如何解决Proguard混淆导致的Jackson反序列化异常？

问题重现 #

开启Proguard混淆后，程序运行时出现Jackson解析异常：

Exception in thread "DefaultDispatcher-worker-2" com.fasterxml.jackson.c.a.S: Instantiation of [simple type, class com.myapp.data.datasource.network.model.Linea] value failed for JSON property p0 due to missing (therefore NULL) value for creator parameter p0 which is a non-nullable type
 at [Source: (okio.RealBufferedSource$inputStream$1); line: 10, column: 1] (through reference chain: java.util.ArrayList[0]->com.myapp.data.datasource.network.model.Linea["p0"])
        at com.fasterxml.jackson.c.a.O.createFromObjectWith(Unknown Source)
        at com.fasterxml.jackson.databind.deser.impl.PropertyBasedCreator.build(Unknown Source)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeUsingPropertyBased(Unknown Source)
        at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(Unknown Source)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(Unknown Source)
        at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(Unknown Source)
        at com.fasterxml.jackson.dataformat.xml.deser.WrapperHandlingDeserializer.deserialize(Unknown Source)
        at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer._deserializeFromArray(Unknown Source)
        at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(Unknown Source)
        at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(Unknown Source)
        at com.fasterxml.jackson.dataformat.xml.deser.XmlDeserializationContext.readRootValue(Unknown Source)
        at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(Unknown Source)
        at com.fasterxml.jackson.databind.ObjectReader.readValue(Unknown Source)
        at retrofit2.converter.jackson.JacksonResponseBodyConverter.convert(Unknown Source)
        at retrofit2.converter.jackson.JacksonResponseBodyConverter.convert(Unknown Source)
        at retrofit2.OkHttpCall.parseResponse(Unknown Source)
        at retrofit2.OkHttpCall$1.onResponse(Unknown Source)
        at okhttp3.internal.connection.RealCall$AsyncCall.run(Unknown Source)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.base/java.lang.Thread.run(Unknown Source)
        Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@32d010be, Dispatchers.IO]

对应的Linea数据类代码：

data class Linea(
    val idLinea: String,
    val nameLinea: String
)

尝试过以下Proguard规则但无效：

-keep class com.myapp.data.datasource.network.model.** { *; }

-keep class com.** { *; }

问题原因 #

Kotlin Data Class的构造函数参数会被Proguard混淆为p0、p1这类无意义名称，而Jackson（尤其是XML解析器）依赖参数名或Kotlin元数据来匹配JSON/XML字段与类属性。之前的规则仅保留了类和成员，但未保护构造函数参数名、Kotlin元数据（@Metadata注解），导致Jackson无法正确识别构造函数的参数对应关系，进而抛出"缺少p0参数"的异常。

正确的Proguard配置方案 #

方案1：针对目标数据类的精准规则 #

直接保留Linea类的构造函数、参数名及必要元数据：

# 保留Linea类的构造函数（参数类型需与原类一致）
-keepclassmembers class com.myapp.data.datasource.network.model.Linea {
    public <init>(java.lang.String, java.lang.String);
}
# 保留类名不被混淆
-keepnames class com.myapp.data.datasource.network.model.Linea
# 保留参数名，供Jackson识别构造参数
-keepattributes ParameterNames
# 保留Kotlin元数据，确保Jackson Kotlin模块能正确解析数据类
-keep class kotlin.Metadata { *; }

方案2：针对整个网络模型包的通用规则 #

如果有多个类似的数据类，可以批量配置：

# 保留网络模型包下所有类的构造函数
-keep class com.myapp.data.datasource.network.model.** {
    <init>(...);
}
# 保留包下所有类名不被混淆
-keepnames class com.myapp.data.datasource.network.model.**
# 保留类成员的getter/setter和字段
-keepclassmembers class com.myapp.data.datasource.network.model.** {
    *** get*();
    void set*(***);
    kotlin.jvm.JvmField *;
}
# 保留Jackson和Kotlin解析所需的属性
-keepattributes Signature, InnerClasses, EnclosingMethod, AnnotationDefault, ParameterNames
-keep class kotlin.Metadata { *; }

规则说明 #

• <init>(...)：保留类的所有构造函数，避免构造函数被混淆或移除
• -keepnames：仅保留类名/成员名不被混淆，不强制保留成员本身
• ParameterNames属性：保留构造函数和方法的参数名，Jackson依赖此匹配字段
• kotlin.Metadata：Kotlin类的元数据注解，Jackson Kotlin模块需要它来识别Data Class的结构
• get*()/set*()：保留属性的访问器，确保Jackson能通过反射读写属性

内容的提问来源于stack exchange，提问作者NullPointerException