Camel 4.0.4升级后SAXParseException报错求助

将Camel版本升级至4.0.4并切换到Java 17后，加载camel-spring.xsd创建Schema时触发org.xml.sax.SAXParseException错误，提示circuitBreakerDefinition元素下存在两个onFallback元素，违反Unique Particle Attribution规则。手动注释其中一个onFallback元素可消除错误，但无法修改Jar包中的xsd文件，急需获取可用Camel 4.x版本Schema的解决方法。

报错堆栈 #

org.xml.sax.SAXParseException; lineNumber: 4268; columnNumber: 51; cos-nonambig: "http://camel.apache.org/schema/spring":onFallback and "http://camel.apache.org/schema/spring":onFallback (or elements from their substitution group) violate "Unique Particle Attribution". During validation against this schema, ambiguity would be created for those two particles.

        at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
        at org.apache.xerces.util.ErrorHandlerWrapper.error(Unknown Source)
        at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
        at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
        at org.apache.xerces.impl.xs.XSConstraints.reportSchemaError(Unknown Source)
        at org.apache.xerces.impl.xs.XSConstraints.fullSchemaChecking(Unknown Source)
        at org.apache.xerces.impl.xs.XMLSchemaLoader.loadGrammar(Unknown Source)
        at org.apache.xerces.impl.xs.XMLSchemaLoader.loadGrammar(Unknown Source)
        at org.apache.xerces.jaxp.validation.XMLSchemaFactory.newSchema(Unknown Source)

测试代码片段 #

import com.google.common.io.Resources;

import javax.xml.XMLConstants;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.SchemaFactory;
import java.io.ByteArrayInputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;


public class Camel
{

    public static void main( String[] args ) throws Exception
    {
       SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

       List<Source> tmp = new ArrayList();

       String loc = "camel-spring.xsd";

       URL url = Resources.getResource(loc);
       byte[] bytes = Resources.toByteArray(url);
       StreamSource src = new StreamSource(new ByteArrayInputStream(bytes));
       tmp.add(src);

       schemaFactory.newSchema((Source[]) tmp.toArray(new Source[tmp.size()]));
    }
}

解决方法 #

• 升级到Camel 4.x修复版本：该Schema重复定义问题是Camel 4.0.4的已知bug，后续版本（如4.0.5及以上）已修复xsd中的重复元素问题，直接升级Camel版本即可获取正确的Schema文件。
• 临时动态修改xsd内容：若暂时无法升级版本，可在加载xsd时动态修改字节流，移除重复的onFallback元素。示例代码修改如下：

// 读取xsd内容转为字符串
String xsdContent = new String(bytes);
// 移除重复的onFallback元素（需根据实际xsd内容调整匹配规则）
xsdContent = xsdContent.replaceAll("<xs:element name=\"onFallback\" type=\"xs:string\" minOccurs=\"0\" maxOccurs=\"1\"/>", "");
// 重新转为输入流
StreamSource src = new StreamSource(new ByteArrayInputStream(xsdContent.getBytes()));

注意：需确保正则匹配的是重复的元素，避免误删正常定义。

• 切换SchemaFactory实现（不推荐）：部分SchemaFactory支持忽略特定错误，但Xerces默认不支持。尝试切换到其他实现（如Apache Santuario）可能绕过错误，但会引入兼容性风险，仅作为临时应急方案。

内容的提问来源于stack exchange，提问作者Rebeca Baptista