java.lang.UnsupportedOperationException: This is supposed to be overridden by subclasses

1.原因不细说了，就是2.5版本里

 public UnknownFieldSet getUnknownFields() {
    throw new UnsupportedOperationException( //在180行可以看到这个方法直接返回一个错误
        "This is supposed to be overridden by subclasses.");
  }

2在Maven

       <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>2.4.1</version>
        </dependency>