SimpleXMLConverter and Retrofit 2.30. Why serialization crashes with ValueRequiredException?

Question

In Android app I'm working with pipeline Retrofit + SimpleXmlConverter to send XMl post requests get XML responses:

@Provides
@AuthorizationScope
Retrofit provideAuthorizationRetrofit(@Named("BASE_CRM_URL") String baseUrl,
                                      OkHttpClient client) {
    return new Retrofit.Builder().baseUrl(baseUrl)
            .addConverterFactory(SimpleXmlConverterFactory.createNonStrict())
            .client(client)
            .build();
}

@Provides
@AuthorizationScope
ApiAuthorizationService provideAuthorizationService(Retrofit retrofit) {
    return retrofit.create(ApiAuthorizationService.class);
}

public interface ApiAuthorizationService {

@POST("/")
Call<CardHolder> searchHolderByPhoneCard(@Body String messageSearchHolders2);
}

In searchHolderByPhoneCard call I send raw String without any headers(my api applies it). The instances of request and response:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Message Action="Search holders 2" Terminal_Type="77" Global_Type="ABC" Unit_ID="1" User_ID="1">
<Include>Holder_Card</Include>
<Item Mode="Clear" />
<Item Mode="Add">
    <Contacts>
        <Phone Value="+79600040318" IsNumber="True" />
    </Contacts>
</Item>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Holders Message_ID="0" IndexFrom="1" IndexTo="1" Count="1" Search_GUID="{5BDE0E0A-2CD4-4B96-AD07-2D4BB5A15409}">
<Holder>
    <Deleted>No</Deleted>
    <Group_ID>1</Group_ID>
    <Group_Name>
        <![CDATA[Владельцы карт "Перец"]]>
    </Group_Name>
    <Division_ID>1</Division_ID>
    <Division_Name>Головное подразделение</Division_Name>
    <Holder_ID>10000000040834</Holder_ID>
    <INN></INN>
    <External_Code></External_Code>
    <Unpay_Type_ID></Unpay_Type_ID>
    <Unpay_Type_Name></Unpay_Type_Name>
    <L_Name>Ермолин</L_Name>
    <F_Name>Павел</F_Name>
    <M_Name>Сергеевич</M_Name>
    <Full_Name>Ермолин Павел Сергеевич</Full_Name>
    <Birth>1992-12-14</Birth>
    <Gender>Male</Gender>
    <Marrital>Unknown</Marrital>
    <Smoke>No</Smoke>
    <Verification>Yes</Verification>
    <Image>No</Image>
    <Language_ID>1049</Language_ID>
    <Language_Name>
        <![CDATA[[RUS] Русский (Россия)]]>
    </Language_Name>
    <Source></Source>
    <Remarks></Remarks>
    <Holders_Cards>
        <Holder_Card>
            <Holder_ID>10000000040834</Holder_ID>
            <Card>
                <Card_Code>900221</Card_Code>
                <Is_Virtual_Card>Yes</Is_Virtual_Card>
                <Is_Confirm_Manager>No</Is_Confirm_Manager>
                <Status>Active</Status>
                <Carrier_Data></Carrier_Data>
                <Offered>2018-08-25</Offered>
                <Expired>2019-08-25</Expired>
                <Group_ID>5</Group_ID>
                <Group_Name>Virtual</Group_Name>
                <Holder_ID>10000000040834</Holder_ID>
                <Owner_ID></Owner_ID>
                <Verification>Yes</Verification>
            </Card>
        </Holder_Card>
    </Holders_Cards>
</Holder>

To parse response I've created non-strict model (I don't have a needy in majority of fields). The code for model:

@Root(name = "Holders", strict = false)
public class CardHolder {

@Attribute(name = "Count")
private int count;

@Element (name = "L_Name", required = false)
@Path("Holder")
private String secondName;

@Element (name = "F_Name", required = false)
@Path("Holder")
private String firstName;

@Element (name = "M_Name", required = false)
@Path("Holder")
private String thirdName;

@Element (name = "Birth", required = false)
@Path("Holder")
private String birth;

@Element (name = "Gender")
@Path("Holder")
private String gender;

@Element(name = "is_Virtual_Card", required = false)
@Path("Holder/Holders_Cards/Holder_Card/Card")
private String isVirtualCard;

public CardHolder() {
}



public int getCount() {
    return count;
}

public void setCount(final int count) {
    this.count = count;
}

public String getIsVirtualCard() {
    return isVirtualCard;
}

public void setIsVirtualCard(final String isVirtualCard) {
    this.isVirtualCard = isVirtualCard;
}

public String getSecondName() {
    return secondName;
}

public void setSecondName(final String secondName) {
    this.secondName = secondName;
}

public String getFirstName() {
    return firstName;
}

public void setFirstName(final String firstName) {
    this.firstName = firstName;
}

public String getThirdName() {
    return thirdName;
}

public void setThirdName(final String thirdName) {
    this.thirdName = thirdName;
}

public String getBirth() {
    return birth;
}

public void setBirth(final String birth) {
    this.birth = birth;
}

public String getGender() {
    return gender;
}

public void setGender(final String gender) {
    this.gender = gender;
}

}

In result, executed api call method throws inside onFailure callback exception with such message:

Caused by: org.simpleframework.xml.core.ValueRequiredException: Unable to satisfy @org.simpleframework.xml.Attribute(empty=, name=Count, required=true) on field 'count' private int

I've read docs about this error and I understand that is related to invalid model structure. But I can't figure out where I'm getting wrong and need your help to fix situation

Answer 1

I have found the solution. The problem is that I was trying to send String raw request as @Body. All "text/plain" requests should be wraped like that:

String requestText = RequestBodyUtil.searchHolderByPhoneCard(phone);
RequestBody requestBody = RequestBody.create(MediaType.parse("text/plain"), requestText);

For this situation it's very usefull to read https://futurestud.io/tutorials/retrofit-2-how-to-send-plain-text-request-body