Java 11：在模块路径或类路径上未找到 JAXB-API 的实现

Question

我有一个小项目，当我让它运行时确实会抛出异常。

问题就在这里（TestObject.java）：

 final JAXBContext jaxbContext = JAXBContext.newInstance(...);

我真的不明白为什么会抛出异常。我还创建了一个非常有效的测试 (TestTest.java)。请原谅我的名字，但这只是一个让它与 Java 11 一起工作的小测试应用程序。

我遵循了这个： javax.xml.bind.JAXBException JAXB-API Implementation has not been found on module path or classpath and added

 compile('javax.xml.bind:jaxb-api:2.3.0')
compile('javax.activation:activation:1.1')
compile('org.glassfish.jaxb:jaxb-runtime:2.3.0')

到我的 build.gradle 但随后它抱怨说

Error:java: module not found: java.activation

不见了。由于这也从 Java 11 中删除，我添加了：

 compile 'com.sun.activation:javax.activation:1.2.0'

但随后会引发很多错误：

 Error:java: the unnamed module reads package com.sun.xml.bind from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.util from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.marshaller from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.api from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.v2 from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.v2.util from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.v2.model.impl from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.v2.model.annotation from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.v2.runtime from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.v2.runtime.unmarshaller from both jaxb.runtime and jaxb.core
Error:java: the unnamed module reads package com.sun.xml.bind.unmarshaller from both jaxb.runtime and jaxb.core
Error:java: module jaxb.runtime reads package com.sun.xml.bind from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.util from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.marshaller from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.api from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.v2 from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.v2.util from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.v2.model.impl from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.v2.model.annotation from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.v2.runtime from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.v2.runtime.unmarshaller from both jaxb.core and jaxb.runtime
Error:java: module jaxb.runtime reads package com.sun.xml.bind.unmarshaller from both jaxb.core and jaxb.runtime
Error:java: module jaxb.core reads package com.sun.xml.bind from both jaxb.core and jaxb.runtime

让我感到困惑的是：测试有效。所以在 junit5 环境中似乎有某种 jaxb 实现。我还找到了一些关于如何将 java 8 应用程序迁移到 java 9 模块的其他信息，我在其中找到了这个：

 compile group: 'javax.xml.bind', name: 'jaxb-api', version: '2.4.0-b180830.0359'
compile group: 'org.glassfish.jaxb', name: 'jaxb-runtime', version: '2.4.0-b180830.0438'
compile group: 'org.glassfish.jaxb', name: 'jaxb-xjc', version: '2.4.0-b180830.0438'

但这也行不通。如果有人可以帮助我运行它，我将非常高兴。我在 64 位 Fedora 29 上使用 java-openjdk-11.0.1.13-11.rolling.fc29.x86_64。

ps.：我想把所有这些都写到主题为“javax.xml.bind.JAXBException …”的帖子的评论中，但我不允许这样做。所以我创建了这个新帖子。

编辑：在该示例应用程序中抛出的异常是这样的：

 Exception in thread "main" java.lang.RuntimeException: javax.xml.bind.JAXBException: Implementation of JAXB-API has not been found on module path or classpath.
 - with linked exception:
[java.lang.ClassNotFoundException: com.sun.xml.bind.v2.ContextFactory]
    at test/com.example.TestObject.doSomething(TestObject.java:21)
    at test/com.example.TestObject.main(TestObject.java:12)
Caused by: javax.xml.bind.JAXBException: Implementation of JAXB-API has not been found on module path or classpath.
 - with linked exception:
[java.lang.ClassNotFoundException: com.sun.xml.bind.v2.ContextFactory]
    at java.xml.bind/javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:269)
    at java.xml.bind/javax.xml.bind.ContextFinder.find(ContextFinder.java:412)
    at java.xml.bind/javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:721)
    at java.xml.bind/javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:662)
    at test/com.example.TestObject.doSomething(TestObject.java:17)
    ... 1 more
Caused by: java.lang.ClassNotFoundException: com.sun.xml.bind.v2.ContextFactory
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    at java.xml.bind/javax.xml.bind.ServiceLoaderUtil.nullSafeLoadClass(ServiceLoaderUtil.java:122)
    at java.xml.bind/javax.xml.bind.ServiceLoaderUtil.safeLoadClass(ServiceLoaderUtil.java:155)
    at java.xml.bind/javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:267)
    ... 5 more

原文由 J. Doe 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

解决方法很简单。首先，使用 jaxb 2.3.1。 beta-stuff 仅用于测试。真正的问题是 module-info.java。 jaxb 需要有 2 个条目：

 requires java.xml.bind;
requires com.sun.xml.bind;

第一个要求定义实现，第二个要求定义 API。

唯一需要的两个依赖项是：

 compile group: 'javax.xml.bind', name: 'jaxb-api', version: '2.3.1'
compile group: 'org.glassfish.jaxb', name: 'jaxb-runtime', version: '2.3.1'

原文由 J. Doe 发布，翻译遵循 CC BY-SA 4.0 许可协议