使用maven和gwt的log4j问题：org.apache.log4j.XAppender对象不可分配

本文介绍了使用maven和gwt的log4j问题：org.apache.log4j.XAppender对象不可分配的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有一个Maven GWT项目。我将Hibernate和HSQLDB作为持久层。运行单元测试很好，但是当它尝试运行服务器组件时，日志记录不起作用，所以我对服务器端的错误一无所知。我遇到的错误是：

lockquote
[错误] log4j：错误org.apache.log4j.RollingFileAppender对象是
不能分配给org.apache.log4j.Appender变量。 [错误]
log4j：错误类org.apache.log4j.Appender由
加载[错误] log4j：错误[sun.misc.Launcher$AppClassLoader@baf1915]而
[ERROR]类型的对象log4j：ERROR
org.apache.log4j.RollingFileAppender由[WebApp
ClassLoader = 1312837549 @ 4e404fad]加载。 [错误] log4j：错误
无法实例化名为file的appender。 [错误] log4j：错误
org.apache.log4j.ConsoleAppender对象不能分配给
org.apache.log4j.Appender变量。 [错误] log4j：错误类
org.apache.log4j.Appender由[错误]加载log4j：错误
[sun.misc.Launcher$AppClassLoader@baf1915]而类型
[错误] log4j：ERRORorg.apache.log4j.ConsoleAppender被
加载[WebAppClas sLoader = 1312837549 @ 4e404fad]。 [错误] log4j：错误可能
没有实例化名为stdout的appender。

从Google搜索中我确定它是因为有两个log4j.jar实例存在。
是否有解决此问题的好方法或最佳实践方法？我从控制台运行开发模式的项目。
My Pom.xml看起来像这样：

 <？xml version =1.0encoding =UTF- 8\" >？; 
< project xmlns =http://maven.apache.org/POM/4.0.0xmlns：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> testproject< / groupId> 
< artifactId> trustme-mdm-gwtp< / artifactId> 
< version> 1.0-SNAPSHOT< / version> 
<包装>战争< / packaging> 
<名称> GWTP基本< /名称> 
< description>基本GWTP应用程序< / description> 
 
 
<属性> 
<！ -  client  - > 
< gwt.version> 2.6.0< /gwt.version> 
< gwtp.version> 1.2.1< /gwtp.version> 
< gin.version> 2.1.2< /gin.version> 
 
 
<！ -  server  - > 
< guice.version> 3.0< /guice.version> 
 
 
 < junit.version> 4.7< /junit.version> 
< jukito.version> 1.4< /jukito.version> 
 
 
 < gwt-maven-plugin.version> 2.6.0< /gwt-maven-plugin.version> 
< maven-surefire-plugin.version> 2.6< /maven-surefire-plugin.version> 
< maven-compiler-plugin.version> 2.3.2< /maven-compiler-plugin.version> 
< maven-resources-plugin.version> 2.5< /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> 
 
 
 
 
< target.jdk> 1.7< /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> 
 
 
< plugins> 
  < plugin> 
< groupId> org.apache.maven.plugins< / groupId> 
< artifactId> maven-surefire-plugin< / artifactId> 
< version> $ {maven-surefire-plugin.version}< / version> 
<配置> 
<包括> 
< include> ** / * Test.java< / include> 
< / includes> 
 < exclude> ** / * GwtTest.java< / exclude> 
< /不包括> 
< / configuration> 
< / plugin> 
< plugin> 
< groupId> org.apache.maven.plugins< / groupId> 
< artifactId> maven-compiler-plugin< / artifactId> 
< version> 2.3.2< / version> 
<配置> 
< source> 1.7< / source> 
< target> 1.7< / target> 
< / configuration> 
< / plugin> 
 
 
     < plugin> 
< groupId> org.codehaus.mojo< / groupId> 
< artifactId> gwt-maven-plugin< / artifactId> 
<版本> $ {gwt.version}< / version> 
<配置> 
 < includes> ** / * GwtTest.java< / includes> 
< extraJvmArgs> -Xss1024K -Xmx1024M -XX：MaxPermSize = 256M< / extraJvmArgs> 
 
 
< copyWebapp> true< / copyWebapp> 
< hostedWebapp> $ {webappDirectory}< / hostedWebapp> 
 
 
< runTarget> Project.html< / runTarget> 
<模块> 
< module> testproject.Project< / module> 
< / modules> 
< / configuration> 
<执行次数> 
<执行> 
<目标> 
< goal>编译< / goal> 
< goal> test< / goal> 
< /目标> 
< /执行> 
< /执行次数> 
< / plugin> 
< / plugins> 
< / build> 
 
 
<依赖关系> 
<！ -  Google Web Toolkit  - > 
< dependency> 
< groupId> com.google.gwt< / groupId> 
< artifactId> gwt-user< / artifactId> 
<版本> $ {gwt.version}< / version> 
< /依赖关系> 
 
 
 < dependency> 
< groupId> com.gwt平台< / groupId> 
< artifactId> gwtp-all< / artifactId> 
< version> $ {gwtp.version}< / version> 
< /依赖关系> 
 
 
 < dependency> 
< groupId> com.google.inject< / groupId> 
< artifactId> guice< / artifactId> 
< version> $ {guice.version}< / version> 
< /依赖关系> 
< dependency> 
< groupId> com.google.inject.extensions< / groupId> 
< artifactId> guice-servlet< / artifactId> 
< version> $ {guice.version}< / version> 
< /依赖关系> 
< dependency> 
< groupId> com.google.inject.extensions< / groupId> 
< artifactId> guice-assistedinject< / artifactId> 
< version> $ {guice.version}< / version> 
< /依赖关系> 
< dependency> 
< groupId> com.google.gwt.inject< / groupId> 
< artifactId> gin< / artifactId> 
< version> $ {gin.version}< / version> 
< /依赖关系> 
 
 
 < dependency> 
< groupId> junit< / groupId> 
< artifactId> junit< / artifactId> 
< version> $ {junit.version}< / version> 
< scope> test< / scope> 
< /依赖关系> 
< dependency> 
< groupId> org.jukito< / groupId> 
< artifactId> jukito< / artifactId> 
< version> $ {jukito.version}< / version> 
< scope> test< / scope> 
< /依赖关系> 
  < dependency> 
< groupId> org.hibernate< / groupId> 
< artifactId> hibernate-entitymanager< / artifactId> 
< version> 4.3.5.Final< / version> 
< /依赖关系> 
 < dependency> 
< groupId> org.hsqldb< / groupId> 
< artifactId> hsqldb< / artifactId> 
< version> 2.3.2< / version> 
< /依赖关系> 
 < dependency> 
< groupId> org.slf4j< / groupId> 
< artifactId> slf4j-log4j12< / artifactId> 
< version> 1.7.7< / version> 
< /依赖关系> 
<！ -  GWT-Log  - > 
< dependency> 
< groupId> com.allen-sauer.gwt.log< / groupId> 
< artifactId> gwt-log< / artifactId> 
< version> 3.3.0< / version> 
< /依赖关系> 
 
< /依赖关系> 
< / project>

当我看看\target ... \lib文件夹时，这些是被部署的罐子：

我将pom.xml更改为：

 <！ -  Google Web Toolkit  - > 
< dependency> 
< groupId> com.google.gwt< / groupId> 
< artifactId> gwt-servlet< / artifactId> 
<版本> $ {gwt.version}< / version> 
< scope>运行时< / scope> 
< /依赖关系> 
< dependency> 
< groupId> com.google.gwt< / groupId> 
< artifactId> gwt-user< / artifactId> 
<版本> $ {gwt.version}< / version> 
< scope>提供< / scope> 
< /依赖关系>

但仍然没有成功...

我插入了依赖关系树的屏幕截图。我的声望不允许粘贴图像。它存储在这里：

解决方案
感谢您的帮助（尤其是托马斯）。
我的项目中使用的指南指出，log4j和slf4j作为pom.xml中的外部引用是必要的。

我只是删除它，它现在正在工作。然而，这教会了我，通过不结合服务器和客户端的依赖关系，它确实使生活更简单。
I have a Maven GWT project. I included Hibernate and HSQLDB as persistence layer. Running the unit tests is fine, but when it try to run the server component, logging does not work and so I am blind to the errors on the server side. The errors I encouter are:
From googling I am pretty sure it is because two instances of the log4j.jar are present.Is there a good way or best practice way to solve this issue? I run the project in development mode from the console.My Pom.xml looks like this:
<?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>testproject</groupId> <artifactId>trustme-mdm-gwtp</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <name>GWTP Basic</name> <description>Basic GWTP application</description> <properties>  <gwt.version>2.6.0</gwt.version> <gwtp.version>1.2.1</gwtp.version> <gin.version>2.1.2</gin.version>  <guice.version>3.0</guice.version>  <junit.version>4.7</junit.version> <jukito.version>1.4</jukito.version>  <gwt-maven-plugin.version>2.6.0</gwt-maven-plugin.version> <maven-surefire-plugin.version>2.6</maven-surefire-plugin.version> <maven-compiler-plugin.version>2.3.2</maven-compiler-plugin.version> <maven-resources-plugin.version>2.5</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> <target.jdk>1.7</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>${webappDirectory}/WEB-INF/classes</outputDirectory> <plugins>   <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <version>${maven-surefire-plugin.version}</version> <configuration> <includes> <include>**/*Test.java</include> </includes> <excludes> <exclude>**/*GwtTest.java</exclude> </excludes> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>2.3.2</version> <configuration> <source>1.7</source> <target>1.7</target> </configuration> </plugin>      <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>gwt-maven-plugin</artifactId> <version>${gwt.version}</version> <configuration>  <includes>**/*GwtTest.java</includes> <extraJvmArgs>-Xss1024K -Xmx1024M -XX:MaxPermSize=256M</extraJvmArgs> <copyWebapp>true</copyWebapp> <hostedWebapp>${webappDirectory}</hostedWebapp> <runTarget>Project.html</runTarget> <modules> <module>testproject.Project</module> </modules> </configuration> <executions> <execution> <goals> <goal>compile</goal> <goal>test</goal> </goals> </execution> </executions> </plugin> </plugins> </build> <dependencies>  <dependency> <groupId>com.google.gwt</groupId> <artifactId>gwt-user</artifactId> <version>${gwt.version}</version> </dependency>  <dependency> <groupId>com.gwtplatform</groupId> <artifactId>gwtp-all</artifactId> <version>${gwtp.version}</version> </dependency>  <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>  <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>   <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>4.3.5.Final</version> </dependency>  <dependency> <groupId>org.hsqldb</groupId> <artifactId>hsqldb</artifactId> <version>2.3.2</version> </dependency>  <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.7.7</version> </dependency>  <dependency> <groupId>com.allen-sauer.gwt.log</groupId> <artifactId>gwt-log</artifactId> <version>3.3.0</version> </dependency> </dependencies> </project>
When I take a look at the \target...\lib folder, these are the jars that are deployed:
I changed the pom.xml to this:
 <dependency> <groupId>com.google.gwt</groupId> <artifactId>gwt-servlet</artifactId> <version>${gwt.version}</version> <scope>runtime</scope> </dependency> <dependency> <groupId>com.google.gwt</groupId> <artifactId>gwt-user</artifactId> <version>${gwt.version}</version> <scope>provided</scope> </dependency>
But still no success...
I inserted a screenshot of the dependency tree. My reputation does not allow to paste images. It is stored here:
解决方案
Thanks for the help (especially Thomas). The guide i used for my project stated log4j and slf4j would be necessary as external references in the pom.xml.
I simply removed it and it is working now. This has taught me however, that it really makes life simpler by not combining server and client dependencies.

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Log4j

使用maven和gwt的log4j问题：org.apache.log4j.XAppender对象不可分配

问题描述