java Maven 上的 POM 是什么？
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What is a POM on maven?
提问by Uder Moreira
I'm trying to follow the get started manual of maven, but I receive this error
我正在尝试按照 maven 的入门手册进行操作，但收到此错误
c:\Ambiente\workspace>mvn archetype:generate \ -DarchetypeGroupId=org.apache.maven.archety
pes \ -DgroupId=com.mycompany.app \ -DartifactId=my-app -X
Apache Maven 3.1.0 (893ca28a1da9d5f51ac03827af98bb730128f9f2; 2013-06-27 23:15:32-0300)
Maven home: C:\Ambiente\apache-maven-3.1.0
Java version: 1.7.0_25, vendor: Oracle Corporation
Java home: C:\Program Files\Java\jdk1.7.0_25\jre
Default locale: pt_BR, platform encoding: Cp1252
OS name: "windows 7", version: "6.1", arch: "x86", family: "windows"
[INFO] Error stacktraces are turned on.
[DEBUG] Reading global settings from C:\Ambiente\apache-maven-3.1.0\conf\settings.xml
[DEBUG] Reading user settings from C:\Users\t316360\.m2\settings.xml
[DEBUG] Using local repository at C:\Users\t316360\.m2\repository
[DEBUG] Using manager EnhancedLocalRepositoryManager with priority 10.0 for C:\Users\t3163
60\.m2\repository
[INFO] Scanning for projects...
[DEBUG] Extension realms for project org.apache.maven:standalone-pom:pom:1: (none)
[DEBUG] Looking up lifecyle mappings for packaging pom from ClassRealm[plexus.core, parent
: null]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.078s
[INFO] Finished at: Mon Jul 22 17:23:03 BRT 2013
[INFO] Final Memory: 11M/247M
[INFO] ------------------------------------------------------------------------
[ERROR] The goal you specified requires a project to execute but there is no POM in this d
irectory (c:\Ambiente\workspace). Please verify you invoked Maven from the correct directo
ry. -> [Help 1]
org.apache.maven.lifecycle.MissingProjectException: The goal you specified requires a proj
ect to execute but there is no POM in this directory (c:\Ambiente\workspace). Please verif
y you invoked Maven from the correct directory.
what is POM and what do I suppose to do to have this file?
什么是 POM，我应该怎么做才能拥有这个文件？
回答by samsquanch
A pom.xml file describes how to build a project. It can be considered the Java version of a Makefile in C/C++ or setup.py in Python. Are you following a specific example?
pom.xml 文件描述了如何构建项目。它可以被认为是 C/C++ 中的 Makefile 或 Python 中的 setup.py 的 Java 版本。您是否在遵循特定示例？
回答by tokhi
The pom.xmlfile is the core of a project's configuration in Maven. It is a single configuration file that contains the majority of information required to build a project in just the way you want. The POM is huge and can be daunting in its complexity, but it is not necessary to understand all of the intricacies just yet to use it effectively.
该pom.xml文件是 Maven 中项目配置的核心。它是一个单一的配置文件，其中包含以您想要的方式构建项目所需的大部分信息。POM 是巨大的，其复杂性可能令人生畏，但为了有效地使用它，没有必要了解所有的复杂性。
Below is just a simple example:
下面只是一个简单的example：
<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.mycompany.app</groupId>
<artifactId>my-app</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>Maven Quick Start Archetype</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.2</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
To build the dependencies that you specified in pom.xmlfile execute:
mvn clean packageAfter a successfull mvn packageyou will see something like below:
要构建您在pom.xml文件中指定的依赖项，请执行：
mvn clean package成功后，mvn package您将看到如下所示的内容：
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2 seconds
[INFO] Finished at: Tue Jul 23 (Time..)
[INFO] Final Memory: 3M/6M
[INFO] -----------------------------
the above command will download all the dependencies to your home directory /home/user/.m2/..
上面的命令会将所有依赖项下载到您的主目录/home/user/.m2/..
- Have a look on this How to create a maven project
- Also have a look to Maven in 5 min
回答by Thiago Soares
The way you tried the command is supposed to work for Linux environment and you are running Windows. Please double check the command (likely removing the \ ) and it should work just fine.
您尝试该命令的方式应该适用于 Linux 环境并且您正在运行 Windows。请仔细检查命令（可能删除 \ ），它应该可以正常工作。
