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Maven问题记录

Maven问题解决记录：

1、远程仓库中有jar，但是编译时找不到。

问题描述：

Failed to execute goal on project amps-dcm: Could not resolve dependencies for project com.zollty.pss:amps-dcm:war:0.0.1-SNAPSHOT: The following artifacts could not be resolved: org.zollty.util:zollty-util:jar:1.0, org.zollty.log:zollty-log:jar:1.0: Failure to find org.zollty.util:zollty-util:jar:1.0 in http://172.27.18.106:8081/nexus/content/groups/public was cached in the local repository, resolution will not be reattempted until the update interval of LocalMirrorId has elapsed or updates are forced -> [Help 1]

[ERROR]

[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.

[ERROR]

解决方案：

打开本地仓库目录，找到那个jar的位置，把残留的文件夹全都删除。然后再重新下载这个jar。

还是不行？有可能是parent项目中也存在xxx.lastUpdate的文件。所以把parent项目也清理一下。

例如：

<groupId>org.zollty</groupId>

<artifactId>zollty-org</artifactId>

</parent>

那么，请检查

D:/C/Java/maven3/repo/org/zollty/zollty-org/1.0目录！！

2、transitive dependencies (if any) will not be available, enable debug logging for more details

详细错误如下：

[WARNING] The POM for org.zollty.util:zollty-util:jar:1.0 is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details

解决方法：显式引入:zollty-util:jar:1.0依赖的jar即可。

3、如何将Maven依赖的jar发布到tomcat的WEB-INF/lib下面

在.classpath文件中设置：

</attributes>

</classpathentry>

注意，有些插件是：<classpathentry kind="con" path="org.maven.ide.eclipse.MAVEN2_CLASSPATH_CONTAINER">

4、配置了拷贝(overlays)引入的war包的Eclipse-Maven 项目，当发布到服务器上时，没有拷贝到war中的文件到发布的服务器上。

pom配置如下：

<plugin>

    <groupId>org.apache.maven.plugins</groupId>

    <artifactId>maven-war-plugin</artifactId>

    <version>2.1.1</version>

    <configuration>

     <attachClasses>true</attachClasses>

     <overlays>

      <overlay>

       <groupId>com.zollty.pss</groupId>

       <artifactId>abframe</artifactId>

      </overlay>

      <overlay>

       <!-- don't remove this tag. empty groupId/artifactId represents the current build -->

      </overlay>

     </overlays>

    </configuration>

   </plugin>

原因：没有配置支持overlays的Eclipse插件，即m2e-wtp插件。

有些Eclipse插件是这样

.project文件

...

<nature>org.maven.ide.eclipse.maven2Nature</nature>

...

</natrues>

.classpath 文件

</attributes>

</classpathentry>

但是有些Eclipse插件是这样

.project文件

...

<nature>org.eclipse.m2e.core.maven2Nature</nature>

...

</natures>

.classpath 文件

</attributes>

</classpathentry>

经测试，第二个配置可以正确使用maven的war包依赖自动发布的功能。

如果是第一个配置，那需要安装m2e-wtp插件。

安装后，完整的配置如下

.project文件

<? xml version = "1.0" encoding = "UTF-8" ?>

< projectDescription >

< name >amps-dcm</ name >

< comment ></ comment >

< projects >

</ projects >

< buildSpec >

< buildCommand >

< name >org.eclipse.wst.jsdt.core.javascriptValidator</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >org.eclipse.wst.common.project.facet.core.builder</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >com.genuitec.eclipse.j2eedt.core.WebClasspathBuilder</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >org.eclipse.jdt.core.javabuilder</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >com.genuitec.eclipse.j2eedt.core.J2EEProjectValidator</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >com.genuitec.eclipse.j2eedt.core.DeploymentDescriptorValidator</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >org.eclipse.wst.validation.validationbuilder</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >com.genuitec.eclipse.ast.deploy.core.DeploymentBuilder</ name >

< arguments >

</ arguments >

</ buildCommand >

< buildCommand >

< name >org.eclipse.m2e.core.maven2Builder</ name >

< arguments >

</ arguments >

</ buildCommand >

</ buildSpec >

< natures >

< nature >org.eclipse.m2e.core.maven2Nature</ nature >

< nature >org.eclipse.jem.workbench.JavaEMFNature</ nature >

< nature >org.eclipse.wst.common.modulecore.ModuleCoreNature</ nature >

< nature >com.genuitec.eclipse.ast.deploy.core.deploymentnature</ nature >

< nature >com.genuitec.eclipse.j2eedt.core.webnature</ nature >

< nature >org.eclipse.jdt.core.javanature</ nature >

< nature >org.eclipse.wst.common.project.facet.core.nature</ nature >

< nature >org.eclipse.wst.jsdt.core.jsNature</ nature >

</ natures >

</ projectDescription >

.classpath 文件

<? xml version = "1.0" encoding = "UTF-8" ?>

< classpath >

< classpathentry kind = "src" output = "target/classes" path = "src/main/java" >

< attributes >

< attribute name = "optional" value = "true" />

< attribute name = "maven.pomderived" value = "true" />

</ attributes >

</ classpathentry >

< classpathentry excluding = "**" kind = "src" output = "target/classes" path = "src/main/resources" >

< attributes >

< attribute name = "maven.pomderived" value = "true" />

</ attributes >

</ classpathentry >

< classpathentry kind = "src" output = "target/test-classes" path = "src/test/java" >

< attributes >

< attribute name = "optional" value = "true" />

< attribute name = "maven.pomderived" value = "true" />

</ attributes >

</ classpathentry >

< classpathentry excluding = "**" kind = "src" output = "target/test-classes" path = "src/test/resources" >

< attributes >

< attribute name = "maven.pomderived" value = "true" />

</ attributes >

</ classpathentry >

< classpathentry

kind = "con"

path = "org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.6" >

< attributes >

< attribute name = "maven.pomderived" value = "true" />

</ attributes >

</ classpathentry >

< classpathentry kind = "con" path = "org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER" >

< attributes >

< attribute name = "maven.pomderived" value = "true" />

< attribute name = "org.eclipse.jst.component.dependency" value = "/WEB-INF/lib" />

</ attributes >

</ classpathentry >

< classpathentry kind = "output" path = "target/classes" />

</ classpath >

5、maven 无法确定 <T>T 的类型参数;对于上限为 long,java.lang.Object 的类型变量 T

无法确定 <X>X 的类型参数；对于上限为 X,java.lang.Object 的类型变量 X，不存在唯一最大实例

原因是，默认编译器（javac）的问题。解决方案：使用其他编译器，比如eclipse所用的编译器（JDT compiler from eclipse）。

在pom.xml中配置如下：

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

<source>${java-version}</source>

<target>${java-version}</target>

<compilerId>eclipse</compilerId>

</configuration>

<groupId>org.codehaus.plexus</groupId>

<artifactId>plexus-compiler-eclipse</artifactId>

</dependency>

</dependencies>

</plugin>

参见：

http://www.eclipse.org/forums/index.php/t/1229/

6、使用JDT compiler时出现枚举类型switch报错问题：

Cannot switch on a value of type. Only convertible int values or enum variables are permitted

例如：

class Foo {

static enum MyEnum { A }

void foo() { switch ( MyEnum.A ) { case A: } }

}

分析和解决方法：

Turns out that the setting org.eclipse.jdt.core.compiler.compliance needs to be set to the target version in order for it to be able to recognize java.lang.Enum .

This setting is only set by plexus-compiler-eclipse when both targetVersion AND optimize is set. [1]

Modify your pom like this and it should work:

< plugins >

< plugin >

< groupId >org.apache.maven.plugins</ groupId >

< artifactId >maven-compiler-plugin</ artifactId >

< version >3.1</ version > 

< configuration >

< compilerId >eclipse</ compilerId >

< source >1.6</ source >

< target >1.6</ target > < optimize >true</ optimize > 

I'm not sure why it was decided in plexus-compiler-eclipse that optimization would affect the compliance level, so this is in fact a workaround.

see:

https://github.com/sonatype/plexus-compiler/blob/master/plexus-compilers/plexus-compiler-eclipse/src/main/java/org/codehaus/plexus/compiler/eclipse/EclipseJavaCompiler.java#L156

7、Maven报错：'version' contains an expression but should be a constant.

是因为父pom还没有发布到仓库中，建议在仓库中检查一下父pom是否正确。

8、Maven WTP无法引用工程中的项目模块(org.eclipse.wst.common.component)

也就是说，在org.eclipse.wst.common.component文件中缺少如下的语句：

<dependent-module archiveName="tre-client-2.0.2-SNAPSHOT.jar" deploy-path="/WEB-INF/lib" handle="module:/resource/tre-client/tre-client">

<dependency-type>uses</dependency-type>

</dependent-module>

那是因为被引用的项目的pom配置有问题，经我检查，问题出在如下一行

<directory>${basedir}/src/main/resources</directory>

</resource>

<directory>${basedir}/src/main/java/com/zollty/report/client</directory>

</includes>