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..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:\dev\erdp2\erdp_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.-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.fasterxml.jackson.core:jackson-core:jar -> duplicate declaration of version (?) @ line , column
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.fasterxml.jackson.core:jackson-databind:jar -> duplicate declaration of version (?) @ line , column
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.fasterxml.jackson.core:jackson-annotations:jar -> duplicate declaration of version (?) @ line , column
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.lkk:erdp_discuss_controller:jar:2.0.-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.lkk:erdp_plan_domain:jar -> duplicate declaration of version (?) @ line , column
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.lkk:erdp_discuss_service:jar:2.0.-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: com.lkk:erdp_system_domain:jar -> duplicate declaration of version (?) @ line , column
[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.-SNAPSHOT [/]
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:3.0.:clean (default-clean) @ erdp_discuss ---
[INFO]
[INFO] -----------------< com.lkk:erdp_discuss_controller >------------------
[INFO] Building erdp_discuss_controller 2.0.-SNAPSHOT [/]
[INFO] --------------------------------[ jar ]---------------------------------
[WARNING] The POM for com.alibaba:dubbo:jar:2.8. is missing, no dependency information available
[INFO]
[INFO] --- maven-clean-plugin:3.0.:clean (default-clean) @ erdp_discuss_controller ---
[INFO] Deleting E:\dev\erdp2\erdp_discuss\erdp_discuss_controller\target
[INFO]
[INFO] --- maven-resources-plugin:3.0.:resources (default-resources) @ erdp_discuss_controller ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying resource
[INFO] Copying resource
[INFO]
[INFO] --- maven-compiler-plugin:3.5:compile (default-compile) @ erdp_discuss_controller ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling source files to E:\dev\erdp2\erdp_discuss\erdp_discuss_controller\target\classes
[INFO]
[INFO] --- maven-resources-plugin:3.0.:testResources (default-testResources) @ erdp_discuss_controller ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying resources
[INFO]
[INFO] --- maven-compiler-plugin:3.5:testCompile (default-testCompile) @ erdp_discuss_controller ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling source files to E:\dev\erdp2\erdp_discuss\erdp_discuss_controller\target\test-classes
[INFO] /E:/dev/erdp2/erdp_discuss/erdp_discuss_controller/src/test/java/com/lkk/ppm/discuss/SysConsumerApplication.java: E:\dev\erdp2\erdp_discuss\erdp_discuss_controller\src\test\java\com\lkk\ppm\discuss\SysConsumerApplication.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.:test (default-test) @ erdp_discuss_controller ---
[INFO] Tests are skipped.
[INFO]
[INFO] --- maven-jar-plugin:3.0.:jar (default-jar) @ erdp_discuss_controller ---
[INFO] Building jar: E:\dev\erdp2\erdp_discuss\erdp_discuss_controller\target\erdp_discuss_controller-2.0.-SNAPSHOT.jar
[INFO]
[INFO] -------------------< com.lkk:erdp_discuss_service >-------------------
[INFO] Building erdp_discuss_service 2.0.-SNAPSHOT [/]
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:3.0.:clean (default-clean) @ erdp_discuss_service ---
[INFO] Deleting E:\dev\erdp2\erdp_discuss\erdp_discuss_service\target
[INFO]
[INFO] --- maven-resources-plugin:3.0.:resources (default-resources) @ erdp_discuss_service ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory E:\dev\erdp2\erdp_discuss\erdp_discuss_service\src\main\resources
[INFO] skip non existing resourceDirectory E:\dev\erdp2\erdp_discuss\erdp_discuss_service\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.5:compile (default-compile) @ erdp_discuss_service ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling source files to E:\dev\erdp2\erdp_discuss\erdp_discuss_service\target\classes
[INFO]
[INFO] --- maven-resources-plugin:3.0.:testResources (default-testResources) @ erdp_discuss_service ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying resources
[INFO]
[INFO] --- maven-compiler-plugin:3.5:testCompile (default-testCompile) @ erdp_discuss_service ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling source files to E:\dev\erdp2\erdp_discuss\erdp_discuss_service\target\test-classes
[INFO]
[INFO] --- maven-surefire-plugin:2.19.:test (default-test) @ erdp_discuss_service ---
[INFO] Tests are skipped.
[INFO]
[INFO] --- maven-jar-plugin:3.0.:jar (default-jar) @ erdp_discuss_service ---
[INFO] Building jar: E:\dev\erdp2\erdp_discuss\erdp_discuss_service\target\erdp_discuss_service-2.0.-SNAPSHOT.jar
[INFO]
[INFO] ---------------------< com.lkk:erdp_discuss_app >---------------------
[INFO] Building ppm_discuss_app 2.0.-SNAPSHOT [/]
[INFO] --------------------------------[ war ]---------------------------------
[WARNING] The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:jar:0.2..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..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..RELEASE is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details
[INFO]
[INFO] --- maven-clean-plugin:3.0.:clean (default-clean) @ erdp_discuss_app ---
[INFO] Deleting E:\dev\erdp2\erdp_discuss\erdp_discuss_app\target
[INFO]
[INFO] --- maven-resources-plugin:3.0.:resources (default-resources) @ erdp_discuss_app ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying resources
[INFO] Copying resource
[INFO]
[INFO] --- maven-compiler-plugin:3.5:compile (default-compile) @ erdp_discuss_app ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling source files to E:\dev\erdp2\erdp_discuss\erdp_discuss_app\target\classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /E:/dev/erdp2/erdp_discuss/erdp_discuss_app/src/main/java/com/lkk/ppm/discuss/DiscussApplication.java:[,] 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:[,] 找不到符号
符号: 类 EnableDiscoveryClient
[INFO] errors
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for erdp_discuss 2.0.-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: --05T15::+:
[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:[,] 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:[,] 找不到符号
[ERROR] 符号: 类 EnableDiscoveryClient
[ERROR] -> [Help ]
[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 ] 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..RELEASE is invalid, transitive dependencies (if any) will not be available: problems were encountered while building the effective model for org.spr
ingframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:0.2..RELEASE
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (posi
tion: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-openfeign-dependencies\2.0..RELEASE\spring-cloud-openfeign-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \
u0 (position: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-openfeign-dependencies\2.0..RELEASE\spring-cloud-openfeign-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-bus-dependencies\2.0..RELEASE\spring-cloud-bus-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (position
: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-bus-dependencies\2.0..RELEASE\spring-cloud-bus-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-gateway-dependencies\2.0..RELEASE\spring-cloud-gateway-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (
position: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-gateway-dependencies\2.0..RELEASE\spring-cloud-gateway-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (posi
tion: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom, line , column [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..Final is invalid, transitive dependencies (if any) will not be available: problem was encountered while building the effective model
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\jboss\netty\netty\3.2..Final\netty-3.2..Final.pom: only whitespace content allowed before start tag and not \u0 (position: START_DOCUMENT seen \u0... @:) @ line , column [WARNING] The POM for org.springframework.cloud:spring-cloud-starter-alibaba-nacos-config:jar:0.2..RELEASE is invalid, transitive dependencies (if any) will not be available: problems were encountered while building the effective model for org.spring
framework.cloud:spring-cloud-starter-alibaba-nacos-config:0.2..RELEASE
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (posi
tion: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-openfeign-dependencies\2.0..RELEASE\spring-cloud-openfeign-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \
u0 (position: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-openfeign-dependencies\2.0..RELEASE\spring-cloud-openfeign-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-bus-dependencies\2.0..RELEASE\spring-cloud-bus-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (position
: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-bus-dependencies\2.0..RELEASE\spring-cloud-bus-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-gateway-dependencies\2.0..RELEASE\spring-cloud-gateway-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (
position: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-gateway-dependencies\2.0..RELEASE\spring-cloud-gateway-dependencies-2.0..RELEASE.pom, line , column
[FATAL] Non-parseable POM C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom: only whitespace content allowed before start tag and not \u0 (posi
tion: START_DOCUMENT seen \u0... @:) @ C:\Users\Administrator\.m2\repository\org\springframework\cloud\spring-cloud-build-dependencies\2.0..RELEASE\spring-cloud-build-dependencies-2.0..RELEASE.pom, line , column
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:\Users\Administrator\.m2\repository )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
