Why we add Query parameters in Get request?

Question

我对android非常陌生，我正在研究用于网络的Retrofit 2，以发送Get Get we we use Query参数？

Answer 1

Retrofit uses annotations to translate defined keys and values into appropriate format. Using the @Query("key") String value annotation will add a query parameter with name key and the respective string value to the request url (of course you can use other types than string :)).

Actually, there are APIs with endpoints allowing you to pass (optionally) multiple query parameters. You want to avoid a service method declaration like the one below with “endless” options for request parameters:

public interface NewsService() {  
    @GET("/news")
    Call<List<News>> getNews(
            @Query("page") int page,
            @Query("order") String order,
            @Query("author") String author,
            @Query("published_at") Date date,
            …
    );
}

You could call the .getNews service method with null values for each of the parameters to make them optional. Retrofit will ignore null values and don't map them as query parameters. However, there is a better solution to work with complex API endpoints having various options for query parameters. Don't worry, Retrofit got you covered!

You can explore more from the given link below:-

https://futurestud.io/tutorials/retrofit-2-add-multiple-query-parameter-with-querymap

Answer 2

Lets say you have following api to call: https://api.themoviedb.org/3/movie/now_playing/api_key=1

So for you to pass the value for "api_key" dynamically, you should use @Query("api_key") as:

@GET("movie/now_playing")
Call<MovieData> getMovieData(@Query("api_key") String apiKey);

Answer 3

It is not necessary to send Query Parameters with GET requests. It is something related to how the end point is configured on the API you are trying to consume.

While designing APIs especially GET methods certain parameters can be kept optional by specifying them as query parameters.

@GET("location") Response getUser(@QueryParam("name") String name);

can be called by both

/location

/location?name=test

Query Parameter is not merely confined to GET requests. It can be used with other methods too eg, DELETE, etc.

This is a concept related to HTTP methods

Answer 4

So here is a simple way to understand it for those that might want to use Retrofit query. Please check as follows ....

• If you specify @GET("Search?one=5"), then any @Query("two") must be appended using &, producing something like Search?one=5&two=7.
• If you specify @GET("Search"), then the first @Query must be appended using ?, producing something like Search?two=7.
• That's how Retrofit works.

• When you specify @GET("Search?"), Retrofit thinks you already gave some query parameter, and appends more query parameters using &. Remove the ?, and you will get the desired result.

   enter String BASE_URL = "https://api.test.com/"; String API_KEY = "SFSDF24242353434"; @GET("Search") //ie https://api.test.com/Search? Call<Products> getProducts( @Query("one") String one, @Query("two") String two, @Query("key") String key ) 

Result: https://api.test.com/Search?one=Whatever&two=here&key=SFSDF24242353434