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Spring Boot 多模組開發-使用dependencyManagement版本管理

 今天,我們來了解下如何管理和優化父專案和子模組的依賴包版本,又或者我們希望子專案B不需要全部依賴父專案A的內容,避免一股腦全部匯入。

首先,來看四個pom檔案:

1、demo-parent

<?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>com.demo</groupId>
	<artifactId>demo-parent</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>pom</packaging>

	<name>demo-parent</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.5.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<modules>
		<module>demo-apply</module>
		<module>demo-common</module>
		<module>demo-static</module>
	</modules>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.1</version>
				<configuration>
					<source>${java.version}</source>
					<target>${java.version}</target>
				</configuration>
			</plugin>
		</plugins>
	</build>

</project>

2、demo-apply

<?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>

    <artifactId>demo-apply</artifactId>
    <packaging>jar</packaging>

    <name>demo-apply</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>com.demo</groupId>
        <artifactId>demo-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath><!-- lookup parent from repository -->
    </parent>

    <dependencies>
        <!-- 加入其餘模組的依賴 -->
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-common</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-static</artifactId>
            <version>0.0.1-SNAPSHOT</version>
            <type>war</type>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <!-- 當所依賴的其他模組,有啟動類的時候,需要以下配置,指定唯一啟動類,
                        本次事例未涉及其他模組有啟動類,可自行測試 -->
                <configuration>
                    <!-- 指定該Main Class為全域性的唯一入口 -->
                    <mainClass>com.demo.demoapply.DemoApplyApplication</mainClass>
                    <layout>ZIP</layout>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal><!--可以把依賴的包都打包到生成的Jar包中-->
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

3、demo-static

<?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>

	<artifactId>demo-static</artifactId>
	<packaging>war</packaging>

	<name>demo-static</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>com.demo</groupId>
		<artifactId>demo-parent</artifactId>
		<version>0.0.1-SNAPSHOT</version>
		<relativePath>../pom.xml</relativePath><!-- lookup parent from repository -->
	</parent>

	<dependencies>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.1</version>
				<configuration>
					<source>${java.version}</source>
					<target>${java.version}</target>
				</configuration>
			</plugin>
		</plugins>
	</build>


</project>

4、demo-common

<?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>

	<artifactId>demo-common</artifactId>
	<packaging>jar</packaging>

	<name>demo-common</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>com.demo</groupId>
		<artifactId>demo-parent</artifactId>
		<version>0.0.1-SNAPSHOT</version>
		<relativePath>../pom.xml</relativePath><!-- lookup parent from repository -->
	</parent>

	<dependencies>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.1</version>
				<configuration>
					<source>${java.version}</source>
					<target>${java.version}</target>
				</configuration>
			</plugin>
		</plugins>
	</build>


</project>

 很明顯,我們的demo-parent為父專案,demo-apply為應用入口,demo-common放的應該是共用工具類,demo-static應該是共用的靜態檔案,如頁面等,demo-apply依賴兩者。

 好,看到這裡,就有疑問了,按理來說,demo-static,存放頁面,打包成war包,應該不需要可以執行,那麼也就不需要依賴springboot的包,那麼我們進行如下改變:

demo-parent:

<?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>com.demo</groupId>
    <artifactId>demo-parent</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>pom</packaging>

    <name>demo-parent</name>
    <description>Demo project for Spring Boot</description>

    <!-- 刪除 -->
    <!--<parent>-->
        <!--<groupId>org.springframework.boot</groupId>-->
        <!--<artifactId>spring-boot-starter-parent</artifactId>-->
        <!--<version>2.0.5.RELEASE</version>-->
        <!--<relativePath/> &lt;!&ndash; lookup parent from repository &ndash;&gt;-->
    <!--</parent>-->

    <modules>
        <module>demo-apply</module>
        <module>demo-common</module>
        <module>demo-static</module>
    </modules>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
                <version>2.0.5.RELEASE</version>
            </dependency>

            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
                <version>2.0.5.RELEASE</version>
            </dependency>

            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <version>2.0.5.RELEASE</version>
                <scope>test</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

demo-apply

<?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>

    <artifactId>demo-apply</artifactId>
    <packaging>jar</packaging>

    <name>demo-apply</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>com.demo</groupId>
        <artifactId>demo-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath><!-- lookup parent from repository -->
    </parent>

    <dependencies>
        <!-- 加入其餘模組的依賴 -->
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-common</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>com.demo</groupId>
            <artifactId>demo-static</artifactId>
            <version>0.0.1-SNAPSHOT</version>
            <type>war</type>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <!-- 當所依賴的其他模組,有啟動類的時候,需要以下配置,指定唯一啟動類,
                        本次事例未涉及其他模組有啟動類,可自行測試 -->
                <configuration>
                    <!-- 指定該Main Class為全域性的唯一入口 -->
                    <mainClass>com.demo.demoapply.DemoApplyApplication</mainClass>
                    <layout>ZIP</layout>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal><!--可以把依賴的包都打包到生成的Jar包中-->
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

大功告成,雖然這樣是OK了,大家檢視依賴發現也對,demo-static和demo-common,已經不依賴springBoot,但是有心人一定會問,demo-parent為何刪除這一段:

 <!-- 刪除 -->
    <!--<parent>-->
        <!--<groupId>org.springframework.boot</groupId>-->
        <!--<artifactId>spring-boot-starter-parent</artifactId>-->
        <!--<version>2.0.5.RELEASE</version>-->
        <!--<relativePath/> &lt;!&ndash; lookup parent from repository &ndash;&gt;-->
    <!--</parent>-->

首先,告訴大家這一段從哪裡來的,idea在生成springBoot專案的時候,會採取官方建議,預設引入該父專案。

那麼問題又來了,這個父專案到底是個啥,我們預設要引入他,大家可以點選進去檢視,其實他只是個pom檔案,管理了一些預設的配置資訊,這樣才能做到,我們在預設生成專案的時候,發現我們的dependency中不需要引入版本,應為他會整合父Pom檔案的版本資訊。

<dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
            </dependency>
            
       	    ...
       	    
        </dependencies>
    </dependencyManagement>

既然知道,原來是這麼回事,那我們順便查下SpringBoot的官網介紹吧,是否還有更好的方式。

果真,還有一種方式:

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.5.1.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

請注意,它的 type 是 pom,scope 是 import,這種型別的 dependency 只能在 dependencyManagement 標籤中宣告。

同樣我們在點進去看,原來這個POM檔案已經預設給我們使用dependencyManagement聲明瞭很多依賴,我們如果需要直接在我們的dependency中加入依賴就行,而無需指定版本。
這樣demo-parent的Pom檔案就變成了這個樣子:

<?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>com.demo</groupId>
    <artifactId>demo-parent</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>pom</packaging>

    <name>demo-parent</name>
    <description>Demo project for Spring Boot</description>

    <modules>
        <module>demo-apply</module>
        <module>demo-common</module>
        <module>demo-static</module>
    </modules>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.0.0.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

這樣parent專案的POM依賴就會特別清晰。

註釋:dependencyManagement 包裹的dependencies只有宣告作用,不會實際匯入,另外關於maven中的繼承、聚合等多多瞭解,就能很好的理解上述的內容。