Using the XPath Filter

此组件定义了一个基于 XPath 的消息过滤器。内部，这些组件使用一个包装 AbstractXPathMessageSelector 实例的 MessageFilter。

This component defines an XPath-based message filter. Internally, these components uses a MessageFilter that wraps an instance of AbstractXPathMessageSelector.

有关详细信息，请参阅 Filter。

See Filter for further details.

要使用 XPath 过滤器，您至少必须通过声明 xpath-expression 元素或在 xpath-expression-ref 属性中引用 XPath 表达式来提供一个 XPath 表达式。

to use the XPath filter you must, at a minimum, provide an XPath expression either by declaring the xpath-expression element or by referencing an XPath Expression in the xpath-expression-ref attribute.

如果提供的 XPath 表达式计算得出一个 boolean 值，则不需要其他配置参数。然而，如果 XPath 表达式计算得出一个 String，您应设置 match-value 属性，对其比对计算结果。

If the provided XPath expression evaluates to a boolean value, no further configuration parameters are necessary. However, if the XPath expression evaluates to a String, you should set the match-value attribute, against which the evaluation result is matched.

match-type 有三个选项：

match-type has three options:

exact：对应于 java.lang.String 中的 equals。基础实现使用 StringValueTestXPathMessageSelector
exact: Correspond to equals on java.lang.String. The underlying implementation uses a StringValueTestXPathMessageSelector
case-insensitive：对应于 java.lang.String 中的 equals-ignore-case。基础实现使用 StringValueTestXPathMessageSelector
case-insensitive: Correspond to equals-ignore-case on java.lang.String. The underlying implementation uses a StringValueTestXPathMessageSelector
regex：匹配 java.lang.String 中的一个操作。基础实现使用 RegexTestXPathMessageSelector
regex: Matches operations one java.lang.String. The underlying implementation uses a RegexTestXPathMessageSelector

当提供 regex 的 'match-type' 值时，随 match-value 属性一起提供的 value 必须是一个有效的正则表达式。

When providing a 'match-type' value of 'regex', the value provided with the match-value attribute must be a valid regular expression.

以下示例显示了 xpath-filter 元素的所有可用属性：

The following example shows all the available attributes for the xpath-filter element:

<int-xml:xpath-filter discard-channel=""                      1
                      id=""                                   2
                      input-channel=""                        3
                      match-type="exact"                      4
                      match-value=""                          5
                      output-channel=""                       6
                      throw-exception-on-rejection="false"    7
                      xpath-expression-ref="">                8
    <int-xml:xpath-expression ... />                          9
    <int:poller ... />                                        10
</int-xml:xpath-filter>

1	您要发送拒绝消息到的消息频道。可选。
2	Message channel where you want rejected messages to be sent. Optional.
3	基础 Bean 定义的 ID。可选。
4	ID for the underlying bean definition. Optional.
5	此端点的接收消息频道。可选。
6	The receiving message channel of this endpoint. Optional.
7	在 XPath 求值结果和 `match-value` 之间应用的匹配类型。默认值为 `exact`。可选。
8	Type of match to apply between the XPath evaluation result and the `match-value`. The default is `exact`. Optional.
9	与 XPath 求值结果进行匹配的字符串值。如果您没有设置此属性，则 XPath 求值必须产生一个布尔结果。可选。
10	String value to be matched against the XPath evaluation result. If you do not set this attribute, the XPath evaluation must produce a boolean result. Optional.
11	将符合筛选条件的消息派发到该频道。可选。
12	The channel to which messages that matched the filter criteria are dispatched. Optional.
13	默认情况下，此属性的值设为 `false`，并且拒绝的消息（不符合筛选条件的信息）会被静默地丢弃。但是，如果设为 `true`，则消息拒绝将导致错误条件，并且异常将沿上行传播到调用方。可选。
14	By default, this property is set to `false` and rejected messages (those did not match the filter criteria) are silently dropped. However, if set to `true`, message rejection results in an error condition and an exception being propagated upstream to the caller. Optional.
15	引用待评估 XPath 表达式实例。
16	Reference to an XPath expression instance to evaluate.
17	此子元素设置要评估的 XPath 表达式。如果您不包含此元素，则必须设置 `xpath-expression-ref` 属性。此外，您只能包含一个 `xpath-expression` 元素。
18	This child element sets the XPath expression to be evaluated. If you do not include this element, you must set the `xpath-expression-ref` attribute. Also, you can include only one `xpath-expression` element.
19	与 XPath 过滤器一同使用轮询器。可选。
20	A poller to use with the XPath filter. Optional.