无法执行目标org.apache.maven.plugins：maven-compiler-plugin：3.1：compile

Question

Given the below pom.xml:

<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.myApp</groupId>
    <artifactId>malloc</artifactId>
    <version>0.0.1</version>
    <packaging>war</packaging>

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

    <repositories>
        <repository>
            <id>project</id>
            <url>file:///${basedir}/lib</url>
        </repository>
    </repositories>

    <dependencies>
        <dependency>
            <groupId>com.myApp</groupId>
            <artifactId>myApp.core</artifactId>
            <version>1.0.0</version>
        </dependency>
        ... //other dependencies
    </dependencies>
    <build>
        <sourceDirectory>src</sourceDirectory>
        <resources>
            <resource>
                <directory>src</directory>
                <excludes>
                    <exclude>**/*.java</exclude>
                </excludes>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <archive>
                        <manifest>
                        <addClasspath>true</addClasspath>
                         </manifest>
                         <addMavenDescriptor>false</addMavenDescriptor>
                    </archive>
                    <webResources>
                         <webResource> 
                           <directory>${project.build.directory}/WebContent/WEB-INF</directory> 
                           <includes> 
                             <include>web.xml</include> 
                           </includes> 
                           <targetPath>WEB-INF</targetPath> 
                           <filtering>true</filtering> 
                         </webResource>
                    </webResources>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.10</version>
                <executions>
                    <execution>
                    <id>copy-dependencies</id>
                    <phase>package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                            <outputDirectory>${project.build.directory}/WebContent/WEB-INF/lib</outputDirectory>
                            <includeScope>runtime</includeScope>
                            <overWriteReleases>false</overWriteReleases>
                            <overWriteSnapshots>false</overWriteSnapshots>
                            <overWriteIfNewer>true</overWriteIfNewer>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

And the following project structure:

I expect the maven-dependency-plugin would copy all the dependencies to the WebContent/WEB-INF/lib but when I run

mvn clean install

The following error is generated:

[INFO] Scanning for projects...
[INFO] 
[INFO] Using the builder org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder with a thread count of 1
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building api-malloc 0.0.1
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for com.oracle:ojdbc6:jar:10.2.0.4.0 is missing, no dependency information available
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ api-malloc ---
[INFO] Deleting C:\Development\malloc\target
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ api-malloc ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ api-malloc ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 8 source files to C:\Development\malloc\target\classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[3,34] package com.myApp.api.core.dto does not exist
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[5,39] cannot find symbol
  symbol: class IDTO
[INFO] 26 errors 
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.209 s
[INFO] Finished at: 2015-11-26T15:33:40-05:00
[INFO] Final Memory: 21M/227M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project malloc: Compilation failure: Compilation failure:
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[3,34] package com.myApp.api.core.dto does not exist
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[5,39] cannot find symbol
[ERROR] symbol: class IDTO

[ERROR] location: class com.myApp.api.malloc.controllers.TestController
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

I noticed the WEB-INF/lib folder is always empty, maven dependencies are not copied over.

I am suspecting the copy-dependencies plugin didn't get run before the compile stage but I can't really figure out - anything that I missed?

Answer 1

The copy-dependencies goal indeed will never be executed if the compilation fails because its binding is to the package phase, which comes after the compile phase (to which by default is linked the Maven Compiler Plugin).

If you want it to run before the compile phase, you need to change the phase value of the execution of the copy-dependencies goal. Changing to process-resources should be fine and should also make sense.

<phase>package</phase>

For a full description of phases, you can check official documentation, here .

You should also fix the compilation errors the build output is pointing at. I see the sourceDirectory element is overriding what Maven uses by default for Java source code ( src\\main\\java ), hence I suppose your code is directly under the src folder.

Updated : the package X does not exist error occurs when the code is referring to a package not resolved by the Java compiler, hence it is not able to see that package in the classpath, which means in the declared dependencies: does myApp.core contain that package and class? If yes, then the repositories element (the lib folder) is probably not properly providing the myApp dependency.

You can try to install the dependency locally in your .m2 maven cache using the Maven Install Plugin as specified here . You could execute from the command line as following:

mvn org.apache.maven.plugins:maven-install-plugin:2.5.2:install-file  
       -Dfile=lib\myApp.core-1.0.0.jar \
       -DgroupId=com.myApp \
       -DartifactId=myApp.core \
       -Dversion=1.0.0 \
       -Dpackaging=jar \

---

Side note: Maven prefers lower case groupid and artifactid tokens. Moreover, instead of using Camel Case (ie myApp ), Maven convention is also use a dash for separating tokens (ie myapp-core ).