使用 google protobuf for Java 的“可选重复”
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'optional repeated' with google protobuf for Java
提问by Harikrishnan
I am using Google Protobuf using java. I wrote a statement like
我正在使用 Java 使用 Google Protobuf。我写了一个声明，如
optional repeated string users = 9;
When I tried to compile I am getting an error like
当我尝试编译时，我收到类似的错误
message.proto:39:57: Missing field number.
All I wanted was to create an array of strings.
我想要的只是创建一个字符串数组。
Can anybody help me to resolve it.
任何人都可以帮我解决它。
PS: If I avoided optional keyword then it is compiling but in java I am getting a class not found error for com.google.protobuf.ProtocolStringList
PS：如果我避免了可选关键字，那么它正在编译，但在 Java 中，我收到了一个找不到类的错误 com.google.protobuf.ProtocolStringList
Thanks in advance
提前致谢
回答by Marc Gravell
All you need is:
所有你需要的是：
repeated string users = 9;
You don't need the optionalmodifier, and it looks like it is confusing the parser. A repeatedfield is inherently optional: you just don't add any values.
您不需要optional修饰符，看起来它使解析器感到困惑。一个repeated领域本质上是optional：你只是不添加任何价值。
As for com.google.protobuf.ProtocolStringList: check that the version of the .proto compiler (protoc) you are using is an exact match for the library version you are using.
至于com.google.protobuf.ProtocolStringList：检查您使用的 .proto 编译器 (protoc) 的版本是否与您使用的库版本完全匹配。
回答by Ted
The generated file contains method for retrieving count. e.g. int getXXXCount(); One issue is that such method wouldn't be available for generated file corresponding to prior versions of the protoc def.
生成的文件包含检索计数的方法。例如 int getXXXCount(); 一个问题是，这种方法不适用于与 protoc def 的先前版本相对应的生成文件。
