WSO2 MI 4.2.0读取含CTRL-CHAR(26)的XML报异常求助

在WSO2 MI 4.2.0中读取包含控制字符（CTRL-CHAR，代码26）的XML文件时，抛出如下异常：
com.ctc.wstx.exc.WstxUnexpectedCharException: Illegal character ((CTRL-CHAR, code 26))

示例XML文件的<value>标签中包含显示为空格的Char26字符，读取时触发上述异常。已按照WSO2 MI官方文档添加XMLOutputFactory.properties文件，但问题仍未解决，寻求解决方法。

代理配置 #

<?xml version="1.0" encoding="UTF-8"?>
<proxy name="readXMLwithWhiteCharacters" startOnLoad="true" transports="http https" xmlns="http://ws.apache.org/ns/synapse">
    <target>
        <inSequence>
            <fileconnector.read>
                <source>file:///opt/data/sample.xml</source>
                <contentType>application/xml</contentType>
                <filePattern>.*/.xml</filePattern>
            </fileconnector.read>
            <property expression="json-eval($)" name="file-content" scope="default" type="STRING"/>
            <log level="full">
                <property expression="get-property('file-content')" name="log-json-response"/>
            </log>
        </inSequence>
        <outSequence/>
        <faultSequence/>
    </target>
</proxy>

示例XML片段：

<readone>
    <value> </value>
</readone>

（注：<value>标签内的空格实际为Code 26控制字符）

错误日志 #

[2023-07-07 02:51:50,296] ERROR {org.wso2.carbon.connector.util.ResultPayloadCreate} - Error while processing the file/folder org.apache.axiom.om.OMException: com.ctc.wstx.exc.WstxUnexpectedCharException: Illegal character ((CTRL-CHAR, code 26))
 at [row,col {unknown-source}]: [2,9]
        at org.apache.axiom.om.impl.builder.StAXOMBuilder.next(StAXOMBuilder.java:296)
        at org.apache.axiom.om.impl.llom.OMElementImpl.buildNext(OMElementImpl.java:653)
        at org.apache.axiom.om.impl.llom.OMElementImpl.getFirstOMChild(OMElementImpl.java:670)
        at org.apache.axiom.om.impl.llom.OMElementImpl.getChildren(OMElementImpl.java:352)
        at org.apache.axiom.om.impl.util.OMSerializerUtil.serializeChildren(OMSerializerUtil.java:554)
        at org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:879)
        at org.apache.axiom.om.impl.util.OMSerializerUtil.serializeChildren(OMSerializerUtil.java:556)
        at org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:879)
        at org.apache.axiom.om.impl.util.OMSerializerUtil.serializeChildren(OMSerializerUtil.java:556)
        at org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:879)
        at org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.internalSerialize(SOAPEnvelopeImpl.java:230)
        at org.apache.axiom.om.impl.llom.OMSerializableImpl.serialize(OMSerializableImpl.java:125)
        at org.apache.axiom.om.impl.llom.OMSerializableImpl.serialize(OMSerializableImpl.java:113)
        at org.apache.axiom.om.impl.llom.OMElementImpl.toString(OMElementImpl.java:992)
        at org.wso2.carbon.connector.util.ResultPayloadCreate.buildFile(ResultPayloadCreate.java:183)
        at org.wso2.carbon.connector.FileRead.connect(FileRead.java:102)
        at org.wso2.carbon.connector.core.AbstractConnector.mediate(AbstractConnector.java:32)
        at org.apache.synapse.mediators.ext.ClassMediator.updateInstancePropertiesAndMediate(ClassMediator.java:178)
        at org.apache.synapse.mediators.ext.ClassMediator.mediate(ClassMediator.java:97)
        at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:110)
        at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:72)
        at org.apache.synapse.mediators.template.TemplateMediator.mediate(TemplateMediator.java:136)
        at org.apache.synapse.mediators.template.InvokeMediator.mediate(InvokeMediator.java:170)
        at org.apache.synapse.mediators.template.InvokeMediator.mediate(InvokeMediator.java:93)
        at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:110)
        at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:72)
        at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
        at org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:240)
        at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
        at org.apache.synapse.startup.tasks.MessageInjector.execute(MessageInjector.java:336)
        at org.wso2.micro.integrator.mediation.ntask.NTaskAdapter.execute(NTaskAdapter.java:105)
        at org.wso2.micro.integrator.ntask.core.impl.TaskQuartzJobAdapter.execute(TaskQuartzJobAdapter.java:63)
        at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
        at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: com.ctc.wstx.exc.WstxUnexpectedCharException: Illegal character ((CTRL-CHAR, code 26))
 at [row,col {unknown-source}]: [2,9]
        at com.ctc.wstx.sr.StreamScanner.throwInvalidSpace(StreamScanner.java:666)
        at com.ctc.wstx.sr.BasicStreamReader.readTextPrimary(BasicStreamReader.java:4576)
        at com.ctc.wstx.sr.BasicStreamReader.nextFromTree(BasicStreamReader.java:2879)
        at com.ctc.wstx.sr.BasicStreamReader.next(BasicStreamReader.java:1072)
        at org.apache.axiom.util.stax.wrapper.XMLStreamReaderWrapper.next(XMLStreamReaderWrapper.java:225)
        at org.apache.axiom.util.stax.dialect.DisallowDoctypeDeclStreamReaderWrapper.next(DisallowDoctypeDeclStreamReaderWrapper.java:34)
        at org.apache.axiom.om.impl.builder.StAXOMBuilder.parserNext(StAXOMBuilder.java:681)
        at org.apache.axiom.om.impl.builder.StAXOMBuilder.next(StAXOMBuilder.java:214)
        ... 37 more

解决方法 #

1. 配置Woodstox解析器允许控制字符 #

WSO2 MI使用Woodstox作为XML解析器，默认会拒绝XML中的控制字符。需要添加XMLInputFactory的配置（而非仅XMLOutputFactory）：

• 在MI的conf目录下创建XMLInputFactory.properties文件，添加内容：

javax.xml.stream.isSupportingExternalEntities=false
com.ctc.wstx.acceptAllXmlCharacters=true

• 或者在MI启动脚本中添加JVM参数：

-Dcom.ctc.wstx.acceptAllXmlCharacters=true

修改后重启MI服务。

2. 修改文件读取逻辑，先过滤控制字符 #

若无法修改解析器配置，可先将文件读取为纯文本，过滤控制字符后再转为XML：

<proxy name="readXMLwithWhiteCharacters" startOnLoad="true" transports="http https" xmlns="http://ws.apache.org/ns/synapse">
    <target>
        <inSequence>
            <fileconnector.read>
                <source>file:///opt/data/sample.xml</source>
                <contentType>text/plain</contentType>
                <filePattern>.*/.xml</filePattern>
            </fileconnector.read>
            <property expression="json-eval($)" name="file-content" scope="default" type="STRING"/>
            <!-- JavaScript脚本过滤ASCII控制字符（保留换行、回车、制表符） -->
            <script language="js"><![CDATA[
                var rawContent = mc.getProperty('file-content');
                var cleanedContent = rawContent.replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, '');
                mc.setProperty('cleaned-file-content', cleanedContent);
            ]]></script>
            <!-- 将清理后的内容转为XML payload -->
            <payloadFactory media-type="xml">
                <format>$1</format>
                <args>
                    <arg evaluator="xml" expression="get-property('cleaned-file-content')"/>
                </args>
            </payloadFactory>
            <log level="full">
                <property expression="get-property('cleaned-file-content')" name="cleaned-content"/>
            </log>
        </inSequence>
        <outSequence/>
        <faultSequence/>
    </target>
</proxy>

3. 预处理源XML文件 #

从XML规范来讲，Code 26属于非法控制字符。若有条件，建议提前清理源XML文件中的此类字符，从根源避免解析错误。

内容的提问来源于stack exchange，提问作者aditi21