Protobuf error when compiling Java runtime library

Question

I'm trying to build the Java run time library for Protocol Buffers. I've got errors on both Windows and OS X by following the README instruction under the Java directory in the Protocol Buffers project (which is cloned from https://github.com/google/protobuf).

The following error occured when I ran mvn test in the protobuf/java directory.

Error from OS X

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.8:run (generate-sources) on project protobuf-java: An Ant BuildException has occured: The following error occurred while executing this line:
[ERROR] /Users/wangsa/Work/ProtoBuffer/protobuf/java/core/generate-sources-build.xml:4: Execute failed: java.io.IOException: Cannot run program "/Users/wangsa/Work/ProtoBuffer/protobuf/java/core/../../src/protoc" (in directory "/Users/wangsa/Work/ProtoBuffer/protobuf/java/core"): error=2, No such file or directory

Error from Windows

[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.google.protobuf:protobuf-java:bundle:2.6.1
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 57, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-surefire-plugin is missing. @ line 64, column 15
[WARNING] 'build.plugins.plugin.version' for org.apache.felix:maven-bundle-plugin is missing. @ line 143, column 15
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Protocol Buffer Java API 2.6.1
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-antrun-plugin:1.3:run (generate-sources) @ protobuf-java ---
[INFO] Executing tasks
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.030 s
[INFO] Finished at: 2016-06-07T10:03:48+12:00
[INFO] Final Memory: 11M/245M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.3:run (generate-sources) on project protobuf-java: An Ant BuildException has occured: Execute failed: java.io.IOException: Cannot run program "..\src\protoc": CreateProcess error=2, The system cannot find the file specified -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

More details

• Maven is properly installed (version 3.3.9)
• Java JDK is properly installed (version 1.7 for OS X and 1.8 for Windows)
• Protobuf is properly installed. I'm able to convert .proto file to .java file using the protoc command.
• The version of protobuf is 2.6.1 for both the installed binary and the Java package I'm trying to build.

Can anyone see what might gone wrong?

Edit: Doing this build process is quite new to me, I assume if this process is done successfully, I will get a .jar file which I can include in my android program in order to use protobuf's methods generated from my proto file to serialise data and send over TCP, which is my end goal.

Answer 1

Finally got it working with the following changes:

Change 1: I changed to use the java source from https://github.com/google/protobuf/releases/tag/v2.6.1 instead of https://github.com/google/protobuf/tree/v2.6.1/java

Change 2: for the Windows machine I need to copy protoc.exe to the src folder that's located in the parent folder of the java folder. Previously I copied protoc.exe into the src inside the java folder which didn't work.

After that I ran mvn test in the java folder, everything worked. I was able to generate the .jar file using mvn install and then mvn package based on the README file.

Note: I don't understand why the code from protobuf/tree/v2.6.1 didn't work, but because on github, the build status also says failing (as of 7th June), so I assume that's why.

Answer 2

I faced the same issue. Made the following changes to get it working:

1. Download the binary from the following link - same version as the one you are trying to compile (I used 3.2.0): https://repo1.maven.org/maven2/com/google/protobuf/protoc/

2. Rename the executable from protoc-3.2.0-windows-x86_64.exe to protoc.exe

3. run the mvn test from ..\protocol_buf\protobuf-3.2.0\java folder