WSO2 EI 6.6.0自定义SOAP签名中介抛出ClassCastException问题

我使用WSO2 EI 6.6.0开发了一个SOAP信封签名中介，代码在Java SE环境测试完全正常，但部署到WSO2 EI后无法运行，抛出类转换异常。

异常触发代码片段 #

private static Document sign(Document doc, String Reference) throws Exception {
    DOMSignContext dsc = null;
    String providerName = System.getProperty("jsr105Provider", "org.jcp.xml.dsig.internal.dom.XMLDSigRI");
    Provider provider = (Provider) Class.forName(providerName).newInstance();

    // 该行抛出异常
    XMLSignatureFactory fac = XMLSignatureFactory.getInstance("DOM", provider);

    // ...省略后续签名逻辑
    return doc;
}

错误堆栈信息 #

java.lang.ClassCastException: class org.jcp.xml.dsig.internal.dom.DOMXMLSignatureFactory cannot be cast to class javax.xml.crypto.dsig.XMLSignatureFactory (org.jcp.xml.dsig.internal.dom.DOMXMLSignatureFactory is in module java.xml.crypto of loader 'platform'; javax.xml.crypto.dsig.XMLSignatureFactory is in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @657e3cda)
        at javax.xml.crypto.dsig.XMLSignatureFactory.findInstance(XMLSignatureFactory.java:202)
        at javax.xml.crypto.dsig.XMLSignatureFactory.getInstance(XMLSignatureFactory.java:250)
        at x.signer.util.Utils.sign(Utils.java:246)
        at x.signer.util.Utils.insertSignSoap(Utils.java:233)
        at x.signer.util.Utils.insertSignSayad(Utils.java:197)
        at x.signer.Signer.mediate(Signer.java:37)
        at org.apache.synapse.mediators.ext.ClassMediator.mediate(ClassMediator.java:94)
        at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:109)
        at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:71)
        at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
        at org.apache.synapse.rest.Resource.process(Resource.java:331)
        at org.apache.synapse.rest.API.process(API.java:441)
        at org.apache.synapse.rest.RESTRequestHandler.apiProcess(RESTRequestHandler.java:135)
        at org.apache.synapse.rest.RESTRequestHandler.dispatchToAPI(RESTRequestHandler.java:113)
        at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:71)
        at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:327)
        at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:98)
        at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
        at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:368)
        at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:427)
        at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:182)
        at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
        at java.base/java.lang.Thread.run(Thread.java:834)

输入示例 #

<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
    <S:Body>
        <InquiryCode xmlns="http://tempuri.org/">
            <RequestCode>12345</RequestCode>
        </InquiryCode>
    </S:Body>
</S:Envelope>

我已经搜索了大量相关问题，尝试过论坛及StackOverflow上的相关方案，但都没有解决问题。

解决方案 #

这个异常是类加载器隔离导致的：WSO2 EI基于OSGi运行，javax.xml.crypto.dsig.XMLSignatureFactory由OSGi类加载器加载，而org.jcp.xml.dsig.internal.dom.DOMXMLSignatureFactory由JDK平台类加载器加载，两个类加载器加载的类无法互相转换。

解决步骤如下：

1. 避免手动指定JDK内置Provider：不要显式实例化org.jcp.xml.dsig.internal.dom.XMLDSigRI，改用无Provider参数的XMLSignatureFactory.getInstance("DOM")，让系统自动选择兼容的Provider。
   修改后的代码：

   private static Document sign(Document doc, String Reference) throws Exception {
       DOMSignContext dsc = null;
       // 移除手动指定Provider的逻辑
       XMLSignatureFactory fac = XMLSignatureFactory.getInstance("DOM");
   
       // ...后续签名逻辑保持不变
       return doc;
   }
   

2. 检查依赖包冲突：如果项目中引入了xmlsec或其他XML签名相关的第三方依赖，需要排除这些依赖，避免和WSO2 EI内置的类冲突。
3. 配置OSGi类加载策略：如果必须使用自定义Provider，需要在WSO2 EI的carbon.properties中添加配置，让OSGi类加载器优先使用JDK平台类加载器加载相关包：

   org.osgi.framework.system.packages.extra=javax.xml.crypto,javax.xml.crypto.dsig,javax.xml.crypto.dsig.dom,javax.xml.crypto.dsig.keyinfo,javax.xml.crypto.dsig.spec
   

   修改后重启WSO2 EI。

优先推荐第一种方案，因为WSO2 EI已经内置了兼容的XML签名Provider，无需手动指定JDK的内置实现。

内容的提问来源于stack exchange，提问作者hesam