为什么要使用聚合工程
在项目初期，人员较少，但是还是需要协作开发。这时如果使用一个整体项目。会有冲突等问题。
dependencies与dependencyManagement的区别
在我们项⽬顶层的POM⽂件中，我们会看到dependencyManagement元素。通过它来管理jar包的版本，让⼦项⽬中引⽤⼀个依赖⽽不⽤显⽰的列出版本号。Maven会沿着⽗⼦层次向上⾛，直到找到⼀个拥有dependencyManagement元素的项⽬，然后它就会使⽤在这个dependencyManagement元素中指定的版本号。
这样做的好处：统⼀管理项⽬的版本号，确保应⽤的各个项⽬的依赖和版本⼀致，才能保证测试的和发布的是相同的成果，因此，在
顶层pom中定义共同的依赖关系。同时可以避免在每个使⽤的⼦项⽬中都声明⼀个版本号，这样想升级或者切换到另⼀个版本时，只需要在
⽗类容器⾥更新，不需要任何⼀个⼦项⽬的修改；如果某个⼦项⽬需要另外⼀个版本号时，只需要在dependencies中声明⼀个版本号即
可。⼦类就会使⽤⼦类声明的版本号，不继承于⽗类版本号。
相对于dependencyManagement，所有⽣命在dependencies⾥的依赖都会⾃动引⼊，并默认被所有的⼦项⽬继承。
dependencies即使在⼦项⽬中不写该依赖项，那么⼦项⽬仍然会从⽗项⽬中继承该依赖项（全部继承）
dependencyManagement⾥只是声明依赖，并不实现引⼊，因此⼦项⽬需要显⽰的声明需要⽤的依赖。如果不在⼦项⽬中声明依赖，是不会从⽗项⽬中继承下来的；只有在⼦项⽬中写了该依赖项，并且没有指定具体版本，才会从⽗项⽬中继承该项，并且version和scope都读取⾃⽗pom;另外如果⼦项⽬中指定了版本号，那么会使⽤⼦项⽬中指定的jar版本。
实践
创建父工程
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| <?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>maven-polymerization</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>maven-polymerization</name>
<packaging>pom</packaging>
<description>父工程</description>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<spring-boot.version>2.3.7.RELEASE</spring-boot.version>
<druid.version>1.2.9</druid.version>
<commons.io.version>2.11.0</commons.io.version>
<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
</properties>
<dependencies>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>${commons.io.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>${spring-boot.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>${druid.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
<encoding>${project.build.sourceEncoding}</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<configuration>
<includeSystemScope>true</includeSystemScope>
</configuration>
<executions>
<execution>
<id>repackage</id>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
<repositories>
<repository>
<id>public</id>
<name>aliyun nexus</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>public</id>
<name>aliyun nexus</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</project>
|
新建common项目
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| <?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>maven-polymerization</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>common</artifactId>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
</project>
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如果使用idea创建的common模块会自动向父pom中添加
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| <modules>
<module>common</module>
</modules>
|
创建模块分歧
1.使用分层进行模块划分
比如api层、service层、dao层、domain层
2.使用功能进玍模块划分
比如 功能A、功能B、功能C
我比较倾向于第二种
第一种：需要在父pom的dependencyManagement中添加各个模块，api依赖service,service依赖dao,dao依赖domain。
第二种：
创建user、store功能
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| <?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>maven-polymerization</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>user</artifactId>
<dependencies>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
</dependency>
</dependencies>
</project>
|
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| <?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>maven-polymerization</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>store</artifactId>
<dependencies>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
</dependency>
</dependencies>
</project>
|
添加启动模块
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| <?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>maven-polymerization</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>admin</artifactId>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
</dependency>
<dependency>
<groupId>com.example</groupId>
<artifactId>user</artifactId>
</dependency>
<dependency>
<groupId>com.example</groupId>
<artifactId>store</artifactId>
</dependency>
</dependencies>
</project>
|
父工程修改
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| <?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>maven-polymerization</artifactId>
<version>0.0.1-SNAPSHOT</version>
<modules>
<module>common</module>
<module>user</module>
<module>admin</module>
<module>store</module>
</modules>
<name>maven-polymerization</name>
<packaging>pom</packaging>
<description>父工程</description>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<spring-boot.version>2.3.7.RELEASE</spring-boot.version>
<druid.version>1.2.9</druid.version>
<commons.io.version>2.11.0</commons.io.version>
<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
</properties>
<dependencies>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>${commons.io.version}</version>
</dependency>
<dependency>
<groupId>com.example</groupId>
<artifactId>common</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>${spring-boot.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>${druid.version}</version>
</dependency>
<dependency>
<groupId>com.example</groupId>
<artifactId>user</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.example</groupId>
<artifactId>store</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
<encoding>${project.build.sourceEncoding}</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>${spring-boot.version}</version>
<configuration>
<includeSystemScope>true</includeSystemScope>
</configuration>
<executions>
<execution>
<id>repackage</id>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
<repositories>
<repository>
<id>public</id>
<name>aliyun nexus</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>public</id>
<name>aliyun nexus</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</project>
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在admin模块添加com.example.admin包
创建spring boot启动类
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| @SpringBootApplication
public class AdminApplication {
public static void main(String[] args) {
SpringApplication.run(AdminApplication.class, args);
}
}
|