java - 服务器启动期间在 Tomcat、Spring、Maven 和 Eclipse 上使用 wicket 的 ClassNotFoundException

Question

服务器启动期间在 Tomcat、Spring 和 Eclipse 上出现 ClassNotFoundException 和 wicket。

在 Eclipse 中，当我尝试加载服务器时遇到一些导致 404 页面的错误。

这是堆栈跟踪:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'plop0' defined in ServletContext resource [/WEB-INF/spring-config/dependenciesInjectionContext.xml]: Cannot resolve reference to bean 'plop1' while setting bean property 'plop1'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'plop1': Injection of persistence fields failed; nested exception is org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [com.plop2.plop3.presentation.WicketApplication] for bean with name 'wicketApplication' defined in ServletContext resource [/WEB-INF/spring-config/wicketContext.xml]; nested exception is java.lang.ClassNotFoundException: com.plop2.plop3.presentation.WicketApplication
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:275) 
    ...
    at java.lang.Thread.run(Unknown Source)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'plop1': Injection of persistence fields failed; nested exception is org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [com.plop2.plop3.presentation.WicketApplication] for bean with name 'wicketApplication' defined in ServletContext resource [/WEB-INF/spring-config/wicketContext.xml]; nested exception is java.lang.ClassNotFoundException: com.plop2.plop3.presentation.WicketApplication
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.postProcessAfterInstantiation(PersistenceAnnotationBeanPostProcessor.java:311)
    ...
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269)
    ... 26 more
Caused by: org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [com.plop2.plop3.presentation.WicketApplication] for bean with name 'wicketApplication' defined in ServletContext resource [/WEB-INF/spring-config/wicketContext.xml]; nested exception is java.lang.ClassNotFoundException: com.plop2.plop3.presentation.WicketApplication
    at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1141)
    ...
    at org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor.postProcessAfterInstantiation(PersistenceAnnotationBeanPostProcessor.java:308)
    ... 37 more
Caused by: java.lang.ClassNotFoundException: com.plop2.plop3.presentation.WicketApplication
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1676)
    ...
    at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1138)
    ... 49 more

plop3-admin-provider-wicket 的 pom.xml :

<parent>
    <groupId>com.plop2.plop3</groupId>
    <artifactId>plop3</artifactId>
    <version>1.0.0</version>
    <relativePath>../pom.xml</relativePath>
</parent>

<artifactId>plop3-admin-provider-wicket</artifactId>
<packaging>jar</packaging>
<name>${project.artifactId}(${project.packaging})</name>

<dependencies>
    ...
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
    </dependency>
    ...
    <dependency>
        <groupId>org.apache.wicket</groupId>
        <artifactId>wicket</artifactId>
    </dependency>       
    <dependency>
        <groupId>org.apache.wicket</groupId>
        <artifactId>wicket-extensions</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.wicket</groupId>
        <artifactId>wicket-datetime</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.wicket</groupId>
        <artifactId>wicket-jmx</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.wicket</groupId>
        <artifactId>wicket-spring</artifactId>
    </dependency>
</dependencies>
<build>
    <resources>         
        <resource>
            <filtering>true</filtering>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.html</include>
                <include>**/*.properties</include>
            </includes>
        </resource>
    </resources>
    <testResources>
        <testResource>
            <filtering>true</filtering>
            <directory>src/test/resources</directory>
        </testResource>
    </testResources>
</build>

plop3-admin-war的pom.xml:

<parent>
    <groupId>com.plop2.plop3</groupId>
    <artifactId>plop3</artifactId>
    <version>1.0.0</version>
    <relativePath>../pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>plop3-admin-war</artifactId>
<packaging>war</packaging>
<name>${project.artifactId}(${project.packaging})</name>
<dependencies>      
    <dependency>
        <groupId>${project.groupId}</groupId>
        <artifactId>plop3-admin-provider-wicket</artifactId>
    </dependency>       
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
    </dependency>
    ...
    <dependency>
        <groupId>org.apache.wicket</groupId>
        <artifactId>wicket</artifactId>
    </dependency>
    ...
</dependencies>
<build>
    <resources>
        <resource>
            <filtering>true</filtering>
            <directory>src/main/resources</directory>
        </resource>
    </resources>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <configuration>
                <webResources>
                    <resource>
                        <directory>src/main/webapp</directory>
                        <filtering>true</filtering>
                    </resource>
                </webResources>
            </configuration>
        </plugin>
    </plugins>
</build>

plop3-admin-war的web.xml:

<!-- Spring param -->
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/spring-config/applicationContext.xml</param-value>
</context-param>
<filter>
    <filter-name>Spring character encoding filter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
    <init-param>
        <param-name>forceEncoding</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>Spring character encoding filter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
<filter>
    <filter-name>gassi.filter</filter-name>
    <filter-class>com.plop2.plop3.gassi.GassiFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>gassi.filter</filter-name>
    <url-pattern>/app/*</url-pattern>
</filter-mapping>   
<filter>
    <filter-name>wicket.filter</filter-name>
    <filter-class>org.apache.wicket.protocol.http.WicketFilter</filter-class>
    <init-param>
        <param-name>applicationFactoryClassName</param-name>
        <param-value>org.apache.wicket.spring.SpringWebApplicationFactory</param-value>
    </init-param>
    <init-param>
        <param-name>configuration</param-name>
        <param-value>${configuration.type}</param-value>
    </init-param>
</filter>   
<filter-mapping>
    <filter-name>wicket.filter</filter-name>
    <url-pattern>/app/*</url-pattern>
</filter-mapping>
<listener>
    <display-name>spring context loader</display-name>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!-- Listener applicatif -->
<listener>
    <display-name>plop3Listener context loader</display-name>
    <listener-class>com.plop2.plop3.plop3Listener</listener-class>
</listener>

/plop3-admin-war/src/main/webapp/WEB-INF/spring-config/applicationContext.xml :

<import resource="applicationPropertiesContext.xml" />
<import resource="dependenciesInjectionContext.xml" />  
<import resource="jpaDaoContext.xml" />
<import resource="transactionContext.xml" />
<import resource="wicketContext.xml" />

然后是/plop3-admin-war/src/main/webapp/WEB-INF/spring-config/wicketContext.xml :

<bean id="wicketApplication" name="wicketApplication"
    class="com.plop2.plop3.presentation.WicketApplication" scope="singleton">
</bean>

我不明白为什么无法加载该类，plop3-admin-provider-wicket 出现在 plop3-admin-war Maven 依赖项列表中。

这让我发疯，两天我就在这上面。

Answer 1

尝试构建一个 WAR 并将其部署到一个完全在 eclipse 之外运行的 tomcat，方法是将 WAR 放入 webapps 目录并运行启动脚本。

这将确定问题是出在库依赖性上还是在 eclipse 工作区设置中。

如果您怀疑工作区设置，请尝试关闭 eclipse 中的所有项目并将它们从工作区中删除。从命令行执行 mvn clean install 并确保有效。

然后删除以下所有eclipse文件:.project、.classpath和.settings，选择Import as Maven Project 再试一次，确保 eclipse 使用与命令行相同的 maven 和相同的 settings.xml。

如果问题仍然存在，请尝试在 web.xml 的最开头添加一个 ServletContextListener，并打印出一些涉及的类的位置:

System.out.println("All locations of missing class WicketApplication: " + getClass().getclassLoader().getResources("com/plop2/plop3/presentation/WicketApplication.class") );

System.out.println("Currently used version of WicketApplication: " + getClass().getclassLoader().getResource("com/plop2/plop3/presentation/WicketApplication.class") );

对于类未找到异常有两种解释:类不在类路径中(因为 jar 不存在或由于 eclipse 类路径问题)，或者类存在但类不可见需要它，因为需要它的类在服务器类加载器中。

同时查看 JHades，这是我编写的一个帮助工具 diagnose classpath problems .