二、Maven继承与聚合

1、继承主要解决版本号统一问题，继承的包类型必须为pom

2、聚合主要解决依赖的包不需要在本地仓库中存在

3、本地创建了四个工程：maven_parent（父模块）、maven_app（主模块）、maven_common（通用模块）、maven_core（基础模块）

4、执行mvn compile时，需要执行maven_parent工程的，执行其他模块时会报XXX.jar报找不到，因为在本地仓库中不存在，除非每个模块都执行了mvn install。

maven_parent配置：

<?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>org.example</groupId>
    <artifactId>maven_parent</artifactId>
    <version>1.0-SNAPSHOT</version>

    <packaging>pom</packaging>
    <modules>
        <module>../maven_core</module>
        <module>../maven_common</module>
        <module>../maven_app</module>
    </modules>
    <properties>
        <junit.version>4.12</junit.version>
        <maven.core.version>1.1-SNAPSHOT</maven.core.version>
        <maven.common.version>1.0-SNAPSHOT</maven.common.version>
    </properties>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>${junit.version}</version>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>org.example</groupId>
                <artifactId>maven_core</artifactId>
                <version>${maven.core.version}</version>
            </dependency>
            <dependency>
                <groupId>org.example</groupId>
                <artifactId>maven_common</artifactId>
                <version>${maven.common.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

---

maven_app配置：

<?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>org.example</groupId>
    <artifactId>maven_app</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <parent>
        <artifactId>maven_parent</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
        <relativePath>../maven_parent/pom.xml</relativePath>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.example</groupId>
            <artifactId>maven_common</artifactId>
        </dependency>
    </dependencies>

</project>

---

maven_common配置：

<?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>org.example</groupId>
    <artifactId>maven_common</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <artifactId>maven_parent</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
        <relativePath>../maven_parent/pom.xml</relativePath>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.example</groupId>
            <artifactId>maven_core</artifactId>
        </dependency>
    </dependencies>

</project>

---

maven_core配置：

<?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>org.example</groupId>
    <artifactId>maven_core</artifactId>
    <version>1.1-SNAPSHOT</version>
    <parent>
        <groupId>org.example</groupId>
        <artifactId>maven_parent</artifactId>
        <version>1.0-SNAPSHOT</version>
        <relativePath>../maven_parent/pom.xml</relativePath>
    </parent>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>