ClassNotFoundException 错误即使 jar 文件存在于 WEB-INF/lib 目录中答案

【问题标题】：ClassNotFoundException Error even though jar file is present in WEB-INF/lib directoryClassNotFoundException 错误即使 jar 文件存在于 WEB-INF/lib 目录中
【发布时间】：2014-03-16 17:38:42
【问题描述】：

我正在尝试设置 tomcat 服务器，所有常见的 spring jar 都进入 tomcat lib 目录，因为我有许多使用 spring 的 web 应用程序。然而，我的一个网络应用程序也使用带有 quartaz jar 的 spring batch。当所有 jars 都在 app1/WEB-INF/lib 目录中时，此 Web 应用程序运行良好。但是，当我尝试将所有常见的 spring jar 移动到 app1/WEB_INF/lib 中的 tomcat/lib 目录和 spring batch 和 quartaz jar 时，我得到了 noclassdefFound 错误。这是堆栈跟踪

Caused by: java.lang.NoClassDefFoundError: org/quartz/ObjectAlreadyExistsException
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
    at java.lang.Class.getDeclaredConstructors(Class.java:1836)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:230)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:972)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:945)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getSingletonFactoryBeanForTypeCheck(AbstractAutowireCapableBeanFactory.java:777)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryBean(AbstractAutowireCapableBeanFactory.java:707)
    at org.springframework.beans.factory.support.AbstractBeanFactory.isTypeMatch(AbstractBeanFactory.java:523)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:357)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:335)
    at org.springframework.beans.factory.BeanFactoryUtils.beanNamesForTypeIncludingAncestors(BeanFactoryUtils.java:187)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:895)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:853)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:768)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:486)
    ... 60 more
Caused by: java.lang.ClassNotFoundException: org.quartz.ObjectAlreadyExistsException
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

但是，当我将同一个 jar 复制到 tomcat/lib 目录时，它可以完美运行。至于我的理解。类文件搜索的顺序是首先jdk->bootstrap->system->common->web-app lib。因此它应该搜索该文件。在 web app/web-inf/lib 目录中。是否需要在 tomcat6 或 maven war 插件中添加任何配置来指定 jar？

**EDIT**

这里是 pom.xml

<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">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.kp</groupId>
    <artifactId>kp-app1</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>kp app1 Maven Webapp</name>
    <url>http://maven.apache.org</url>

    <parent>
        <groupId>com.kp.parent</groupId>
        <artifactId>kp-common</artifactId>
        <version>1.0.0.0</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <cxf.version>2.7.5</cxf.version>
        <spring.version>3.2.3.RELEASE</spring.version>
        <aspectj.version>1.7.3</aspectj.version>
        <jstl.version>1.2</jstl.version>
        <servlet.version>3.0-alpha-1</servlet.version>
        <spring.batch.version>2.2.1.RELEASE</spring.batch.version>
        <quartz.version>1.8.5</quartz.version>
        <skipTests>true</skipTests>
    </properties>

    <dependencies>


        <!-- Spring framework -->

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>3.0.2.RELEASE</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-expression</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aspects</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>aopalliance</groupId>
            <artifactId>aopalliance</artifactId>
            <version>1.0</version>
            <scope>provided</scope>
        </dependency>

        <!-- ================== -->
        <!-- AOP -->
        <!-- ================== -->

        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${aspectj.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>${aspectj.version}</version>
            <scope>provided</scope>
        </dependency>

        <!-- ================== -->
        <!-- SPRING BATCH -->
        <!-- ================== -->
        <dependency>
            <groupId>org.springframework.batch</groupId>
            <artifactId>spring-batch-core</artifactId>
            <version>${spring.batch.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.batch</groupId>
            <artifactId>spring-batch-infrastructure</artifactId>
            <version>${spring.batch.version}</version>
        </dependency>


        <!-- Required for cache/ lazy loading -->
        <dependency>
            <groupId>cglib</groupId>
            <artifactId>cglib-nodep</artifactId>
            <version>2.2.2</version>
        </dependency>

        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>

        <!-- Quartz framework -->
        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz</artifactId>
            <version>${quartz.version}</version>
        </dependency>

        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.1.1</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>




    <build>

        <finalName>kp-app1</finalName>
        <outputDirectory>${project.basedir}/target/classes</outputDirectory>
        <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>

        <pluginManagement>
            <plugins>

                <plugin>
                    <groupId>org.eclipse.m2e</groupId>
                    <artifactId>lifecycle-mapping</artifactId>
                    <version>1.0.0</version>
                    <configuration>
                        <lifecycleMappingMetadata>
                            <pluginExecutions>
                                <pluginExecution>
                                    <pluginExecutionFilter>
                                        <groupId>org.apache.maven.plugins</groupId>
                                        <artifactId>maven-dependency-plugin</artifactId>
                                        <versionRange>[2.8,)</versionRange>
                                        <goals>
                                            <goal>copy-dependencies</goal>
                                        </goals>
                                    </pluginExecutionFilter>
                                    <action>
                                        <execute />
                                    </action>
                                </pluginExecution>
                            </pluginExecutions>
                        </lifecycleMappingMetadata>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>

        <plugins>

            <!-- Tomcat 6 plugin -->
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat6-maven-plugin</artifactId>
                <configuration>
                    <url>${serverUrl}:${port}/manager</url>
                    <path>/${contextpath}</path>
                    <username>${username}</username>
                    <password>${password}</password>
                </configuration>
            </plugin>

            <!-- Maven compiler -->
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>


            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <webResources>
                        <resource>
                            <directory>src/main/webapp/WEB-INF/</directory>
                            <targetPath>WEB-INF</targetPath>
                            <includes>
                                <include>web.xml</include>
                            </includes>
                            <filtering>true</filtering>
                        </resource>
                    </webResources>
                </configuration>
            </plugin>

            <!--  Copy all the provided jars-->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.8</version>
                <configuration>
                    <outputDirectory>${project.build.directory}/provided-jars</outputDirectory>
                    <transitive>true</transitive>
                    <includeScope>provided</includeScope>
                </configuration>
                <executions>
                    <execution>
                        <id>cop-dependencies</id>
                        <phase>prepare-package</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <!-- Create a zip of all the provided jars -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <descriptors>
                        <descriptor>src/main/resources/assembly/zip.xml</descriptor>
                    </descriptors>
                    <finalName>nms-tomcat-jars</finalName>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id> <!-- this is used for inheritance merges -->
                        <phase>package</phase> <!-- append to the packaging phase. -->
                        <goals>
                            <goal>single</goal> <!-- goals == mojos -->
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

【问题讨论】：

发布你的 Maven 配置
并检查 tomcat/lib 和 webapp lib 中是否存在重复的 jars
classnotfound 有时意味着“无法加载此类”

标签： java spring maven tomcat6

【解决方案1】：

子类加载器可以找到父类加载器加载的类，但父类加载器找不到子类加载器加载的类。这里的spring类需要quartz类来创建bean但失败了，因为石英类是由子类加载器加载的。

【讨论】：

那么如何让它显式搜索呢？
我没有尝试过，但 VirtualWebAppLoader 可以提供帮助。请检查链接，有人有类似的问题stackoverflow.com/questions/13704915/…
我宁愿为您的每个 Web 应用程序单独部署 Spring。没有理由节省几兆字节的空间，因为您现在看到的影响比您想象的要大。
是的........@Gimby 我现在也这么想。但是我有 mybatis 依赖，它是如何被初始化的。因为spring context是tomcat lib的一部分，而mybatis是app lib的一部分。 mybatis 相关是使用上下文加载自动装配的。希望通过战争规模和 Permgen 空间来节省一些空间。我有大约 8 个使用 spring 的 Web 应用程序

【解决方案2】：

由于应用程序上下文加载类。当我移动 Spring-context.jar、Spring-web.jar 和 spring-context-support.jar 时。它开始工作了。正如@Naveen Ramawat 所建议的那样。上下文加载器不会从 web-inf/classes 目录（子节点）加载类。因此，当我将这些 jar 移动到 web-inf/lib 时，子类能够从 tomcat lib 目录加载父类。

【讨论】：