红帽全球峰会32.7. predicates
基本 predicates
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您可以在 Java DSL 中，或者在 predicate 期望的上下文中使用 xpath，作为 filter（） 处理器的参数，或作为 when（） 子句的参数。
例如，以下路由过滤传入的消息，允许一条信息传递，仅当 /person/city 元素包含值 伦敦 时：
from("direct:tie")
.filter().xpath("/person/city = 'London'").to("file:target/messages/uk");
from("direct:tie")
.filter().xpath("/person/city = 'London'").to("file:target/messages/uk");
以下路由评估 when（） 子句中的 XPath predicate：
from("direct:tie")
.choice()
.when(xpath("/person/city = 'London'")).to("file:target/messages/uk")
.otherwise().to("file:target/messages/others");
from("direct:tie")
.choice()
.when(xpath("/person/city = 'London'")).to("file:target/messages/uk")
.otherwise().to("file:target/messages/others");XPath predicate operator
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XPath 语言支持标准 XPath predicate 运算符，如 表 32.2 “XPath 语言的 Operator” 所示。
| Operator | 描述 |
|---|---|
|
| 等于。 |
|
| 不等于. |
|
| 大于. |
|
| 大于或等于。 |
|
| 小于. |
|
| 小于或等于。 |
|
| 将两个 predicates 与逻辑 和 组合。 |
|
| 将两个 predicates 与逻辑 inclusive 或 组合。 |
|
| negate predicate 参数. |
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