggested that I use the name of the entity as a path variable for the controller, and this has proved to provide a very nice solution for the problem at hand.
The two methods now look like this:
#RequestMapping(value = "{entityName}/create", method = RequestMethod.GET)
public String create(#PathVariable("entityName") String entityName, #ModelAttribute("entity") BaseEntity entity, BindingResult errors) {
LOG.debug("Displaying create page for entity named: [{}]", entityName);
return handlerFactory.getHandler(entityName).getCreateView();
}
#RequestMapping(value = "{entityName}/create", method = RequestMethod.POST)
public String save(#PathVariable("entityName") String entityName, #ModelAttribute("entity") BaseEntity entity, BindingResult errors) {
LOG.debug("Saving entity of type {}", entityName);
CrudHandler handler = handlerFactory.getHandler(entityName);
handler.getCreateValidator().validate(entity, errors);
if (errors.hasErrors()) {
return create(entityName, entity, errors);
}
handler.preSave(entity);
handler.getService().save(entity);
return "redirect:" + DASHBOARD_URL;
}
The CrudHandler interface has implementations for each entity, and provides the controller with the entity specific classes that it needs, such as service and validator. A sample CrudHandler implementation looks like this for me:
#Component
public class RoleCrudHandler implements CrudHandler {
private static final String ENTITY_NAME = "role";
public static final String CREATE_VIEW = "role/create";
public static final String EDIT_VIEW = "role/edit";
#Resource
private RoleService roleService;
#Resource
private RoleValidator validator;
#Resource
private CrudHandlerFactory handlerFactory;
#PostConstruct
public void init() {
handlerFactory.register(ENTITY_NAME, this);
}
#Override
public GenericService getService() {
return roleService;
}
#Override
public Validator getCreateValidator() {
return validator;
}
#Override
public Validator getUpdateValidator() {
return validator;
}
#Override
public BaseEntity createEntity() {
return new Role();
}
#Override
public void preSave(BaseEntity entity) {
}
#Override
public String getCreateView() {
return CREATE_VIEW;
}
#Override
public String getUpdateView() {
return EDIT_VIEW;
}
}
If someone sees some ways to improve this, feel free to share. Hope this will be of use for someone.
I would like to know how to read a flash attributes after redirection in Spring MVC 3.1.
I have the following code:
#Controller
#RequestMapping("/foo")
public class FooController {
#RequestMapping(value = "/bar", method = RequestMethod.GET)
public ModelAndView handleGet(...) {
// I want to see my flash attributes here!
}
#RequestMapping(value = "/bar", method = RequestMethod.POST)
public ModelAndView handlePost(RedirectAttributes redirectAttrs) {
redirectAttrs.addFlashAttributes("some", "thing");
return new ModelAndView().setViewName("redirect:/foo/bar");
}
}
What I am missing?
Use Model, it should have flash attributes prepopulated:
#RequestMapping(value = "/bar", method = RequestMethod.GET)
public ModelAndView handleGet(Model model) {
String some = (String) model.asMap().get("some");
// do the job
}
or, alternatively, you can use RequestContextUtils#getInputFlashMap:
#RequestMapping(value = "/bar", method = RequestMethod.GET)
public ModelAndView handleGet(HttpServletRequest request) {
Map<String, ?> inputFlashMap = RequestContextUtils.getInputFlashMap(request);
if (inputFlashMap != null) {
String some = (String) inputFlashMap.get("some");
// do the job
}
}
P.S. You can do return return new ModelAndView("redirect:/foo/bar"); in handlePost.
EDIT:
JavaDoc says:
A RedirectAttributes model is empty when the method is called and is
never used unless the method returns a redirect view name or a
RedirectView.
It doesn't mention ModelAndView, so maybe change handlePost to return "redirect:/foo/bar" string or RedirectView:
#RequestMapping(value = "/bar", method = RequestMethod.POST)
public RedirectView handlePost(RedirectAttributes redirectAttrs) {
redirectAttrs.addFlashAttributes("some", "thing");
return new RedirectView("/foo/bar", true);
}
I use RedirectAttributes in my code with RedirectView and model.asMap() method and it works OK.
Try this:
#Controller
public class FooController
{
#RequestMapping(value = "/foo")
public String handleFoo(RedirectAttributes redirectAttrs)
{
redirectAttrs.addFlashAttribute("some", "thing");
return "redirect:/bar";
}
#RequestMapping(value = "/bar")
public void handleBar(#ModelAttribute("some") String some)
{
System.out.println("some=" + some);
}
}
works in Spring MVC 3.2.2
For all those like me who were having problems with seeing the POST url in the browser when a validation would fail.
The POST url is a private url that should not be exposed to users but it was automatically rendered when a validation failed. i.e. if a field was below a minimum length. I was using #Valid. I wanted the original GET url of the form to show at all times even when validation bounced back to the form, so I did the following:
if (validation.hasErrors()) {
redirectAttributes.addFlashAttribute("org.springframework.validation.BindingResult.story", validation);
redirectAttributes.addFlashAttribute("story", story);
return new ModelAndView("redirect:/january/2015");
where story is the form object representation, redirectAttributes are RedirectAttributes you put in the method signature and validation is the BindingResult. /january/2015 is the mapping to the GET controller where the form lives.
After this implementation, in the mapping for /january/2015, story comes in intact as follows:
Story story= (Story) model.asMap().get("story");
//story from the POST method
I had to augment my GET method and check if this was not null. If not null, then send this to the form else I would send a newly initialized Story type to the form as default behaviour before.
In this manner, I am able to return to the form with the bindingresults intact (errors show on form) but have my GET url in place of the post url.
Just looking at the petclinic sample application, and trying to learn form handling.
It seems the form maps to an entity 1:1 correct? Is there any other configuration that has to be done, or will spring just know that all the form inputs map to the entity because that is what was added to the model in the GET request?
#Controller
#RequestMapping("/owners/*/pets/{petId}/visits/new")
#SessionAttributes("visit")
public class AddVisitForm {
private final Clinic clinic;
#Autowired
public AddVisitForm(Clinic clinic) {
this.clinic = clinic;
}
#InitBinder
public void setAllowedFields(WebDataBinder dataBinder) {
dataBinder.setDisallowedFields("id");
}
#RequestMapping(method = RequestMethod.GET)
public String setupForm(#PathVariable("petId") int petId, Model model) {
Pet pet = this.clinic.loadPet(petId);
Visit visit = new Visit();
pet.addVisit(visit);
model.addAttribute("visit", visit);
return "pets/visitForm";
}
#RequestMapping(method = RequestMethod.POST)
public String processSubmit(#ModelAttribute("visit") Visit visit, BindingResult result, SessionStatus status) {
new VisitValidator().validate(visit, result);
if (result.hasErrors()) {
return "pets/visitForm";
}
else {
this.clinic.storeVisit(visit);
status.setComplete();
return "redirect:/owners/" + visit.getPet().getOwner().getId();
}
}
}
Note the #SessionAttributes annotation on the class:
When the original GET request comes, the newly created Visit is stored in a session.
When the subsequent POST comes, object stored in the session is updated with the input values from the form.
When Visit is finally persisted, status.setComplete() removes the session attribute.
Without #SesssionAttributes, Visit would be recreated using the form input values when POST comes.
On the jsp you have to spring form tags and bind each variable to the modal attribute using the tags and also have to specify the modalattribute name in the form tag. Tag ref