In my Spring 3 MVC webapp, I need to be able to access all the submitted form fields.
Normally, I know what forms fields exist in the form and process the submitted entry using #RequestParam
But this form I am processing will not know what is coming in. So the only way, I know of, seems to be to do a #RequestBody and process the incoming POST data. My form could possibly contain arrays in it. For example. my #RequestBody could look like
id=1&q1_selectMultiple[]=1&q1_selectMultiple[]=2&q_2=&q_3=&Submit=Submit
So, to process this above string, I would need to first split the whole string at '&' and then look again for another array like q1_selectMultiple[ ] inside it and parse that as well.
This seems to be a lot of work when using a framework like Spring. Is there a better way to do this?
PS: I looked at #ModelAttribute. I don't think I can use it in my case since the form is being created by one controller and the responses are being handled by a completely different controller of a different class.
Maybe I didn't understand your problem, but I think it would be simpler to use any of those standard ServletResponse methods such as getParameterMap(). This one returns a Map containing pairs of parameter name/values for everything submitted.
Related
I have the GET method in my Spring REST controller. This method returns the list of users by the filter.
I have a few ways to implement it:
Add #PathVariable like - /users/{type}/{age}/{name}/...(bad approach in this case)
Add #RequestParam like - /users?type=type,age=age,name=name...(usual approach in this case)
Use RequestDto (the best approach) like
public class UsersRequestDto {
private String type;
private int age;
private String name;
...
}
But I can not use GET method for this. I must use POST method with #RequestBody
And it breaks the rules. My method doesn't change state and doesn't create any entities. It workes as the GET method but in reality, it is POST.
And I have 2 ways:
Use the GET method with many parameters
Use the POST method with DTO which works as the GET method and confuses users.
Which way is better?
Short version: you might be looking for How to bind #RequestParam to object in Spring. (See also: https://stackoverflow.com/a/16942352/54734 )
On the web, we would have an html form with a GET action. When the form is submitted, the browser would process the input controls and create the application/x-www-form-urlencoded representation of the form data. For a GET action, that representation is used as the query string.
Using GET, and encoding all of the information into the query string, allows us to take advantage of general purpose caching of the results.
But the query parameters aren't accessible by themselves - they are actually embedded within the larger context of the HTTP request. We don't usually see that because, once again, general purpose components can do a lot of the heavy lifting.
So we don't see the parser that extracts the target-uri from the request, or the parser that splits the target URI into its separate components, or the parser that splits the query part into a sequence of key value pairs....
In general, what we do is ride the "general purpose" implementation as far as we can, then get off and do the rest of the work ourselves. If the framework offered no better support for object mapping, that could mean implementing that mapping ourselves.
So if our framework lacked the capability to map the query string directly to an object representation, we would hand roll that part of the implementation ourselves (either by copying each parameter "by hand", or writing our own reflection code to do the mapping automagically).
But it seems that Spring has that capability already built into it; and that it is the default option (no annotation required); you just have to be sure that the object implementation provides the interface that Spring needs to execute the mapping.
How many different parameters are you including in your query?
Personally, I prefer the option of a GET method with many different parameters. It has other benefits such as being cacheable as well. Also, compare it to something like a the URL that a Google search generates - lots of query string parameters.
The POST option feels dirty - it's a violation of what a POST should actually do (creating or updating a resource).
See these discussions: https://softwareengineering.stackexchange.com/questions/233164/how-do-searches-fit-into-a-restful-interface and REST API Best practices: Where to put parameters?
1st of all when you are using RequestParam then key will be added with & symbol not with comma(,) .
when you want to filter ( as you have mentioned) something then best approach would be to use RequestParam.
To minimize the code you can opt to "MultiValueMap" or "HttpservletRequest" .
1)HttpServletRequest
#GetMapping("/user")
public List<User> getFilteredUser(HttpServletRequest httpservlet)
httpservlet.getQuesryString() //will return all request param.
2)MultiValueMap
#RequestParam MultiValueMap<String,String> params
NOTE:- Generally POST is for create/update record.
I have a Spring-REST service that has support for GET, POST, PUT requests and they all have been mapped in a #Controller (Sorry for stating the obvious, just new to the technology)
Now each method (RequestMapping) has its own parameters like one takes in id
other takes in name and third one takes in secretKey
I want to validate these request parameters in my own custom manner
Now tried looking up as many tutorials online as possible but did not come across any solution that would best serve my situation.
Here is what I mean:
I saw a tutorial for POST request parametes by using #RequestParam or #Valid but that does not work for GET requests (That's what I read)
I saw most people recommending JS303 but that does not suit my need as I need to validate the secretKey against the DB (id and name may be I can use JSR #Size but even the id and name would need further validation)
I also saw some recommending #Validator but that would mean I will need a validator class for each and and every parameter like IdValidator, NameValidator etc
Here is something that I am hoping to accomplish:
One Validator (Can be either something that implements Validator or COnstraintValidator) however its implementation should cater to validation of all kinds of requests (can definitely have multiple methods inside it based on what request its validating) and should throw a CustomException that I created
I am not posting what I have tried because it is actually too much code that I just copy pasted from what I searched online. If you want I can post the links that I copied the code from.
P.S. I am not an expert on Spring, but trying to learn
Here is the thing! At the company where I work there are two applications builted in MVC, one of these is used for loguin and some special funtionalities and the other one is used for global user's (I don't realy know why there are two applications. I think it most be just one).
Well, that is the context, now what I need to do is to pass a model from one application to the other, the problem is that I need to do it in the Action method to another Action method. The only method I found to do it is Redirect() but it only receive an url string and I can't pass query string's.
Is there a way to pass an encrypted model(I'm not sure if encrypted is the right word, but I think you know what I mean)?
I am newer to Spring, previously I've worked in PHP and Python. I am having some issues understanding how Spring forms work and are validated. My understanding thus far is that when you are using the your form is backed by a bean, meaning you must provide a bean to the JSP. You can also use the stand HTML forms but then you have to manually retrieve the request parameters in the controller.
Here is the issue I am having. I have a User bean that is using Hibernate Validator, and I have add, edit pages for users. The issue is I don't want the password field to appear on the Edit page, the password is going to be garbage anyway because its using BCrypt. However when the form is submitted validation fails because it expects the password to be present. There doesn't seem to be anyway to do partial bean implementation using Spring Form.
I would like to use Spring Form if possible because it reduces repetitive validation code, and its always nice to work with objects. My thoughts now are do I create an intermediate object and then translate the data from that to my bean. Seems tedious and can lead to the creation of way to many objects. My other thought is to just using plain old HTML forms and pull the params myself and set the values in the object.
I'm not sure what is the best approach or if I'm even thinking on the right track. Spring Forms and the validation is offers seems great, but seems like it isn't particularly flexible. Like I said I'm new to Spring so I may just be missing something or not understanding.
Another issue I have been wrestling with is having multiple objects needed on a form. Lets say I have a User bean, which has the following Properties.
private Role role;
private Country country;
So I need to pass User, List, and List to my JSP. I can get them to display fine, however if the form validation fails when it returns to that page, I lose my role and country objects, unless I re-add them to the model before returning the view name. Am I missing something here or is that the norm. It's a request object so I guess that makes sense but seems tedious to have to re-add them every time.
My understanding thus far is that when you are using the your form is
backed by a bean, meaning you must provide a bean to the JSP.
I'd say mostly true. The form is backed by a bean, but the Spring JSTL tags know how to get to the bean based on the set modelAttribute. The bean is living in what you would consider "page" scope, unless you add set your model attribute to be in session. Either way, if you are using the Spring JSTL tags, they are going to one or the other place to get it.
You can also use the stand HTML forms but then you have to manually
retrieve the request parameters in the controller.
Not true. You can "simulate" the same thing that the Spring JSTL tags are doing. Understand that JSTL tags are very much like macros. They are simply copying in some pre-determined block of code into the output with some very rudimentary conditional statements. The key bit that Spring MVC needs to wire the Model Attribute on the Controller side is the name and value, which are easy to decipher how those get generated/wired together.
However when the form is submitted validation fails because it expects
the password to be present.
You could create a "DTO" or "Data Transmission Object", which is basically a go-between to take the values from the UI and are converted in the Controller/Service layer to the real Model objects on the backend. Or, if you are lazy like me, put the User in session scope, in which case you don't have to post the value as Spring will take the one out of session and just updated the one or two fields you did post. Don't post the password, Spring wont set the password.
My thoughts now are do I create an intermediate object and then
translate the data from that to my bean.
Yes, this is the DTO I referred to. You only need to do it where you need to.
I'm not sure what is the best approach or if I'm even thinking on the
right track.
There are probably thousands of ways to do anything in coding, some more right or wrong than others. I know some developers who are design-Nazi's and would say you should always do it one way or another, but I am not one of those people. I think as long as you are consistent, and you are not doing something completely boneheaded you are on the right track. My #1 concern with all the code I write is maintainability. I
Don't want to spend 20hrs trying to re-learn what I did 6mo ago, so I tend to choose the simpler option
Hate repeating code, so I tend to choose more module designs
Hate having to spend 20hrs trying to re-learn what I did 6mo ago, so tend to make heavy use of JavaDoc and comments where I find the code is tricky (lots of loops, doing something weird, etc)
Another issue I have been wrestling with is having multiple objects
needed on a form.
There are several ways to deal with this too. I have never used it, but you CAN actually have more than one Model Attribute associated with the same form and Controller handler. I think you use a <spring:bind> tag or something. I have seen samples around, so Google it if you think you need that.
My approach is usually to either put something in session or build a DTO to hold all the things I need. The first I use more for things like lists to drive building the view, for instance if I have a drop down of States coming from a table. I would have a List of the States put into session and just use them from there, that way I only go after them once and done.
I use the DTO approach (some might call it a Form Bean) when I have a complex gaggle of things I need to change all at once, but the things are not necessarily connected directly. Just to point out: You can have nested objects in your model attributes and use them in your Spring JSTL tags. You can also have Collections (List, Set, Map) in your Model Attribute and get to those as well, although Spring doesn't handle nested Collections very well.
Hope that helps.
Most of the article's talk about how to work with the forms like <form:form> Spring tags just with one bean(entity), but in my web app I have more then one bean(actually 3 of them, wich is mirror to my data model in DB(MySql)). What I want is to put values for all of the properties in my entities classes from one form(it may be a jsp or xhtml or html, whatever).
So, I'm kinda new in Spring MVC and as far as I know it has backing object which comes with <commandName> tag in <form:form> tag and I suppose to think that it may be just one commandName backing object for each form??
Q: - Could you please tell me how to easily(or direct me to any example's) to fulfil my pleasant headache.
Q: - It also may have something to get attributes in one controller class but by different methods. Do I have to store them in session or request? I'm thinking to have ModelAndView class for store multiple attributes in map and after store them in ModelAndView (in model). What you suggest?
hope you are having a wonderful day!
I'd suggest you investigate the technique detailed here:
http://forum.springsource.org/showthread.php?58993-Need-to-Populate-Form-data-into-multiple-java-beans
Also, I'm wondering if there could be a terminology issue here. Do you mean you actually want to have just one form on your UI, with a lot of inputs, or do you really mean you want it all on one SCREEN or page? I say that as its also possible to have multiple forms on one UI screen and go that route... which in fact might be easier, as you could then break up your processing into multiple controllers.
Another consideration on the above relates to screen design... if you are going to be populating the data for several beans from one screen, potentially that could be a LOT of data and your screen could get very cluttered and hard to read. So from that standpoint it might also be better to consider breaking your input controls up into multiple (related) screens. There is a little more about that at the bottom of the article I linked above.
You can refer: https://stackoverflow.com/a/4986410/1882833
One approach would be to have a seperate class which encapsules the required objects. And then use it as a command to set and get the data.