moshi自定义限定符批注仅在一个属性上序列化null [英] moshi custom qualifier annotation to serialise null on one property only
问题描述
我只想为要进行PUT的JSON正文中的一个属性序列化null.我不想为对象中的任何其他类型序列化null.模型类就是这样
I'd like to serialise null for only one property in my JSON body that is going on a PUT. I don't want to serialize null for any other types in the object. Model class is like this
@Parcel
class User @ParcelConstructor constructor(var college: College?,
var firstname: String?,
var lastname: String?,
var email: String?,
var active: Boolean = true,
var updatedAt: String?,
var gender: String?,
var picture: String?,
var id: String?,
@field: [CollegeField] var collegeInput: String?,
@field: [CollegeField] var otherCollege: String?,)
如果它们中的任何一个为null,我只想序列化CollegeInput和otherCollege字段.例如
I only want to serialise collegeInput and otherCollege fields if either of them are null. For example
val user = User(firstname = "foo", lastname=null, collegeInput="abcd", otherCollege = null)
Json看起来像这样:
Json will look something like this:
{"user":{
"firstname": "foo",
"collegeInput": "abcd",
"otherCollege": null
}}
otherCollege为null的情况下,对象会省略姓氏,因为默认情况下,moshi不会序列化我想要的null,但是应将qualifer字段序列化为null值
Where otherCollege is null, lastname is omitted from the object as by default moshi does not serialise nulls which is what I want, but qualifer fields should be serialized with null values
我尝试使用
class UserAdapter {
@FromJson
@CollegeField
@Throws(Exception::class)
fun fromJson(reader: JsonReader): String? {
return when (reader.peek()) {
JsonReader.Token.NULL ->
reader.nextNull()
JsonReader.Token.STRING -> reader.nextString()
else -> {
reader.skipValue() // or throw
null
}
}
}
@ToJson
@Throws(IOException::class)
fun toJson(@CollegeField b: String?): String? {
return b
}
@Retention(AnnotationRetention.RUNTIME)
@JsonQualifier
annotation class CollegeField
我将适配器添加到了moshi,但是它从未被调用
I added the adapter to moshi but it never gets called
@Provides
@Singleton
fun provideMoshi(): Moshi {
return Moshi.Builder()
.add(UserAdapter())
.build()
}
@Provides
@Singleton
fun provideRetrofit(client: OkHttpClient, moshi: Moshi, apiConfig: ApiConfig): Retrofit {
return Retrofit.Builder()
.baseUrl(apiConfig.baseUrl)
.client(client)
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.addConverterFactory(ScalarsConverterFactory.create())
.addConverterFactory(MoshiConverterFactory.create(moshi))
.build()
}
推荐答案
当限定的字符串值为null时,您的toJson适配器方法将返回null,并且JsonWriter不会写入该null值.
Your toJson adapter method will return null when the qualified string value is null, and the JsonWriter will not write the null value.
这里是要安装的限定符和适配器工厂.
Here is a qualifier and adapter factory to install that will work.
@Retention(RUNTIME)
@JsonQualifier
public @interface SerializeNulls {
JsonAdapter.Factory JSON_ADAPTER_FACTORY = new JsonAdapter.Factory() {
@Nullable @Override
public JsonAdapter<?> create(Type type, Set<? extends Annotation> annotations, Moshi moshi) {
Set<? extends Annotation> nextAnnotations =
Types.nextAnnotations(annotations, SerializeNulls.class);
if (nextAnnotations == null) {
return null;
}
return moshi.nextAdapter(this, type, nextAnnotations).serializeNulls();
}
};
}
现在,以下内容将通过.
Now, the following will pass.
class User(
var firstname: String?,
var lastname: String?,
@SerializeNulls var collegeInput: String?,
@SerializeNulls var otherCollege: String?
)
@Test fun serializeNullsQualifier() {
val moshi = Moshi.Builder()
.add(SerializeNulls.JSON_ADAPTER_FACTORY)
.add(KotlinJsonAdapterFactory())
.build()
val userAdapter = moshi.adapter(User::class.java)
val user = User(
firstname = "foo",
lastname = null,
collegeInput = "abcd",
otherCollege = null
)
assertThat(
userAdapter.toJson(user)
).isEqualTo(
"""{"firstname":"foo","collegeInput":"abcd","otherCollege":null}"""
)
}
请注意,您应该使用 Moshi中的Kotlin支持,以避免@field:
奇怪.
Note that you should use the Kotlin support in Moshi to avoid the @field:
oddities.
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