maven传递性依赖与NoSuchMethodError

    对于maven, 很多人看似很熟悉，其实貌似根本不了解，本文旨在解决某些方面的疑惑。

       当我在service模块引入公司某业务的一个接口，由于该接口依赖了公司写的各种东西和spring等第三方依赖，所以我一下子啥都不用显示依赖了，这叫传递性。而dependencyManagement的作用在于仍然让子模块显示写依赖，但依赖的版本和设置不用写了，简化了。关于jar包的传递依赖，你可以在idea的maven窗口中选定子模块右键show dependencies。

       在idea环境中，有时你不得不执行reimport和clean，才能看到jar包引入。另外，请注意你写的version是仓库中确实存在的。

       如果公司没有maven私服，完全依赖apache maven库，也许是够用的，碰到其他公司的接口需要你引入他们的jar包时，可以把jar包放在jvm/ext/lib下。

       值得一提的是，在模块组织方面，你完全可以把紧密相关的几个系统的放在一起，各个系统的web模块公用一套common, do及dao模块，而不必为每个系统打开一个idea窗口。

       pom里已经引入dependency，但很多时候我们需要reimport一下甚至很多下才能看到jar包被真正引入，如果module被ignore了，那么也很可能引入不了jar包。注意，只要dependency没变红，就是OK的。

       本地install时，请把当前模块依赖的模块先install一下。

       本地测试时，idea开启了自动indexing时，很有可能远程的包会覆盖本地的包，导致本地要重新install。

       maven的传递性依赖会导致间接进入一些包而与显示引入的发生冲突，例如，某依赖间接引入了spring2.5.6，模块里显示依赖的是spring3.1.1，spring2.5.6里ThreadPoolTaskExecutor没有submit(Runnable)方法，spring3.1.1里有，程序运行时极有可能加载spring2.5.6的ThreadPoolTaskExecutor.class而发生java.lang.NoSuchMethodError。

 

maven其他注意点：

  由于历史原因，maven的核心插件之一——compiler插件默认只支持编译Java 1.3，因此需要配置该插件使其支持Java 5.

典型的maven配置示例：

 父pom

Xml代码   <?xml version="1.0" encoding="UTF-8"?>  <project xmlns="http://maven.apache.org/POM/4.0.0"           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <modelVersion>4.0.0</modelVersion>        <groupId>com.ixhong</groupId>      <artifactId>ixhong</artifactId>      <packaging>pom</packaging>      <version>1.0-SNAPSHOT</version>      <modules>          <module>ixhong-common</module>          <module>ixhong-admin-web</module>          <module>ixhong-domain</module>          <module>ixhong-dao</module>          <module>ixhong-manager</module>          <module>ixhong-fs-web</module>          <module>ixhong-support-web</module>          <module>ixhong-lender-web</module>          <module>ixhong-base</module>          <module>ixhong-tomcat-web</module>      </modules>        <properties>          <spring.version>3.2.11.RELEASE</spring.version>          <ibatis.version>3.2.7</ibatis.version>          <rootdir>${basedir}</rootdir>      </properties>      <dependencies>          <dependency>              <groupId>commons-lang</groupId>              <artifactId>commons-lang</artifactId>              <version>2.6</version>          </dependency>          <dependency>              <groupId>commons-collections</groupId>              <artifactId>commons-collections</artifactId>              <version>3.2.1</version>          </dependency>            <dependency>              <groupId>commons-codec</groupId>              <artifactId>commons-codec</artifactId>              <version>1.10</version>          </dependency>          <!-- -->          <dependency>              <groupId>log4j</groupId>              <artifactId>log4j</artifactId>              <version>1.2.12</version>          </dependency>      </dependencies>      <dependencyManagement>          <dependencies>              <dependency>                  <groupId>javax.servlet</groupId>                  <artifactId>javax.servlet-api</artifactId>                  <version>3.0.1</version>                  <scope>provided</scope>              </dependency>              <dependency>                  <groupId>redis.clients</groupId>                  <artifactId>jedis</artifactId>                  <version>2.8.0</version>              </dependency>              <dependency>                  <groupId>org.apache.struts</groupId>                  <artifactId>struts2-core</artifactId>                  <version>2.2.3.1</version>              </dependency>              <dependency>                  <groupId>org.apache.tomcat</groupId>                  <artifactId>tomcat-catalina</artifactId>                  <version>7.0.57</version>                  <scope>provided</scope>              </dependency>              <dependency>                  <groupId>org.apache.tomcat</groupId>                  <artifactId>tomcat-coyote</artifactId>                  <version>7.0.57</version>                  <scope>provided</scope>              </dependency>          </dependencies>      </dependencyManagement>      <!--<scm>          <connection>scm:git:git@git.qwexyz.com:qwexyz/qwexyz.git</connection>          <url>scm:git:git@git.qwexyz.com:qwexyz/qwexyz.git</url>          <developerConnection>scm:git:git@git.qwexyz.com:qwexyz/qwexyz.git</developerConnection>      </scm>-->      <build>          <plugins>              <plugin>                  <artifactId>maven-compiler-plugin</artifactId>                  <version>3.1</version>                  <configuration>                      <source>1.6</source>                      <target>1.6</target>                      <encoding>UTF-8</encoding>                  </configuration>              </plugin>              <plugin>                  <artifactId>maven-resources-plugin</artifactId>                  <version>2.6</version>                  <configuration>                      <encoding>UTF-8</encoding>                  </configuration>              </plugin>              <plugin>                  <groupId>org.apache.maven.plugins</groupId>                  <artifactId>maven-release-plugin</artifactId>                  <version>2.1</version>              </plugin>          </plugins>      </build>    </project>  

  web

Xml代码   <?xml version="1.0" encoding="UTF-8"?>  <project xmlns="http://maven.apache.org/POM/4.0.0"           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <parent>          <artifactId>ixhong</artifactId>          <groupId>com.ixhong</groupId>          <version>1.0-SNAPSHOT</version>      </parent>      <modelVersion>4.0.0</modelVersion>        <artifactId>ixhong-lender-web</artifactId>        <packaging>war</packaging>      <name>ixhong-user-web</name>      <url>http://maven.apache.org</url>      <!-- 依赖包 -->      <dependencies>            <dependency>              <groupId>com.ixhong</groupId>              <artifactId>ixhong-manager</artifactId>              <version>1.0-SNAPSHOT</version>          </dependency>          <dependency>              <groupId>com.ixhong</groupId>              <artifactId>ixhong-common</artifactId>              <version>1.0-SNAPSHOT</version>          </dependency>          <dependency>              <groupId>org.mybatis</groupId>              <artifactId>mybatis-spring</artifactId>              <version>1.2.2</version>          </dependency>          <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-context</artifactId>              <version>${spring.version}</version>          </dependency>          <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-context-support</artifactId>              <version>${spring.version}</version>          </dependency>          <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-webmvc</artifactId>              <version>${spring.version}</version>          </dependency>          <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-jdbc</artifactId>              <version>${spring.version}</version>          </dependency>          <dependency>              <groupId>mysql</groupId>              <artifactId>mysql-connector-java</artifactId>              <version>5.1.32</version>          </dependency>            <dependency>              <groupId>org.apache.velocity</groupId>              <artifactId>velocity</artifactId>              <version>1.7</version>          </dependency>          <dependency>              <groupId>javax.servlet</groupId>              <artifactId>javax.servlet-api</artifactId>              <version>3.0.1</version>              <scope>provided</scope>          </dependency>              <dependency>              <groupId>commons-dbcp</groupId>              <artifactId>commons-dbcp</artifactId>              <version>1.4</version>          </dependency>          <dependency>              <groupId>commons-fileupload</groupId>              <artifactId>commons-fileupload</artifactId>              <version>1.3.1</version>          </dependency>          <dependency>              <groupId>org.apache.velocity</groupId>              <artifactId>velocity-tools</artifactId>              <version>2.0</version>              <exclusions>                  <exclusion>                      <groupId>org.apache.struts</groupId>                      <artifactId>*</artifactId>                  </exclusion>              </exclusions>          </dependency>            <dependency>              <groupId>org.apache.activemq</groupId>              <artifactId>activemq-client</artifactId>              <version>5.11.1</version>          </dependency>          <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-jms</artifactId>              <version>${spring.version}</version>          </dependency>                <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-test</artifactId>              <version>${spring.version}</version>              <scope>test</scope>          </dependency>          <dependency>              <groupId>junit</groupId>              <artifactId>junit</artifactId>              <version>4.8.2</version>              <scope>test</scope>          </dependency>        </dependencies>      <build>          <finalName>ROOT</finalName>          <outputDirectory>src/main/webapp/WEB-INF/classes</outputDirectory>          <resources>              <resource>                  <directory>src/main/resources</directory>                  <filtering>true</filtering>              </resource>          </resources>      </build>        <profiles>          <profile>              <id>development</id>              <activation>                  <activeByDefault>true</activeByDefault>              </activation>              <build>                  <filters>                      <filter>../profile/development.properties</filter>                  </filters>              </build>          </profile>          <profile>              <id>test</id>              <build>                  <filters>                      <filter>../profile/test.properties</filter>                  </filters>              </build>          </profile>          <profile>              <id>production</id>              <build>                  <filters>                      <filter>../profile/production.properties</filter>                  </filters>              </build>          </profile>      </profiles>      </project>  

  dao

Xml代码   <?xml version="1.0" encoding="UTF-8"?>  <project xmlns="http://maven.apache.org/POM/4.0.0"           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <parent>          <artifactId>ixhong</artifactId>          <groupId>com.ixhong</groupId>          <version>1.0-SNAPSHOT</version>      </parent>      <modelVersion>4.0.0</modelVersion>        <artifactId>ixhong-dao</artifactId>        <packaging>jar</packaging>      <name>ixhong-dao</name>      <url>http://maven.apache.org</url>      <build>          <finalName>ixhong-dao</finalName>          <resources>              <resource>                  <directory>src/main/resources</directory>                  <filtering>true</filtering>              </resource>          </resources>      </build>      <dependencies>          <dependency>              <groupId>com.ixhong</groupId>              <artifactId>ixhong-domain</artifactId>              <version>1.0-SNAPSHOT</version>          </dependency>          <dependency>              <groupId>org.mybatis</groupId>              <artifactId>mybatis</artifactId>              <version>${ibatis.version}</version>          </dependency>        </dependencies>      </project>  

  domain

Xml代码   <?xml version="1.0" encoding="UTF-8"?>  <project xmlns="http://maven.apache.org/POM/4.0.0"           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <parent>          <artifactId>ixhong</artifactId>          <groupId>com.ixhong</groupId>          <version>1.0-SNAPSHOT</version>      </parent>      <modelVersion>4.0.0</modelVersion>        <artifactId>ixhong-domain</artifactId>        <packaging>jar</packaging>      <name>ixhong-domain</name>      <url>http://maven.apache.org</url>      <build>          <finalName>ixhong-domain</finalName>      </build>      <dependencies>          <dependency>              <groupId>net.sf.json-lib</groupId>              <artifactId>json-lib</artifactId>              <version>2.4</version>              <classifier>jdk15</classifier>          </dependency>      </dependencies>      </project>  

 

maven的核心仅仅定义了抽象的生命周期，具体的任务是交由插件完成的，插件以独立的构建形式存在，因此，maven核心的分发包只有不到3MB的大小，Maven会在需要的时候下载并使用插件。一个插件可能会对应多个目标，一个目标就是一个功能，如maven-dependency-plugin有十多个目标，dependency:analyze,dependency:tree,dependency:list等。

可以使用jetty-maven-plugin启动web应用进行测试。

 

配置文件

settings.xml中的profile是pom.xml中的profile的简洁形式。它包含了激活(activation)，仓库(repositories)，插件仓库(pluginRepositories)和属性(properties)元素。profile元素仅包含这四个元素是因为他们涉及到整个的构建系统，而不是个别的POM配置。

如果settings中的profile被激活，那么它的值将重载POM或者profiles.xml中的任何相等ID的profiles。

激活(activation)

activations是profile的关键，就像POM中的profiles，profile的能力在于它在特定情况下可以修改一些值。而这些情况是通过activation来指定的。

 

 

Xml代码   <?xml version="1.0" encoding="UTF-8"?>  <settings xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd" xmlns="http://maven.apache.org/SETTINGS/1.0.0"      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">    <profiles>      <profile>        <repositories>          <repository>            <snapshots>              <enabled>false</enabled>            </snapshots>            <id>central</id>            <name>libs-releases</name>            <url>http://maven.whatsmars.com/libs-releases</url>          </repository>          <repository>            <snapshots />            <id>snapshots</id>            <name>libs-snapshots</name>            <url>http://maven.whatsmars.com/libs-snapshots</url>          </repository>        </repositories>        <pluginRepositories>          <pluginRepository>            <snapshots>              <enabled>false</enabled>            </snapshots>            <id>central</id>            <name>plugins-releases</name>            <url>http://maven.whatsmars.com/plugins-releases</url>          </pluginRepository>          <pluginRepository>            <snapshots />            <id>snapshots</id>            <name>plugins-snapshots</name>            <url>http://maven.whatsmars.com/plugins-snapshots</url>          </pluginRepository>        </pluginRepositories>        <id>artifactory</id>      </profile>    </profiles>    <activeProfiles>      <activeProfile>artifactory</activeProfile>    </activeProfiles>  </settings>  

 mvn package-DskipTests  打包并且跳过测试

mvn clean install-Pdev  激活dev下的profile,这样properties中的配置就会替换成实际值

 

maven可继承的pom元素

Xml代码   groupId ：项目组 ID ，项目坐标的核心元素；  version ：项目版本，项目坐标的核心元素；  description ：项目的描述信息；  organization ：项目的组织信息；  inceptionYear ：项目的创始年份；  url ：项目的 url 地址  develoers ：项目的开发者信息；  contributors ：项目的贡献者信息；  distributionManagerment ：项目的部署信息；  issueManagement ：缺陷跟踪系统信息；  ciManagement ：项目的持续继承信息；  scm ：项目的版本控制信息；  mailingListserv ：项目的邮件列表信息；  properties ：自定义的 Maven 属性；  dependencies ：项目的依赖配置；  dependencyManagement ：醒目的依赖管理配置；  repositories ：项目的仓库配置；  build ：包括项目的源码目录配置、输出目录配置、插件配置、插件管理配置等；  reporting ：包括项目的报告输出目录配置、报告插件配置等。   原文链接：[http://wely.iteye.com/blog/2270414 ]