maven的依赖

<?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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.caiz.maven</groupId>
  <artifactId>hello-first</artifactId>
  <version>SNAPSHOT-0.0.1</version>
  
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.10</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

</project>

一、maven的pom.xml配置依赖

1、结构

<!--依赖集合-->

 <dependencies> 

<!--依赖-->
    <dependency>

<!--组id-->
      <groupId>junit</groupId>

<!--模块id-->
      <artifactId>junit</artifactId>

<!--版本号-->
      <version>4.10</version>

<!--依赖范围-->
      <scope>test</scope>
    </dependency>
  </dependencies>

2、依赖是通过坐标来搜索的（GAV的方式）

G—— groupId

A——artifactId

V——version

3、依赖的查询

jar包查询顺序

本地仓库——>私服仓库(企业)——>中央仓库

本机在settings.xml文件配置：

      <localRepository>E:/apache-maven-3.1.0/Repository</localRepository>

代理方式访问私服

     <proxy>
      <id>optional</id>
      <active>true</active>
      <protocol>http</protocol>
      <username>proxyuser</username>
      <password>proxypass</password>
      <host>proxy.host.net</host>
      <port>80</port>
      <nonProxyHosts>local.net|some.host.com</nonProxyHosts>
    </proxy>

中央仓库查询访问

     1）http://www.mvnrepository.com/

     2）http://www.sonatype.org/nexus/

4、scope代表范围

1）test 测试范围依赖，编译和打包时候无效

2）compile编译时有效，是scope默认值

3）provided 在编译和测试的时候依赖，打成.war的时候不依赖

4）runtime运行时依赖，编译时候不依赖

 二、依赖的冲突

1、依赖存在传递性，当依赖冲突时，会先加载配置考前的依赖

a——>b1.0 c——>b1.2 ，e——>a+c,则a依赖b1.0;

2、路径最短原则

a——>b——>c1.0,e——>c1.1 ,f——>a+e 则f依赖c1.1

3、2例中如果f要依赖c1.0 则在依赖e时用，这样可以精确依赖

<exclusions>

    <groupId></groupId>

    <artifactId></artfactId>

</exclusions>

4、直接添加依赖，不通过传递依赖加入

 三、依赖的聚合问题

<?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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.cai.maven</groupId>
  <artifactId>hello-second</artifactId>
  <version>SNAPSHOT-0.0.1</version>
<!--打包的方式-->
<pakaging>pom<packaging> 
 
    

<!--模块方案-->
 <modules>
	<module>../user-vo<module>
	<module>../user-service<module>
	<module>../user-dao<module>
 <modules>
</project>

 三、依赖的继承

<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.caiz.core</groupId>
  <artifactId>user-core</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>user-core</name>
  <url>http://maven.apache.org</url>

<parent>
<groupId>com.caiz.user</groupId>
<artfactId>user-parent</artfactId>
<version>snapshot0.0.1</version>
<ralativePath>../user-parent/pom.xml</relativePaht>
<parent>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    
  
  <junit.version>4.10<junit.version>
</properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>${junit.version}</version>
      <scope>test</scope>
    </dependency>
    </dependencies>
</project>

设定子类不全部继承用dependencyManagement

<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.caiz.core</groupId>
  <artifactId>user-core</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>user-core</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    
  </properties>

<dependencyManageMent>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.10</version>
      <scope>test</scope>
    </dependency>
    <dependency>
		<groupId>log4j</groupId>
		<artifactId>log4j</artifactId>
		<version>1.2.17</version>
	</dependency>
  </dependencies>
</dependencyManageMent>
</project>