#xpath SpEL Function

从 3.0 版本开始，Spring Integration 提供内置的 #xpath SpEL 函数，它会调用 XPathUtils.evaluate(…​) 静态方法。此方法委托给 org.springframework.xml.xpath.XPathExpression。以下列表显示了一些使用示例：

Spring Integration, since version 3.0, provides the built-in #xpath SpEL function, which invokes the XPathUtils.evaluate(…​) static method. This method delegates to an org.springframework.xml.xpath.XPathExpression. The following listing shows some usage examples:

<transformer expression="#xpath(payload, '/name')"/>

<filter expression="#xpath(payload, headers.xpath, 'boolean')"/>

<splitter expression="#xpath(payload, '//book', 'document_list')"/>

<router expression="#xpath(payload, '/person/@age', 'number')">
    <mapping channel="output1" value="16"/>
    <mapping channel="output2" value="45"/>
</router>

#xpath() 还支持第三个可选参数，用于转换 XPath 评估的结果。它可以是字符串常量（string、boolean、number、node、node_list 和 document_list）或 org.springframework.xml.xpath.NodeMapper 实例。默认情况下，#xpath SpEL 函数会返回 XPath 评估的 String 表示形式。

The #xpath() also supports a third optional parameter for converting the result of the XPath evaluation. It can be one of the String constants (string, boolean, number, node, node_list and document_list) or an org.springframework.xml.xpath.NodeMapper instance. By default, the #xpath SpEL function returns a String representation of the XPath evaluation.

为启用 #xpath SpEL 函数，你可以将 spring-integration-xml.jar 添加到类路径。你不需要从 Spring 集成 XML 命名空间声明任何组件。

To enable the #xpath SpEL function, you can add the spring-integration-xml.jar to the classpath. You need no declare any components from the Spring Integration XML Namespace.

有关详细信息，请参见“`Spring Expression Language (SpEL).

For more information, see "`Spring Expression Language (SpEL).