Maven 高级玩法

实用技巧

Maven 提速

多线程

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# 用 4 个线程构建,以及根据 CPU 核数每个核分配 1 个线程进行构建
$ mvn -T 4 clean install
$ mvn -T 1C clean install

跳过测试

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-DskipTests               # 不执行测试用例,但编译测试用例类生成相应的 class 文件至 target/test-classes 下
-Dmaven.test.skip=true # 不执行测试用例,也不编译测试用例类

# 结合上文的`并行执行`
$ mvn -T 1C clean install -Dmaven.test.skip=true

# 如果还是阻塞: 资源管理器 - shutdown all java app

# 如果 jar 包过大,可以下载按照路径放在 repository 中,之后可能还需要 mvn clean 来下载 groovy-all-2.3.11.pom 文件 (mvnrepository.com)
D:\apps\maven\repository\org\codehaus\groovy\groovy-all\2.3.11\groovy-all-2.3.11.jar

编译失败后,接着编译

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# 如果是 Apache Eagle 之类带有几十个子项目的工程,如果从头编译所有的模块,会很耗功夫
# 通过指定之前失败的模块名,可以继续之前的编译
$ mvn -rf :moduleName clean install

跳过失败的模块,编译到最后再报错

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$ mvn clean install --fail-at-end

使用 Nexus 本地私服

 可参考 Maven 学习(四):使用 Nexus 搭建 Maven 私服

使用 Aliyun 国内镜像

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<mirror>
<id>alimaven</id>
<name>aliyun maven</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<mirrorOf>central</mirrorOf>
</mirror>

指定 Repository 目录

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<!-- Default: ~/.m2/repository  -->
<localRepository>D:\apps\maven\repository</localRepository>

如何使用 Maven 编译指定 module

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$ mvn install -pl <module_name> -am

-pl, --projects (Build specified reactor projects instead of all project)
-am, --also-make (If project list is specified, also build projects required by the list)
-amd, --also-make-dependents (If project list is specified, also build projects that depend on)

Maven 标准目录结构

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src/main/java             Application/Library sources
src/main/resources Application/Library resources
src/main/filters Resource filter files
src/main/webapp Web application sources
src/test/java Test sources
src/test/resources Test resources
src/test/filters Test resource filter files
src/it Integration Tests (primarily for plugins)
src/assembly Assembly descriptors
src/site Site
LICENSE.txt Project's license
NOTICE.txt Notices and attributions required by libraries that the project depends on
README.txt Project's readme

如何在 Maven 中使用多个 source

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<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>src/main/scala</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>

Using Scala UnitTest by Maven

安装 Scala

Maven 依赖

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<dependency>
<groupId>org.scalatest</groupId>
<artifactId>scalatest_2.10</artifactId>
<version>2.2.1</version>
</dependency>

创建 unittest 需要的 trait

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import org.scalatest._
abstract class UnitTestStyle extends FlatSpec
with Matchers with OptionValues with Inside with Inspectors

编写测试

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import spark.streaming.detect.SendNetflow
class SendNetflowTest extends UnitTestStyle {

"Clean method" should "output a string" in {

val s = "0,tcp,http,SF,229,9385,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,9,9,0.00,0.00,0.00,0.00,1.00,0.00,0.00,9,90,1.00,0.00,0.11,0.04,0.00,0.00,0.00,0.00,normal."
SendNetflow.clean(s) should be("0,229,9385,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,9,9,0.00,0.00,0.00,0.00,1.00,0.00,0.00,9,90,1.00,0.00,0.11,0.04,0.00,0.00,0.00,0.00\tnormal.")
}

it should "throw Exception if an empty string is inputted" in {
val emptyS = ""
a[RuntimeException] should be thrownBy {
SendNetflow.clean(emptyS)
}
}

Tips: Full code is here.

Using slf4j by Maven

Maven 配置

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<slf4j.version>1.7.12</slf4j.version>
<logback.version>1.1.3</logback.version>

<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>${logback.version}</version>
</dependency>

<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>${logback.version}</version>
<exclusions>
<exclusion>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
</exclusion>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>${slf4j.version}</version>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>${slf4j.version}</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>log4j-over-slf4j</artifactId>
<version>${slf4j.version}</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jul-to-slf4j</artifactId>
<version>${slf4j.version}</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>

logback.xml in resources directory

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<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<!-- %p:Level %m:Message %c.%M:Package+Method %F:%L:File+Line -->
<property name="pattern" value="%d{yyyy-MM-dd HH:mm:ss.SSS} | %p | %m | %c.%M | %F:%L %n"/>

<!-- Print in Console -->
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder charset="UTF-8">
<pattern>${pattern}</pattern>
</encoder>
</appender>

<root level="ALL">
<appender-ref ref="STDOUT"/>
</root>
</configuration>

编码

示例
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private static final Logger _log = LoggerFactory.getLogger(ZKEventWatch.class);
_log.info(state);
遇到的坑
SLF4J multi bindings
  • 描述
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SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/D:/apps/maven/repository/ch/qos/logback/logback-classic/1.1.3/logback-classic-1.1.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/D:/apps/maven/repository/org/slf4j/slf4j-log4j12/1.6.1/slf4j-log4j12-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
  • 解决
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<!-- 使用 Apache Curator 需要 exclusion slf4j-log4j12,否则会出现问题 -->
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-recipes</artifactId>
<version>${apache.curator.version}</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
</exclusion>
</exclusions>
</dependency>

Tips: Full code is here.

导出依赖 Jar

 如何利用 Maven 将依赖的 jar 都导入到一个文件夹下

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<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.10</version>
<configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
<excludeTransitive>false</excludeTransitive>
<stripVersion>false</stripVersion>
</configuration>
</plugin>
</plugins>
</build>

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$ mvn clean dependency:copy-dependencies

# 将 yuzhouwan-flume 依赖的 jars 都 导出到一个文件夹
# 用相对路径,不能是 绝对路径,否则 maven 会报错:Unknown lifecycle phase "Java"
$ mvn dependency:copy-dependencies -f yuzhouwan-flume/pom.xml -DoutputDirectory=yuzhouwan-flume/target/lib
$ mvn dependency:copy-dependencies -f yuzhouwan-api/yuzhouwan-admin-api/pom.xml -DoutputDirectory=target/lib

Profiles

Tips: Full code is here.

日志级别

 -Dorg.slf4j.simpleLogger.defaultLogLevel=error

Generate Code for Antlr

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$ mvn clean install -T 1C -DskipTests=true -Dorg.slf4j.simpleLogger.defaultLogLevel=error -B

Maven Properties

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$ mvn clean install -Dmy.property=propertyValue

Maven Check Style

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$ mvn clean install -Dcheckstyle.skip

Maven Update

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$ mvn clean install -U
# -U means force update of dependencies.

Maven License Check

 可参考 License Maven Plugin

Maven Dependency

Pre-download

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$ mvn dependency:go-offline

Version-compare

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# 在开发一些 Coprocessor 的时候,需要保证和 HBase 集群的依赖 jar 版本一致,可以使用该方法
$ mvn versions:compare-dependencies -DremotePom=org.apache.hbase:hbase:0.98.8-hadoop2 -DreportOutputFile=depDiffs.txt
参考

Maven Proxy

命令行设置

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# Linux (bash)
$ export MAVEN_OPTS="-DsocksProxyHost=10.10.10.10 -DsocksProxyPort=8080"
# Windows
$ set MAVEN_OPTS="-DsocksProxyHost=10.10.10.10 -DsocksProxyPort=8080"

配置文件

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$ vim $MAVEN_HOME/conf/settings.xml

<proxies>
<!--<proxy>
<id>http-proxy</id>
<active>true</active>
<protocol>http</protocol>
<host>10.10.10.10</host>
<port>8888</port>
<nonProxyHosts>*.yuzhouwan.com</nonProxyHosts>
</proxy>-->

<proxy>
<id>socks-proxy</id>
<active>true</active>
<protocol>socks5</protocol>
<host>127.0.0.1</host>
<port>1080</port>
<nonProxyHosts>*.yuzhouwan.com</nonProxyHosts>
</proxy>
</proxies>

Avro 插件

创建 avsc 文件

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{
"namespace": "com.yuzhouwan.hacker.avro",
"type": "record",
"name": "User",
"fields": [
{
"name": "name",
"type": "string"
},
{
"name": "favorite_number",
"type": [
"int",
"null"
]
},
{
"name": "favorite_color",
"type": [
"string",
"null"
]
}
]
}

使用 avro-tools 工具生成 Avro 类

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# 下载 avro-tools
# https://mvnrepository.com/artifact/org.apache.avro/avro-tools/1.8.1
# http://archive.apache.org/dist/avro/avro-1.8.1/java/ (better)
$ wget http://archive.apache.org/dist/avro/avro-1.8.1/java/avro-tools-1.8.1.jar -c avro-tools-1.8.1.jar

# 利用 avsc 文件中的 Schema 生成 Avro 类
$ java -jar avro-tools-1.8.1.jar compile schema user.avsc .

使用 avro-plugin 插件生成 Avro 类

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<properties>
<apache.avro.version>1.7.7</apache.avro.version>
</properties>

<dependencies>
<!-- apache avro -->
<dependency>
<groupId>org.apache.avro</groupId>
<artifactId>avro</artifactId>
<version>${apache.avro.version}</version>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>org.apache.avro</groupId>
<artifactId>avro-maven-plugin</artifactId>
<version>${apache.avro.version}</version>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>schema</goal>
</goals>
<configuration>
<sourceDirectory>${project.basedir}/src/main/resources/avsc/</sourceDirectory>
<outputDirectory>${project.basedir}/src/main/java/</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

Tips: Full code is here.

Shade 插件解决 Jar 多版本共存

适用场景

 在整合大型项目时,可能都依赖 commons-collections 此类的工具包,但是也可能 commons-collections 的版本却因为不一致,导致冲突。可以通过 Shade 插件的 relocation 方法进行重定向,此时冲突的依赖 package 名,会被重命名,并且依赖该 jar 的程序,都会被自动替换为新的 package 名

基本用法

实例一
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<properties>
<maven.shade.plugin.version>2.4.3</maven.shade.plugin.version>
</properties>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.4.3</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<shadedArtifactAttached>false</shadedArtifactAttached>
<createSourcesJar>true</createSourcesJar>
<artifactSet>
<excludes>
<exclude>org.mapdb.*</exclude>
</excludes>
</artifactSet>
<relocations>
<relocation>
<pattern>org.apache.commons.collections</pattern>
<shadedPattern>com.yuzhouwan.org.apache.commons.collections</shadedPattern>
</relocation>
</relocations>
</configuration>
</execution>
</executions>
</plugin>
实例二
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<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>${maven.shade.plugin.version}</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<shadedArtifactAttached>true</shadedArtifactAttached>
<shadedClassifierName>all</shadedClassifierName>
<createSourcesJar>true</createSourcesJar>
<artifactSet>
<!-- 因为 org.glassfish 里面存在类似 public static class Builder implements javax.ws.rs.client.Invocation.Builder 全限定名的写法 -->
<!-- 所以只能用 shade 去隐藏 com.sun.jersey -->
<excludes>
<exclude>org.glassfish.*</exclude>
</excludes>
</artifactSet>
<relocations>
<relocation>
<pattern>javax.ws</pattern>
<shadedPattern>shade.javax.ws</shadedPattern>
</relocation>
<relocation>
<pattern>org.apache.curator</pattern>
<shadedPattern>shade.org.apache.curator</shadedPattern>
</relocation>
<!--<relocation>
<pattern>org.glassfish</pattern>
<shadedPattern>shade.org.glassfish</shadedPattern>
</relocation>
<relocation>
<pattern>com.sun.jersey</pattern>
<shadedPattern>shade.com.sun.jersey</shadedPattern>
</relocation>-->
</relocations>
</configuration>
</execution>
</executions>
</plugin>

踩过的坑

Error creating shaded jar: Error in ASM processing class
描述
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Failed to execute goal org.apache.maven.plugins:maven-shade-plugin:2.1:shade (default) on project base-k2d-flow: Error creating shaded jar: Error in ASM processing class com/yuzhouwan/bigdata/k2d/K2DPartitioner.class: 52264 -> [Help 1]
解决

 升级 maven-shade-plugin 版本到 2.4.x

通过 Shade 将问题解决后,部署上线后,依赖冲突复现
解决

 因为官方明确指出 java.io.File.listFiles() 方法返回的文件序列顺序,是不做保证的。所以,上线后运行环境发生变化,加载 lib 目录下的 jar 包顺序,可能会发生变化。这时候,就需要利用不同 lib 目录,并修改 classpath 的方式,将 jar 包加载顺序确定下来

 例如,在整合 Druid 这类依赖树比较庞大的工程,就遇到了这么一种情况。Druid 中 com.sun.jersey (1.19) 和 Dataflow 中 org.glassfish.jersey (2.25.1) 发生冲突。增加了上述实例二中的 Shade 操作仍然会在线上环境,复现依赖冲突。这时,我们可以通过增加一个 lib_jersey 目录,存放 javax.ws.rs-api-2.1.jar,并修改 classpath 为 lib_jersey/*:lib/*。以此,保证了 lib_jersey 中的依赖得以优先加载,从而解决冲突

参考

Assembly 插件

不同模块的依赖,打包到不同的目录下

具体步骤

 第一步,先在负责打包分发的 distribution 模块中,设置 pom.xml 文件

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<properties>
<maven.assembly.plugin.version>2.3</maven.assembly.plugin.version>
</properties>

<packaging>pom</packaging>

<dependencies>
<dependency>
<groupId>com.yuzhouwan</groupId>
<artifactId>core</artifactId>
</dependency>
<dependency>
<groupId>com.yuzhouwan</groupId>
<artifactId>ai</artifactId>
</dependency>
<dependency>
<groupId>com.yuzhouwan</groupId>
<artifactId>bigdata</artifactId>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>${maven.assembly.plugin.version}</version>
<executions>
<execution>
<id>assemble</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>src/assembly/bin.xml</descriptor>
<descriptor>src/assembly/src.xml</descriptor>
</descriptors>
<tarLongFileMode>gnu</tarLongFileMode>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

 第二步,创建好对应的 bin.xml 和 src.xml

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<assembly xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">

<id>bin</id>

<formats>
<format>dir</format>
<format>tar.gz</format>
</formats>

<baseDirectory>yuzhouwan-${project.version}-bin</baseDirectory>

<fileSets>
<fileSet>
<directory>../</directory>

<excludes>
<exclude>**/target/**</exclude>
<exclude>**/.classpath</exclude>
<exclude>**/.project</exclude>
<exclude>**/.settings/**</exclude>
<exclude>lib/**</exclude>
<exclude>conf/**</exclude>
</excludes>

<includes>
<include>README</include>
<include>LICENSE</include>
<include>NOTICE</include>
<include>CHANGELOG</include>
<include>RELEASE-NOTES</include>
<include>conf/</include>
</includes>
</fileSet>

<fileSet>
<directory>../</directory>
<includes>
<include>bin/yuzhouwan-cli.sh</include>
</includes>
<fileMode>0777</fileMode>
<directoryMode>0755</directoryMode>
</fileSet>
</fileSets>

<moduleSets>
<moduleSet>
<includeSubModules>false</includeSubModules>
<useAllReactorProjects>true</useAllReactorProjects>
<includes>
<include>com.yuzhouwan:yuzhouwan-core</include>
</includes>
<excludes>
<exclude>com.yuzhouwan:ai</exclude>
<exclude>com.yuzhouwan:bigdata</exclude>
</excludes>
<binaries>
<outputDirectory>lib/core</outputDirectory>
<unpack>false</unpack>
<dependencySets>
<dependencySet>
<useProjectArtifact>false</useProjectArtifact>
<useTransitiveDependencies>true</useTransitiveDependencies>
<unpack>false</unpack>
<excludes>
<exclude>com.yuzhouwan:ai</exclude>
<exclude>com.yuzhouwan:bigdata</exclude>
</excludes>
</dependencySet>
</dependencySets>
</binaries>
</moduleSet>

<moduleSet>
<includeSubModules>false</includeSubModules>
<useAllReactorProjects>true</useAllReactorProjects>
<includes>
<include>com.yuzhouwan:ai</include>
</includes>
<excludes>
<exclude>com.yuzhouwan:bigdata</exclude>
</excludes>
<binaries>
<outputDirectory>lib/plugins/ai</outputDirectory>
<unpack>false</unpack>
<dependencySets>
<dependencySet>
<useProjectArtifact>false</useProjectArtifact>
<useTransitiveDependencies>true</useTransitiveDependencies>
<unpack>false</unpack>
<excludes>
<exclude>com.yuzhouwan:bigdata</exclude>
</excludes>
</dependencySet>
</dependencySets>
</binaries>
</moduleSet>

<moduleSet>
<includeSubModules>false</includeSubModules>
<useAllReactorProjects>true</useAllReactorProjects>
<includes>
<include>com.yuzhouwan:bigdata</include>
</includes>
<excludes>
<exclude>com.yuzhouwan:ai</exclude>
</excludes>
<binaries>
<outputDirectory>lib/plugins/bigdata</outputDirectory>
<unpack>false</unpack>
<dependencySets>
<dependencySet>
<useProjectArtifact>false</useProjectArtifact>
<useTransitiveDependencies>true</useTransitiveDependencies>
<unpack>false</unpack>
<excludes>
<exclude>com.yuzhouwan:ai</exclude>
</excludes>
</dependencySet>
</dependencySets>
</binaries>
</moduleSet>
</moduleSets>
</assembly>
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<assembly xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">

<id>src</id>

<formats>
<format>dir</format>
<format>tar.gz</format>
</formats>

<baseDirectory>yuzhouwan-${project.version}-src</baseDirectory>

<fileSets>
<fileSet>
<directory>../</directory>

<excludes>
<exclude>**/target/**</exclude>
<exclude>**/.classpath</exclude>
<exclude>**/.project</exclude>
<exclude>**/*.iml</exclude>
<exclude>**/.settings/**</exclude>
<exclude>lib/**</exclude>
</excludes>

<includes>
<include>.ci</include>
<include>.gitignore</include>
<include>DEVNOTES</include>
<include>README</include>
<include>LICENSE</include>
<include>NOTICE</include>
<include>CHANGELOG</include>
<include>RELEASE-NOTES</include>
<include>bin/**</include>
<include>conf/**</include>
<include>native/**</include>
<include>pom.xml</include>
<include>dev-conf/**</include>
<include>yuzhouwan-core/**</include>
<include>yuzhouwan-ai/**</include>
<include>yuzhouwan-bigdata/**</include>
</includes>
</fileSet>
</fileSets>
</assembly>

 构建完成之后,即可看到 yuzhouwan-aiyuzhouwan-bigdata 模块的依赖,分别被打包到了 plugins/aiplugins/bigdata 目录下

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# 需要预先安装 tree 命令(yum install tree -y)
$ tree
.
├── bin
│   └── yuzhouwan-cli.sh
└── lib
├── core
└── plugins
├── ai
└── bigdata
踩过的坑
模块间存在版本冲突的 jar 包
  • 问题描述

    1
    Currently, inclusion of module dependencies may produce unpredictable results if a version conflict occurs
  • 解决

    如果上述 yuzhouwan-aiyuzhouwan-bigdata 模块,与 yuzhouwan-common 模块存在版本冲突的 jar 包,则需要将 bin.xml 拆解成 bin-common.xmlbin-ai.xmlbin-bigdata.xml 三个 assembly 配置文件,依次进行构建(此时需要将 id 设置成一样的,不然会被构建到不同的目录下)。否则,版本冲突的 jar 包,将只能保留其中一个版本,且具体保留哪个版本是不确定的

参考

常见问题

如何使用其他语言编译出来的 Jar

Clojar

 如果需要在 Maven 中,添加新的 Repository,这里以 Clojar 为例,配置如下:

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<repositories>
<repository>
<id>clojars.org</id>
<url>http://clojars.org/repo</url>
</repository>
</repositories>

本地缓存

 Maven 中出现 Repository 被缓存在本地,则可以进一步添加下面属性,以配置更新策略:

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<repository>
<id>clojars.org</id>
<url>http://clojars.org/repo</url>
<releases>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</releases>
<snapshots>
<enabled>true</enabled>
<updatePolicy>always</updatePolicy>
</snapshots>
</repository>

下载问题

已 download,未 import

 如果发现 pom.xml 中的 依赖虽然在 .m2 中被下载了,但是没有被 import 到项目中
 尝试在 Intellij Idea 的 setting 中 找到 Maven -> Ignored Files,看看对应的 pom.xml 有没有被勾选

如果仍然无法解决,也有可能是 Intellij Idea 自身的问题,可尝试通过 Just Restart 来解决

编译问题

JDK 版本不一致

描述
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Error:java: Compilation failed: internal java compiler error
解决

 调整 compiler 的级别,并在 pom.xml 中添加 build 标签,规定 compiler 的级别

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<build>
<finalName>elastic-netflow-v5</finalName>

<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-release-plugin</artifactId>
<version>2.4.1</version>
</plugin>
</plugins>
</build>

Scala 版本不一致

描述
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[ERROR] error: error while loading <root>, Error accessing D:\.m2\repository\org\apache\curator\curator-client\2.4.0\curator-client-2.4.0.jar
[ERROR] error: scala.reflect.internal.MissingRequirementError: object java.lang.Object in compiler mirror not found.
解决

 查看 pom 文件中指定的 scala 版本,切换到对应的版本,进行编译即可

存在没有下载好的依赖

描述
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Error creating properties files for forking; nested exception is java.io.IOException: No such file or directory
解决

 安装依赖

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$ mvn dependency::tree

 离线 build (offline)

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$ mvn install -o

本地 mvn clean install 到 .m2/repository 中的 jar 和 仓库中的不一致时

描述
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"Class not found 'xxxx' Empty test suite" in java unittest, after change the modules' names
解决
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Maven           ->        Reimport            ->        Generte Source and Update Folder
Ctrl + F9 -> Make Project

打包存在脏程序

 war:war 之前需要先执行 mvn clean install。否则,会因为 profiles 的缘故,导致 war 包中 缺少文件

语法问题

Maven 中无法识别 ${project.version}

 需要将所有(除了 root / parent 模块)的 <version>1.0</version> 中的具体版本号(如 1.0.0)全部替换成 "${project.version}"

插件问题

xxx module must not contain source root. the root already belongs to module xxx

解决
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Artifacts Setting  ->  Modules -> Sourc tab
delete the fold by clicking on the X icon to the right of it

ExecutionException The forked VM terminated without properly saying goodbye

描述
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[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.19.1:test (default-test) on project eagle-app-streamproxy: ExecutionException The forked VM terminated without properly saying goodbye. VM crash or System.exit called?
解决
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<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>${maven-surefire.version}</version>
<configuration>
<!-- 增加 argLine 参数以调整 JVM -->
<argLine>-Xmx2048m -Xms1024m -XX:MaxPermSize=512m -XX:-UseGCOverheadLimit</argLine>
<forkMode>always</forkMode>
</configuration>
</plugin>

详见:Eagle-RP-897

Fatal error compiling: 无效的目标发行版: 1.8

 需要在 IDE 的 Project Structure(Ctrl+Alt+Shift+S) 里设置 Project JDKjdk1.8,并在 Settings(Ctrl+Alt+S) 里设置 Java Compilerbytecode version1.8

Assembly 插件报错 java.lang.StackOverflowError

解决
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# 调大默认的堆栈大小
export MAVEN_OPTS=-Xss2m
补充
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-Xms:jvm 进程启动时分配的内存
-Xmx:jvm 进程运行过程中最大能分配到的内存
-Xss:jvm 进程中启动线程,为每个线程分配的内存大小

如何跳过 gpg 插件

 增加 <skip>true</skip> 配置即可

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<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-gpg-plugin</artifactId>
<executions>
<execution>
<id>sign-artifacts</id>
<phase>verify</phase>
<goals>
<goal>sign</goal>
</goals>
</execution>
</executions>
<configuration>
<skip>true</skip>
</configuration>
</plugin>

依赖问题

Maven 中央仓库找不到对应版本的依赖

如何将其他项目的 jar 安装到 maven 仓库中
利用命令安装
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$ mvn install:install-file -Dfile=<jar 包的位置> -DgroupId=<上面的 groupId> -DartifactId=<上面的 artifactId> -Dversion=<上面的 version> -Dpackaging=jar -DgeneratePom=true -DpomFile=<指定一个 pom.xml 添加进去>

$ mvn install:install-file -Dfile=G:\ES\yuzhouwan_netflow-rest\lib\ite-esmanage-0.7.2-SNAPSHOT.jar -DgroupId=ite -DartifactId=esmanage -Dversion=0.7.2-SNAPSHOT -Dpackaging=jar -DgeneratePom=true -DpomFile=C:\yuzhouwan\Maven\pom.xml

# -DgeneratePom 没有成功
# 原因是 这个第三方的 jar 中,pom.xml 路径不对,必须手动 copy 出来,并用 -DpomFile 的方式导入
利用插件安装
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<!-- 注意:${project.basedir} 是当前模块的根目录,需要把依赖包,放对位置 -->
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
<executions>
<execution>
<id>install-external</id>
<phase>clean</phase>
<configuration>
<file>${project.basedir}/lib/flume-hdfs-sink-${flume.version}.jar</file>
<repositoryLayout>default</repositoryLayout>
<groupId>org.apache.flume.flume-ng-sinks</groupId>
<artifactId>flume-hdfs-sink</artifactId>
<version>${flume.version}</version>
<packaging>jar</packaging>
<generatePom>true</generatePom>
</configuration>
<goals>
<goal>install-file</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</pluginManagement>
</build>

控制 Scope 范围

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# compile(编译范围)
 compile 范围是默认的。编译范围依赖在所有的 classpath 中可用,同时它们也会被打包

# provided(已提供范围)
 provided 范围只有在当 JDK 或者一个容器已提供该依赖之后才使用。它们不是传递性的,也不会被打包。适用于在实现了公共 common 模块,其中有很多依赖,但是只有在其他依赖了 common 模块的子模块中,重新声明依赖,才会真正被打包到子模块中。这样,既可以保证 common 模块的正常编译,又可以减少子模块中的依赖包大小

# runtime(运行时范围)
 runtime 范围在运行和测试系统的时候需要,但在编译的时候不需要。例如,在编译的时候,如果只需要 JDBC API Jar,但只有在运行的时候才需要 JDBC 驱动的具体实现

# test(测试范围)
 test 范围在一般的编译和运行时都不需要,它们只有在测试编译和测试运行阶段可用。常用于 JUnit 的依赖

# system(系统范围)
 system 范围与 provided 类似,但是必须显式的提供一个对于本地系统中 Jar 文件的路径。这么做是为了允许基于本地对象编译(systemPath),而这些对象是系统类库的一部分。这样的构件应该是一直可用的,Maven 也不会在仓库中去寻找它(不推荐使用)

引入某一个本身依赖树很庞大的 Dependency

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# 依赖列表
$ mvn dependency:list

# 依赖树(这里推荐直接用 Intellij Idea 中自带的 "Show Dependencies" 功能,可视化地展示依赖树 和 对应依赖冲突,并能够直接对 依赖树进行修剪)
$ mvn dependency:tree

# 依赖分析
$ mvn dependency:analyze
Unused declared dependencies 表示项目中未使用的,但显示声明的依赖
Used undeclared dependencies 表示项目中使用到的,但是没有显示声明的依赖

Detected both log4j-over-slf4j.jar AND slf4j-log4j12.jar on the class path, preempting StackOverflowError.

解决
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<spark.scala.version>2.11</spark.scala.version>
<apache.kafka.version>0.9.0.1</apache.kafka.version>

<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka_${spark.scala.version}</artifactId>
<version>${apache.kafka.version}</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
</exclusion>
<exclusion>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
</exclusion>
</exclusions>
</dependency>

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人工智能 (高级)& (进阶)| BigData | 算法

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