如何使用 Gson @SerializedName 注释在 Kotlin 中反序列化嵌套的 Json API 响应

Posted 2023-03-22

【中文标题】如何使用 Gson @SerializedName 注释在 Kotlin 中反序列化嵌套的 Json API 响应

【英文标题】：How to deserialize nested Json API response in Kotlin using Gson @SerializedName annotations

【发布时间】：2022-01-13 15:10:35

【问题描述】：

我正在将一个项目迁移到一个新的 API，因此必须更新反序列化和数据类。使用旧 API 和数据类一切正常，但使用更新版本我得到 以下错误

java.lang.ClassNotFoundException: Didn't find class "fooapp.component.ui.cafeteria.model.CafeteriaData" on path: DexPathList[[zip file "/data/app/~~Wji9DkrkAr7qFGIIJ3Aglg==/fooapp-dbYvbr8le25I8FGioIrW6w==/base.apk"],nativeLibraryDirectories=[/data/app/~~Wji9DkrkAr7qFGIIJ3Aglg==/fooapp-dbYvbr8le25I8FGioIrW6w==/lib/x86_64, /system/lib64, /system_ext/lib64]]

尝试访问嵌套字段时，例如：

response.cafeterias[0]

请注意，response.cafeterias 已正确解析且可访问。因此看起来 解析适用于嵌套级别 1，但不知何故 在进入下一级。

我知道映射中缺少 prices 字段，现在不需要它。明天我会检查将其添加到序列化层次结构中是否可以解决问题。

到目前为止我所尝试的

使缓存失效并重新启动 清理和重建项目 Disabling Hot swapping 获取一个小样本 JSON 并直接解析它，而不是让 GSON 在后台解析它 涉及的数据类中的字段的 val 和 var

示例 JSON

"canteens": [
    
        "version": "2.1",
        "canteen_id": "best-canteen",
        "weeks": [
            
                "number": 48,
                "year": 2021,
                "days": [
                    
                        "date": "2021-11-29",
                        "dishes": [
                            
                                "name": "Tasty food 1",
                                "prices": 
                                    "students": 
                                        "base_price": 0,
                                        "price_per_unit": 0.33,
                                        "unit": "100g"
                                    ,
                                    "staff": 
                                        "base_price": 0,
                                        "price_per_unit": 0.55,
                                        "unit": "100g"
                                    ,
                                    "guests": 
                                        "base_price": 0,
                                        "price_per_unit": 0.66,
                                        "unit": "100g"
                                    
                                ,
                                "ingredients": [
                                    "Gl",
                                    "GlW",
                                    "Kn"
                                ],
                                "dish_type": "Daily 4"
                            ]
                    ]
            ]
    ]

Proguard 规则

proguard-gson.pro

## GSON 2.2.4 specific rules ##

# Gson uses generic type information stored in a class file when working with fields. Proguard
# removes such information by default, so configure it to keep all of it.
-keepattributes Signature

# For using GSON @Expose annotation
-keepattributes *Annotation*

-keepattributes EnclosingMethod

# Gson specific classes
-keep class sun.misc.Unsafe  *; 
-keep class com.google.gson.stream.**  *; 

proguard-square-okhttp.pro

# OkHttp
-keepattributes Signature
-keepattributes *Annotation*
-keep class com.squareup.okhttp.**  *; 
-keep interface com.squareup.okhttp.**  *; 
-dontwarn com.squareup.okhttp.**

proguard-square-okhttp3.pro

# OkHttp
-keepattributes Signature
-keepattributes *Annotation*
-keep class okhttp3.**  *; 
-keep interface okhttp3.**  *; 
-dontwarn okhttp3.**

proguard-square-retrofit.pro

# Retrofit 1.X

-keep class com.squareup.okhttp.**  *; 
-keep class retrofit.**  *; 
-keep interface com.squareup.okhttp.**  *; 

-dontwarn com.squareup.okhttp.**
-dontwarn okio.**
-dontwarn retrofit.**
-dontwarn rx.**

-keepclasseswithmembers class * 
    @retrofit.http.* <methods>;


# If in your rest service interface you use methods with Callback argument.
-keepattributes Exceptions

# If your rest service methods throw custom exceptions, because you've defined an ErrorHandler.
-keepattributes Signature

# Also you must note that if you are using GSON for conversion from JSON to POJO representation, you must ignore those POJO classes from being obfuscated.
# Here include the POJO's that have you have created for mapping JSON response to POJO for example.

proguard-square-retrofit2.pro

# Retrofit 2.X
## https://square.github.io/retrofit/ ##

-dontwarn retrofit2.**
-keep class retrofit2.**  *; 
-keepattributes Signature
-keepattributes Exceptions

-keepclasseswithmembers class * 
    @retrofit2.http.* <methods>;

proguard-guava.pro

# Configuration for Guava 18.0
#
# disagrees with instructions provided by Guava project: https://code.google.com/p/guava-libraries/wiki/UsingProGuardWithGuava

-keep class com.google.common.io.Resources 
    public static <methods>;

-keep class com.google.common.collect.Lists 
    public static ** reverse(**);

-keep class com.google.common.base.Charsets 
    public static <fields>;


-keep class com.google.common.base.Joiner 
    public static com.google.common.base.Joiner on(java.lang.String);
    public ** join(...);


-keep class com.google.common.collect.MapMakerInternalMap$ReferenceEntry
-keep class com.google.common.cache.LocalCache$ReferenceEntry

# http://***.com/questions/9120338/proguard-configuration-for-guava-with-obfuscation-and-optimization
-dontwarn javax.annotation.**
-dontwarn javax.inject.**
-dontwarn sun.misc.Unsafe

# Guava 19.0
-dontwarn java.lang.ClassValue
-dontwarn com.google.j2objc.annotations.Weak
-dontwarn org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement

# Guava 20.0
-dontwarn com.google.**

# Guava 23.5
-dontwarn afu.org.checkerframework.**
-dontwarn org.checkerframework.** 

proguard-project-rules.pro

# Add project specific ProGuard rules here.
#
# For more details, see
#   http://developer.android.com/guide/developing/tools/proguard.html

-dontobfuscate

-keep class fooapp.models.***;

proguard-simple-xml.pro

# Simple-Xml Proguard Config
# NOTE: You should also include the Android Proguard config found with the build tools:
# $ANDROID_HOME/tools/proguard/proguard-android.txt

# Keep public classes and methods.
-dontwarn com.bea.xml.stream.**
-dontwarn org.simpleframework.xml.stream.**
-keep class org.simpleframework.xml.** *; 
-keepclassmembers,allowobfuscation class * 
    @org.simpleframework.xml.* <fields>;
    @org.simpleframework.xml.* <init>(...);

proguard-sqlite.pro

-keep class org.sqlite.**  *; 
-keep class org.sqlite.database.**  *; 

proguard-square-okio.pro

# Okio
-keep class sun.misc.Unsafe  *; 
-dontwarn java.nio.file.*
-dontwarn org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement
-dontwarn okio.**

proguard-tikxml.pro

-keep class com.tickaroo.tikxml.**  *; 
-keep class **$$TypeAdapter  *; 

-keepclasseswithmembernames class * 
    @com.tickaroo.tikxml.* <fields>;


-keepclasseswithmembernames class * 
    @com.tickaroo.tikxml.* <methods>;

数据类

自助餐厅响应

data class CafeteriaResponse(
    @SerializedName("canteens")
    var cafeterias: List<CafeteriaData>,
)

自助餐厅数据

data class CafeteriaData(
        @SerializedName("version")
        var version: String? = null,
        @SerializedName("canteen_id")
        var cafeteriaSlug: String? = null,
        @SerializedName("weeks")
        var menusByWeeks: List<WeeklyMenu>
)

每周菜单

data class WeeklyMenu(
        @SerializedName("number")
        var weekOfYear: Short = -1,
        @SerializedName("year")
        var year: Short = -1,
        @SerializedName("days")
        var dishesForWeek: List<DailyMenu>
)

每日菜单

data class DailyMenu(
        @SerializedName("date")
        var date: DateTime? = null,
        @SerializedName("dishes")
        var dishesForDay: List<Dish>
)

菜

data class Dish(
        @SerializedName("name")
        var name: String? = null,
        @SerializedName("ingredients")
        var ingredients: List<String>,
        @SerializedName("dish_type")
        var type: String? = null
)

所有这些数据类都在同一个包中。

【问题讨论】：

是否在构建中启用了 Proguard？我认为不知何故该类在运行时丢失。

是的，该项目在其构建中使用了 proguard。如果我也提供 gradle buildscripts 会有帮助吗？

请发布您的 proguard 规则。

还有 4 个文件用于 appcompat 和 google play 服务，但这些文件似乎与此问题无关，如果您认为它们可能相关，请告诉我，我会再次更新。顺便说一句，谢谢您的帮助。

我已经尝试在禁用 proguard 的情况下运行该应用程序，并且肯定可以这样运行。所以它似乎确实与proguard有关。

【参考方案1】：

问题

proguard-square-retrofit.pro 需要更新，包括用于 API 数据反序列化的新 POJO。

解决方案

我将所有 POJO 添加到以下 proguard 规则集。我将它们全部放在一个单独的包中，以获得更精细的混淆粒度并避免保留不必要的类。

更新了 proguard-square-retrofit.pro

# Retrofit 1.X

-keep class com.squareup.okhttp.**  *; 
-keep class retrofit.**  *; 
-keep interface com.squareup.okhttp.**  *; 

-dontwarn com.squareup.okhttp.**
-dontwarn okio.**
-dontwarn retrofit.**
-dontwarn rx.**

-keepclasseswithmembers class * 
    @retrofit.http.* <methods>;


# If in your rest service interface you use methods with Callback argument.
-keepattributes Exceptions

# If your rest service methods throw custom exceptions, because you've defined an ErrorHandler.
-keepattributes Signature

# Also you must note that if you are using GSON for conversion from JSON to POJO representation, you must ignore those POJO classes from being obfuscated.
# Here include the POJO's that have you have created for mapping JSON response to POJO for example.
-keep class fooapp.component.ui.cafeteria.model.deserialization.*

【讨论】：

我建议你使用@Keep注解而不是手动添加proguard条目。从长远来看，这将对您有所帮助，因为有时很容易错过这些规则。