Swagger documentation for Spring Pageable interface - json

Question

I have developed a microservice using Spring Boot. The documentation for the REST API is made with Swagger. Some REST resources make use of Spring concepts to provide pagination for free. Below is an example:
#RequestMapping(value = "/buckets", method = GET)
public PagedResources list(Pageable pageable, PagedResourcesAssembler assembler) {
return bucketService.listBuckets(pageable, assembler);
}
If I open the Swagger page, the following form is available for the resource:
The issue I have is that the pageable parameter is detected with content-type application/json and I don't know how to pass a value to change the page size for example. All values seem to be ignored.
Is it possible to pass the query parameters as JSON object? or is it possible to configure Swagger to generate independent query parameter fields for getters contained by the Pageable interface?
Please note that I am using Springfox with Gradle:
compile 'io.springfox:springfox-spring-web:2.3.1'
compile 'io.springfox:springfox-swagger2:2.3.1'
compile 'io.springfox:springfox-swagger-ui:2.3.1'

Answer 1

This is a known issue with Spring-Fox. See Issue #755. Based on zdila's comment 2 at this time alternative is to add #ApiImplicitParams which is not ideal but it does work.
#ApiImplicitParams({
#ApiImplicitParam(name = "page", dataType = "integer", paramType = "query",
value = "Results page you want to retrieve (0..N)"),
#ApiImplicitParam(name = "size", dataType = "integer", paramType = "query",
value = "Number of records per page."),
#ApiImplicitParam(name = "sort", allowMultiple = true, dataType = "string", paramType = "query",
value = "Sorting criteria in the format: property(,asc|desc). " +
"Default sort order is ascending. " +
"Multiple sort criteria are supported.")
})
[
1 https://github.com/springfox/springfox/issues/755
2 https://github.com/springfox/springfox/issues/755#issuecomment-135059871

Answer 2

Building on Vineet Bhatia's answer, you can wrap the solution up in a custom annotation for reusability:
#Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE, ElementType.TYPE })
#Retention(RetentionPolicy.RUNTIME)
#ApiImplicitParams({
#ApiImplicitParam(name = "page", dataType = "int", paramType = "query", value = "Results page you want to retrieve (0..N)"),
#ApiImplicitParam(name = "size", dataType = "int", paramType = "query", value = "Number of records per page."),
#ApiImplicitParam(name = "sort", allowMultiple = true, dataType = "string", paramType = "query", value = "Sorting criteria in the format: property(,asc|desc). "
+ "Default sort order is ascending. " + "Multiple sort criteria are supported.") })
#interface ApiPageable {
}
Which can then be used like so:
#ApiPageable
public Page<Data> getData(Pageable pageRequest) {

Answer 3

Vineet Bhatia's answer with #ApiImplicitParams looks fine. But I faced with situation, when #ApiIgnor and #ApiParam(hidden = true) doesn't work and you can still observe the asembler and pageable params. I fixed this problem by adding next line
docket.ignoredParameterTypes(Pageable.class, PagedResourcesAssembler.class);
to the Docket bean in my SwaggerConfig.

Answer 4

Java example:
Bean:
#Bean
public Docket api() {
return new Docket(DocumentationType.SWAGGER_2)
.select()
.paths(PathSelectors.any())
.build()
.directModelSubstitute(Pageable.class, SwaggerPageable.class);
}
SwaggerPageable:
#Getter
private static class SwaggerPageable {
#ApiParam(value = "Number of records per page", example = "0")
#Nullable
private Integer size;
#ApiParam(value = "Results page you want to retrieve (0..N)", example = "0")
#Nullable
private Integer page;
#ApiParam(value = "Sorting criteria in the format: property(,asc|desc). Default sort order is ascending. Multiple sort criteria are supported.")
#Nullable
private String sort;
}
Swagger:

Answer 5

Here is the version of the annotation that was integrated into springdoc-openapi-data-rest for OpenAPI v3:
#Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
#Retention(RetentionPolicy.RUNTIME)
#Parameter(in = ParameterIn.QUERY
, description = "Zero-based page index (0..N)"
, name = "page"
, content = #Content(schema = #Schema(type = "integer", defaultValue = "0")))
#Parameter(in = ParameterIn.QUERY
, description = "The size of the page to be returned"
, name = "size"
, content = #Content(schema = #Schema(type = "integer", defaultValue = "20")))
#Parameter(in = ParameterIn.QUERY
, description = "Sorting criteria in the format: property(,asc|desc). "
+ "Default sort order is ascending. " + "Multiple sort criteria are supported."
, name = "sort"
, content = #Content(array = #ArraySchema(schema = #Schema(type = "string"))))
public #interface PageableAsQueryParam {
}
See https://springdoc.github.io/springdoc-openapi-demos/faq.html#how-can-i-map-pageable-spring-date-commons-object-to-correct-url-parameter-in-swagger-ui

Answer 6

Open API 3.0 has seamless integration.
For example,
#GetMapping("/filter")
public Page<Employee> filterEmployees(Pageable pageable) {
return repository.getEmployees(pageable);
}
Add springdoc-openapi-data-rest dependency
implementation 'org.springdoc:springdoc-openapi-data-rest:1.5.2'
Note: You may add '#ParameterObject' if you have multiple parameters
public Page<Employee> filterEmployees(#ParameterObject Pageable pageable)

Answer 7

This solution works without the need to annotate every single API method in every single controller. First we create a replacement for Pageable class with the correct property names and descriptions (Kotlin code, you can use a Interface for Java):
data class SwaggerPageable(
#ApiModelProperty("Number of records per page", example = "20")
val size: Int?,
#ApiModelProperty("Results page you want to retrieve (0..N)", example = "0")
val page: Int?,
#ApiModelProperty("Sorting criteria in the format: property(,asc|desc)." +
"Default sort order is ascending. Multiple sort criteria are supported.")
var sort: String?
)
Then in the Swagger config, just add a direct substitute from Pageable to this class (again Kotlin code, but Java should be pretty similar):
#Bean
fun api(): Docket {
return Docket(DocumentationType.SWAGGER_2)
.select()
.paths(PathSelectors.any())
.build()
.directModelSubstitute(Pageable::class.java, SwaggerPageable::class.java)
}
The result looks like this:
The downside is not being able to define the default value in the ApiModelProperty, but this is more than good enough for my project.

Answer 8

Answer of Vineet Bhatia will have validation problem when you are not running on localhost. It will argue for integer parameters that they are not corresponding to json schema.
So I changed integer to string:
#ApiImplicitParams({
#ApiImplicitParam(name = "page", dataType = "string", paramType = "query",
value = "Results page you want to retrieve (0..N)"),
#ApiImplicitParam(name = "size", dataType = "string", paramType = "query",
value = "Number of records per page."),
#ApiImplicitParam(name = "sort", allowMultiple = true, dataType = "string", paramType = "query",
value = "Sorting criteria in the format: property(,asc|desc). " +
"Default sort order is ascending. " +
"Multiple sort criteria are supported.")
})

Answer 9

For people who wants to solve this problem in 2019. This configuration via springfox documentation works fine except you can't set description for parameters.
Code is here.
https://github.com/springfox/springfox/blob/ef1721afc4c910675d9032bee59aea8e75e06d27/springfox-data-rest/src/main/java/springfox/documentation/spring/data/rest/configuration/SpringDataRestConfiguration.java

Answer 10

here is a solution for springdoc-openapi-ui
SpringDocUtils.getConfig()
.replaceWithClass(org.springframework.data.domain.Pageable.class, SwaggerPageable.class);
#Getter
private static class SwaggerPageable {
#ApiParam(value = "Number of records per page", example = "0")
#Nullable
private Integer size;
#ApiParam(value = "Results page you want to retrieve (0..N)", example = "0")
#Nullable
private Integer page;
#ApiParam(value = "Sorting criteria in the format: property(,asc|desc). Default sort order is ascending. Multiple sort criteria are supported.")
#Nullable
private String sort;
}

Answer 11

Answer to validation problem indicated by Evgeny.
Using
#ApiImplicitParams({
#ApiImplicitParam(name = "page", dataType = "int", paramType = "query", value = "Results page you want to retrieve (0..N)"),
#ApiImplicitParam(name = "size", dataType = "int", paramType = "query", value = "Number of records per page."),
#ApiImplicitParam(name = "sort", allowMultiple = true, dataType = "string", paramType = "query", value = "Sorting criteria in the format: property(,asc|desc). "
+ "Default sort order is ascending. " + "Multiple sort criteria are supported.") })
throws an exception:
Illegal DefaultValue for parameter type integer
java.lang.NumberFormatException: For input string: ""
at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:68)
at java.base/java.lang.Long.parseLong(Long.java:709)
at java.base/java.lang.Long.valueOf(Long.java:1151)
at io.swagger.models.parameters.AbstractSerializableParameter.getExample(AbstractSerializableParameter.java:412)
at jdk.internal.reflect.GeneratedMethodAccessor366.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:688)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:119)
at com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serialize(IndexedListSerializer.java:79)
(at least, it does with springfox-swagger2 and springfox-swagger2-ui version 2.9.2)
You can avoid the exception by following Evgeny's answer or by adding default values and example values for the integer parameters:
#ApiImplicitParams({
#ApiImplicitParam(name = "page", dataType = "int", paramType = "query", value = "Results page you want to retrieve (0..N)", defaultValue = "0", example = "2"),
#ApiImplicitParam(name = "size", dataType = "int", paramType = "query", value = "Number of records per page.", defaultValue = "20", example = "10"),
#ApiImplicitParam(name = "sort", allowMultiple = true, dataType = "string", paramType = "query", value = "Sorting criteria in the format: property(,asc|desc). "
+ "Default sort order is ascending. " + "Multiple sort criteria are supported.") })

Answer 12

An update:
Use org.springdoc.core.converters.models.DefaultPageable instead of Pageable. It already has the #ParameterObject which makes it breakdown in to 3 parameters when the Swagger JSON is generated.

Answer 13

Although the solution with the implicit parameters works, it introduces a lot of extra, brittle code. In the end we went with the following solution:
#GetMapping(value = "/")
public HttpEntity<PagedResources<Item>> getItems(
#RequestParam(value = "page", required = false) Integer page,
#RequestParam(value = "size", required = false) Integer size,
PagedResourcesAssembler assembler) {
Page<Item> itemPage = itemService.listItems(PageRequest.of(page, size, Sort.unsorted()));
return new ResponseEntity<>(assembler.toResource(itemPage), HttpStatus.OK);
}
We pass a PageRequest (which implements Pageable) to our service, which returns a Page. (all from org.springframework.data.domain).
The org.springframework.data.web.PagedResourcesAssembler gets injected automagically via the controller method and allows mapping Items to org.springframework.hateoas.PagedResources
We didn't require dynamic sorting so we omitted that; it poses some challenges to add sorting since springfox does not play nice with org.springframework.data.domain.Sort.