My understanding so far is on our controller request mapping method we can specify RedirectAttributes parameter and populate it with attributes for when the request gets redirected.
Example:
#RequestMapping(value="/hello", method=GET)
public String hello(RedirectAttributes redirAttr)
{
// should I use redirAttr.addAttribute() or redirAttr.addFlashAttribute() here ?
// ...
return "redirect:/somewhere";
}
The redirect attributes will then be available on the target page where it redirects to.
However RedirectAttributes class has two methods:
addAttribute()
addFlashAttribute()
Have been reading Spring documentation for a while but I'm a bit lost. What is the fundamental difference between those two, and how should I choose which one to use?
Here is the difference:
addFlashAttribute() actually stores the attributes in a flashmap
(which is internally maintained in the users session and removed
once the next redirected request gets fulfilled)
addAttribute() essentially constructs request parameters out of
your attributes and redirects to the desired page with the request
parameters.
So the advantage of addFlashAttribute() will be that you can store pretty much any object in your flash attribute (as it is not serialized into request params at all, but maintained as an object), whereas with addAttribute() since the object that you add gets transformed to a normal request param, you are pretty limited to the object types like String or primitives.
Assume you have 2 controllers.If you redirect from one controller to
another controller the values in model object won't be available in the
other controller. So if you want to share the model object values
then you have to say in first controller
addFlashAttribute("modelkey", "modelvalue");
Then second controller's model contains now the above key value pair..
Second question ? What is difference between addAttribute and addFlashAttribute in RedirectAttributes class
addAttribute will pass the values as requestparameters instead of model,so when you add some using addAttribute you can access those values from request.getParameter
Here is the code.I have used to find out what is going on :
#RequestMapping(value = "/rm1", method = RequestMethod.POST)
public String rm1(Model model,RedirectAttributes rm) {
System.out.println("Entered rm1 method ");
rm.addFlashAttribute("modelkey", "modelvalue");
rm.addAttribute("nonflash", "nonflashvalue");
model.addAttribute("modelkey", "modelvalue");
return "redirect:/rm2.htm";
}
#RequestMapping(value = "/rm2", method = RequestMethod.GET)
public String rm2(Model model,HttpServletRequest request) {
System.out.println("Entered rm2 method ");
Map md = model.asMap();
for (Object modelKey : md.keySet()) {
Object modelValue = md.get(modelKey);
System.out.println(modelKey + " -- " + modelValue);
}
System.out.println("=== Request data ===");
java.util.Enumeration<String> reqEnum = request.getParameterNames();
while (reqEnum.hasMoreElements()) {
String s = reqEnum.nextElement();
System.out.println(s);
System.out.println("==" + request.getParameter(s));
}
return "controller2output";
}
Javadoc description:
"A FlashMap provides a way for one request to store attributes intended for use in another. This is most commonly needed when redirecting from one URL to another -- e.g. the Post/Redirect/Get pattern. A FlashMap is saved before the redirect (typically in the session) and is made available after the redirect and removed immediately."
Related
I'm trying to check if my method works through the API
#GetMapping(value = "/ads/in/rubrics/{ids}")
public List<Ad> findAllAdInRubricByIds(#PathVariable("ids") List<Integer> ids) {
return adService.findAllAdInRubricByIds(ids);
}
how can i set some parameters in get request?
that's how i tried
http://localhost:9999/mvc/ad/ads/in/rubrics/ids&ids=1&ids=2
http://localhost:9999/mvc/ad/ads/in/rubrics/ids&ids1=1&ids2=2
always get error 400 Bad Request
You're confusing PathVariables with RequestParams.
A PathVariable is a variable in the request path. It doesn't need to be the last character.
#GetMapping("/api/{version}/foo/{idFoo}")
public Void getFooNumber(#PathVariable("version") Integer version, #PathVariable("idFoo") Integer idFoo){
return "1";
}
Since PathVariables are part of the path, they're always required. If you don't incluide them in the request you'll end up invoking another endpoint or getting a 404 if the request can't be mapped to any endpoint.
The RequestParams are the parameters received at the end of the request URL, after the "?" character.
#GetMapping("/api/foo")
public Void getFooNumber(#RequestParam(value="version", required=false) Integer version, #RequestParam(value="idFoo", required=true) Integer idFoo){
return "1";
}
With RequestParams you can define for each one of them if it's required or not.
You can also mix them and have in the same method PathVariables and RequestParams.
In the first example the request URL would be ".../api/1/foo/25", while in the second example it would be ".../api/foo?version=1&idFoo=25"
As for having an array or a list, if you define the parameter as a List you can send multiple parameters of the same name:
#GetMapping("/ads/in/rubrics")
public Void findAllAdInRubricByIds(#RequestParam(value="ids", required=true) List<Integer> ids){
return adService.findAllAdInRubricByIds(ids);
}
In this case, you can use ".../ads/in/rubrics?ids=1&ids=2&ids=3&ids=4"
http://localhost:9999/mvc/ad/ads/in/rubrics/?ids1=1&ids2=2
For the first parameter use a ? and after that for each additional parameter a &
I want to implement some simple endpoint in spring, trying to be as much Restful as possible and reduce the number of URL to use. Here are the GET url I want to call: (this is a simplified version)
GET /users
GET /users?id=123
GET /users?username=xyz
I used this controller:
#GetMapping()
public #ResponseBody
OutputUserDTO getUserByParameter(#RequestParam(required = false) String id,
#RequestParam(required = false) String username) {
if (id != null && !id.isEmpty()) {
return userService.getUserById(id);
}
if (username != null && !username.isEmpty()) {
return userService.getUserByUsername(username);
}
throw new MissingParameterException("...some message...");
}
#GetMapping()
public #ResponseBody
List<OutputUserDTO> getUsers() {
return userService.getUsers();
}
Of course I get an error, that is Ambiguous mapping.
I thought to always return a List so that I can merge the 2 endpoints and, in case you pass some parameters, return a Singleton... even though I don't know if it's a correct practice.
Or else, create one endpoint for each parameter, GET /users/{userId}, GET /users/{username}, ... but I don't like it neither (If I have 10 different way to get a user then I'll have to implement 10 endpoints :S)
What are some good practices in this case??
Thanks.
Replace MissingParameterException with return userService.getUsers();, and get rid of the other method, you know, the one with exactly the same mapping as the first method.
To make that work, you'd have to change return type to Object, which is not going to be a problem, since it's the actual object returned that controls the effect of #ResponseBody, not the declared type.
#GetMapping()
#ResponseBody
public Object getUserByParameter(#RequestParam(required = false) String id,
#RequestParam(required = false) String username) {
if (id != null && ! id.isEmpty()) {
return userService.getUserById(id);
}
if (username != null && ! username.isEmpty()) {
return userService.getUserByUsername(username);
}
return userService.getUsers();
}
FYI: #ResponseBody is a method-level annotation, so it should be listed before any keyword modifiers.
The Java Language Specification, section 8.3.1. Field Modifiers, says:
FieldModifier:
(one of)
Annotation public protected private
static final transient volatile
[...]
If two or more (distinct) field modifiers appear in a field declaration, it is customary, though not required, that they appear in the order consistent with that shown above in the production for FieldModifier.
It should be like #GetMapping("/users") on respective method
http://www.appsdeveloperblog.com/pathvariable-spring-mvc/
I suppose that the reason for that is, in getUserByParameter, both parameters are optional but if both the parameters are not passed it will conflict with your second getMapping.
more over, what is returned changes in the three scenarios. scenario 1 returns a list of DTOs while scenarios 2 & 3 return a single DTO
i dont think you can handle all three scenarios using your request path /users unless you want to wrap even a single DTO in a list, in which case you can simply merge your two methods. call getUsers() when both parameters are missing, in other cases, do what you currently do but wrap the response in a list.
if you want to keep them separate and return DTO or List, you should probably separate them out into /users and /user by specifying #GetMapping("/user") on method one and #GetMapping("/users") on method two
hope this helps
I have a REST API which accepts MediaType.MULTIPART_FORM_DATA.
I know I can use something like #FormDataParam("field1") String field1 to get to form field values in my rest API code.
What I want to know is that is there any way I can handle case where number of form fields is not fixed. ie. form submitter can add more input fields from UI and then post that form. So in my REST API I can never take a call how many fields will be coming.
How can this be handled in jersey?
thanks,
Sandeep
Get away with #FormParam in jersey and use the context field. Something like
#Context
private HttpServletRequest request;
#POST
#Path("/testForSandeep")
#Produces("application/xml")
public String func() throws IOException
{
//gives you all params
final Map<String, String[]> params = request.getParameterMap();
//you can iterated and get whatever you want
for(String fieldName : params.keySet())
{
String[] fieldValues = params.get(fieldName);
}
//more code
}
I have used following, in a JSP file to retrieve URL parameter.This JSP file represent a web page with a form which I am validating with Struts validator.
<% String tempVal= (String)request.getParameter("parm");%>
When the form initially loads, the tempVal parameter's value is null if there is no URL parameter with the name parm.Then I submit the form with some invalid data in the form, and the come to the same page(After hitting Validate method in the ActionForm class) with validate error messages.
But this time the tempVal parameter's value is -1.
Following is my Validate method in the ActionForm class.
#Override
public ActionErrors validate(ActionMapping mapping, HttpServletRequest request)
{
ActionErrors errors = null;
errors = super.validate(mapping, request);
String temp2 = request.getParameter("param3");
if(temp2 == null){
errors.add("some Error");
}
return errors;
}
Any reason for this behavior ?
Thanks in advance
Your URL parameter must be in string format if you are trying to receive request at other form.
But if your Url parameter are not in string format then I will recommend to use getAttribute
Here same happening, Because you are trying to getParameter from Object and ten converting to String which give you -1.
First page
//first page: first.jsp
<% request.setAttribute("PAGE", "param");%>
<jsp:forward page="/second.jsp"/>
and second.jsp:
<%=request.getAttribute("PAGE")%>
It is crucial to know that attributes are not parameters.
The return type for attributes is an Object, whereas the return type for a parameter is a String. When calling the getAttribute(String name) method, bear in mind that the attributes must be cast.
Additionally, there is no servlet specific attributes, and there are no session parameters.
Hope this may help you.
Question is pretty self explanatory. I want to send 2 different arrays of objects through a POST form without ajax to my controller.
I changed my question to using ajax and using a get request due to the size of the params. Currently getting a 400 (Bad Request). I have no idea why. Please take a look...
I have objects:
var phone = {phoneId:"", phoneNumber:"", phoneType:""};
var schedule = {scheduleId:"", time:"", day:""};
Which I place into a javascript arrays:
var phones = [phone1, phone2, phone3];
var schedules = [schedule1, schedule2];
and I use ajax to send:
var data = {
index: id,
schedules: schedules,
phones: phones
}
var url = "/myController/myUrl"
$.getJSON(url, data, function(result){
if(result.ok){
$('#messageAlertSuccess').show();
} else {
$('#messageAlertError').show();
}
});
I created wrapping classes to map them like so:
public class PhoneWrapper(){
private String phoneId;
private String phoneNumber;
private String phoneType;
}
And of course the scheduleWrapper follows the same convention.
Here's the method in my controller:
#ResponseBody
#RequestMapping(value="/myUrl", method=RequestMethod.GET)
public Result doSomething(#RequestParam("index") int index,
#RequestParam("phones") Set<PhoneWrapper> phoneWrappers,
#RequestParam("schedules") Set<ScheduleWrapper> scheduleWrappers,
Model model,
HttpSession session){
//do stuff here.
}
I am currently getting a 400. So what's wrong?
Update: here's the url that the .getJSON jquery method is building:
http://localhost:8080/myApp/myController/myUrl?index=9&schedules%5B0%5D%5BscheduleId%5D=1&schedules%5B0%5D%5BfromDay%5D=Monday&schedules%5B0%5D%5BtoDay%5D=Friday&schedules%5B0%5D%5BfromTime%5D=08%3A30%3A00&schedules%5B0%5D%5BtoTime%5D=16%3A00%3A00&schedules%5B1%5D%5BscheduleId%5D=5&schedules%5B1%5D%5BfromDay%5D=Saturday&schedules%5B1%5D%5BtoDay%5D=Monday&schedules%5B1%5D%5BfromTime%5D=09%3A00%3A00&schedules%5B1%5D%5BtoTime%5D=13%3A00%3A00&phones%5B0%5D%5BphoneId%5D=6&phones%5B0%5D%5BphoneNumber%5D=787-788-1111&phones%5B0%5D%5BphoneType%5D=PHONE&phones%5B1%5D%5BphoneId%5D=106&phones%5B1%5D%5BphoneNumber%5D=787-795-4095&phones%5B1%5D%5BphoneType%5D=FAX
I see a few things that don't look right
unless you have getters and setters in your wrappers (DTO is a better name), i don't use them for my DTOs for xhr calls, you need to change
public class PhoneWrapper(){
private String phoneId;
private String phoneNumber;
private String phoneType;
}
to have public fields vs private
public class PhoneWrapper(){
public String phoneId;
public String phoneNumber;
public String phoneType;
}
Your js arrays are not arrays but objects;
var phones = {phone1, phone2, phone3};
var schedules = {schedule1, schedule2};
Here they are as arrays
var phones = [phone1, phone2, phone3];
var schedules = [schedule1, schedule2];
Make sure you naming is the same of both the js and java sides. I find it very helpful to turn on the debugging when troubleshooting these problems. log4j -
<logger name="org.springframework.web.servlet.mvc" >
<level value="debug" />
</logger>
EDIT
So after the question was updated with more info I notice that it was the same problem as Binding a list in #RequestParam
I would say that you are almost there! The first thing the you need is a wrapper to hold the two Set<> parameters since spring is not able to map a collection directly to parameters (yet?).
Also, there are two ways to handle this kind of requests:
use a json request and #Requestbody with a single javascript object in the request body an map this into a java class (automatically by spring). This means you need to change a little how the data is send down and this approach has one side effect: you cannot merge data simply by defining the parameter as a model attribute.
a second possibility is to stay with the post form submit. Also here you need to create the wrapper and use this one as a requestparam. Either one per Set<> parameter like #Sotirios mentioned in his answer or one parameter which holds both sets. Then you need to modify your submit data to send the phone and schedule information like input fields. I haven't used sets in this case but
lists and the parameter names would look like phoneWrapper[0].phoneId.
The advantage of the second approach is that you can merge the request data with existing values so you do not need to send down a complete phone information all the time.
var phones = {phone1, phone2, phone3};
var schedules = {schedule1, schedule2};
These two are not arrays (square brackets), but objects (curly brackets).
Compare with
var phones = ["phone1", "phone2", "phone3"];
var schedules = ["schedule1", "schedule2"];
and if you are to pass actual object references (phone1, phone2, phone3, schedule1 and schedule2 are object variables) then you need to use
var phones = [phone1, phone2, phone3];
var schedules = [schedule1, schedule2];
For spring the map request parameters to Class instance fields, they have to match the name of the parameter.
So with
<input type="hidden" name="someParameter" value="123"/>
and
public class SomeClass {
private String someParameter;
// getters and setters
}
a Spring controller will be able to be injected with a SomeClass instance whose field someParameter has the value 123 that comes from the html hidden input request parameter. This is also known as a command object.
A javascript array has no meaning to either html or http.
As for the solution, I would keep your class PhoneWrapper, use javascript to populate 3 <input> elements, and change the method definition to
#RequestMapping(value=MY_URL, method=RequestMethod.POST)
public String doSomething(#RequestParam("index") int index,
PhoneWrappers phoneWrappers,
ScheduleWrappers scheduleWrappers,
Model model,
HttpSession session){
Notice there are no more array [] brackets. (You would do the same for ScheduleWrappers).