com.google.protobuf.GeneratedMessageV3.isStringEmpty should be public

[ochinchina]

Version: v3.19.1
Language: Java
OS: Windows 10

When compiling the protoc 3.19.1 generated java source codes from a .proto file, following error is raised:

 error: cannot find symbol
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(appId_)) {
                                               ^
  symbol:   method isStringEmpty(Object)
  location: class GeneratedMessageV3

After checking the source code of the java class com.google.protobuf.GeneratedMessageV3 and found the method isStringEmpty is defined as protected instead of public.

[elharo]

What file is the error found in? Do you have the complete source code of that file handy?

[ochinchina]

detailed steps for re-produce this bug:

1. download the protoc v3.19.1 from https://github.com/protocolbuffers/protobuf/releases/download/v3.19.1/protoc-3.19.1-linux-x86_64.zip

$ wget https://github.com/protocolbuffers/protobuf/releases/download/v3.19.1/protoc-3.19.1-linux-x86_64.zip

2. unzip the downloaded protoc

$ unzip protoc-3.19.1-linux-x86_64.zip
$ cd protoc-3.19.1

3. compile the following helloworld.proto

syntax = "proto3";

option java_multiple_files = true;
option java_package = "io.grpc.examples.helloworld";
option java_outer_classname = "HelloWorldProto";
option objc_class_prefix = "HLW";

package helloworld;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

with command:

$ mkdir java_output
$ bin/protoc --java_output=java_output helloworld.proto

go to the directory java_output/io/grpc/examples/helloworld and grep the com.google.protobuf.GeneratedMessageV3.isStringEmpty

$ cd java_output/io/grpc/examples/helloworld
$ grep com.google.protobuf.GeneratedMessageV3.isStringEmpty *.java
HelloReply.java:    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(message_)) {
HelloReply.java:    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(message_)) {
HelloRequest.java:    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(name_)) {
HelloRequest.java:    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(name_)) {

The protected method isStringEmpty in class com.google.protobuf.GeneratedMessageV3 is used by class HelloReply and HelloRequest. When trying to compile the above generated source code, we get the error:

 error: cannot find symbol
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(appId_)) {
                                               ^
  symbol:   method isStringEmpty(Object)
  location: class GeneratedMessageV3

[perezd]

Can you confirm you're using the newest runtime when compiling the source code produced by that version of protoc? I think we've seen a similar issue in the past.

[toffentoffen]

I've experienced a similar issue will trying to use the latest version of protoc, protbuf-java and grpc-java to being able to compile the protos in a Mac M1 trough the protobuf maven plugin.

com.google.protobuf.protoc = 3.19.1
protoc-gen-grpc-java.plugin = 1.42.1 (has an internal dependency on protobuf-java = 3.17.2) (does not contain com.google.protobuf.GeneratedMessageV3.isStringEmpty)
protobuf-java = 3.19.1
protobuf-java-util = 3.19.1

The problem is that the latest protoc generates code that depends on function (com.google.protobuf.GeneratedMessageV3.isStringEmpty) that are available from 3.17.3+.

So, as @perezd said, probably your compiling agains an older version of protobuf-java.

So a workaround would be using protoc 3.17.3 as I've mentioned #8062 (comment) and grpc/grpc-java#8724 (where if also asked to upgrade to the latest protobuf 3.19.1 release)

[Tridu33]

protobuf has changed in the new version, and configure work here:

    <dependencies>
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.19.1</version> 
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.xolstice.maven.plugins</groupId>
                <artifactId>protobuf-maven-plugin</artifactId>
                <version>0.5.0</version>
                <extensions>true</extensions>
                <configuration>
                    <protoSourceRoot>${project.basedir}/proto</protoSourceRoot>
                    <outputDirectory>${project.build.sourceDirectory}</outputDirectory>
                    <clearOutputDirectory>true</clearOutputDirectory>
                    <temporaryProtoFileDirectory>
                        ${project.build.directory}/protoc-temp
                    </temporaryProtoFileDirectory>
                    <protocExecutable>
                        D:/arch/myexe/protoc/bin/protoc.exe <!-- libprotoc 3.19.1 -->
                    </protocExecutable>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

[elharo]

Just a = guess: there is no official protobuf maven plugin and the one you're using here is several versions behind what that developer has released. It could be that the old version of this plugin is pulling in older versions of the proto library.

[ricardoseb]

To solve this issue, you must explicitly indicate the version of protobuf-java(3.17.3+), for example in your build.gradle file:
implementation 'com.google.protobuf:protobuf-java:3.19.1'

[gregorypa]

I succeeded to compile protobuf after following instructions from here - https://github.com/grpc/grpc-java

[elharo]

Thanks, good to hear

[EasyG0ing1]

@elharo I've been trying to teach myself how to code and decode protocolbuffers because of a specific need I have to be able to migrate GoogleAuthenticator app exports into an app that I'm writing in Java. My search to learn how to do this led me to this Issue on Github - where the solution was not one that I understood at all ... which started my pursuit to understand how to do this stuff ... that Issue has a .proto file listed as one that will work to accomplish the task. Here is the .proto file:

syntax = "proto3";

message MigrationPayload {
	enum Algorithm {
		ALGORITHM_UNSPECIFIED = 0;
		ALGORITHM_SHA1 = 1;
		ALGORITHM_SHA256 = 2;
		ALGORITHM_SHA512 = 3;
		ALGORITHM_MD5 = 4;
	}
	enum DigitCount {
		DIGIT_COUNT_UNSPECIFIED = 0;
		DIGIT_COUNT_SIX = 1;
		DIGIT_COUNT_EIGHT = 2;
	}
	enum OtpType {
		OTP_TYPE_UNSPECIFIED = 0;
		OTP_TYPE_HOTP = 1;
		OTP_TYPE_TOTP = 2;
	}
	message OtpParameters {
		bytes secret = 1;
		string name = 2;
		string issuer = 3;
		Algorithm algorithm = 4;
		DigitCount digits = 5;
		OtpType type = 6;
		int64 counter = 7;
	}
	repeated OtpParameters otp_parameters = 1;
	int32 version = 2;
	int32 batch_size = 3;
	int32 batch_index = 4;
	int32 batch_id = 5;
}

I then found this tutorial on Google for protocol buffers, which instructed me to download the proto command which ultimately led me here to get the compiled version for MacOS.

I then ran the command and received a generated .java class file which has multiple places in it with these statements in it:

com.google.protobuf.GeneratedMessageV3.isStringEmpty

But 'isStringEmpty' seems to be a reference to something that does not exist...

From where I stand, the proto command that generates the .java class is the point where this is failing as it seems to be inserting code into the class that it generates that makes calls to another class that do not exist.

What I would like to know ... is how do I fix the class that it generated?

This is the dependency that I'm using in my project by the way:

<dependency>
    <groupId>com.google.protobuf</groupId>
    <artifactId>protobuf-java</artifactId>
    <version>3.19.1</version>
</dependency>

Edit:

When I downloaded proto version 3.17.3 from here and re-generated the class from that same .proto file, the resulting class did not contain the call to isStringEmpty and caused no errors while still using dependency version 3.19.1.

[rafaribe]

@elharo I've been trying to teach myself how to code and decode protocolbuffers because of a specific need I have to be able to migrate GoogleAuthenticator app exports into an app that I'm writing in Java. My search to learn how to do this led me to this Issue on Github - where the solution was not one that I understood at all ... which started my pursuit to understand how to do this stuff ... that Issue has a .proto file listed as one that will work to accomplish the task. Here is the .proto file:

syntax = "proto3";

message MigrationPayload {
	enum Algorithm {
		ALGORITHM_UNSPECIFIED = 0;
		ALGORITHM_SHA1 = 1;
		ALGORITHM_SHA256 = 2;
		ALGORITHM_SHA512 = 3;
		ALGORITHM_MD5 = 4;
	}
	enum DigitCount {
		DIGIT_COUNT_UNSPECIFIED = 0;
		DIGIT_COUNT_SIX = 1;
		DIGIT_COUNT_EIGHT = 2;
	}
	enum OtpType {
		OTP_TYPE_UNSPECIFIED = 0;
		OTP_TYPE_HOTP = 1;
		OTP_TYPE_TOTP = 2;
	}
	message OtpParameters {
		bytes secret = 1;
		string name = 2;
		string issuer = 3;
		Algorithm algorithm = 4;
		DigitCount digits = 5;
		OtpType type = 6;
		int64 counter = 7;
	}
	repeated OtpParameters otp_parameters = 1;
	int32 version = 2;
	int32 batch_size = 3;
	int32 batch_index = 4;
	int32 batch_id = 5;
}

I then found this tutorial on Google for protocol buffers, which instructed me to download the proto command which ultimately led me here to get the compiled version for MacOS.

I then ran the command and received a generated .java class file which has multiple places in it with these statements in it:

com.google.protobuf.GeneratedMessageV3.isStringEmpty

But 'isStringEmpty' seems to be a reference to something that does not exist...

From where I stand, the proto command that generates the .java class is the point where this is failing as it seems to be inserting code into the class that it generates that makes calls to another class that do not exist.

What I would like to know ... is how do I fix the class that it generated?

This is the dependency that I'm using in my project by the way:

<dependency>
    <groupId>com.google.protobuf</groupId>
    <artifactId>protobuf-java</artifactId>
    <version>3.19.1</version>
</dependency>

Edit:

When I downloaded proto version 3.17.3 from here and re-generated the class from that same .proto file, the resulting class did not contain the call to isStringEmpty and caused no errors while still using dependency version 3.19.1.

Thanks for your hint. It really helped me solve my issue.
I also tried using 3.19.2 but it didn't solve this problem.

I did the following:

1. Downloaded the proto version 3.17.3 and copied it over to /usr/local/bin/protoc-3.17.3
2. Included this proto version on my plugin settings on pom.xml as follows:

 <plugin>
        <groupId>org.xolstice.maven.plugins</groupId>
        <artifactId>protobuf-maven-plugin</artifactId>
        <extensions>true</extensions>
        <version>${protobuf-plugin.version}</version>
        <configuration>
          <protocArtifact>
            com.google.protobuf:protoc:${protoc.version}:exe:${os.detected.classifier}
          </protocArtifact>
          <pluginId>grpc-java</pluginId>
          <pluginArtifact>
            io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}
          </pluginArtifact>
          <protoSourceRoot>
            src/submodules/grpc/streamm
          </protoSourceRoot>
          <protocExecutable>
            /usr/local/bin/protoc-3.17.3
          </protocExecutable>
        </configuration>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <goal>compile-custom</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

Also since this is still happening, should this issue be reopened or a new issue? @elharo

[elharo]

I do not believe there is a bug here. This is caused by a mismatch between the protoc compiler version and the runtime version.

[rafaribe]

<protocExecutable>
            /usr/local/bin/protoc-3.17.3
</protocExecutable>

Removing this line and adding the 3.17.3 version to the protobuf-java-util solves the issue, however it still doesn't work with any version newer than that.

I do not believe there is a bug here. This is caused by a mismatch between the protoc compiler version and the runtime version.

Can you please elaborate? How can I use version 3.19.2 then?

[ulvimardaliyev]

Grpc was upgraded to 1.44.0 version on 27 Jan 2022 : both grpc-stub and grpc-protobuf. I used 1.43.2 version of grpc and this version solved isStringEmpty error.

grpc-stub in maven repository

[lucas-g-simoes]

Using Spring Boot Starter (https://github.com/yidongnan/grpc-spring-boot-starter) with Spring 2.6.4 I got the same problem, I solved it by fixing the following versions:

<protobuf.version>3.14.0</protobuf.version>
<protobuf-plugin.version>0.6.1</protobuf-plugin.version>
<grpc.version>1.35.0</grpc.version>

[whiskey21]

I got same problem and solved by fixing the following versions:

implementation 'net.devh:grpc-server-spring-boot-starter:2.13.1.RELEASE'
protobufVersion = '3.19.2' protobufPluginVersion = '0.8.18' grpcVersion = '1.43.2'