问题是： 我的应用的pom 并没有任何报错，但是代码报错，而且编译不通过。
如下，我本地项目，从 spring-cloud-alibaba-dependencies 0.2.1.RELEASE 升级到 0.2.2.RELEASE：
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Finchley.SR1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-alibaba-dependencies</artifactId>
<version>0.2.2.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
就出现了类找不到的情况 cannot resolve symbol "xxx" ，比如这个：
import org.springframework.cloud.client.discovery.EnableDiscoveryClient; < --- cannot resolve symbol "xxx"
EnableDiscoveryClient 是spring-cloud-commons jar 的内容， 而spring-cloud-commons 是dubbo-registry-nacos，spring-cloud-starter-alibaba-nacos-config 和 spring-cloud-starter-alibaba-nacos-discovery的 依赖。
spring cloud 相关的类/接口 似乎都不能用了， 但是之前都是好好的啊！ 查看maven 的dependencies 图发现， 某些 jar 似乎缺少没有被依赖尽量。 不是某几个， 而是很多的。。。
似乎某些 dependency 被切断了。。 于是手动添加了几个 dependency 并写上了版本号，要是不写版本号， 那么问题依旧。 难道需要一个个的处理问题？
之前都不需要手动加入的dependency， 现在一个个手动添加， 也太麻烦了吧！
观察发现dubbo-registry-nacos-0.0.2.pom 似乎不对， 里面怎么全是NUL 这种黑色字符，经验告诉我，这个是文件格式不对或者编码格式问题， 也可能是文件没有正确结尾，或者是被修改了/截断了.. 怎么办？ 这个版本的dubbo-registry-nacos-0.0.2 就是这样的？ 查看了同事的这个dubbo-registry-nacos-0.0.2.pom 文件,发现没有这个问题！ 删除重新下载吧！（同一个目录下的其他文件 包括jar 也一并全部删除） 就好了 ！ 重新下载后pom 是正常了，但是问题依旧。
经验告诉我，maven 出了问题了， clean 一下吧：
E:deverdp2erdp_discuss>mvn clean package [INFO] Scanning for projects... [WARNING] [WARNING] Some problems were encountered while building the effective model for com.lkk:erdp_discuss_app:war:2.0.0-SNAPSHOT [WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.fasterxml.jackson.core:jackson-core:jar -> duplicate declaration of version (?) @ line 141, column 21 [WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.fasterxml.jackson.core:jackson-databind:jar -> duplicate declaration of version (?) @ line 145, column 21 [WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.fasterxml.jackson.core:jackson-annotations:jar -> duplicate declaration of version (?) @ line 149, column 21 [WARNING] [WARNING] Some problems were encountered while building the effective model for com.lkk:erdp_discuss_controller:jar:2.0.0-SNAPSHOT [WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.lkk:erdp_plan_domain:jar -> duplicate declaration of version (?) @ line 86, column 21 [WARNING] [WARNING] Some problems were encountered while building the effective model for com.lkk:erdp_discuss_service:jar:2.0.0-SNAPSHOT [WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.lkk:erdp_system_domain:jar -> duplicate declaration of version (?) @ line 48, column 21 [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] Reactor Build Order: [INFO] [INFO] erdp_discuss [pom] [INFO] erdp_discuss_controller [jar] [INFO] erdp_discuss_service [jar] [INFO] ppm_discuss_app [war] [INFO] [INFO] -----------------------< com.lkk:erdp_discuss >----------------------- [INFO] Building erdp_discuss 2.0.0-SNAPSHOT [1/4] [INFO] --------------------------------[ pom ]--------------------------------- [INFO] [INFO] --- maven-clean-plugin:3.0.0:clean (default-clean) @ erdp_discuss --- [INFO] [INFO] -----------------< com.lkk:erdp_discuss_controller >------------------ [INFO] Building erdp_discuss_controller 2.0.0-SNAPSHOT [2/4] [INFO] --------------------------------[ jar ]--------------------------------- [WARNING] The POM for com.alibaba:dubbo:jar:2.8.4 is missing, no dependency information available [INFO] [INFO] --- maven-clean-plugin:3.0.0:clean (default-clean) @ erdp_discuss_controller --- [INFO] Deleting E:deverdp2erdp_discusserdp_discuss_controller arget [INFO] [INFO] --- maven-resources-plugin:3.0.1:resources (default-resources) @ erdp_discuss_controller --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] Copying 1 resource [INFO] Copying 0 resource [INFO] [INFO] --- maven-compiler-plugin:3.5:compile (default-compile) @ erdp_discuss_controller --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 2 source files to E:deverdp2erdp_discusserdp_discuss_controller argetclasses [INFO] [INFO] --- maven-resources-plugin:3.0.1:testResources (default-testResources) @ erdp_discuss_controller --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] Copying 5 resources [INFO] [INFO] --- maven-compiler-plugin:3.5:testCompile (default-testCompile) @ erdp_discuss_controller --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 2 source files to E:deverdp2erdp_discusserdp_discuss_controller arget est-classes [INFO] /E:/dev/erdp2/erdp_discuss/erdp_discuss_controller/src/test/java/com/lkk/ppm/discuss/SysConsumerApplication.java: E:deverdp2erdp_discusserdp_discuss_controllersrc estjavacomlkkppmdiscussSysConsumerApplication.java使用或覆盖了已过 时的 API。 [INFO] /E:/dev/erdp2/erdp_discuss/erdp_discuss_controller/src/test/java/com/lkk/ppm/discuss/SysConsumerApplication.java: 有关详细信息, 请使用 -Xlint:deprecation 重新编译。 [INFO] [INFO] --- maven-surefire-plugin:2.19.1:test (default-test) @ erdp_discuss_controller --- [INFO] Tests are skipped. [INFO] [INFO] --- maven-jar-plugin:3.0.2:jar (default-jar) @ erdp_discuss_controller --- [INFO] Building jar: E:deverdp2erdp_discusserdp_discuss_controller argeterdp_discuss_controller-2.0.0-SNAPSHOT.jar [INFO] [INFO] -------------------< com.lkk:erdp_discuss_service >------------------- [INFO] Building erdp_discuss_service 2.0.0-SNAPSHOT [3/4] [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-clean-plugin:3.0.0:clean (default-clean) @ erdp_discuss_service --- [INFO] Deleting E:deverdp2erdp_discusserdp_discuss_service arget [INFO] [INFO] --- maven-resources-plugin:3.0.1:resources (default-resources) @ erdp_discuss_service --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] skip non existing resourceDirectory E:deverdp2erdp_discusserdp_discuss_servicesrcmain esources [INFO] skip non existing resourceDirectory E:deverdp2erdp_discusserdp_discuss_servicesrcmain esources [INFO] [INFO] --- maven-compiler-plugin:3.5:compile (default-compile) @ erdp_discuss_service --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 2 source files to E:deverdp2erdp_discusserdp_discuss_service argetclasses [INFO] [INFO] --- maven-resources-plugin:3.0.1:testResources (default-testResources) @ erdp_discuss_service --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] Copying 2 resources [INFO] [INFO] --- maven-compiler-plugin:3.5:testCompile (default-testCompile) @ erdp_discuss_service --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 2 source files to E:deverdp2erdp_discusserdp_discuss_service arget est-classes [INFO] [INFO] --- maven-surefire-plugin:2.19.1:test (default-test) @ erdp_discuss_service --- [INFO] Tests are skipped. [INFO] [INFO] --- maven-jar-plugin:3.0.2:jar (default-jar) @ erdp_discuss_service --- [INFO] Building jar: E:deverdp2erdp_discusserdp_discuss_service argeterdp_discuss_service-2.0.0-SNAPSHOT.jar [INFO] [INFO] ---------------------< com.lkk:erdp_discuss_app >--------------------- [INFO] Building ppm_discuss_app 2.0.0-SNAPSHOT [4/4] [INFO] --------------------------------[ war ]--------------------------------- [WARNING] The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:jar:0.2.2.RELEASE is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details [WARNING] The POM for org.jboss.netty:netty:jar:3.2.5.Final is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details [WARNING] The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-config:jar:0.2.2.RELEASE is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details [INFO] [INFO] --- maven-clean-plugin:3.0.0:clean (default-clean) @ erdp_discuss_app --- [INFO] Deleting E:deverdp2erdp_discusserdp_discuss_app arget [INFO] [INFO] --- maven-resources-plugin:3.0.1:resources (default-resources) @ erdp_discuss_app --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] Copying 2 resources [INFO] Copying 1 resource [INFO] [INFO] --- maven-compiler-plugin:3.5:compile (default-compile) @ erdp_discuss_app --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 7 source files to E:deverdp2erdp_discusserdp_discuss_app argetclasses [INFO] ------------------------------------------------------------- [ERROR] COMPILATION ERROR : [INFO] ------------------------------------------------------------- [ERROR] /E:/dev/erdp2/erdp_discuss/erdp_discuss_app/src/main/java/com/lkk/ppm/discuss/DiscussApplication.java:[10,50] 程序包org.springframework.cloud.client.discovery不存在 [ERROR] /E:/dev/erdp2/erdp_discuss/erdp_discuss_app/src/main/java/com/lkk/ppm/discuss/DiscussApplication.java:[28,2] 找不到符号 符号: 类 EnableDiscoveryClient [INFO] 2 errors [INFO] ------------------------------------------------------------- [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary for erdp_discuss 2.0.0-SNAPSHOT: [INFO] [INFO] erdp_discuss ....................................... SUCCESS [ 0.313 s] [INFO] erdp_discuss_controller ............................ SUCCESS [ 6.453 s] [INFO] erdp_discuss_service ............................... SUCCESS [ 2.553 s] [INFO] ppm_discuss_app .................................... FAILURE [ 1.628 s] [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] Total time: 11.844 s [INFO] Finished at: 2019-05-05T15:36:09+08:00 [INFO] ------------------------------------------------------------------------ [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.5:compile (default-compile) on project erdp_discuss_app: Compilation failure: Compilation failure: [ERROR] /E:/dev/erdp2/erdp_discuss/erdp_discuss_app/src/main/java/com/lkk/ppm/discuss/DiscussApplication.java:[10,50] 程序包org.springframework.cloud.client.discovery不存在 [ERROR] /E:/dev/erdp2/erdp_discuss/erdp_discuss_app/src/main/java/com/lkk/ppm/discuss/DiscussApplication.java:[28,2] 找不到符号 [ERROR] 符号: 类 EnableDiscoveryClient [ERROR] -> [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/MojoFailureException [ERROR] [ERROR] After correcting the problems, you can resume the build with the command [ERROR] mvn <goals> -rf :erdp_discuss_app
问题并不能这么简单的解决。但是上面的信息并不能告诉我具体什么原因。 经验告诉我，通过-X 参数：
[DEBUG] ======================================================================= [WARNING] The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:jar:0.2.2.RELEASE is invalid, transitive dependencies (if any) will not be available: 5 problems were encountered while building the effective model for org.spr ingframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:0.2.2.RELEASE [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom: only whitespace content allowed before start tag and not u0 (posi tion: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-openfeign-dependencies2.0.3.RELEASEspring-cloud-openfeign-dependencies-2.0.3.RELEASE.pom: only whitespace content allowed before start tag and not u0 (position: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-openfeign-dependencies2.0.3.RELEASEspring-cloud-openfeign-dependencies-2.0.3.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-bus-dependencies2.0.1.RELEASEspring-cloud-bus-dependencies-2.0.1.RELEASE.pom: only whitespace content allowed before start tag and not u0 (position : START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-bus-dependencies2.0.1.RELEASEspring-cloud-bus-dependencies-2.0.1.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-gateway-dependencies2.0.3.RELEASEspring-cloud-gateway-dependencies-2.0.3.RELEASE.pom: only whitespace content allowed before start tag and not u0 ( position: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-gateway-dependencies2.0.3.RELEASEspring-cloud-gateway-dependencies-2.0.3.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom: only whitespace content allowed before start tag and not u0 (posi tion: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom, line 1, column 1 [DEBUG] Using mirror lkk-public (http://192.168.11.200:8081/repository/lkk-public/) for maven2-repository.dev.java.net (http://download.java.net/maven/2/). [WARNING] The POM for org.jboss.netty:netty:jar:3.2.5.Final is invalid, transitive dependencies (if any) will not be available: 1 problem was encountered while building the effective model [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgjboss etty etty3.2.5.Final etty-3.2.5.Final.pom: only whitespace content allowed before start tag and not u0 (position: START_DOCUMENT seen u0... @1:1) @ line 1, column 1 [WARNING] The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-config:jar:0.2.2.RELEASE is invalid, transitive dependencies (if any) will not be available: 5 problems were encountered while building the effective model for org.spring framework.cloud:spring-cloud-starter-alibaba-nacos-config:0.2.2.RELEASE [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom: only whitespace content allowed before start tag and not u0 (posi tion: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-openfeign-dependencies2.0.3.RELEASEspring-cloud-openfeign-dependencies-2.0.3.RELEASE.pom: only whitespace content allowed before start tag and not u0 (position: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-openfeign-dependencies2.0.3.RELEASEspring-cloud-openfeign-dependencies-2.0.3.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-bus-dependencies2.0.1.RELEASEspring-cloud-bus-dependencies-2.0.1.RELEASE.pom: only whitespace content allowed before start tag and not u0 (position : START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-bus-dependencies2.0.1.RELEASEspring-cloud-bus-dependencies-2.0.1.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-gateway-dependencies2.0.3.RELEASEspring-cloud-gateway-dependencies-2.0.3.RELEASE.pom: only whitespace content allowed before start tag and not u0 ( position: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-gateway-dependencies2.0.3.RELEASEspring-cloud-gateway-dependencies-2.0.3.RELEASE.pom, line 1, column 1 [FATAL] Non-parseable POM C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom: only whitespace content allowed before start tag and not u0 (posi tion: START_DOCUMENT seen u0... @1:1) @ C:UsersAdministrator.m2 epositoryorgspringframeworkcloudspring-cloud-build-dependencies2.0.5.RELEASEspring-cloud-build-dependencies-2.0.5.RELEASE.pom, line 1, column 1
果然： The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:jar:0.2.2.RELEASE is invalid
确定无疑， pom 问题， 观察发现 spring-cloud-starter-alibaba-nacos-config-0.2.2.RELEASE ，以及 spring-cloud-starter-alibaba-nacos-discovery-0.2.2.RELEASE 也有同样的问题。删除重新下载，但还是有问题。
另外观察到 spring-cloud-build-dependencies-2.0.5.RELEASE.pom 也有问题：
难道maven 私服出现了问题？ 登录上去一看， 发现maven 私服的 spring-cloud-build-dependencies-2.0.5.RELEASE.pom 等 都是正常的！
难道要一个个的检查repository目录中的 pom 是否有问题？ 这太多了，干脆全部删除出现下载。不得已， 把 程序全部关闭，idea退出，整个repository目录(C:UsersAdministrator.m2 epository )删除,重启idea ，刷新maven， 问题解决！
忽而想到了， 我上午的时候， 电脑电源线松动了， 电脑异常关机了一次， 然后， 电脑还自动升级了很久。 可能正是这个原因导致了 某些的 pom 文件损坏了吧！！！
真是奇了怪了， 这个问题是怎么引起的呢？ 是什么原因呢？ 网上并没有找到这种问题现象，bing 上面搜索 maven pom damaged 或 maven pom corrupted 都无果。
似乎大家都没有遇到， 就我一个人遇到？ 真是活久见！！！
参考：
https://blog.csdn.net/cuiy6642/article/details/49789763
http://www.cnblogs.com/enjoyjava/p/9743460.html
https://grokbase.com/t/ant/user/09771k6h5v/maven2-pom-is-corrupt