When to use @QueryParam vs @PathParam

I am not asking the question that is already asked here: https://stackoverflow.com/questions/5579744/what-is-the-difference-between-pathparam-and-queryparam

This is a "best practices" or convention question.

When would you use @PathParam vs @QueryParam.

What I can think of that the decision might be using the two to differentiate the information pattern. Let me illustrate below my LTPO - less than perfect observation.

PathParam use could be reserved for information category, which would fall nicely into a branch of an information tree. PathParam could be used to drill down to entity class hierarchy.

Whereas, QueryParam could be reserved for specifying attributes to locate the instance of a class.

For example,

• /Vehicle/Car?registration=123
• /House/Colonial?region=newengland

/category?instance

@GET
@Path("/employee/{dept}")
Patient getEmployee(@PathParam("dept")Long dept, @QueryParam("id")Long id) ;

vs /category/instance

@GET
@Path("/employee/{dept}/{id}")
Patient getEmployee(@PathParam("dept")Long dept, @PathParam("id")Long id) ;

vs ?category+instance

@GET
@Path("/employee")
Patient getEmployee(@QueryParam("dept")Long dept, @QueryParam("id")Long id) ;

I don't think there is a standard convention of doing it. Is there? However, I would like to hear of how people use PathParam vs QueryParam to differentiate their information like I exemplified above. I would also love to hear the reason behind the practice.

REST may not be a standard as such, but reading up on general REST documentation and blog posts should give you some guidelines for a good way to structure API URLs. Most rest APIs tend to only have resource names and resource IDs in the path. Such as:

/departments/{dept}/employees/{id}

Some REST APIs use query strings for filtering, pagination and sorting, but Since REST isn't a strict standard I'd recommend checking some REST APIs out there such as github and stackoverflow and see what could work well for your use case.

I'd recommend putting any required parameters in the path, and any optional parameters should certainly be query string parameters. Putting optional parameters in the path will end up getting really messy when trying to write URL handlers that match different combinations.

This is what I do.

If there is a scenario to retrieve a record based on id, for example you need to get the details of the employee whose id is 15, then you can have resource with @PathParam.

GET /employee/{id}

If there is a scenario where you need to get the details of all employees but only 10 at a time, you may use query param

GET /employee?start=1&size=10

This says that starting employee id 1 get ten records.

To summarize, use @PathParam for retrieval based on id. User @QueryParam for filter or if you have any fixed list of options that user can pass.

I think that if the parameter identifies a specific entity you should use a path variable. For example, to get all the posts on my blog I request

GET: myserver.com/myblog/posts

to get the post with id = 123, I would request

GET: myserver.com/myblog/posts/123

but to filter my list of posts, and get all posts since Jan 1, 2013, I would request

GET: myserver.com/myblog/posts?since=2013-01-01

In the first example "posts" identifies a specific entity (the entire collection of blog posts). In the second example, "123" also represents a specific entity (a single blog post). But in the last example, the parameter "since=2013-01-01" is a request to filter the posts collection not a specific entity. Pagination and ordering would be another good example, i.e.

GET: myserver.com/myblog/posts?page=2&order=backward

Hope that helps. :-)

I personally used the approach of "if it makes sense for the user to bookmark a URLwhich includes these parameters then use PathParam".

For instance, if the URL for a user profile includes some profile id parameter, since this can be bookmarked by the user and/or emailed around, I would include that profile id as a path parameter. Also, another considerent to this is that the page denoted by the URL which includes the path param doesn't change -- the user will set up his/her profile, save it, and then unlikely to change that much from there on; this means webcrawlers/search engines/browsers/etc can cache this page nicely based on the path.

If a parameter passed in the URL is likely to change the page layout/content then I'd use that as a queryparam. For instance, if the profile URL supports a parameter which specifies whether to show the user email or not, I would consider that to be a query param. (I know, arguably, you could say that the &noemail=1 or whatever parameter it is can be used as a path param and generates 2 separate pages -- one with the email on it, one without it -- but logically that's not the case: it is still the same page with or without certain attributes shown.

Hope this helps -- I appreciate the explanation might be a bit fuzzy :)

You can use query parameters for filtering and path parameters for grouping. The following link has good info on this When to use pathParams or QueryParams

It's a very interesting question.

You can use both of them, there's not any strict rule about this subject, but using URI path variables has some advantages:

• Cache: Most of the web cache services on the internet don't cache GET request when they contains query parameters. They do that because there are a lot of RPC systems using GET requests to change data in the server (fail!! Get must be a safe method)

But if you use path variables, all of this services can cache your GET requests.

• Hierarchy: The path variables can represent hierarchy: /City/Street/Place

It gives the user more information about the structure of the data.

But if your data doesn't have any hierarchy relation you can still use Path variables, using comma or semi-colon:

/City/longitude,latitude

As a rule, use comma when the ordering of the parameters matter, use semi-colon when the ordering doesn't matter:

/IconGenerator/red;blue;green

Apart of those reasons, there are some cases when it's very common to use query string variables:

• When you need the browser to automatically put HTML form variables into the URI
• When you are dealing with algorithm. For example the google engine use query strings:

http:// www.google.com/search?q=rest

To sum up, there's not any strong reason to use one of this methods but whenever you can, use URI variables.

From Wikipedia: Uniform Resource Locator

A path, which contains data, usually organized in hierarchical form, that appears as a sequence of segments separated by slashes.

An optional query, separated from the preceding part by a question mark (?), containing a query string of non-hierarchical data.

— According with the conceptual design of the URL, we might implement a PathParam for hierarchical data/directives/locator components, or implement a QueryParam when the data are not hierarchical. This makes sense because paths are naturally ordered, whereas queries contain variables which may be ordered arbitrarily (unordered variable/value pairs).

A previous commenter wrote,

> I think that if the parameter identifies a specific entity you should use a path variable.

Another wrote,

> Use @PathParam for retrieval based on id. User @QueryParam for filter or if you have any fixed list of options that user can pass.

Another,

> I'd recommend putting any required parameters in the path, and any optional parameters should certainly be query string parameters.

— However, one might implement a flexible, non-hierarchical system for identifying specific entities! One might have multiple unique indexes on an SQL table, and allow entities to be identified using any combination of fields that comprise a unique index! Different combinations (perhaps also ordered differently), might be used for links from various related entities (referrers). In this case, we might be dealing with non-hierarchical data, used to identify individual entities — or in other cases, might only specify certain variables/fields — certain components of unique indexes — and retrieve a list/set of records. In such cases, it might be easier, more logical and reasonable to implement the URLs as QueryParams!

Could a long hexadecimal string dilute/diminish the value of keywords in the rest of the path? It might be worth considering the potential SEO implications of placing variables/values in the path, or in the query, and the human-interface implications of whether we want users to be able to traverse/explore the hierarchy of URLs by editing the contents of the address bar. My 404 Not Found page uses SSI variables to automatically redirect broken URLs to their parent! Search robots might also traverse the path hierarchy. On the other hand, personally, when I share URLs on social media, I manually strip out any private unique identifiers — typically by truncating the query from the URL, leaving only the path: in this case, there is some utility in placing unique identifiers in the path rather than in the query. Whether we want to facilitate the use of path components as a crude user-interface, perhaps depends on whether the data/components are human-readable or not. The question of human-readability relates somewhat to the question of hierarchy: often, data that may be expressed as human-readable keywords are also hierarchical; while hierarchical data may often be expressed as human-readable keywords. (Search engines themselves might be defined as augmenting the use of URLs as a user-interface.) Hierarchies of keywords or directives might not be strictly ordered, but they are usually close enough that we can cover alternative cases in the path, and label one option as the "canonical" case.

There are fundamentally several kinds of questions we might answer with the URL for each request:

1. What kind of record/ thing are we requesting/ serving?
2. Which one(s) are we interested in?
3. How do we want to present the information/ records?

Q1 is almost certainly best covered by the path, or by PathParams. Q3 (which is probably controlled via a set of arbitrarily ordered optional parameters and default values); is almost certainly best covered by QueryParams. Q2: It depends…

Before talking about QueryParam & PathParam. Let's first understand the URL & its components. URL consists of endpoint + resource + queryParam/ PathParam.

For Example,

URL: https://app.orderservice.com/order?order=12345678

or

URL: https://app.orderservice.com/orders/12345678

where

endpoint: https://app.orderservice.com

resource: orders

queryParam: order=12345678

PathParam: 12345678

@QueryParam:

QueryParam is used when the requirement is to filter the request based on certain criteria/criterias. The criteria is specified with ? after the resource in URL. Multiple filter criterias can be specified in the queryParam by using & symbol.

For Example:

> https://app.orderservice.com/orders?order=12345678 & customername=X

@PathParam:

PathParam is used when the requirement is to select the particular order based on guid/id. PathParam is the part of the resource in URL.

For Example:

> https://app.orderservice.com/orders/12345678

PATH PARAMETER - Path Parameter is a variable in URL path that helps to point some specific resource.

Example - https://sitename.com/questions/115

Here, if 115 is a path parameter it can be changed with other valid number to fetch/point to some other resource on the same application.

QUERY PARAMETER - Query Parameters are variables in URL path that filter some particular resources from the list.

Example - https://sitename.com/questions/115?qp1=val1&qp2=val2&qp3=val3

Here qp1, qp2 and qp3 are Query Variables with their values as val1, val2 and val3. These can be used to apply as filters while fetching/saving our data. Query variables are always appended in URL after a question Mark(?).

As theon noted, REST is not a standard. However, if you are looking to implement a standards based URI convention, you might consider the oData URI convention. Ver 4 has been approved as an OASIS standard and libraries exists for oData for various languages including Java via Apache Olingo. Don't let the fact that it's a spawn from Microsoft put you off since it's gained support from other industry player's as well, which include Red Hat, Citrix, IBM, Blackberry, Drupal, Netflix Facebook and SAP

More adopters are listed here

You can support both query parameters and path parameters, e.g., in the case of aggregation of resources -- when the collection of sub-resources makes sense on its own.

/departments/{id}/employees
/employees?dept=id

Query parameters can support hierarchical and non-hierarchical subsetting; path parameters are hierarchical only.

Resources can exhibit multiple hierarchies. Support short paths if you will be querying broad sub-collections that cross hierarchical boundaries.

/inventory?make=toyota&model=corolla
/inventory?year=2014

Use query parameters to combine orthogonal hierarchies.

/inventory/makes/toyota/models/corolla?year=2014
/inventory/years/2014?make=toyota&model=corolla
/inventory?make=toyota&model=corolla&year=2014

Use only path parameters in the case of composition -- when a resource doesn't make sense divorced from its parent, and the global collection of all children is not a useful resource in itself.

/words/{id}/definitions
/definitions?word=id   // not useful

The reason is actually very simple. When using a query parameter you can take in characters such as "/" and your client does not need to html encode them. There are other reasons but that is a simple example. As for when to use a path variable. I would say whenever you are dealing with ids or if the path variable is a direction for a query.

I am giving one exapmle to undersand when do we use @Queryparam and @pathparam

For example I am taking one resouce is carResource class

If you want to make the inputs of your resouce method manadatory then use the param type as @pathaparam, if the inputs of your resource method should be optional then keep that param type as @QueryParam param

@Path("/car")
class CarResource
{
	@Get
	@produces("text/plain")
	@Path("/search/{carmodel}")
	public String getCarSearch(@PathParam("carmodel")String model,@QueryParam("carcolor")String color) {
		//logic for getting cars based on carmodel and color
			-----
		return cars
	}
}

For this resouce pass the request

req uri ://address:2020/carWeb/car/search/swift?carcolor=red

If you give req like this the resouce will gives the based car model and color

 req uri://address:2020/carWeb/car/search/swift

If you give req like this the resoce method will display only swift model based car

req://address:2020/carWeb/car/search?carcolor=red

If you give like this we will get ResourceNotFound exception because in the car resouce class I declared carmodel as @pathPram that is you must and should give the carmodel as reQ uri otherwise it will not pass the req to resouce but if you don't pass the color also it will pass the req to resource why because the color is @quetyParam it is optional in req.

1. @QueryParam can be conveniently used with the Default Value annotation so that you can avoid a null pointer exception if no query parameter is passed.

When you want to parse query parameters from a GET request, you can simply define respective parameter to the method that will handle the GET request and annotate them with @QueryParam annotation

2. @PathParam extracts the URI values and matches to @Path. And hence gets the input parameter. 2.1 @PathParam can be more than one and is set to methods arguments

    @Path("/rest")
    public class Abc {
   
        @GET
        @Path("/msg/{p0}/{p1}")
        @Produces("text/plain")
        public String add(@PathParam("p0") Integer param1, @PathParam("p1")  Integer param2 )
        {
    	    return String.valueOf(param1+param2);
        }
    } 
   

In the above example,
http://localhost:8080/Restr/rest/msg/{p0}/{p1},
p0 matches param1 and p1 matches param2. So for the URI
http://localhost:8080/Restr/rest/msg/4/6,
we get the result 10.

In REST Service, JAX-RS provides @QueryParam and @FormParam both for accepting data from HTTP request. An HTTP form can be submitted by different methods like GET and POST.

@QueryParam : Accepts GET request and reads data from query string.

@FormParam: Accepts POST request and fetches data from HTML form or any request of the media

In nutshell,

@Pathparam works for value passing through both Resources and Query String

• /user/1
• /user?id=1

@Queryparam works for value passing only Query String

• /user?id=1

For resource names and IDs, I use @PathParams. For optional variables, I use @QueryParams

As per my understanding:

1. Use @PathParam - when it is a mandatory item such as an Id

   GET /balloon/{id}

2. Use @QueryParam - when you have the exact resource but need to filter that on some optional traits such as color, size, etc.

   GET /balloon/123?color=red&size=large