Hi I am new to Spring MVC i am following Spring reference documentaion I have doubt in view resolver. Here is my sample code.
#Controller
#RequestMapping("/form")
public class MyController {
#RequestMapping(method = RequestMethod.GET)
public String setupForm() {
// do my stuff
return "myform";
}
#RequestMapping(method = RequestMethod.POST)
public String processForm(ModelMap model) {
// process form data
model.addAttribute("notification", "Successfully did it!");
return "redirect:/form";
}
}
here i am using two controllers, the first one returns "myform" and second one returns "redirect:/form". My question is, what is the difference between these two and how it works?
If you are familiar with jsp servlet, I think you can know the difference between redirect and forward, or you can get tons of answers from google. Then I want to explain a bit about how Spring does this. in setupForm method, it returns myform, then according to your view resovler configuration, it will try to find a myform.jsp or another likes this, and if your view resovler is internalresourceviewresovler, Spring will do a forward automatically and try to find this jsp in web-inf directory, if not, you have to specify a forward prefix. and for processForm method, that after return redirect:/form, it will force browser to send a new request /form to server which can be got by spring mvc and it will handle it with the related method.
Related
I am new to Spring MVC. I am trying to create a REST API in which I have to read data from a website and then parse it.
I am so confused please help.
The question is generic, could you tell where exactly you stopped?
Maybe you want to do something like this in your rest API:
#RequestMapping(value = "yourUrl", method = RequestMethod.GET)
public ResponseEntity<List<Exercicio>> listarExercicios(YourObject object) {
object = restTemplate.getForObject("http://gturnquist-quoters.cfapps.io/api/random", YourObject.class);
return ResponseEntity.status(HttpStatus.OK).body(object);
}
I got a problem with my WCF service. Here is the
[OperationContract]
[WebGet(UriTemplate = "/needs", ResponseFormat = WebMessageFormat.Json)]
List<CustomerNeed> getAllCustomerNeeds();
When I go on the page which call this service, I got this error
GET http://localhost:666/rest/Service1.svc/needs net::ERR_CONNECTION_RESET
When I'm trying to return a string instead of a List, it works.
CustomerNeed is a class generate from my database via EntityFramework.
In my service, I'm only calling an other method which is in an other class;
public List<CustomerNeed> getAllCustomerNeeds()
{
var needs = from cn in db.CustomerNeeds
select cn;
List<CustomerNeed> list = new List<CustomerNeed>();
foreach (CustomerNeed cusN in needs)
{
list.Add(cusN);
}
return list;
}
Maybe is it because I have a foreign key in my table CustomerNeed ?
When I do "LINQ to entities" to import my database, do I have to import tables that were created because of many to many relation ?
I will recommend you to create a simple custom class which will represent your CustomerNeeds database entity, initiate this object on the server side and pass to the client application. It can help you to avoid this problem and also it is recommended way to transfer data accross the WCF services.
In this case you need to do the next steps:
1) Create a public class CustomerNeeds and mark it with the DataContract attribute. For example:
[DataContract]
public class CustomerNeeds
{
[DataMember]
public SomeDataType PropertyName {get; set;}
}
2) Initiate this object on the service, change return datatype in getAllCustomerNeeds() method from the entity class to the newly created class CustomerNeed and pass this data to the clien
And that`s all.
You haven't shown where/what db is, but I'm assuming if you're using entity framework as your tag implies it's a entities context. You might be having some issues with the context already being disposed or not newed up correctly (though I would have expected you to receive a slightly different error if that's the case.)
It looks like you're going through some unnecessary steps in your function, I would think something like this would work:
public List<CustomerNeed> getAllCustomerNeeds()
{
using (var db = new YourContext()) // plug in your context object
{
return db.CustomerNeeds.ToList();
}
}
Additionally when you say it "works as a string" are you returning something small like "hello world"? you might need to take a look at your WCF configuration to make sure it can handle the amount of data you're trying to pass back and forth.
Hope this helps!
I'm upgrading a custom solution where I can dynamically register and unregister Web Api controllers to use the new attribute routing mechanism. However, it seems to recent update to RTM break my solution.
My solution exposes a couple of Web Api controllers for administration purposes. These are registered using the new HttpConfigurationExtensions.MapHttpAttributeRoutes method call.
The solution also allows Web Api controllers to be hosted in third-party assemblies and registered dynamically. At this stage, calling HttpConfigurationExtensions.MapHttAttributeRoutes a second time once the third-party controller is loaded would raise an exception. Therefore, my solution uses reflection to inspect the RoutePrefix and Route attributes and register corresponding routes on the HttpConfiguration object.
Unfortunately, calling the Web Api results in the following error:
"No HTTP resource was found that matches the request URI".
Here is a simple controller that I want to use:
[RoutePrefix("api/ze")]
public sealed class ZeController : ApiController
{
[HttpGet]
[Route("one")]
public string GetOne()
{
return "One";
}
[HttpGet]
[Route("two")]
public string GetTwo()
{
return "Two";
}
[HttpPost]
[Route("one")]
public string SetOne(string value)
{
return String.Empty;
}
}
Here is the first solution I tried:
configuration.Routes.MapHttpRoute("ZeApi", "api/ze/{action}");
Here is the second solution I tried:
var type = typeof(ZeController);
var routeMembers = type.GetMethods().Where(m => m.IsPublic);
foreach (MethodInfo method in routeMembers)
{
var routeAttribute = method.GetCustomAttributes(false).OfType<RouteAttribute>().FirstOrDefault();
if (routeAttribute != null)
{
string controllerName = type.Name.Substring(0, type.Name.LastIndexOf("Controller"));
string routeTemplate = string.Join("/", "api/Ze", routeAttribute.Template);
configuration.Routes.MapHttpRoute(method.Name, routeTemplate);
}
}
I also have tried a third solution, whereby I create custom classes that implement IHttpRoute and trying to register them with the configuration to no avail.
Is it possible to use legacy-style route mapping based upon the information contained in the new routing attributes ?
Update
I have installed my controller in a Web Application in order to troubleshoot the routing selection process with the Web Api Route Debugger. Here is the result of the screenshot:
As you can see, the correct action seems to be selected, but I still get a 404 error.
Update2
After further analysis, and per Kiran Challa's comment below, it seems that the design of Web Api prevents mixing attribute routing and conventional routing, and that what I want to do is not possible using this approach.
I have created a custom attribute [RouteEx] that serves the same purpose of the Web Api [Route] attribute, and now my code works perfectly.
I guess, since this is not possible using the conventional attribute routing, none of the answers on this question could legitimately be consisered valid. So I'm not nominating an answer just yet.
You shouldn't be required to use reflection and inspect the attribute-routing based attributes yourself. Attribute routing uses existing Web API features to get list of controllers to scan through.
Question: Before the switch to attribute routing, how were you loading these assemblies having the
controllers?
If you were doing this by IAssembliesResolver service, then this solution should work even with attribute routing and you should not be needing to do anything extra.
Regarding your Update: are you calling MapHttpAttributeRoutes?
I am using the Asp.Net Web Api. I would like to be able to filter out certain fields on the response objects based on the connected clients access rights.
Example:
class Foo
{
[AccessFilter("Uberlord")]
string Wibble { get; set; }
string Wobble { get; set; }
}
When returning data the filed Wibble should only be returned if the current users context can satisfy the value of "Uberlord".
There are three avenues that I am exploring but I have not got a working solution:
A custom WebApi MediaTypeFormatter.
A custom json.net IContractResolver.
Some sort of AOP wrapper for controllers that manipulates the response object
My issue with these are:
The custom formatter does not feel like the right place to do it but might be the only option.
The custom json serializer would not have access to the current context so I would have to work that out.
With the first two options you would require specific implementations for each response format, json, xml, some custom format, etc. This would mean that if another response type is supported then a custom formatter / serializer is required to prevent sensitive data leaking.
The AOP controller wrapper would require a lot of reflection.
An additional bonus would be to strip out values from the fields on an inbound request object using the same mechanism.
Have I missed an obvious hook? Has this been solved by another way?
It was actually a lot simpler than I first thought. What I did not realise is that the DelegatingHandler can be used to manipulate the response as well as the request in the Web Api Pipeline.
Lifecycle of an ASP.NET Web API Message
Delegating Handler
Delegating handlers are an extensibility point in the message pipeline allowing you to massage the Request before passing it on to the rest of the pipeline. The response message on its way back has to pass through the Delegating Handler as well, so any response can also be monitored/filtered/updated at this extensibility point.
Delegating Handlers if required, can bypass the rest of the pipeline too and send back and Http Response themselves.
Example
Here is an example implementation of a DelegatingHandler that can either manipulate the response object or replace it altogether.
public class ResponseDataFilterHandler : DelegatingHandler
{
protected override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
return base.SendAsync(request, cancellationToken)
.ContinueWith(task =>
{
var response = task.Result;
//Manipulate content here
var content = response.Content as ObjectContent;
if (content != null && content.Value != null)
{
((SomeObject)content.Value).SomeProperty = null;
}
//Or replace the content
response.Content = new ObjectContent(typeof(object), new object(), new JsonMediaTypeFormatter());
return response;
});
}
}
Microsoft article on how to implement a delegating handler and add it to the pipeline.HTTP Message Handlers in ASP.NET Web API
I have a similar question in the works over here: ASP.NET WebAPI Conditional Serialization based on User Role
A proposed solution that I came up with is to have my ApiController inherit from a BaseApiController which overrides the Initalize function to set the appropriate formatter based on the user's role. I haven't decided if I will go this way yet, but perhaps it will work for you.
protected override void Initialize(System.Web.Http.Controllers.HttpControllerContext controllerContext)
{
base.Initialize(controllerContext);
// If the user is in a sensitive-data access role
controllerContext.Configuration.Formatters.Add(/*My Formatter*/);
// Otherwise use the default ones added in global app_start that defaults to remove sensitive data
}
I'm having trouble setting something up that I'm pretty sure /should/ be easy, so I thought I'd throw it to the crowd. I can't seem to find what I'm looking for elsewhere on the web or on SE.
I am simplifying my project of course, but basically I have a JAX-WS annontated Jersey resource class that looks something like this:
#Path("myresource")
public class MyResource {
#Autowired
MyComplexObjectDAO daoInstance;
#Path("findObject/{id}")
#GET
public MyComplexObject findObject( #PathParam(value="id") String id ) {
return daoInstance.findObject( id );
}
#Path("saveObject")
#PUT
public MyComplexObject saveObject( MyComplexObject objectToSave ) {
MyComplexObject savedObject = daoInstance.saveObject( objectToSave );
return savedObject;
}
}
So you can see I'm autowiring a DAO object using spring, and then I use the DAO methods in the REST handlers.
The 'findObject' call seems to work fine - so far it works exactly as I expect it to.
The 'saveObject' call is not working the way I want and that's what I need some advice on.
You can see that I'm trying to directly take an instance of my complex object as a parameter to the REST method. Additionally I would like to return an instance of the complex object after it's been saved.
I put together some 'client' code for testing this out.
#Test
public void saveTest() {
WebResource wsClient = createWebServiceClient();
MyComplexObject unsavedInstance = createMyComplexObject();
MyComplexObject savedInstance =
wsClient
.path("saveObject")
.accept(MediaType.APPLICATION_XML)
.put(MyComplexObject.class, unsavedInstance);
assertNotNull(savedIntent);
}
Which is returning the following error:
com.sun.jersey.api.client.UniformInterfaceException: PUT http://localhost:8081/rest/myresource/save returned a response status of 400 Bad Request
I don't see why this isn't working and I think I've tried just about everything I can think of. Any help or direction would be very much appreciated.
Thanks so much!
I see that you call the accept() method in your test client (which means that a "Accept:" header is added to the request, indicating the server what type of representation you would like). However, you don't call the type() method to add a "Content-type:" header and inform the server that you are sending XML data. See http://jersey.java.net/nonav/documentation/latest/client-api.html#d4e644 for examples.
Side remark: your URLs are not RESTful - you should avoid verbs in your path:
So, instead of:
/api/findObject/{id}
/api/saveObject
You should use:
/api/objects/{id}
/api/objects
Last note: to create an object on calling /api/objects, you should do a POST and not a PUT to adhere to REST best practices and widely adopted patterns.
switching to the 'concrete class' solution I alluded to in my earlier comment is what fixed things up for me.