How to manage REST API versioning with spring?

Regardless whether versioning can be avoided by doing backwards compatible changes (which might not always possible when you are bound by some corporate guidelines or your API clients are implemented in a buggy way and would break even if they should not) the abstracted requirement is an interesting one:

How can I do a custom request mapping that does arbitrary evaluations of header values from the request without doing the evaluation in the method body?

As described in this SO answer you actually can have the same @RequestMapping and use a different annotation to differentiate during the actual routing that happens during runtime. To do so, you will have to:

Create a new annotation VersionRange. Implement a RequestCondition. Since you will have something like a best-match algorithm you will have to check whether methods annotated with other VersionRange values provide a better match for the current request. Implement a VersionRangeRequestMappingHandlerMapping based on the annotation and request condition (as described in the post How to implement @RequestMapping custom properties ). Configure spring to evaluate your VersionRangeRequestMappingHandlerMapping before using the default RequestMappingHandlerMapping (e.g. by setting its order to 0).

This wouldn't require any hacky replacements of Spring components but uses the Spring configuration and extension mechanisms so it should work even if you update your Spring version (as long as the new version supports these mechanisms).

---

I just created a custom solution. I'm using the @ApiVersion annotation in combination with @RequestMapping annotation inside @Controller classes.

Example:

@Controller
@RequestMapping("x")
@ApiVersion(1)
class MyController {

    @RequestMapping("a")
    void a() {}         // maps to /v1/x/a

    @RequestMapping("b")
    @ApiVersion(2)
    void b() {}         // maps to /v2/x/b

    @RequestMapping("c")
    @ApiVersion({1,3})
    void c() {}         // maps to /v1/x/c
                        //  and to /v3/x/c

}

Implementation:

ApiVersion.java annotation:

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ApiVersion {
    int[] value();
}

ApiVersionRequestMappingHandlerMapping.java (this is mostly copy and paste from RequestMappingHandlerMapping):

public class ApiVersionRequestMappingHandlerMapping extends RequestMappingHandlerMapping {

    private final String prefix;

    public ApiVersionRequestMappingHandlerMapping(String prefix) {
        this.prefix = prefix;
    }

    @Override
    protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
        RequestMappingInfo info = super.getMappingForMethod(method, handlerType);
        if(info == null) return null;

        ApiVersion methodAnnotation = AnnotationUtils.findAnnotation(method, ApiVersion.class);
        if(methodAnnotation != null) {
            RequestCondition<?> methodCondition = getCustomMethodCondition(method);
            // Concatenate our ApiVersion with the usual request mapping
            info = createApiVersionInfo(methodAnnotation, methodCondition).combine(info);
        } else {
            ApiVersion typeAnnotation = AnnotationUtils.findAnnotation(handlerType, ApiVersion.class);
            if(typeAnnotation != null) {
                RequestCondition<?> typeCondition = getCustomTypeCondition(handlerType);
                // Concatenate our ApiVersion with the usual request mapping
                info = createApiVersionInfo(typeAnnotation, typeCondition).combine(info);
            }
        }

        return info;
    }

    private RequestMappingInfo createApiVersionInfo(ApiVersion annotation, RequestCondition<?> customCondition) {
        int[] values = annotation.value();
        String[] patterns = new String[values.length];
        for(int i=0; i<values.length; i++) {
            // Build the URL prefix
            patterns[i] = prefix+values[i]; 
        }

        return new RequestMappingInfo(
                new PatternsRequestCondition(patterns, getUrlPathHelper(), getPathMatcher(), useSuffixPatternMatch(), useTrailingSlashMatch(), getFileExtensions()),
                new RequestMethodsRequestCondition(),
                new ParamsRequestCondition(),
                new HeadersRequestCondition(),
                new ConsumesRequestCondition(),
                new ProducesRequestCondition(),
                customCondition);
    }

}

Injection into WebMvcConfigurationSupport:

public class WebMvcConfig extends WebMvcConfigurationSupport {
    @Override
    public RequestMappingHandlerMapping requestMappingHandlerMapping() {
        return new ApiVersionRequestMappingHandlerMapping("v");
    }
}

---

I have implemented a solution which handles PERFECTLY the problem with rest versioning.

General Speaking there are 3 major approaches for rest versioning:

Path-based approch, in which the client defines the version in URL: http://localhost:9001/api/v1/user http://localhost:9001/api/v2/user

Content-Type header, in which the client defines the version in Accept header: http://localhost:9001/api/v1/user with Accept: application/vnd.app-1.0+json OR application/vnd.app-2.0+json

Custom Header, in which the client defines the version in a custom header.

The problem with the first approach is that if you change the version let's say from v1 -> v2, probably you need to copy-paste the v1 resources that haven't changed to v2 path

The problem with the second approach is that some tools like http://swagger.io/ cannot distinct between operations with same path but different Content-Type (check issue https://github.com/OAI/OpenAPI-Specification/issues/146)

The solution

Since i am working a lot with rest documentation tools, i prefer to use the first approach. My solution handles the problem with the first approach, so you don't need to copy-paste the endpoint to the new version.

Let's say we have v1 and v2 versions for the User controller:

package com.mspapant.example.restVersion.controller;

import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * The user controller.
 *
 * @author : Manos Papantonakos on 19/8/2016.
 */
@Controller
@Api(value = "user", description = "Operations about users")
public class UserController {

    /**
     * Return the user.
     *
     * @return the user
     */
    @ResponseBody
    @RequestMapping(method = RequestMethod.GET, value = "/api/v1/user")
    @ApiOperation(value = "Returns user", notes = "Returns the user", tags = {"GET", "User"})
    public String getUserV1() {
         return "User V1";
    }

    /**
     * Return the user.
     *
     * @return the user
     */
    @ResponseBody
    @RequestMapping(method = RequestMethod.GET, value = "/api/v2/user")
    @ApiOperation(value = "Returns user", notes = "Returns the user", tags = {"GET", "User"})
    public String getUserV2() {
         return "User V2";
    }
 }

The requirement is if i request the v1 for the user resource i have to take the "User V1" repsonse, otherwise if i request the v2, v3 and so on i have to take the "User V2" response.

https://i.stack.imgur.com/pCP7v.png

In order to implement this in spring, we need to override the default RequestMappingHandlerMapping behavior:

package com.mspapant.example.restVersion.conf.mapping;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class VersionRequestMappingHandlerMapping extends RequestMappingHandlerMapping {

    @Value("${server.apiContext}")
    private String apiContext;

    @Value("${server.versionContext}")
    private String versionContext;

    @Override
    protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
        HandlerMethod method = super.lookupHandlerMethod(lookupPath, request);
        if (method == null && lookupPath.contains(getApiAndVersionContext())) {
            String afterAPIURL = lookupPath.substring(lookupPath.indexOf(getApiAndVersionContext()) + getApiAndVersionContext().length());
            String version = afterAPIURL.substring(0, afterAPIURL.indexOf("/"));
            String path = afterAPIURL.substring(version.length() + 1);

            int previousVersion = getPreviousVersion(version);
            if (previousVersion != 0) {
                lookupPath = getApiAndVersionContext() + previousVersion + "/" + path;
                final String lookupFinal = lookupPath;
                return lookupHandlerMethod(lookupPath, new HttpServletRequestWrapper(request) {
                    @Override
                    public String getRequestURI() {
                        return lookupFinal;
                    }

                    @Override
                    public String getServletPath() {
                        return lookupFinal;
                    }});
            }
        }
        return method;
    }

    private String getApiAndVersionContext() {
        return "/" + apiContext + "/" + versionContext;
    }

    private int getPreviousVersion(final String version) {
        return new Integer(version) - 1 ;
    }

}

The implementation reads the version in the URL and asks from spring to resolve the URL .In case this URL does not exists (for example the client requested v3) then we try with v2 and so one until we find the most recent version for the resource.

In order to see the benefits from this implementation, let's say we have two resources: User and Company:

http://localhost:9001/api/v{version}/user
http://localhost:9001/api/v{version}/company

Let's say we made a change in company "contract" that breaks the client. So we implement the http://localhost:9001/api/v2/company and we ask from client to change to v2 instead on v1.

So the new requests from client are:

http://localhost:9001/api/v2/user
http://localhost:9001/api/v2/company

instead of:

http://localhost:9001/api/v1/user
http://localhost:9001/api/v1/company

The best part here is that with this solution the client will get the user information from v1 and company information from v2 without the need to create a new (same) endpoint from user v2!

Rest Documentation As i said before the reason i select the URL-based versioning approach is that some tools like swagger do not document differently the endpoints with the same URL but different content type. With this solution, both endpoints are displayed since have different URL:

https://i.stack.imgur.com/Hbeln.png

GIT

Solution implementation at: https://github.com/mspapant/restVersioningExample/

---

I would still recommend using URL's for versioning because in URLs @RequestMapping supports patterns and path parameters, which format could be specified with regexp.

And to handle client upgrades (which you mentioned in comment) you can use aliases like 'latest'. Or have unversioned version of api which uses latest version (yeah).

Also using path parameters you can implement any complex version handling logic, and if you already want to have ranges, you very well might want something more soon enough.

Here is a couple of examples:

@RequestMapping({
    "/**/public_api/1.1/method",
    "/**/public_api/1.2/method",
})
public void method1(){
}

@RequestMapping({
    "/**/public_api/1.3/method"
    "/**/public_api/latest/method"
    "/**/public_api/method" 
})
public void method2(){
}

@RequestMapping({
    "/**/public_api/1.4/method"
    "/**/public_api/beta/method"
})
public void method2(){
}

//handles all 1.* requests
@RequestMapping({
    "/**/public_api/{version:1\\.\\d+}/method"
})
public void methodManual1(@PathVariable("version") String version){
}

//handles 1.0-1.6 range, but somewhat ugly
@RequestMapping({
    "/**/public_api/{version:1\\.[0123456]?}/method"
})
public void methodManual1(@PathVariable("version") String version){
}

//fully manual version handling
@RequestMapping({
    "/**/public_api/{version}/method"
})
public void methodManual2(@PathVariable("version") String version){
    int[] versionParts = getVersionParts(version);
    //manual handling of versions
}

public int[] getVersionParts(String version){
    try{
        String[] versionParts = version.split("\\.");
        int[] result = new int[versionParts.length];
        for(int i=0;i<versionParts.length;i++){
            result[i] = Integer.parseInt(versionParts[i]);
        }
        return result;
    }catch (Exception ex) {
        return null;
    }
}

Based on the last approach you can actually implement something like what you want.

For example you can have a controller that contains only method stabs with version handling.

In that handling you look (using reflection/AOP/code generation libraries) in some spring service/component or in the same class for method with the same name/signature and required @VersionRange and invoke it passing all parameters.

---

The @RequestMapping annotation supports a headers element that allows you to narrow the matching requests. In particular you can use the Accept header here.

@RequestMapping(headers = {
    "Accept=application/vnd.company.app-1.0+json",
    "Accept=application/vnd.company.app-1.1+json"
})

This isn't exactly what you're describing, since it doesn't directly handle ranges, but the element does support the * wildcard as well as !=. So at least you could get away with using a wildcard for cases where all versions support the endpoint in question, or even all minor versions of a given major version (e.g. 1.*).

I don't think I've actually used this element before (if I have I don't remember), so I'm just going off the documentation at

http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestMapping.html

---

I already tried to version my API using the URI Versioning, like:

/api/v1/orders
/api/v2/orders

But there are some challenges when trying to make this work: how organize your code with different versions? How manage two (or more) versions at the same time? What's the impact when removing some version?

The best alternative that I found was not version the entire API, but control the version on each endpoint. This pattern is called Versioning using Accept header or Versioning through content negotiation:

This approach allows us to version a single resource representation instead of versioning the entire API which gives us a more granular control over versioning. It also creates a smaller footprint in the code base as we don’t have to fork the entire application when creating a new version. Another advantage of this approach is that it doesn’t require implementing URI routing rules introduced by versioning through the URI path.

Implementation on Spring

First, you create a Controller with a produces attribute, that will applied by default on each endpoint inside the same class.

@RestController
@RequestMapping(value = "/api/orders/", produces = "application/vnd.company.etc.v1+json")
public class OrderController {

}

After that, we can imagine a possible scenario where you have two versions (v1 and v2) of an endpoint for "create an order":

@Deprecated
@PostMapping
public ResponseEntity<OrderResponse> createV1(
        @RequestBody OrderRequest orderRequest) {

    OrderResponse response = createOrderService.createOrder(orderRequest);
    return new ResponseEntity<>(response, HttpStatus.CREATED);
}

@PostMapping(
        produces = "application/vnd.company.etc.v2+json",
        consumes = "application/vnd.company.etc.v2+json")
public ResponseEntity<OrderResponseV2> createV2(
        @RequestBody OrderRequestV2 orderRequest) {

    OrderResponse response = createOrderService.createOrder(orderRequest);
    return new ResponseEntity<>(response, HttpStatus.CREATED);
}

Done! Just call each endpoint using the desired Http Header version:

Content-Type: application/vnd.company.etc.v1+json

Or, to call the v2:

Content-Type: application/vnd.company.etc.v2+json

About your worries:

And since not all methods in an API change in the same release, I don't want to go to each of my controllers and change anything for a handler that hasn't changed between versions

As explained, this strategy maintains each Controller and endpoint with his actual version. You only modify the endpoint that have modifications and needs a new version.

And the Swagger?

Setup the Swagger with different versions is also very easy using this strategy. See this answer to more details.

---

What about just using inheritance to model versioning? That is what I'm using in my project and it requires no special spring configuration and gets me exactly what I want.

@RestController
@RequestMapping(value = "/test/1")
@Deprecated
public class Test1 {
...Fields Getters Setters...
    @RequestMapping(method = RequestMethod.GET)
    @Deprecated
    public Test getTest(Long id) {
        return serviceClass.getTestById(id);
    }
    @RequestMapping(method = RequestMethod.PUT)
    public Test getTest(Test test) {
        return serviceClass.updateTest(test);
    }

}

@RestController
@RequestMapping(value = "/test/2")
public class Test2 extends Test1 {
...Fields Getters Setters...
    @Override
    @RequestMapping(method = RequestMethod.GET)
    public Test getTest(Long id) {
        return serviceClass.getAUpdated(id);
    }

    @RequestMapping(method = RequestMethod.DELETE)
    public Test deleteTest(Long id) {
        return serviceClass.deleteTestById(id);
    }
}

This set up allows for little duplication of code and the ability to overwrite methods into new versions of the api with little work. It also saves the need to complicate your source code with version switching logic. If you don't code an endpoint in a version it will grab the previous version by default.

Compared to what others are doing this seems way easier. Is there something I'm missing?

---

In produces you can have negation. So for method1 say produces="!...1.7" and in method2 have the positive.

The produces is also an array so you for method1 you can say produces={"...1.6","!...1.7","...1.8"} etc (accept all except 1.7)

Ofcourse not as ideal as ranges that you have in mind but I think easier to maintain than other custom stuff if this is something uncommon in your system. Good luck!

---

You can use AOP, around interception

Consider having a request mapping which receives all the /**/public_api/* and in this method do nothing;

@RequestMapping({
    "/**/public_api/*"
})
public void method2(Model model){
}

After

@Override
public void around(Method method, Object[] args, Object target)
    throws Throwable {
       // look for the requested version from model parameter, call it desired range
       // check the target object for @VersionRange annotation with reflection and acquire version ranges, call the function if it is in the desired range


}

The only constraint is that all has to be in the same controller.

For AOP configuration have a look at http://www.mkyong.com/spring/spring-aop-examples-advice/

---