我們在很多場景下會碰到j(luò)ava包沖突的問題：

• 代碼由第三方開發(fā)伍茄，無法對包名或依賴做管控
• 跑在同一個進(jìn)程里的代碼敷矫，更新步調(diào)不一致。比如底層sdk整葡，jvm agent。這些組件更新頻率較低

最出名的解決路數(shù)還是類加載機(jī)制俱萍，諸如flink，osgi都給我們提供了很多方案岳颇，這些方案都非常重型话侧。在代碼可信任的情況下悲立，其中有一個很輕量級的解決方案就是maven-shade包。

舉個例子寥殖，比方說我想在java agent中打印日志，但是又不希望和業(yè)務(wù)代碼中的log4j等沖突粤策，agent里依賴的pom文件是這樣子的:

 <dependencies>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.30</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.13.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.13.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-slf4j-impl</artifactId>
            <version>2.13.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-jcl</artifactId>
            <version>2.13.3</version>
        </dependency>
    </dependencies>

這里我們log4j,slf4j可能用的版本太高或者太低柔吼，我們就可以通過打shade包的方式修改log4j和slf4j的包名,避免和業(yè)務(wù)沖突

<plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <artifactSet>
                                <includes>
                                    <include>org.slf4j:slf4j-api</include>
                                    <include>org.apache.logging.log4j:log4j-api</include>
                                    <include>org.apache.logging.log4j:log4j-core</include>
                                    <include>org.apache.logging.log4j:log4j-slf4j-impl</include>
                                    <include>org.apache.logging.log4j:log4j-jcl</include>
                                </includes>
                            </artifactSet>
                            <filters>
                                <filter>
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                            <relocations>
                                <relocation>
                                    <pattern>org.slf4j</pattern>
                                    <shadedPattern>com.github.shoothzj.org.slf4j</shadedPattern>
                                </relocation>
                                <relocation>
                                    <pattern>org.apache.logging</pattern>
                                    <shadedPattern>com.github.shoothzj.org.apache.logging</shadedPattern>
                                </relocation>
                            </relocations>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

通過上面的配置胡本，artifactSet選擇要修改的pom依賴侧甫，通過relocation修改包名咒锻，達(dá)到不沖突的效果。mvn clean package 后查看效果

image-20201230145531225

可以發(fā)現(xiàn)敦捧，包名已經(jīng)被修改完成,達(dá)到了避免沖突的目的。