在使用GWTP的样板机制之后，我得到了类（生成的地方）已经存在的错误。
文件夹target / generated-sources包含“annotations”和“apt”但不包含“gwt”。文件夹“annotations”和“apt”都有相同的内容。
我的pom.xml：
<?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>de.s.pp</groupId>
<artifactId>projectplanning</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<name>Projekt Planung</name>
<description>Basic GWTP application</description>
<properties>
<!-- client -->
<gwt.version>2.7.0</gwt.version>
<gwtp.version>1.4</gwtp.version>
<gin.version>2.1.2</gin.version>
<!-- server -->
<guice.version>3.0</guice.version>
<!-- testing -->
<junit.version>4.11</junit.version>
<jukito.version>1.1</jukito.version>
<!-- maven -->
<gwt-maven-plugin.version>2.7.0</gwt-maven-plugin.version>
<maven-surefire-plugin.version>2.18.1</maven-surefire-plugin.version>
<maven-compiler-plugin.version>3.2</maven-compiler-plugin.version>
<maven-resources-plugin.version>2.7</maven-resources-plugin.version>
<maven-processor-plugin.version>2.0.5</maven-processor-plugin.version>
<maven-build-helper-plugin.version>1.7</maven-build-helper-plugin.version>
<source.jdk>1.6</source.jdk>
<target.jdk>1.6</target.jdk>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<webappDirectory>${project.build.directory}/${project.build.finalName}</webappDirectory>
</properties>
<build>
<outputDirectory>${webappDirectory}/WEB-INF/classes</outputDirectory>
<resources>
<resource>
<directory>src/main/resources</directory>
</resource>
<resource>
<directory>${project.build.directory}/generated-sources/apt</directory>
</resource>
<resource>
<directory>${project.build.directory}/generated-sources/gwt</directory>
</resource>
</resources>
<plugins>
<!-- Run annotation processors on src/home/java sources -->
<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<version>2.2.4</version>
<executions>
<execution>
<id>process</id>
<goals>
<goal>process</goal>
</goals>
<phase>generate-sources</phase>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-processors</artifactId>
<version>${gwtp.version}</version>
</dependency>
</dependencies>
</plugin>
<!-- Copy the generated classses -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.5</version>
<executions>
<execution>
<id>add-source</id>
<phase>generate-sources</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>${project.build.directory}/generated-sources/apt</source>
<source>${project.build.directory}/generated-sources/gwt</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<source>${source.jdk}</source>
<target>${target.jdk}</target>
<encoding>${project.build.sourceEncoding}</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.1</version>
</plugin>
<!-- JUnit Testing - skip *.GwtTest cases -->
<!-- 'mvn test' - runs the Jukito tests -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>${maven-surefire-plugin.version}</version>
<configuration>
<includes>
<include>**/*Test.java</include>
</includes>
<excludes>
<exclude>**/*GwtTest.java</exclude>
</excludes>
</configuration>
</plugin>
<!-- GWT -->
<!-- 'mvn gwt:run' - runs development mode -->
<!-- 'mvn gwt:debug' - runs debug mode -->
<!-- 'mvn gwt:compile' - compiles gwt -->
<!-- 'mvn integration-test' - runs the gwt tests (*GwtTest.java) -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<version>${gwt.version}</version>
<configuration>
<!-- With multiple tests use GwtTestSuite.java for speed -->
<includes>**/*GwtTest.java</includes>
<extraJvmArgs>-Xss1024K -Xmx1024M -XX:MaxPermSize=256M</extraJvmArgs>
<copyWebapp>true</copyWebapp>
<hostedWebapp>${webappDirectory}</hostedWebapp>
<!-- <logLevel>DEBUG</logLevel> -->
<runTarget>index.html</runTarget>
<modules>
<module>de.s.pp.projectplanning</module>
</modules>
</configuration>
<executions>
<execution>
<id>compileAndTest</id>
<goals>
<goal>compile</goal>
<goal>test</goal>
</goals>
</execution>
<execution>
<id>packageGeneration</id>
<phase>prepare-package</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-maven-plugin</artifactId>
<version>3.2.0-release</version>
<configuration>
<fork>false</fork>
<api>JDO</api>
<!-- <ddlFile>${basedir}/servicecenter.ddl</ddlFile> -->
<props>${basedir}/datanucleus.properties</props>
<log4jConfiguration>${basedir}/log4j.properties</log4jConfiguration>
<verbose>true</verbose>
</configuration>
<executions>
<execution>
<phase>process-classes</phase>
<goals>
<goal>enhance</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
<pluginManagement>
<plugins>
<!--This plugin's configuration is used to store Eclipse m2e settings
only. It has no influence on the Maven build itself. -->
<plugin>
<groupId>org.eclipse.m2e</groupId>
<artifactId>lifecycle-mapping</artifactId>
<version>1.0.0</version>
<configuration>
<lifecycleMappingMetadata>
<pluginExecutions>
<pluginExecution>
<pluginExecutionFilter>
<groupId>
org.datanucleus
</groupId>
<artifactId>
datanucleus-maven-plugin
</artifactId>
<versionRange>
[3.2.0-release]
</versionRange>
<goals>
<goal>enhance</goal>
</goals>
</pluginExecutionFilter>
<action>
<ignore></ignore>
</action>
</pluginExecution>
<pluginExecution>
<pluginExecutionFilter>
<groupId>org.bsc.maven</groupId>
<artifactId>
maven-processor-plugin
</artifactId>
<versionRange>
[2.2.4,)
</versionRange>
<goals>
<goal>process</goal>
</goals>
</pluginExecutionFilter>
<action>
<ignore></ignore>
</action>
</pluginExecution>
<pluginExecution>
<pluginExecutionFilter>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<versionRange>[2.2.4,)</versionRange>
<goals>
<goal>generate-sources</goal>
</goals>
</pluginExecutionFilter>
<action>
<execute />
</action>
</pluginExecution>
<pluginExecution>
<pluginExecutionFilter>
<groupId>
org.codehaus.mojo
</groupId>
<artifactId>
build-helper-maven-plugin
</artifactId>
<versionRange>
[1.5,)
</versionRange>
<goals>
<goal>add-source</goal>
</goals>
</pluginExecutionFilter>
<action>
<ignore></ignore>
</action>
</pluginExecution>
</pluginExecutions>
</lifecycleMappingMetadata>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
<dependencies>
<!-- Google Web Toolkit -->
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt-user</artifactId>
<version>${gwt.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt-servlet</artifactId>
<version>${gwt.version}</version>
<scope>runtime</scope>
</dependency>
<!-- GWT-Platform -->
<!-- MVP component -->
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-mvp-client</artifactId>
<version>${gwtp.version}</version>
<scope>provided</scope>
</dependency>
<!-- Dispatch component -->
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-dispatch-rpc-client</artifactId>
<version>${gwtp.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-dispatch-rpc-server-guice</artifactId>
<!-- Or, if you use spring: <artifactId>gwtp-dispatch-server-spring</artifactId> -->
<version>${gwtp.version}</version>
</dependency>
<!-- Crawler component -->
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-crawler</artifactId>
<version>${gwtp.version}</version>
</dependency>
<!-- Annotation component -->
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-processors</artifactId>
<version>${gwtp.version}</version>
<scope>provided</scope>
</dependency>
<!-- Tester component -->
<dependency>
<groupId>com.gwtplatform</groupId>
<artifactId>gwtp-tester</artifactId>
<version>${gwtp.version}</version>
<scope>test</scope>
</dependency>
<!-- DI -->
<dependency>
<groupId>com.google.inject</groupId>
<artifactId>guice</artifactId>
<version>${guice.version}</version>
</dependency>
<dependency>
<groupId>com.google.inject.extensions</groupId>
<artifactId>guice-servlet</artifactId>
<version>${guice.version}</version>
</dependency>
<dependency>
<groupId>com.google.inject.extensions</groupId>
<artifactId>guice-assistedinject</artifactId>
<version>${guice.version}</version>
</dependency>
<dependency>
<groupId>com.google.gwt.inject</groupId>
<artifactId>gin</artifactId>
<version>${gin.version}</version>
</dependency>
<!-- Test -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>${junit.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.jukito</groupId>
<artifactId>jukito</artifactId>
<version>${jukito.version}</version>
<scope>test</scope>
</dependency>
<!-- Guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>16.0</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava-gwt</artifactId>
<version>16.0</version>
</dependency>
<!-- Database -->
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>[3.2.0, 3.2.99)</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>javax.jdo</groupId>
<artifactId>jdo-api</artifactId>
<version>3.0.1</version>
</dependency>
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-api-jdo</artifactId>
<version>[3.2.0, 3.2.99)</version>
</dependency>
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-rdbms</artifactId>
<version>[3.2.0, 3.2.99)</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.hsqldb</groupId>
<artifactId>hsqldb</artifactId>
<version>2.2.9</version>
</dependency>
<dependency>
<groupId>org.mindrot</groupId>
<artifactId>jbcrypt</artifactId>
<version>0.3m</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>3.11</version>
</dependency>
<dependency>
<groupId>org.apache.shiro</groupId>
<artifactId>shiro-core</artifactId>
<version>1.2.2</version>
</dependency>
<dependency>
<groupId>org.apache.shiro</groupId>
<artifactId>shiro-guice</artifactId>
<version>1.2.2</version>
</dependency>
<dependency>
<groupId>org.apache.shiro</groupId>
<artifactId>shiro-web</artifactId>
<version>1.2.2</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.10-beta1</version>
</dependency>
</dependencies>
<repositories>
<repository>
<id>maven-restlet</id>
<name>Public online Restlet repository</name>
<url>http://maven.restlet.org</url>
</repository>
<repository>
<id>mvnrepository</id>
<name>Public online Restlet repository</name>
<url>http://mvnrepository.com/artifact</url>
</repository>
</repositories>
</project>
输出：
[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 Projekt Planung 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] >>> gwt-maven-plugin:2.7.0:run (default-cli) @ projectplanning >>>
[INFO]
[INFO] --- maven-processor-plugin:2.2.4:process (process) @ projectplanning ---
[WARNING] No processors specified. Using default discovery mechanism.
[INFO]
[INFO] --- build-helper-maven-plugin:1.5:add-source (add-source) @ projectplanning ---
[INFO] Source directory: C:\Workspaces\s\projectplanning\target\generated-sources\apt added.
[INFO] Source directory: C:\Workspaces\s\projectplanning\target\generated-sources\gwt added.
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ projectplanning ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 57 resources
[INFO] Copying 2 resources
[INFO] skip non existing resourceDirectory C:\Workspaces\s\projectplanning\target\generated-sources\gwt
[INFO]
[INFO] --- maven-compiler-plugin:3.2:compile (default-compile) @ projectplanning ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 187 source files to C:\Workspaces\s\projectplanning\target\projectplanning-1.0-SNAPSHOT\WEB-INF\classes
[INFO] /C:/Workspaces/s/projectplanning/src/main/java/de/s/pp/server/security/UserPermissionActionValidator.java: C:\Workspaces\s\projectplanning\src\main\java\de\s\pp\server\security\UserPermissionActionValidator.java uses unchecked or unsafe operations.
[INFO] /C:/Workspaces/s/projectplanning/src/main/java/de/s/pp/server/security/UserPermissionActionValidator.java: Recompile with -Xlint:unchecked for details.
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /C:/Workspaces/s/projectplanning/target/generated-sources/apt/de/s/pp/shared/dispatch/actionresult/GetAllClustersResult.java:[7,8] duplicate class: de.s.pp.shared.dispatch.actionresult.GetAllClustersResult
[ERROR] /C:/Workspaces/s/projectplanning/target/generated-sources/annotations/de/s/pp/shared/dispatch/actionresult/GetAllClustersAction.java:[5,8] duplicate class: de.s.pp.shared.dispatch.actionresult.GetAllClustersAction
[INFO] 2 errors
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 6.458 s
[INFO] Finished at: 2015-01-20T18:11:43+01:00
[INFO] Final Memory: 30M/277M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.2:compile (default-compile) on project projectplanning: Compilation failure: Compilation failure:
[ERROR] /C:/Workspaces/s/projectplanning/target/generated-sources/apt/de/s/pp/shared/dispatch/actionresult/GetAllClustersResult.java:[7,8] duplicate class: de.s.pp.shared.dispatch.actionresult.GetAllClustersResult
[ERROR] /C:/Workspaces/s/projectplanning/target/generated-sources/annotations/de/s/pp/shared/dispatch/actionresult/GetAllClustersAction.java:[5,8] duplicate class: de.s.pp.shared.dispatch.actionresult.GetAllClustersAction
[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
答案 0 :(得分：3)
问题在于maven-processor-plugin和maven-compiler-plugin在哪里生成（相同）源到不同的文件夹。解决方案是禁用一个处理器。我决定禁用maven-processor-plugin。
另一个选择是将<compilerArgument>-proc:none</compilerArgument>添加到maven-compiler-plugin。这具有mvn generate-sources正在发挥作用的好处。