Retrofit — Multiple Query Parameters of Same Name
original source: https://futurestud.io/tutorials/retrofit-multiple-query-parameters-of-same-name
Query Parameters
Query parameters are a common way to pass data from clients to servers. We all know them for requests. Let’s face the example below which requests a specific task with id=123 from our example API.
https://api.example.com/tasks?id=123
The response from example API is only a single task with id=123.
The Retrofit method definition for query parameters is straight forward.
Retrofit 2
public interface TaskService {
@GET("/tasks")
Call<Task> getTask(@Query("id") long taskId);
}
Retrofit 1.9
public interface TaskService {
@GET("/tasks")
Task getTask(@Query("id") long taskId);
}
The method getTask(…) requires the parameter taskId. This parameter will be mapped by Retrofit to given @Query() parameter name. In this case the parameter name is id which will result in a final request url part like
/tasks?id=<taskId>
Multiple Query Parameters
Some use cases require to pass multiple query parameters of the same name. Regarding the previous example of requesting tasks from an API, we can extend the query parameter to accept a list with multiple task ids.
The request url we want to create should look like
https://api.example.com/tasks?id=123&id=124&id=125
The expected server response should be a list of tasks with the given ids=[123, 124, 125] from url query parameters.
The Retrofit method to perform requests with multiple query parameters of the same name is done by providing a list of ids as a parameter. Retrofit concatenates the given list to multiple query parameters of same name.
Retrofit 2
public interface TaskService {
@GET("/tasks")
Call<List<Task>> getTask(@Query("id") List<Long> taskIds);
}
Retrofit 1.9
public interface TaskService {
@GET("/tasks")
List<Task> getTask(@Query("id") List<Long> taskIds);
}
The resulting request url will look like the example above in the beginning of this section (Multiple Query Parameters).
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