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Java 11：在模块路径或类路径上找不到 JAXB-API 的实现

java java-11 java-platform-module-system
2022-09-03 17:32:53

我有一个小项目，当我让它运行时，它确实会引发异常。

问题就在这里（TestObject.java）：

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

我真的不明白为什么这会引发异常。我还创建了一个像超级按钮一样的测试（TestTest.java）。请原谅我的名字，但这只是一个小型测试应用程序，可以让它与java 11一起使用。

我遵循了这个：javax.xml.bind.JAXBException 在模块路径或类路径上找不到 JAXB-API 的实现并添加

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，但后来它抱怨说

Error:java: module not found: java.activation

丢失。由于这也从Java 11中删除，我添加了：

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

但后来它抛出了很多错误：

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

令我感到困惑的是：测试有效。因此，在 junit5 环境中似乎存在某种 jaxb 实现。我还在如何将java 8应用程序迁移到java 9模块中发现了一些其他信息，在那里我发现了这个：

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。如果有人能帮助我运行，我会非常高兴。我在 Fedora 29， 64 位上使用 java-openjdk-11.0.1.13-11.rolling.fc29.x86_64。

ps.：我想把所有这些写进帖子的评论中，主题是“javax.xml.bind.JAXBException...”但我不被允许这样做。所以我创建了这个新帖子。

edit：在该示例应用程序中引发的异常是这样的：

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

答案 1

解决方案非常简单。首先，使用 jaxb 2.3.1。beta-stuff仅用于测试。真正的问题是模块信息.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。

只需要两个依赖项是：

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

答案 2

为了完成其他答案：

JAXB 使用绑定到当前线程的类加载器来查找 JAXB 类 （），并且在某些情况下（例如，对于 jetty 线程），绑定的类加载器是 一个 ，它具有不知道类路径的特殊性，与 相反。ContextFactoryThread.currentThread().getContextClassLoader()PlatformClassLoaderAppClassLoader

要解决此问题，JAXB API 和运行时必须位于模块路径中（可通过 访问）。PlatformClassLoader

例如，应用程序打包了以下依赖项：

<dependency>
    <groupId>jakarta.xml.bind</groupId>
    <artifactId>jakarta.xml.bind-api</artifactId>
    <version>2.3.3</version>
</dependency>
<dependency>
    <groupId>org.glassfish.jaxb</groupId>
    <artifactId>jaxb-runtime</artifactId>
    <version>2.3.3</version>
</dependency>

因此，应用程序应使用及其模块依赖项启动，如下所示：jaxb-runtime

### Set the module-path
MODULEPATH="./lib/jaxb-runtime-2.3.3.jar"
MODULEPATH="${MODULEPATH}:./lib/jakarta.activation-1.2.2.jar"
MODULEPATH="${MODULEPATH}:./lib/jakarta.xml.bind-api-2.3.3.jar"
MODULEPATH="${MODULEPATH}:./lib/txw2-2.3.3.jar"
MODULEPATH="${MODULEPATH}:./lib/istack-commons-runtime-3.0.11.jar"

java --module-path ${MODULEPATH} --add-modules ALL-MODULE-PATH [...]

注意：ALL-MODULE-PATH 可以替换为特定的模块名称


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