一 war永遠依賴于jar

從來只有war包中含有jar包，而沒有jar包中含有war包
web工程依賴的java工程，就是jar包，這個jar包經(jīng)過自動化部署后,會放在web工程的web-inf/lib目錄下

1. 在web工程的項目2中,加入項目1的路徑依賴

在 pro02-maven-web 工程的 pom.xml 中，找到 dependencies 標簽，在 dependencies 標簽中做如下配置

<dependency>
<!--
通過指定被依賴工程的坐標完成依賴
-->
  <groupId>com.xyt.maven</groupId>
  <artifactId>pro01-maven-java</artifactId>
  <version>1.0-SNAPSHOT</version>
  <scope>compiler</scope>
 
</dependency>

2 在web工程中，加入測試代碼

證明在Web工程中可以使用Java工程中創(chuàng)建的那個類：Calculator

2.1 創(chuàng)建目錄

mkdir src\test\java\com\xyt\maven

2.2 確認依賴junit

<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.12</version>
  <scope>test</scope>
</dependency>

2.3創(chuàng)建測試類

2.4 運行測試

mvn test

2.5 打包

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn package
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- resources:3.0.2:resources (default-resources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\resources

確實生成了一個jar包

2.6 查看依賴列表

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn dependency:list
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------

	[INFO]
	[INFO] The following files have been resolved:
	[INFO]    junit:junit:jar:4.11:test
	[INFO]    com.xyt.maven:pro01-maven-java:jar:1.0-SNAPSHOT:compile
	[INFO]    org.hamcrest:hamcrest-core:jar:1.3:test
	[INFO]    javax.servlet:javax.servlet-api:jar:3.1.0:provided

2.7 樹形結(jié)構(gòu)查看

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn dependency:tree
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- dependency:2.8:tree (default-cli) @ pro02-maven-web ---
[WARNING] Parameter 'localRepository' is deprecated core expression; Avoid use of ArtifactRepository type. If you need access to local repository, switch to '${repositorySystemSession}' expression and get LRM from it instead.
[INFO] com.xyt.maven:pro02-maven-web:war:1.0-SNAPSHOT
[INFO] +- junit:junit:jar:4.11:test
[INFO] |  \- org.hamcrest:hamcrest-core:jar:1.3:test
[INFO] +- javax.servlet:javax.servlet-api:jar:3.1.0:provided
[INFO] \- com.xyt.maven:pro01-maven-java:jar:1.0-SNAPSHOT:compile
[INFO] ------------------------------------------------------------------------

二 測試依賴的范圍

一個depency里面有四個元素

<dependency>
<!--
通過指定被依賴工程的坐標完成依賴
-->
  <groupId>com.xyt.maven</groupId>
  <artifactId>pro01-maven-java</artifactId>
  <version>1.0-SNAPSHOT</version>
  <scope>compile</scope>
 
</dependency>

scope代表作用范圍，標簽的作用范圍
scope提供這么多依賴的原因就是，把它測試用的test，本地提供的provided，和常規(guī)complie區(qū)分開來

compile/test/provided/system/runtime/import

開發(fā)過程有效的含義就是，在IDEA中寫項目時候，我們能不能把它點出來
部署到服務(wù)器有效的含義是，把war包丟到tomcat里面時，是否包含對應(yīng)文件

將這個文件里面導(dǎo)入

1 compile的編譯過程

1.1 compile編譯Calulator

在 HelloServlet 類中導(dǎo)入 Calculator 類，然后編譯就說明有效。

D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\java\xyt\maven\HelloServlet.java

引入一個測試文件

/**
* 通過import語句將要測試的類引入當前類
引入后，編譯通過，可以使用，這個范圍的依賴對當前類有效
引入后，編譯失敗，不可以使用，這個范圍的依賴對當前類無效

*main目錄下的java類：HelloServlet
*complie范圍引入的·依賴：pro01-maven-java
*pro01-maven-java中的類：Calculator
*驗證的目標：
*
*
*
*
*/
import com.xyt.maven.Calculator;
  
public class HelloServlet extends HttpServlet{
  
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    response.getWriter().write("hello maven web");
    
  }
  
}

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn clean compile
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.1.0:clean (default-clean) @ pro02-maven-web ---
[INFO] Deleting D:\maven_workspace\spaceVideo\pro02-maven-web\target
[INFO]
[INFO] --- resources:3.0.2:resources (default-resources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\resources
[INFO]
[INFO] --- compiler:3.8.0:compile (default-compile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS

D:\maven_workspace\spaceVideo\pro02-maven-web\pom.xml

<dependency>
<!--
通過指定被依賴工程的坐標完成依賴
-->
  <groupId>com.xyt.maven</groupId>
  <artifactId>pro01-maven-java</artifactId>
  <version>1.0-SNAPSHOT</version>
  <scope>compile</scope>
 
</dependency>

1.2 編譯CalculatorTest

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn clean test-compile
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.1.0:clean (default-clean) @ pro02-maven-web ---
[INFO] Deleting D:\maven_workspace\spaceVideo\pro02-maven-web\target
[INFO]
[INFO] --- resources:3.0.2:resources (default-resources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\resources
[INFO]
[INFO] --- compiler:3.8.0:compile (default-compile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\classes
[INFO]
[INFO] --- resources:3.0.2:testResources (default-testResources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\test\resources
[INFO]
[INFO] --- compiler:3.8.0:testCompile (default-testCompile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\test-classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

• 通過import語句將要測試的類引入當前類
  引入后，編譯通過，可以使用，這個范圍的依賴對當前類有效
  引入后，編譯失敗，不可以使用，這個范圍的依賴對當前類無效

• main目錄下的java類：HelloServlet

• complie范圍引入的·依賴：pro01-maven-java

• pro01-maven-java中的類：Calculator

1.3 打包成war包

主體功能放在這個compile里面99%
打war包：

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn clean compile
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.1.0:clean (default-clean) @ pro02-maven-web ---
[INFO] Deleting D:\maven_workspace\spaceVideo\pro02-maven-web\target
[INFO]
[INFO] --- resources:3.0.2:resources (default-resources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\resources
[INFO]
[INFO] --- compiler:3.8.0:compile (default-compile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

2 test的編譯過程

2.1 main空間里面編譯信息

在HttpSevelet里面導(dǎo)入信息

import org.junit.Test;

編譯失?。候炞Cmain空間下編譯這個Test依賴，會出問題

D:\maven_workspace\spaceVideo\pro02-maven-web>mvn clean compile
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.1.0:clean (default-clean) @ pro02-maven-web ---
[INFO] Deleting D:\maven_workspace\spaceVideo\pro02-maven-web\target
[INFO]
[INFO] --- resources:3.0.2:resources (default-resources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\resources
[INFO]
[INFO] --- compiler:3.8.0:compile (default-compile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /D:/maven_workspace/spaceVideo/pro02-maven-web/src/main/java/xyt/maven/HelloServlet.java:[25,17] 程序包org.junit不存在
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.318 s
[INFO] Finished at: 2023-05-04T23:43:22+08:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.0:compile (default-compile) on project
 pro02-maven-web: Compilation failure
[ERROR] /D:/maven_workspace/spaceVideo/pro02-maven-web/src/main/java/xyt/maven/HelloServlet.java:[25,17] 程序包org.junit不存在

在pro01-maven-java\src\main\java\com\xyt\maven目錄下修改Calculator.java

2.2 test空間下編譯

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

沒問題，test必然可以在test下編譯，本身test就是為test服務(wù)的
在HttpSevelet里面注釋信息

//import org.junit.Test;


```bash
D:\maven_workspace\spaceVideo\pro02-maven-web>mvn clean test
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< com.xyt.maven:pro02-maven-web >--------------------
[INFO] Building pro02-maven-web Maven Webapp 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.1.0:clean (default-clean) @ pro02-maven-web ---
[INFO] Deleting D:\maven_workspace\spaceVideo\pro02-maven-web\target
[INFO]
[INFO] --- resources:3.0.2:resources (default-resources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\main\resources
[INFO]
[INFO] --- compiler:3.8.0:compile (default-compile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\classes
[INFO]
[INFO] --- resources:3.0.2:testResources (default-testResources) @ pro02-maven-web ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory D:\maven_workspace\spaceVideo\pro02-maven-web\src\test\resources
[INFO]
[INFO] --- compiler:3.8.0:testCompile (default-testCompile) @ pro02-maven-web ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:\maven_workspace\spaceVideo\pro02-maven-web\target\test-classes
[INFO]
[INFO] --- surefire:2.22.1:test (default-test) @ pro02-maven-web ---
[WARNING] Parameter 'localRepository' is deprecated core expression; Avoid use of ArtifactRepository type. If you need access to local repository, switch to '${repositorySystemSession}' expression and get LRM from it instead.
[INFO]
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.xyt.maven.CalculatorTest
輸出測試的程序代碼
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.03 s - in com.xyt.maven.CalculatorTest
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

3 provided的編譯過程

3.1 test和provided不參與部署到服務(wù)器

• compile范圍依賴的jar包會放入war包，通過test范圍依賴的jar包不會放入war包。
• 所有東西都發(fā)給服務(wù)器，會增加服務(wù)器的負擔
• 編譯程序類似于火箭發(fā)射，junit類似于腳手架，不會交房交個腳手架
  
  

3.2 provided已經(jīng)提供的意思

說明Tomcat里面有這個依賴，如果非要提供，會造成依賴沖突的問題
比方說jsp-api沒有注明provided帶進war包部署，會造成視圖顯示錯誤，造成空指針異常
NULLPOINTEREXCEPTION,

三 測試依賴的總結(jié)

1 compile:

使用第三方框架的jar包，或者項目真正需要部署的功能依賴，都用這個scope修飾
詳細解釋：
1)編譯依賴范圍（compile），該范圍就是默認依賴范圍，此依賴范圍對 于編譯、測試、運行三種classpath都有效，舉個簡單的例子，假如項目中有spring-core的依賴，那么spring-core不管是在編譯，測試，還是運行都會被用到，因此spring-core必須是編譯范圍（構(gòu)件默認的是編譯范圍，所以依賴范圍是編譯范圍的無須顯示指定）

<dependency>
 <groupId>org.springframework</groupId>
 <artifactId>spring-core</artifactId>
 <version>2.5</version>
 <scope>compile</scope> <!--默認為該依賴范圍，無須顯示指定--〉
</dependency>

2 test

測試過程中使用的jar包，以test范圍寫進來，比如junit
詳細解釋

顧名思義就是針對于測試的，使用此依賴范圍的依賴，只對測試classpath有效，在編譯主代碼和項目運行時，都將無法使用該依賴，最典型的例子就是 Junit, 構(gòu)件在測試時才需要，所以它的依賴范圍是測試，因此它的依賴范圍需要顯示指定為test ,當然不顯示指定依賴范圍也不會報錯，但是該依賴會被加入到編譯和運行的classpath中,造成不必要的浪費 。

 <dependency>
     <groupId>junit</groupId>
     <artifactId>junit</artifactId>
     <version>4.7</version>
    <scope>test</scope>
    </dependency>

3 provided

主要是為了減輕服務(wù)器的負擔，避免依賴沖突，比方說本地項目中有jsp-api.jar,但是tomcat里面也有這個文件，如果硬要導(dǎo)入，就會產(chǎn)生沖突，報空指針異常

典型的例子就是servlet-api， 編譯和測試該項目的時候需要該依賴，但是在運行時，web容器已經(jīng)提供的該依賴，所以運行時就不再需要此依賴，如果不顯示指定該依賴范圍，并且容器依賴的版本和maven依賴的版本不一致的話，可能會引起版本沖突，造成不良影響。文章來源地址http://www.zghlxwxcb.cn/news/detail-434316.html

到了這里，關(guān)于maven從入門到精通 第三章 Maven中形成web對Java工程的依賴的文章就介紹完了。如果您還想了解更多內(nèi)容，請在右上角搜索TOY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！