GWT Maven Classpath问题(BoneCP依赖于slf4j-api)

Question

使用原型gwt-maven-plugin 2.5.0创建了一个gwt maven项目。

GWT服务器端依赖于BoneCP ( ServletContextListener应该实例化连接池)。BoneCP依赖于slf4j-api。启动DevMode会引发NoClassDefFoundError，尽管slf4j-api是作为maven依赖项添加的，就像BoneCP一样：

Starting Jetty on port 8888
   [WARN] failed com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload@12271e{/,/home/user/workspace/project/target\moduleName-0.0.1-SNAPSHOT}
java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at com.jolbox.bonecp.BoneCPConfig.<clinit>(BoneCPConfig.java:62)
    at my.group.artifact.server.db.ConnectionPool.<init>(ConnectionPool.java:41)
    at my.group.artifact.server.db.ConnectionPool.getInstance(ConnectionPool.java:23)
    at my.group.artifact.server.MyServletContextListener.contextInitialized(MyServletContextListener.java:26)

检查org.slf4j.LoggerFactory实际上存在于maven添加的jar中。还可以找到通过maven添加的其他依赖项(例如BoneCP)。

Pom.xml和web.xml在下面。

<?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/maven-v4_0_0.xsd">

  <!-- POM file generated with GWT webAppCreator -->
  <modelVersion>4.0.0</modelVersion>
  <groupId>my.group/groupId>
  <artifactId>artifact</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>ModuleName</name>

  <properties>
    <!-- Convenience property to set the GWT version -->
    <gwtVersion>2.5.0</gwtVersion>
    <!-- GWT needs at least java 1.5 -->
    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>

    <webappDirectory>${project.build.directory}/${project.build.finalName}</webappDirectory>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>com.google.gwt</groupId>
      <artifactId>gwt-servlet</artifactId>
      <version>${gwtVersion}</version>
      <scope>runtime</scope>
    </dependency>
    <dependency>
      <groupId>com.google.gwt</groupId>
      <artifactId>gwt-user</artifactId>
      <version>${gwtVersion}</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.7</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>javax.validation</groupId>
      <artifactId>validation-api</artifactId>
      <version>1.0.0.GA</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>javax.validation</groupId>
      <artifactId>validation-api</artifactId>
      <version>1.0.0.GA</version>
      <classifier>sources</classifier>
      <scope>test</scope>
    </dependency>

    <!-- mine -->
    <dependency>
        <groupId>com.google.inject</groupId>
        <artifactId>guice</artifactId>
        <version>3.0</version>
    </dependency>

    <dependency>
        <groupId>com.google.gwt.inject</groupId>
        <artifactId>gin</artifactId>
        <version>2.1.2</version>
    </dependency>

    <dependency>
        <groupId>com.jolbox</groupId>
        <artifactId>bonecp</artifactId>
        <version>0.8.0.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.27</version>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.5</version>
    </dependency>

    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>

    <dependency>
        <groupId>com.google.guava</groupId>
        <artifactId>guava</artifactId>
        <version>15.0</version>
    </dependency>

    <dependency>
        <groupId>com.google.guava</groupId>
        <artifactId>guava-gwt</artifactId>
        <version>15.0</version>
    </dependency>


  </dependencies>

  <build>
    <!-- Generate compiled stuff in the folder used for developing mode -->
    <outputDirectory>${webappDirectory}/WEB-INF/classes</outputDirectory>

    <plugins>

      <!-- GWT Maven Plugin -->
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>gwt-maven-plugin</artifactId>
        <version>2.5.0</version>
        <executions>
          <execution>
            <goals>
              <goal>compile</goal>
              <!--<goal>test</goal>-->
              <!--<goal>i18n</goal>-->
              <goal>generateAsync</goal>
            </goals>
          </execution>
        </executions>
        <!-- Plugin configuration. There are many available options, see 
          gwt-maven-plugin documentation at codehaus.org -->
        <configuration>
          <runTarget>ModuleName.html</runTarget>
          <hostedWebapp>${webappDirectory}</hostedWebapp>
          <!--<i18nMessagesBundle>my.group.artifact.client.Messages</i18nMessagesBundle>-->
        </configuration>
      </plugin>

      <!-- Copy static web files before executing gwt:run -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-war-plugin</artifactId>
        <version>2.1.1</version>
        <executions>
          <execution>
            <phase>compile</phase>
            <goals>
              <goal>exploded</goal>
            </goals>
          </execution>
        </executions>
        <configuration>
          <webappDirectory>${webappDirectory}</webappDirectory>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>2.3.2</version>
        <configuration>
          <source>1.6</source>
          <target>1.6</target>
        </configuration>
      </plugin>
    </plugins>
  </build>

</project>

相关web.xml部分

  <listener>
    <listener-class>
        my.group.artifact.server.MyServletContextListener
    </listener-class>
  </listener>

整个堆栈迹

[WARN] Server class 'com.mysql.jdbc.Driver' could not be found in the web app, but was found on the system classpath
   [WARN] Adding classpath entry 'file:/C:/Documents%20and%20Settings/thomas/.m2/repository/mysql/mysql-connector-java/5.1.27/mysql-connector-java-5.1.27.jar' to the web app classpath for this session
   For additional info see: file:/C:/Documents%20and%20Settings/thomas/Desktop/eclipse/plugins/com.google.gwt.eclipse.sdkbundle_2.5.1/gwt-2.5.1/doc/helpInfo/webAppClassPath.html
[WARN] Server class 'com.jolbox.bonecp.BoneCPConfig' could not be found in the web app, but was found on the system classpath
   [WARN] Adding classpath entry 'file:/C:/Documents%20and%20Settings/thomas/.m2/repository/com/jolbox/bonecp/0.8.0.RELEASE/bonecp-0.8.0.RELEASE.jar' to the web app classpath for this session
   For additional info see: file:/C:/Documents%20and%20Settings/thomas/Desktop/eclipse/plugins/com.google.gwt.eclipse.sdkbundle_2.5.1/gwt-2.5.1/doc/helpInfo/webAppClassPath.html
Starting Jetty on port 8888
   [WARN] failed com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload@12271e{/,/home/user/workspace\project\target\moduleName-0.0.1-SNAPSHOT}
java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at com.jolbox.bonecp.BoneCPConfig.<clinit>(BoneCPConfig.java:62)
    at my.group.artifact.server.db.ConnectionPool.<init>(ConnectionPool.java:41)
    at my.group.artifact.server.db.ConnectionPool.getInstance(ConnectionPool.java:23)
    at my.group.artifact.server.MyServletContextListener.contextInitialized(MyServletContextListener.java:26)
    at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:543)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:136)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1220)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:513)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:468)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.handler.RequestLogHandler.doStart(RequestLogHandler.java:115)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.Server.doStart(Server.java:222)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:672)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:509)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1093)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
    at com.google.gwt.dev.DevMode.main(DevMode.java:311)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload$WebAppClassLoaderExtension.findClass(JettyLauncher.java:372)
    at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:366)
    at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:337)
    ... 22 more
   [WARN] failed RequestLogHandler@19e9785
java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at com.jolbox.bonecp.BoneCPConfig.<clinit>(BoneCPConfig.java:62)
    at my.group.artifact.server.db.ConnectionPool.<init>(ConnectionPool.java:41)
    at my.group.artifact.server.db.ConnectionPool.getInstance(ConnectionPool.java:23)
    at my.group.artifact.server.MyServletContextListener.contextInitialized(MyServletContextListener.java:26)
    at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:543)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:136)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1220)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:513)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:468)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.handler.RequestLogHandler.doStart(RequestLogHandler.java:115)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.Server.doStart(Server.java:222)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:672)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:509)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1093)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
    at com.google.gwt.dev.DevMode.main(DevMode.java:311)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload$WebAppClassLoaderExtension.findClass(JettyLauncher.java:372)
    at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:366)
    at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:337)
    ... 22 more
   [WARN] Error starting handlers
java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at com.jolbox.bonecp.BoneCPConfig.<clinit>(BoneCPConfig.java:62)
    at my.group.artifact.server.db.ConnectionPool.<init>(ConnectionPool.java:41)
    at my.group.artifact.server.db.ConnectionPool.getInstance(ConnectionPool.java:23)
    at my.group.artifact.server.MyServletContextListener.contextInitialized(MyServletContextListener.java:26)
    at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:543)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:136)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1220)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:513)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:468)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.handler.RequestLogHandler.doStart(RequestLogHandler.java:115)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.Server.doStart(Server.java:222)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:39)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:672)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:509)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1093)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
    at com.google.gwt.dev.DevMode.main(DevMode.java:311)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload$WebAppClassLoaderExtension.findClass(JettyLauncher.java:372)
    at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:366)
    at org.mortbay.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:337)
    ... 22 more

Answer 1

警告服务器类“com.mysql.jdbc.Driver”无法在web应用程序中找到，但是在系统类路径警告中发现了将类路径条目'file:/C:/Documents%20and%20Settings/thomas/.m2/repository/mysql/mysql-connector-java/5.1.27/mysql-connector-java-5.1.27.jar‘添加到web应用程序类路径中，以获取更多信息(参见: file:/C:/Documents%20and%20Settings/thomas/Desktop/eclipse/plugins/com.google.gwt.eclipse.sdkbundle_2.5.1/gwt-2.5.1/doc/ )。警告服务器类“com.jolbox.bonecp.BoneCPConfig”在web应用程序中找不到，但是在系统类路径警告中发现了将类路径条目'file:/C:/Documents%20and%20Settings/thomas/.m2/repository/com/jolbox/bonecp/0.8.0.RELEASE/bonecp-0.8.0.RELEASE.jar‘添加到web应用程序类路径中，以获取更多信息(参见: file:/C:/Documents%20and%20Settings/thomas/Desktop/eclipse/plugins/com.google.gwt.eclipse.sdkbundle_2.5.1/gwt-2.5.1/doc/helpInfo/webAppClassPath.html )。

这就是线索。JAR应该从WEB-INF/lib加载，而不是从类路径加载。

这里有两件事需要注意：

• 您正在使用，但显然没有使用M2Eclipse将您的Maven项目导入Eclipse (否则，警告不会链接到sdkbundle Eclipse插件)
• 即使是这样，您也必须运行mvn package一次(每次更改类路径/构建路径)，以便将所有依赖项复制到target/中的WEB-INF/lib文件夹中，这样DevMode就可以在预期的位置找到它们。