Android应用中Retrofit调用API无法获取帖子问题求助

开发Android社交应用时，使用Retrofit发起API请求获取帖子，请求成功但响应中未返回任何帖子。

API相关信息 #

API端点：https://api.example.com/api/v1/post/post
请求方法：GET
必填参数：page（整数）、size（整数）
请求头：Authorization（包含有效认证令牌）

已确认请求发起正确且请求头包含有效令牌，但响应中无帖子数据。

Android Studio日志 #

2023-07-07 16:21:23.737  I  Auth Token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJqb2huQGdtYWlsLmNvbSIsInJvbGVzIjpbIlVTRVIiXSwiaXNzIjoiL2FwaS92MS9sb2dpbiIsImV4cCI6MTY4ODc0MzI4Mn0.LaYnVqLrUtAG7weC0hk56W7anVt9nWmYet8Zg1lAuOg
2023-07-07 16:21:32.075  I  we should get the posts here retrofit2.OkHttpCall$NoContentResponseBody@df0ef6d
2023-07-07 16:21:32.076  I  number of posts: 0
2023-07-07 16:21:32.076  I  total pages: 0
2023-07-07 16:21:32.076  I  total elements: 3

日志显示返回帖子数为0，但实际存在3条帖子，且Postman请求该API能正常返回包含3条帖子的响应体。

Android端请求代码片段 #

// Make the API call to fetch the list of posts
PostService postService = retrofit.create(PostService.class);
Call<PostPage> call = postService.getAllPosts(authToken,10, 15); // Replace page and size with your desired values
call.enqueue(new Callback<PostPage>() {
    @Override
    public void onResponse(Call<PostPage> call, Response<PostPage> response) {
        System.out.println("we should get the postts here " + response.raw().body().toString());
        System.out.println("header check "  + response.headers());
        if (response.isSuccessful() && response.body()!=null) {
            PostPage postResponse = response.body();
            List<Post> posts = postResponse.getPosts();
            if (posts != null) {
                int totalPages = postResponse.getTotalPages();
                long totalElements = postResponse.getTotalElements();
                System.out.println("number of posts: " + posts.size());
                System.out.println("total pages: " + totalPages);
                System.out.println("total elements: " + totalElements);
                postAdapter.setPostList(posts);
            } else {
                // Handle the case when the 'posts' list is null
                System.out.println("Received null posts list");
            }
        } else {
            // Handle error
            // Handle the login error here
            System.out.println("Something went wrong displaying the post");
            Toast.makeText(MainActivity.this, "Login Error", Toast.LENGTH_SHORT).show();

        }
    }
});

服务器端控制器代码片段 #

@GetMapping("/api/v1/post/post")
public ResponseEntity<PostPage> getAllPost(@RequestParam(defaultValue = "0") int page,
                                           @RequestParam(defaultValue = "10") int size,
                                           @RequestHeader("Authorization") String authorizationHeader) {
    // Extract email from the authorization header and retrieve the user
    // ...

    // Retrieve the posts using the page and size parameters
    Page<Post> post = postService.getAllPost(PageRequest.of(page, size));
    List<Post> posts = post.get().toList();

    // Create a PostPage object and set the necessary fields
    PostPage postPage = new PostPage();
    postPage.setPosts(posts);
    postPage.setTotalPages(post.getTotalPages());
    postPage.setTotalElements(post.getTotalElements());
    postPage.setCurrentPage(post.getNumber());

    return ResponseEntity.ok().body(postPage);
}

排查建议 #

1. 检查分页参数顺序与取值
   你调用getAllPosts(authToken,10,15)时传入的page=10、size=15，但服务器端总共只有3条数据，按每页15条计算仅存在第0页数据，第10页自然无内容。将page参数改为0或1（取决于服务器分页索引规则），比如getAllPosts(authToken,0,15)再测试。同时确认PostService接口中page和size的参数顺序与服务器接收顺序一致。

2. 核对JSON字段映射
   确保PostPage类的字段名与服务器返回的JSON字段完全匹配，若存在字段名不一致情况，需添加@SerializedName注解指定映射关系。另外，PostPage类必须提供无参构造函数，否则Gson无法正常解析响应体。示例：

   public class PostPage {
       @SerializedName("posts") // 若服务器返回字段名不同需修改
       private List<Post> posts;
       private int totalPages;
       private long totalElements;
       private int currentPage;
   
       public PostPage() {} // 必须有无参构造函数
   
       // Getter和Setter方法
       public List<Post> getPosts() { return posts; }
       public void setPosts(List<Post> posts) { this.posts = posts; }
       // 其他Getter/Setter...
   }
   

3. 确认Retrofit转换器配置
   检查Retrofit是否添加了Gson转换器工厂，否则无法解析JSON响应体：

   Retrofit retrofit = new Retrofit.Builder()
       .baseUrl("https://api.example.com/")
       .addConverterFactory(GsonConverterFactory.create())
       .build();
   

4. 抓包验证请求详情
   添加OkHttp日志拦截器查看完整请求与响应内容，确认发送的参数、请求头与Postman一致：

   HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
   logging.setLevel(HttpLoggingInterceptor.Level.BODY);
   OkHttpClient client = new OkHttpClient.Builder()
       .addInterceptor(logging)
       .build();
   
   // 在Retrofit构建中使用该client
   Retrofit retrofit = new Retrofit.Builder()
       .baseUrl("https://api.example.com/")
       .client(client)
       .addConverterFactory(GsonConverterFactory.create())
       .build();
   

内容的提问来源于stack exchange，提问作者ABAB