protobuf/java/lite.md

Protocol Buffers - Google's data interchange format

Copyright 2008 Google Inc.

https://developers.google.com/protocol-buffers/

Use Protobuf Java Lite Runtime

Protobuf Java Lite runtime is separated from the main Java runtime because it's designed/implemented with different constraints. In particular, Java Lite runtime has a much smaller code size which makes it more suitable to be used on Android.

Note that in order to achieve maximum performance and code size, we will NOT guarantee API/ABI stability for Java Lite. If this is not acceptable for your use-case, please use the full Java runtime instead. Note that the latest version of Java Lite is not compatible with the 3.0.0 version.

You can generate Java Lite code for your .proto files:

$ protoc --java_out=lite:${OUTPUT_DIR} path/to/your/proto/file

Note that "optimize_for = LITE_RUNTIME" option in proto file is deprecated and will not have any effect any more.

Include the generated Java files in your project and add a dependency on the protobuf Java runtime. If you are using Maven, use the following:

<dependency>
  <groupId>com.google.protobuf</groupId>
  <artifactId>protobuf-javalite</artifactId>
  <version>3.18.1</version>
</dependency>

R8 rule to make production app builds work

The Lite runtime internally uses reflection to avoid generating hashCode/equals/(de)serialization methods. R8 by default obfuscates the field names, which makes the reflection fail causing exceptions of the form java.lang.RuntimeException: Field {NAME}_ for {CLASS} not found. Known fields are [ {FIELDS} ] in MessageSchema.java.

There are open issues for this on the protobuf Github project and R8.

Until the issues is resolved you need to add the following line to your proguard-rules.pro file inside your project:

-keep class * extends com.google.protobuf.GeneratedMessageLite { *; }

Older versions

For the older version of Java Lite (v3.0.0), please refer to:

https://github.com/protocolbuffers/protobuf/blob/javalite/java/lite.md