背景

因业务需要使用protobuf3对数据进行压缩，spark自带的protobuf-java-2.5.0.jar。需要在spark环境上跑代码，所以项目引入spark的jar包都是provided，没办法屏蔽掉spark的protobuf，又需要同时存在protobuf3.

protobuf使用

proto 文件

syntax = "proto3";
option java_package = "com.xxx.protobuf";
//生成的java名
option java_outer_classname = "Foo";
message FooItem {
  string bar = 1;
}

maven依赖

    <properties>
        <protobuf-maven-plugin-version>0.6.1</protobuf-maven-plugin-version>
        <protoc.version>3.18.1</protoc.version>
        <os-maven-plugin-version>1.6.2</os-maven-plugin-version>
        <maven-clean-plugin.version>3.1.0</maven-clean-plugin.version>
    </properties>


        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.18.1</version>
        </dependency>
        <dependency>
            <groupId>com.googlecode.protobuf-java-format</groupId>
            <artifactId>protobuf-java-format</artifactId>
            <version>1.2</version>
        </dependency>

    <build>

        <extensions>
            <extension>
                <groupId>kr.motd.maven</groupId>
                <artifactId>os-maven-plugin</artifactId>
                <version>${os-maven-plugin-version}</version>
            </extension>
        </extensions>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>2.4.3</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <relocations>
                                <relocation>
                                    <pattern>com.google.protobuf</pattern>
                                    <shadedPattern>shaded.com.google.protobuf</shadedPattern>
                                </relocation>
                            </relocations>
                            <minimizeJar>false</minimizeJar>
                            <shadedArtifactAttached>true</shadedArtifactAttached>
                            <artifactSet>
                                <includes>
                                    <!-- Include here the dependencies you
                                        want to be packed in your fat jar -->
                                    <include>*:*</include>
                                </includes>
                            </artifactSet>
                            <filters>
                                <filter>
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                        <exclude>**/log4j.properties</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                            <transformers>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                    <resource>reference.conf</resource>
                                </transformer>
                                <transformer
                                        implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                    <resource>
                                        META-INF/services/org.apache.spark.sql.sources.DataSourceRegister
                                    </resource>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.3.2</version>
                <executions>
                    <execution>
                        <id>scala-compile-first</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>scala-test-compile-first</id>
                        <phase>process-test-resources</phase>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <groupId>org.xolstice.maven.plugins</groupId>
                <artifactId>protobuf-maven-plugin</artifactId>
                <version>${protobuf-maven-plugin-version}</version>
                <configuration>
                    <includes>
                        <include>**/*.proto</include>
                    </includes>
                        <protoSourceRoot>${basedir}/src/main/scala/com/foo/protobuf</protoSourceRoot>
                        <outputDirectory>${basedir}/src/main/scala</outputDirectory>
                    <!-- 生成文件前是否把目标目录清空，这个最好设置为false，以免误删项目文件 -->
                    <clearOutputDirectory>false</clearOutputDirectory>
                    <protocArtifact>
                        com.google.protobuf:protoc:${protoc.version}:exe:${os.detected.classifier}
                    </protocArtifact>
                </configuration>
                <executions>
                    <execution>
                        <id>compile</id>
                        <goals>
                            <goal>compile</goal>
                            <!--<goal>compile-custom</goal>-->
                        </goals>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <goals>
                            <goal>test-compile</goal>
                            <!--<goal>test-compile-custom</goal>-->
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

build 中protobuf-maven-plugin 会在打包时编译proto文件，会覆盖原来的文件，os-maven-plugin获取系统信息

问题排查过程

尝试一
拉下来protobuf java部分源码，自行编译，需要先对整个protobuf进行c++编译，然后对java部分进行maven编译，目的是为了直接把protobuf3的源码复制到项目里，改掉包路径，这样就不用引protobuf的依赖。
存在问题

protobuf core包有java部分有父依赖，引包会非常复杂

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

protobuf编译的过程中会生成很多proto java文件，这些proto文件需要在pom里面进行非常多的配置才能在打包的时候动态生成

放弃

依赖冲突解决方案一

使用jarjar.jar 更改protobuf的包名然后打包到本地仓库，可正常打包
问题1: 因为打包时会自动编译protobuf文件，但是编译出来的proto文件包名还是com.google.protobuf，打进来会报错
问题2:所以需要手动把改过的proto文件压进jar包里（这个操作比较复杂，可以网上搜索相关方法）

这个方法虽然复杂，但是这个方法的确可以解决依赖冲突