Spring Integration中如何配置自定义ISOEntities实体解析器？

场景与现有配置 #

使用Spring Integration执行XML元素提取，相关配置如下：

<bean id="myDmTypeXPathExpression" class="org.springframework.xml.xpath.XPathExpressionFactoryBean">
    <property name="expression" value="/root/level0/*[last()]/local-name()"/>
</bean>
    
<int-xml:xpath-header-enricher>
    <int-xml:header name="dmType" xpath-expression-ref="myDmTypeXPathExpression" overwrite="true"/>
</int-xml:xpath-header-enricher>

输入XML的DOCTYPE包含本地ISOEntities引用：

<!DOCTYPE mydocument [
<!ENTITY % ISOEntities PUBLIC "ISO 8879-1986//ENTITIES ISO Character Entities 20030531//EN//XML" "ent/ISOEntities">
%ISOEntities;
]>

所有ISOEntities文件存放在本地目录，单元测试已验证实体解析器有效性：

@Test
void check_document_parse() throws Exception {
    // GIVEN
    Resource xmlResource = loadMyXmlWithISOEntities();

    // WHEN
    DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    documentBuilder.setEntityResolver(loadMyCatalogResolver());
    
    // THEN
    documentBuilder.parse(xmlResource.getFile());
}

但Spring Integration流程抛出异常：

Caused by: java.io.FileNotFoundException: path/to/my/app/ent/ISOEntities 
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1910) 
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1512) 
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:646) 
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:1301) 
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:1237) 
at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.startPE(XMLDTDScannerImpl.java:739) 
at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.skipSeparator(XMLDTDScannerImpl.java:2108) 
at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.scanDecls(XMLDTDScannerImpl.java:2071) 
at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.scanDTDInternalSubset(XMLDTDScannerImpl.java:363) 
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.dispatch(XMLDocumentScannerImpl.java:1128)

解决方案 #

可以为Spring Integration的XML组件配置自定义实体解析器，核心是替换默认的DocumentBuilder或XmlPayloadConverter，具体步骤如下：

1. 定义带有实体解析器的DocumentBuilder Bean #

复用单元测试中的实体解析器逻辑，创建自定义的DocumentBuilderFactory和DocumentBuilder：

@Bean
public DocumentBuilderFactory documentBuilderFactory() {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setNamespaceAware(true); // 根据业务需求调整命名空间配置
    return factory;
}

@Bean
public DocumentBuilder documentBuilder(DocumentBuilderFactory factory) throws ParserConfigurationException {
    DocumentBuilder builder = factory.newDocumentBuilder();
    builder.setEntityResolver(loadMyCatalogResolver()); // 加载你已验证的实体解析器
    return builder;
}

2. 配置XPath Header Enricher使用自定义组件 #

有两种方式让Spring Integration的XML组件使用自定义的DocumentBuilder：

方式一：通过XmlPayloadConverter注入

创建自定义的DefaultXmlPayloadConverter，关联上面的DocumentBuilder，然后配置给xpath-header-enricher：

<bean id="customXmlConverter" class="org.springframework.integration.xml.DefaultXmlPayloadConverter">
    <constructor-arg ref="documentBuilder"/>
</bean>

<int-xml:xpath-header-enricher xml-converter="customXmlConverter">
    <int-xml:header name="dmType" xpath-expression-ref="myDmTypeXPathExpression" overwrite="true"/>
</int-xml:xpath-header-enricher>

方式二：为XPathExpressionFactoryBean配置DocumentBuilderFactory

直接给XPathExpressionFactoryBean指定自定义的DocumentBuilderFactory，确保XPath解析XML时使用正确的实体规则：

<bean id="myDmTypeXPathExpression" class="org.springframework.xml.xpath.XPathExpressionFactoryBean">
    <property name="expression" value="/root/level0/*[last()]/local-name()"/>
    <property name="documentBuilderFactory" ref="documentBuilderFactory"/>
</bean>

原理说明 #

Spring Integration的XML组件默认使用的DocumentBuilder未配置实体解析器，解析带有本地实体的XML时，默认解析器会将相对路径当作HTTP URL尝试加载，导致FileNotFoundException。替换为自定义的DocumentBuilder后，会使用你已验证的实体解析器加载本地ISOEntities文件，解决异常问题。

内容的提问来源于stack exchange，提问作者Valeriane