Spring Boot可執行jar引發java.lang.ClassNotFoundException：org.apache.tomcat.util.descriptor.web.ServletDef

Question

我創建了一個簡單的測試用例，顯示了我當前面臨的問題。

我試圖做的是從CommandLineRunner手動啟動嵌入的Tomcat，並手動部署文件系統上某處可用的war文件：

package example;

import java.io.File;

import org.apache.catalina.Context;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.startup.Tomcat;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
public class MyCommandLineRunner implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {

        File tomcatBaseDir = new File("<tomcat-base-dir>");
        File warToBeDeployed = new File("<war-to-be-deployed>");

        Tomcat tomcat = new Tomcat();
        tomcat.setPort(8080);
        tomcat.setBaseDir(tomcatBaseDir.getAbsolutePath());
        tomcat.getHost().setAppBase(tomcatBaseDir.getAbsolutePath());
        tomcat.getHost().setAutoDeploy(true);
        tomcat.getHost().setDeployOnStartup(true);

        try {
            tomcat.start();
            System.out.println("Tomcat started on " + tomcat.getHost());
        } catch (LifecycleException e) {
            System.err.println("Tomcat could not be started");
            System.exit(-1);
        }

        Context appContext = tomcat.addWebapp(tomcat.getHost(), "/hello-world", warToBeDeployed.getAbsolutePath());
        System.out.println("Deployed " + appContext.getBaseName() + " on " + tomcat.getHost());

        tomcat.getServer().await();

    }

}

這是我簡單的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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.5.RELEASE</version>
</parent>

<artifactId>spring-boot-tomcat-embedded-manually</artifactId>
<version>0.0.1-SNAPSHOT</version>

<properties>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-catalina</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-util</artifactId>
        <version>${tomcat.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-core</artifactId>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-jasper</artifactId>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

這就是發生的情況：

1. 如果我從Eclipse中運行該應用程序，那完全沒問題；

2. 如果我運行“ mvn clean package”，然后運行“ java -jar [path-to-jar]”，則會得到：

    java.lang.ClassNotFoundException: org.apache.tomcat.util.descriptor.web.ServletDef at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1305) ~[tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1139) ~[tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.tomcat.util.IntrospectionUtils.callMethod1(IntrospectionUtils.java:359) ~[tomcat-util-8.0.33.jar!/:8.0.33] at org.apache.tomcat.util.digester.SetNextRule.end(SetNextRule.java:145) ~[tomcat-util-scan-8.0.33.jar!/:8.0.33] at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:956) [tomcat-util-scan-8.0.33.jar!/:8.0.33] at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source) [na:1.8.0_91] at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source) [na:1.8.0_91] at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1451) [tomcat-util-scan-8.0.33.jar!/:8.0.33] at org.apache.tomcat.util.descriptor.web.WebXmlParser.parseWebXml(WebXmlParser.java:120) [tomcat-util-scan-8.0.33.jar!/:8.0.33] at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1115) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:779) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:306) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:95) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5150) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.startup.Tomcat.addWebapp(Tomcat.java:558) [tomcat-catalina-8.0.33.jar!/:8.0.33] at org.apache.catalina.startup.Tomcat.addWebapp(Tomcat.java:523) [tomcat-catalina-8.0.33.jar!/:8.0.33] at example.MyCommandLineRunner.run(MyCommandLineRunner.java:37) [spring-boot-tomcat-embedded-manually-0.0.1-SNAPSHOT.jar!/:0.0.1-SNAPSHOT] at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:806) [spring-boot-1.3.5.RELEASE.jar!/:1.3.5.RELEASE] at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:790) [spring-boot-1.3.5.RELEASE.jar!/:1.3.5.RELEASE] at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:777) [spring-boot-1.3.5.RELEASE.jar!/:1.3.5.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:308) [spring-boot-1.3.5.RELEASE.jar!/:1.3.5.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1191) [spring-boot-1.3.5.RELEASE.jar!/:1.3.5.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1180) [spring-boot-1.3.5.RELEASE.jar!/:1.3.5.RELEASE] at example.Main.main(Main.java:10) [spring-boot-tomcat-embedded-manually-0.0.1-SNAPSHOT.jar!/:0.0.1-SNAPSHOT] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_91] at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_91] at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_91] at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_91] at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:54) [spring-boot-tomcat-embedded-manually-0.0.1-SNAPSHOT.jar!/:0.0.1-SNAPSHOT] at java.lang.Thread.run(Unknown Source) [na:1.8.0_91] 

3. 如果我用maven-shade-plugin替換spring-boot-maven-plugin，然后嘗試“ mvn clean package”，然后嘗試“ java -jar [path-to-jar]”，則一切正常。

我是否在spring-boot-maven-plugin上缺少一些配置以使我的可執行jar實際起作用？

更新1

我的問題與此有關。 我嘗試了在那里提出的解決方案，並且確實可以從命令行和Eclipse中使用。

但是，我仍然不明白在我的特定情況下表現出的不一致行為：

• 為什么它可以在Eclipse中運行，而不能在命令行中運行？
• 如果我用maven-shade-plugin替換spring-boot-maven-plugin，為什么會起作用？

Answer 1

有點奇怪，我會以為您的pom看起來還可以。 就是說，嘗試將pom中的tomcat條目替換為：

                <dependency>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-starter-tomcat</artifactId>
                </dependency>

希望能幫助到你

Answer 2

看這個問題 。 您應該將類​​加載器添加到上下文中。 直接在行下添加

Context appContext = tomcat.addWebapp(tomcat.getHost(), "/hello-world", warToBeDeployed.getAbsolutePath());

這段代碼

WebappLoader loader = new WebappLoader(Thread.currentThread().getContextClassLoader());
appContext.setLoader(loader);

就我而言，它奏效了。