Maven 快照



  • 概述

    大型软件应用程序通常由多个模块组成,这是常见的情况,其中多个团队正在同一应用程序的不同模块上工作。例如,假设有一个团队在应用程序的前端app-ui项目(app-ui.jar:1.0)工作,并且他们正在使用data-service项目(data-service.jar:1.0)。现在可能发生的情况是,从事数据服务的团队正在迅速进行错误修复或增强,他们几乎每隔一天就会将库发布到远程存储库中。现在,如果数据服务团队每隔一天上传一次新版本,则将出现以下问题
    • 每次发布更新的代码时,数据服务团队都应告知app-ui团队。
    • app-ui团队需要定期更新其pom.xml以获得更新的版本。
    为了处理这种情况,SNAPSHOT(快照)概念开始发挥作用。
  • 什么是快照?

    SNAPSHOT是一个特殊版本,指示当前的开发副本。与常规版本不同,Maven为每个构建都在远程存储库中检查新的SNAPSHOT版本。现在,数据服务团队将每次将SNAPSHOT更新的代码发布到存储库,例如data-service:1.0-SNAPSHOT,以替换旧的SNAPSHOT jar。
  • 快照与版本

    对于Version,如果Maven一旦下载了提到的版本,例如data-service:1.0,它将永远不会尝试下载存储库中可用的较新的1.0。要下载更新的代码,数据服务版本将升级到1.1。对于SNAPSHOT,每次app-ui团队构建项目时,Maven都会自动获取最新的SNAPSHOT(data-service:1.0-SNAPSHOT)。
    app-ui pom.xml
    app-ui项目正在使用1.0-SNAPSHOT的数据服务。
    
    <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>app-ui</groupId>
       <artifactId>app-ui</artifactId>
       <version>1.0</version>
       <packaging>jar</packaging>
       <name>health</name>
       <url>http://maven.apache.org</url>
       <properties>
          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
       </properties>
       <dependencies>
          <dependency>
          <groupId>data-service</groupId>
             <artifactId>data-service</artifactId>
             <version>1.0-SNAPSHOT</version>
             <scope>test</scope>
          </dependency>
       </dependencies>
    </project>
    
    
    data-service pom.xml
    data-service项目针对每个小的更改都发布了1.0-SNAPSHOT。
    
    <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>data-service</groupId>
       <artifactId>data-service</artifactId>
       <version>1.0-SNAPSHOT</version>
       <packaging>jar</packaging>
       <name>health</name>
       <url>http://maven.apache.org</url>
       <properties>
          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
       </properties>
    </project>
    
    
    尽管对于SNAPSHOT,Maven每天自动获取最新的SNAPSHOT,但是您可以使用-U切换到任何maven命令,强制maven下载最新的快照构建。
    
    mvn clean package -U
    
    
    让我们打开命令控制台,转到C:\>MVN>app-ui目录,然后执行以下mvn命令。
    
    C:\MVN\app-ui>mvn clean package -U
    
    
    在下载最新的数据服务快照后,Maven将开始构建项目。
    
    [INFO] Scanning for projects...
    [INFO]--------------------------------------------
    [INFO] Building consumerBanking
    [INFO]    task-segment: [clean, package]
    [INFO]--------------------------------------------
    [INFO] Downloading data-service:1.0-SNAPSHOT
    [INFO] 290K downloaded.
    [INFO] [clean:clean {execution: default-clean}]
    [INFO] Deleting directory C:\MVN\app-ui\target
    [INFO] [resources:resources {execution: default-resources}]
    
    [WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources,
    i.e. build is platform dependent!
    
    [INFO] skip non existing resourceDirectory C:\MVN\app-ui\src\main\resources
    [INFO] [compiler:compile {execution:default-compile}]
    [INFO] Compiling 1 source file to C:\MVN\app-ui\target\classes
    [INFO] [resources:testResources {execution: default-testResources}]
    
    [WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources,
    i.e. build is platform dependent!
    
    [INFO] skip non existing resourceDirectory C:\MVN\app-ui\src\test\resources
    [INFO] [compiler:testCompile {execution: default-testCompile}]
    [INFO] Compiling 1 source file to C:\MVN\app-ui\target\test-classes
    [INFO] [surefire:test {execution: default-test}]
    [INFO] Surefire report directory: C:\MVN\app-ui\target\
    surefire-reports
    
    --------------------------------------------------
     T E S T S
    --------------------------------------------------
    
    Running com.companyname.bank.AppTest
    Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.027 sec
    
    Results :
    
    Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
    
    [INFO] [jar:jar {execution: default-jar}]
    [INFO] Building jar: C:\MVN\app-ui\target\
    app-ui-1.0-SNAPSHOT.jar
    [INFO]--------------------------------------------------------
    [INFO] BUILD SUCCESSFUL
    [INFO]--------------------------------------------------------
    [INFO] Total time: 2 seconds
    [INFO] Finished at: 2015-09-27T12:30:02+05:30
    [INFO] Final Memory: 16M/89M
    [INFO]------------------------------------------------------------------------