How to write multiple messages in one protobuf file?

Take the google's tutorial for examples:

message Person {
  required string name = 1;
  required int32 id = 2;
  optional string email = 3;

  enum PhoneType {
    MOBILE = 0;
    HOME = 1;
    WORK = 2;
  }

  message PhoneNumber {
    required string number = 1;
    optional PhoneType type = 2 [default = HOME];
  }

  repeated PhoneNumber phone = 4;
}

message AddressBook {
  repeated Person person = 1;
}

It uses an AddressBook wrapper message as storing multiple Person messages. If I serialize or deserialize it I use methods like AddressBook.mergeFrom(FileInputStream) addressBook.build.().writeTo()

but it will obviously overflow if I have 20 million Person records. And also google says if I want to store multiple messages in one file without using the wrapper message I need to record each message's length, which is not possible for string types.

Is there a good way to serialize a large amount of messages in one file? And I am using Java by the way.

Jon Skeet
people
quotationmark

I haven't tried this, but I'd expect it to work:

Writing:

CodedOutputStream output = CodedOutputStream.newInstance(...);

while (...) {
    Person person = ...;
    output.writeMessageNoTag(person);
}

Reading:

CodedInputStream input = CodedInputStream.newInstance(...);
while (!input.isAtEnd()) {
    Person.Builder builder = Person.newBuilder();
    input.readMessage(builder, null); // Or specify extension registry
    Person person = builder.build();
    // Use person
}

people

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