JAXB对象转XML时随机抛出空指针及数组越界异常求助

问题现象 #

将JAXB对象转换为XML时，随机出现以下非必现异常：

异常1：NullPointerException #

Caused by: java.lang.NullPointerException: Cannot invoke "com.sun.org.apache.xml.internal.dtm.ref.ExtendedType.getNodeType()" because "this.m_extendedTypes[ExpandedNameID]" is null
    at com.sun.org.apache.xml.internal.dtm.ref.ExpandedNameTable.getType(ExpandedNameTable.java:348) ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.dom.SAXImpl.getMapping(SAXImpl.java:568) ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.dom.DOMAdapter.getMapping(DOMAdapter.java:105) ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.dom.DOMAdapter.getExpandedTypeID(DOMAdapter.java:224) ~[?:?]
    at die.verwandlung.GregorSamsa.applyTemplates() ~[?:?]
    at die.verwandlung.GregorSamsa.transform() ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet.transform(AbstractTranslet.java:627) ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:782) ~[?:?]

异常2：ArrayIndexOutOfBoundsException（添加-XX:+ShowCodeDetailsInExceptionMessages后获取） #

Caused by: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 71
    at com.sun.org.apache.xalan.internal.xsltc.dom.DOMAdapter.getExpandedTypeID(DOMAdapter.java:227) ~[?:?]
    at die.verwandlung.GregorSamsa.applyTemplates() ~[?:?]
    at die.verwandlung.GregorSamsa.transform() ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet.transform(AbstractTranslet.java:627) ~[?:?]
    at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:782) ~[?:?]

环境信息 #

• Java版本：

openjdk version "17.0.8" 2023-07-18
OpenJDK Runtime Environment Temurin-17.0.8+7 (build 17.0.8+7)
OpenJDK 64-Bit Server VM Temurin-17.0.8+7 (build 17.0.8+7, mixed mode, sharing)

• Maven依赖：

<dependency>
    <groupId>javax.xml.bind</groupId>
    <artifactId>jaxb-api</artifactId>
    <version>2.3.1</version>
</dependency>

<dependency>
    <groupId>javax.activation</groupId>
    <artifactId>activation</artifactId>
    <version>1.1</version>
</dependency>

<dependency>
    <groupId>org.glassfish.jaxb</groupId>
    <artifactId>jaxb-runtime</artifactId>
    <version>2.3.1</version>
</dependency>

解决方案 #

1. 修复Transformer实例的线程安全问题 #

JDK自带的TransformerImpl（Xalan XSLTC实现）非线程安全，多线程环境下复用同一个实例会导致内部状态混乱，触发随机异常。

解决方式：

• 每次转换时重新创建Transformer实例；
• 或用ThreadLocal为每个线程维护独立的实例，兼顾性能与安全性。

示例代码：

// 错误：复用Transformer实例（多线程不安全）
// private static Transformer transformer = TransformerFactory.newInstance().newTransformer();

// 正确：每次转换新建实例
public String jaxbToXml(Object jaxbObject) throws Exception {
    Transformer transformer = TransformerFactory.newInstance().newTransformer();
    // 后续转换逻辑
}

// 优化：用ThreadLocal减少实例创建开销
private static ThreadLocal<Transformer> transformerThreadLocal = ThreadLocal.withInitial(() -> {
    try {
        return TransformerFactory.newInstance().newTransformer();
    } catch (TransformerConfigurationException e) {
        throw new RuntimeException(e);
    }
});

public String jaxbToXml(Object jaxbObject) throws Exception {
    Transformer transformer = transformerThreadLocal.get();
    // 后续转换逻辑
}

2. 升级JAXB依赖版本 #

当前使用的JAXB 2.3.1与Java 17存在兼容性隐患，建议升级到Jakarta EE版本的最新依赖：

<dependency>
    <groupId>jakarta.xml.bind</groupId>
    <artifactId>jakarta.xml.bind-api</artifactId>
    <version>4.0.2</version>
</dependency>
<dependency>
    <groupId>org.glassfish.jaxb</groupId>
    <artifactId>jaxb-runtime</artifactId>
    <version>4.0.2</version>
    <scope>runtime</scope>
</dependency>

3. 替换XSLT实现库 #

若上述方法无效，可替换JDK默认的Xalan为Saxon实现：

<dependency>
    <groupId>net.sf.saxon</groupId>
    <artifactId>Saxon-HE</artifactId>
    <version>12.4</version>
</dependency>

创建TransformerFactory时指定Saxon实现类：

TransformerFactory factory = TransformerFactory.newInstance("net.sf.saxon.TransformerFactoryImpl", null);
Transformer transformer = factory.newTransformer();

4. 检查JAXB对象的并发访问 #

确保待转换的JAXB对象未被多线程并发读写，对象内部状态不稳定也会导致转换异常。

内容的提问来源于stack exchange，提问作者Raviteja