关于Maven依赖冲突解决之exclusions

目录

• Maven依赖冲突解决之exclusions
• 1. 背景
• 2. 解决方式
• 场景
• 解决方式
• Maven解决依赖冲突总结
• 实例分析
• 解决办法
• 命令分析
• 小试牛刀

Maven依赖冲突解决之exclusions

1. 背景

• 作为java生态下开发者，往往需要使用大量线程的第三方库，一般都是以jar包形式存在。
• maven作为事实上主流的jar包依赖管理工具，Idea和Eclipse都支持创建maven工程来管理jar包依赖。
• 使用maven进行jar包依赖管理时，maven会自行管理jar包及其依赖链条，但往往会遇到依赖冲突问题，这时候就可以尝试使用exclusion来进行依赖管理。

2. 解决方式

场景

假如hadoop集群中hadoop版本是3.2.1，这时候为了保证程序能够顺利操作hadoop，需要引入hadoop-client的3.2.1版本。但这里也可以看到，spark-core_2.12内部也有对hadoop-client的依赖，而且版本是低版本的2.7.4，这时候往往就会产生冲突或者未知错误。所以需要使用exclusions做依赖排除。

解决方式

使用exclusions来对某一个第三方库引入的依赖jar包做排除

<dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.12</artifactId>
            <version>${spark.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>org.apache.hadoop</groupId>
                    <artifactId>hadoop-client</artifactId>
                </exclusion>

                <exclusion>
                    <groupId>com.google.guava</groupId>
                    <artifactId>guava</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

Maven解决依赖冲突总结

如果存在jar包的依赖冲突，在项目启动时总是报类似这样的错：NoSuchMethodError、ClassNotFoundException、成员变量找不到等等。真的很让人不好受。

Maven采用的是“最近获胜的策略”来处理依赖的冲突，即如果一个项目最终依赖于相同artifact的多个版本，在依赖树中离项目最近的那个版本将被使用。让我们来看看一个实际的例子。

实例分析

我们有一个web应用resolve-web，该工程依赖于project-A和project-B，project-A依赖于project-common的1.0版本并调用其中的sayHello()方法。project-B依赖于project-C，而project-C又进一步依赖于project-common的2.0版本并调用其中的sayGoodBye()方法。project-common的1.0和2.0版本是不同的，1.0中之包含sayHello()方法，而2.0中包含了sayHello()和sayGoodBye()两个方法。整个项目的依赖关系如下图：

根据Maven的最近原则依赖机制，resolve-web将同时依赖于project-common的1.0和2.0版本，这就造成了依赖冲突。而根据最近获胜策略，Maven将选择project-common的1.0版本作为最终的依赖。这和Gradle不同，Gradle在默认情况下将选择最新的版本作为获胜版本。而对于Maven，由于proejct-common的1.0版本比2.0版本在依赖树中离resolve-web更近，故1.0版本获胜。在resolve-web中执行\"mvn dependency:tree -Dverbose\"可以看到resolve-web的依赖关系：

[INFO] resolve-web:resolve-web:war:1.0-SNAPSHOT
 
[INFO] +- junit:junit:jar:3.8.1:test
 
[INFO] +- project-B:project-B:jar:1.0:compile
 
[INFO] |  \\- project-C:project-C:jar:1.0:compile
 
[INFO] |     \\- (project-common:project-commmon:jar:2.0:compile - omitted for conflict with 1.0)
 
[INFO] +- project-A:project-A:jar:1.0:compile
 
[INFO] |  \\- project-common:project-commmon:jar:1.0:compile
 
[INFO] \\- javax.servlet:servlet-api:jar:2.4:provided

由上可知，project-common:project-commmon:jar:2.0被忽略掉了。此时在resolve-web的war包中将只包含project-common的1.0版本，于是问题来了。由于project-common的1.0版本中不包含sayGoodBye()方法，而该方法正是project-C所需要的，所以运行时将出现“NoSuchMethodError”。

解决办法

方法1：显式加入对project-common 2.0版本的依赖。先前的2.0版本不是离resolve-web远了点吗，那我们就直接将它作为resolve-web的依赖，这不就比1.0版本离resolve-web还近吗？在resove-web的pom.xml文件中直接加上对project-common 2.0 的依赖

<dependency>       
   <groupId>project-common</groupId>      
   <artifactId>project-commmon</artifactId>  
   <version>2.0</version>   
</dependency>  

方法2：resolve-web对project-A的dependency声明中，将project-common排除掉。在resolve-web的pom.xml文件中修改对project-A的dependency声明

<dependency>  
          <groupId>project-A</groupId>  
          <artifactId>project-A</artifactId>  
          <version>1.0</version>  
          <exclusions>  
              <exclusion>  
                  <groupId>project-common</groupId>  
                  <artifactId>project-commmon</artifactId>  
              </exclusion>  
          </exclusions>  
</dependency>

此时再在resolve-web中执行\"mvn dependency:tree -Dverbose\"，如下：

......
 
[INFO] resolve-web:resolve-web:war:1.0-SNAPSHOT
 
[INFO] +- junit:junit:jar:3.8.1:test
 
[INFO] +- project-B:project-B:jar:1.0:compile
 
[INFO] |  \\- project-C:project-C:jar:1.0:compile
 
[INFO] |     \\- project-common:project-commmon:jar:2.0:compile
 
[INFO] +- project-A:project-A:jar:1.0:compile
 
[INFO] \\- javax.servlet:servlet-api:jar:2.4:provided
 
......

这样的话，就可以完美解决冲突了。

命令分析

这里我们对我们执行的命令做一个简单的说明。

mvn dependency:tree -Dverbose -Dincludes=<groupId>:<artifactId>

1、第一部分mvn dependency:tree是maven依赖的分析命令，作用是对我们的项目的依赖进行分析，并输出项目依赖树

2、第二部分-Dverbose的作用是添加了verbose一个环境变量，起的作用是在分析项目依赖时输出明细，这样项目中依赖的所有3、引用都会被输出出来，包含了所有的间接引用，会有很多很多，我们只需要我们要找的，所以就需要第三个参数了第三部分-Dincludes=<groupId>:<artifactId>的作用就是进行过滤，只包含我们想要的依赖的依赖时，排除掉其它不需要的，依赖树的所有叶子节点就是我们的找的依赖包。其中的groupId和artifactId可以只填写一个，为了保证准确性，一般都会填两个（填写时不包括尖括号）。

小试牛刀

在自己的项目上，启动时发现如下异常：

21-Mar-2019 15:51:33.527 信息 [RMI TCP Connection(2)-127.0.0.1] org.apache.catalina.core.ApplicationContext.log Initializing Spring root WebApplicationContext
21-Mar-2019 15:52:08.905 严重 [RMI TCP Connection(2)-127.0.0.1] org.apache.catalina.core.StandardContext.listenerStart Exception sending context initialized event to listener instance of class [org.springframework.web.context.ContextLoaderListener]
org.springframework.beans.factory.BeanCreationException: Error creating bean with name \'org.springframework.web.socket.server.support.WebSocketHandlerMapping#0\': Cannot resolve reference to bean \'org.springframework.web.socket.sockjs.support.SockJsHttpRequestHandler#0\' while setting bean property \'urlMap\' with key [/websocket/**]; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name \'org.springframework.web.socket.sockjs.support.SockJsHttpRequestHandler#0\': Cannot resolve reference to bean \'org.springframework.web.socket.sockjs.transport.handler.DefaultSockJsService#0\' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name \'org.springframework.web.socket.sockjs.transport.handler.DefaultSockJsService#0\': Cannot resolve reference to bean \'SockJsScheduler\' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name \'SockJsScheduler\': Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyException: Invalid property \'removeOnCancelPolicy\' of bean class [org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler]: Bean property \'removeOnCancelPolicy\' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:359)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:108)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveManagedMap(BeanDefinitionValueResolver.java:407)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:165)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1531)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1276)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:443)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:325)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4817)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5283)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:754)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:730)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1736)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:483)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:432)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at com.sun.jmx.remote.security.MBeanServerAccessController.invoke(MBeanServerAccessController.java:468)
at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
at java.security.AccessController.doPrivileged(Native Method)
at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1408)
at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:357)
at sun.rmi.transport.Transport$1.run(Transport.java:200)
at sun.rmi.transport.Transport$1.run(Transport.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

执行命令分析下，项目的jar包的依赖情况，只过滤并分析spring框架的jar包依赖树情况，使用的命令如下：

mvn dependency:tree -Dverbose -Dincludes=org.springframework:

在新引入的项目jar包中，发现其再次引入了spring的相关包并且该spring包的层级属于第二层级，实际已有的spring的包处在第三或者第四层级，根据就近原则，低版本的3.2.5的jar包覆盖了高版本的jar包，导致出现找不到某变量的异常。剔除这些jar包如下配置：

<exclusion>
       <groupId>org.springframework</groupId>
       <artifactId>spring-beans</artifactId>
</exclusion>
<exclusion>
       <groupId>org.springframework</groupId>
       <artifactId>spring-context</artifactId>
</exclusion>
<exclusion>
       <groupId>org.springframework</groupId>
       <artifactId>spring-context-support</artifactId>
</exclusion>

重新查看jar包的依赖树：

xujiaqingdeMacBook-Pro:mos jaycee$ mvn dependency:tree -Dverbose -Dincludes=org.springframework:
[WARNING] 
[WARNING] Some problems were encountered while building the effective settings
[WARNING] Unrecognised tag: \'mirror\' (position: START_TAG seen ...e the preferred\\n   | server for that repository.\\n   |-->\\n <mirror>... @153:10)  @ /software/apache-maven-3.6.0/conf/settings.xml, line 153, column 10
[WARNING] 
[INFO] Scanning for projects...
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for fish:core-db:jar:1.0-SNAPSHOT
[WARNING] \'build.plugins.plugin.version\' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ fish:core-db:[unknown-version], /projects/mos/core-db/pom.xml, line 79, 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] FishParent                                                         [pom]
[INFO] core-db                                                            [jar]
[INFO] core                                                               [war]
[INFO] 
[INFO] --------------------------< fish:FishParent >---------------------------
[INFO] Building FishParent 1.0-SNAPSHOT                                   [1/3]
[INFO] --------------------------------[ pom ]---------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ FishParent ---
[INFO] 
[INFO] ----------------------------< fish:core-db >----------------------------
[INFO] Building core-db 1.0-SNAPSHOT                                      [2/3]
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ core-db ---
[INFO] fish:core-db:jar:1.0-SNAPSHOT
[INFO] \\- com.hand:hap-db:jar:3.5.4-RELEASE:compile
[INFO]    \\- com.hand:hap-core-db:jar:3.5.4-RELEASE:compile
[INFO]       \\- org.springframework:spring-core:jar:4.3.11.RELEASE:compile
[INFO] 
[INFO] -----------------------------< fish:core >------------------------------
[INFO] Building core 1.0-SNAPSHOT                                         [3/3]
[INFO] --------------------------------[ war ]---------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ core ---
[INFO] fish:core:war:1.0-SNAPSHOT
[INFO] +- com.hand:hap-db:jar:3.5.4-RELEASE:compile
[INFO] |  \\- com.hand:hap-core-db:jar:3.5.4-RELEASE:compile
[INFO] |     \\- org.springframework:spring-core:jar:4.3.11.RELEASE:compile
[INFO] +- com.hand:hap-pom:pom:3.5.4-RELEASE:provided
[INFO] |  +- com.hand:hap-core:jar:classes:3.5.4-RELEASE:provided
[INFO] |  |  +- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework:spring-jdbc:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  +- org.springframework:spring-beans:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  |  \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  \\- (org.springframework:spring-tx:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework:spring-test:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework:spring-context:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  +- org.springframework:spring-aop:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  |  +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  |  \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  \\- org.springframework:spring-expression:jar:4.3.11.RELEASE:provided
[INFO] |  |  |     \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework:spring-context-support:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework:spring-web:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-aop:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework:spring-webmvc:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-aop:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-expression:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  \\- (org.springframework:spring-web:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  +- org.springframework.data:spring-data-redis:jar:1.7.0.RELEASE:provided
[INFO] |  |  |  +- org.springframework.data:spring-data-keyvalue:jar:1.1.0.RELEASE:provided
[INFO] |  |  |  |  +- org.springframework.data:spring-data-commons:jar:1.12.0.RELEASE:provided
[INFO] |  |  |  |  |  +- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  |  \\- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  \\- (org.springframework:spring-tx:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-tx:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- org.springframework:spring-oxm:jar:4.2.5.RELEASE:provided
[INFO] |  |  |  |  +- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  \\- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-aop:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-context-support:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework.security:spring-security-web:jar:4.0.4.RELEASE:provided
[INFO] |  |  |  +- org.springframework.security:spring-security-core:jar:4.0.4.RELEASE:provided
[INFO] |  |  |  |  +- (org.springframework:spring-aop:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  +- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  +- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  |  \\- (org.springframework:spring-expression:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-expression:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-web:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework.security:spring-security-config:jar:4.0.4.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-aop:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework.security:spring-security-cas:jar:4.0.4.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-web:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework.security.oauth:spring-security-oauth2:jar:2.0.7.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.0.9.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.0.9.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.0.9.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-webmvc:jar:4.0.9.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework.security:spring-security-ldap:jar:4.0.4.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-beans:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-tx:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- com.ryantenney.metrics:metrics-spring:jar:3.1.3:provided
[INFO] |  |  |  \\- (org.springframework:spring-context-support:jar:4.1.6.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework.amqp:spring-rabbit:jar:1.7.1.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-web:jar:4.3.7.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-messaging:jar:4.3.7.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- org.springframework.amqp:spring-amqp:jar:1.7.1.RELEASE:provided
[INFO] |  |  |  |  \\- (org.springframework:spring-core:jar:4.3.7.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  +- (org.springframework:spring-tx:jar:4.3.7.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-context:jar:4.3.7.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  +- org.springframework:spring-websocket:jar:4.3.11.RELEASE:provided
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  +- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  |  \\- (org.springframework:spring-web:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |  \\- org.springframework:spring-messaging:jar:4.3.11.RELEASE:provided
[INFO] |  |     +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |     +- (org.springframework:spring-context:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  |     \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |  +- com.hand:hap-workflow:jar:classes:3.5.4-RELEASE:provided
[INFO] |  |  +- org.activiti:activiti-spring:jar:6.0.0:provided
[INFO] |  |  |  +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  |  \\- (org.springframework:spring-jdbc:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |  \\- org.activiti:activiti-rest:jar:6.0.0:provided
[INFO] |  |     +- (org.springframework:spring-context:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  |     \\- (org.springframework:spring-webmvc:jar:4.2.5.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] |  \\- com.hand:hap-report:jar:classes:3.5.4-RELEASE:provided
[INFO] |     \\- com.bstek.ureport:ureport2-console:jar:2.2:provided
[INFO] |        \\- com.bstek.ureport:ureport2-core:jar:2.2:provided
[INFO] |           +- (org.springframework:spring-web:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] |           \\- (org.springframework:spring-jdbc:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO] \\- hscs:core:jar:classes:2.2.1-SNAPSHOT:provided
[INFO]    \\- org.springframework.kafka:spring-kafka:jar:1.3.0.RELEASE:provided
[INFO]       +- (org.springframework:spring-messaging:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO]       +- org.springframework:spring-tx:jar:4.3.11.RELEASE:provided
[INFO]       |  +- (org.springframework:spring-beans:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO]       |  \\- (org.springframework:spring-core:jar:4.3.11.RELEASE:provided - omitted for duplicate)
[INFO]       \\- org.springframework.retry:spring-retry:jar:1.2.0.RELEASE:provided
[INFO]          \\- (org.springframework:spring-core:jar:4.3.3.RELEASE:provided - omitted for conflict with 4.3.11.RELEASE)
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for FishParent 1.0-SNAPSHOT:
[INFO] 
[INFO] FishParent ......................................... SUCCESS [  0.922 s]
[INFO] core-db ............................................ SUCCESS [  0.539 s]
[INFO] core ............................................... SUCCESS [  4.020 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  5.780 s
[INFO] Finished at: 2019-03-21T15:38:44+08:00
[INFO] ------------------------------------------------------------------------
xujiaqingdeMacBook-Pro:mos jaycee$ 

实际上，对于omitted for duplicate的提示，我们可以不用去解决，只是提示了该包的重复定义。在实际情况上，更多的是根据就近原则引用了一个低版本的jar包，这样本身高版本的Jar包包含的方法，在低版本却没有，导致项目在调用时，出现了“方法找不到”类似的异常信息。

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。