如何解决java.lang.NoClassDefFoundError:javax/xml/bind/JAXBException [英] How to resolve java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException

问题描述

我有一些使用JAXB API类的代码，这些类已作为Java 6/7/8中JDK的一部分提供.当我使用Java 9运行相同的代码时，在运行时出现错误，指示找不到JAXB类.

I have some code that uses JAXB API classes which have been provided as a part of the JDK in Java 6/7/8. When I run the same code with Java 9, at runtime I get errors indicating that JAXB classes can not be found.

自Java 6以来，JAXB类已作为JDK的一部分提供，那么Java 9为什么不能再找到这些类?

The JAXB classes have been provided as a part of the JDK since Java 6, so why can Java 9 no longer find these classes?

推荐答案

JAXB API被视为Java EE API，因此不再包含在Java SE 9的默认类路径中.在Java 11中，它们已被完全删除.来自JDK.

The JAXB APIs are considered to be Java EE APIs and therefore are no longer contained on the default classpath in Java SE 9. In Java 11, they are completely removed from the JDK.

Java 9引入了模块的概念，默认情况下， java.se 聚合模块在类路径(或更确切地说是模块路径)上可用.顾名思义， java.se 聚合模块不不包括传统上与Java 6/7/8捆绑在一起的Java EE API.

Java 9 introduces the concepts of modules, and by default, the java.se aggregate module is available on the classpath (or rather, module-path). As the name implies, the java.se aggregate module does not include the Java EE APIs that have been traditionally bundled with Java 6/7/8.

幸运的是，JDK 6/7/8中提供的这些Java EE API仍在JDK中，但是默认情况下它们不在类路径中.以下模块提供了额外的Java EE API:

Fortunately, these Java EE APIs that were provided in JDK 6/7/8 are still in the JDK, but they just aren't on the classpath by default. The extra Java EE APIs are provided in the following modules:

java.activation
java.corba
java.transaction
java.xml.bind  << This one contains the JAXB APIs
java.xml.ws
java.xml.ws.annotation

快速而肮脏的解决方案:(仅JDK 9/10)

要在运行时使JAXB API可用，请指定以下命令行选项:

To make the JAXB APIs available at runtime, specify the following command-line option:

-添加模块java.xml.bind

但是我仍然需要它才能与Java 8一起使用！！！

如果您尝试使用较旧的JDK指定-add-modules ，则由于无法识别该选项，它会爆炸.我建议使用以下两种方法之一:

If you try specifying --add-modules with an older JDK, it will blow up because it's an unrecognized option. I suggest one of two options:

1. 您可以使用 JDK_JAVA_OPTIONS 环境变量设置任何仅Java 9+的选项.此环境变量为自动读取通过Java 9+版的 java 启动器.
2. 您可以添加 -XX:+ IgnoreUnrecognizedVMOptions ，以使JVM静默忽略无法识别的选项，而不会崩溃.但是要当心！JVM将不再为您验证您使用的任何其他命令行参数.此选项可与Oracle/OpenJDK以及IBM JDK(从JDK 8sr4开始)一起使用.

1. You can set any Java 9+ only options using the JDK_JAVA_OPTIONS environment variable. This environment variable is automatically read by the java launcher for Java 9+.
2. You can add the -XX:+IgnoreUnrecognizedVMOptions to make the JVM silently ignore unrecognized options, instead of blowing up. But beware! Any other command-line arguments you use will no longer be validated for you by the JVM. This option works with Oracle/OpenJDK as well as IBM JDK (as of JDK 8sr4).

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替代快速解决方案:(仅JDK 9/10)

请注意，您可以通过指定-add-modules java.se.ee 选项使上述所有Java EE模块在运行时可用. java.se.ee 模块是一个聚合模块，其中包括 java.se.ee 以及上述Java EE API模块.请注意，此不适用于Java 11 ，因为 java.se.ee 已在Java 11中删除.

Note that you can make all of the above Java EE modules available at run time by specifying the --add-modules java.se.ee option. The java.se.ee module is an aggregate module that includes java.se.ee as well as the above Java EE API modules. Note, this doesn't work on Java 11 because java.se.ee was removed in Java 11.

上面列出的Java EE API模块都标记为 @Deprecated(forRemoval = true)，因为它们与 Java 11 中="="已计划删除.因此，-add-module 方法在现成的Java 11中将不再起作用.

The Java EE API modules listed above are all marked @Deprecated(forRemoval=true) because they are scheduled for removal in Java 11. So the --add-module approach will no longer work in Java 11 out-of-the-box.

在Java 11及更高版本中，您需要做的是在类路径或模块路径上包含您自己的Java EE API副本.例如，您可以像这样将JAX-B API添加为Maven依赖项:

What you will need to do in Java 11 and forward is include your own copy of the Java EE APIs on the classpath or module path. For example, you can add the JAX-B APIs as a Maven dependency like this:

<!-- API, java.xml.bind module -->
<dependency>
    <groupId>jakarta.xml.bind</groupId>
    <artifactId>jakarta.xml.bind-api</artifactId>
    <version>2.3.2</version>
</dependency>

<!-- Runtime, com.sun.xml.bind module -->
<dependency>
    <groupId>org.glassfish.jaxb</groupId>
    <artifactId>jaxb-runtime</artifactId>
    <version>2.3.2</version>
</dependency>

有关JAXB的更多详细信息，请参见 JAXB参考实现页面.

See the JAXB Reference Implementation page for more details on JAXB.

有关Java模块化的完整详细信息，请参见 JEP 261:模块系统

For full details on Java modularity, see JEP 261: Module System

对于Gradle或Android Studio开发者:(JDK 9及更高版本)

在您的 build.gradle 文件中添加以下依赖项:

Add the following dependencies to your build.gradle file:

dependencies {
    // JAX-B dependencies for JDK 9+
    implementation "jakarta.xml.bind:jakarta.xml.bind-api:2.3.2"
    implementation "org.glassfish.jaxb:jaxb-runtime:2.3.2"
}

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