java - 修改 REST API 响应以仅包含查询参数中请求的字段

Question

我想发送仅包含 GET API 请求字段的响应。减少响应的总大小。

例如，默认行为，何时请求特定字段:

GET /v1/users/

{
   "data" : 
     [
        {
            "name" : "User1",
            "phone" : "800-999-9999",
            "city" : "XYZ1",
            "country" : "PQR1"
        },
        {
            "name" : "User2",
            "phone" : "800-999-9999",
            "city" : "XYZ2",
            "country" : "PQR2"
         }
     ]
}

用例，其中所需的字段作为查询参数传递

GET /v1/users/?fields=name,city

{
   "data" : 
     [
        {
            "name" : "User1",
            "city" : "XYZ1"
        },
        {
            "name" : "User2",
            "city" : "XYZ2"
         }
     ]
}

遇到“https://github.com/monitorjbl/json-view”。但被团队击落。

如何使用 Spring Boot 实现此功能？使用java微服务的组织如何实现此功能？

Answer 1

方法一:将对象转为Map，去掉多余的key，将Map转为Json

@GetMapping("/v1/users")
@ResponseBody
public List<Map> getUsers(@RequestParam(required = false) Set<String> fields) { 
    List<User> users = ...;
    ObjectMapper oMapper = new ObjectMapper();
    return users.stream().map(u -> oMapper.convertValue(u, Map.class))
       .peek(map -> { 
          if (fields != null) map.keySet().retainAll(fields)
       })
       .collect(Collectors.toList());
}

方法二:使用Gson

@GetMapping("/v1/users")
@ResponseBody
public String getUsers(@RequestParam(required = false) Set<String> fields) { 
    List<User> users = ...;
    Gson gson = new GsonBuilder()
            .setExclusionStrategies(new ExclusionStrategy() {
                @Override
                public boolean shouldSkipField(FieldAttributes f) {
                    return f.getDeclaringClass().equals(User.class)
                             && fields != null 
                             && !fields.contains(f.getFieldName())
                            ;
                }

                @Override
                public boolean shouldSkipClass(Class<?> clazz) {
                    return false;
                }
            }).create();
    return gson.toJson(users); 
}

Came across "https://github.com/monitorjbl/json-view". But was shot down by the team.

顺便说一句，Jackson 有 @JsonView 注释支持，但它不允许根据需要动态包含/排除字段。您可以定义字段子集，然后返回这些子集

public class Views {
    public static class Short {
    }
}

public class User {
    @JsonView(Views.Short.class)
    public String city;

    @JsonView(Views.Short.class)
    public String name;

    public String phone;

    public String country;
}

@GetMapping("/v1/users")
@ResponseBody
public String getUsers(@RequestParam(required = false) boolean shortView) { 
    List<User> users = ...;
    ObjectMapper mapper = new ObjectMapper();
    if (shortView) mapper = mapper.writerWithView(Views.Short.class);
    return mapper.writeValueAsString(users);
}