将 Spring Integration 标头值设置为 bean 属性 [英] Set Spring Integration header value to bean property

问题描述

无论如何将 spring 集成头的值设置为 bean 属性.

Is there anyway to set value of spring integration header to bean property.

<int:header-enricher>
  <int:header name="bId" expression="T(java.util.UUID).randomUUID()" />
</int:header-enricher>

现在在 bean 定义中

Now in bean definition

<bean id="" class="">
    <property name="bId" value="#{headers['bId']}" />
</bean>

以上代码不起作用.这引发异常

This above code doesn't work. this throws exception

 Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 0): Property or field 'headers' cannot be found on object of type 'org.spri
ngframework.beans.factory.config.BeanExpressionContext' - maybe not public?

我尝试了以下方法，它们不起作用

I tried below ways, they don't work

<bean id="" class="">
    <property name="bId" value="headers['bId']" />
</bean>

<bean id="" class="">
    <property name="bId" ref="headers['bId']" />
</bean>

下面本来是理想的，但是这个表达式不可用

Below would've been ideal, but this expression is not available

<bean id="" class="">
    <property name="bId" expression="headers['bId']" />
</bean>

推荐答案

Spring Integration 表达式如

Spring Integration expressions such as

<int:header name="bId" expression="T(java.util.UUID).randomUUID()" />

是运行时表达式 - 它们适用于流经系统的消息；在大多数情况下，表达式计算的根对象是 Message.

are runtime expressions - they apply to messages flowing through the system; in most cases the root object for the expression evaluation is the Message.

表达式如

<property name="bId" value="#{...}" />

是初始化时间 SpEL 表达式 - 它们在上下文初始化期间进行评估.还没有 Message 对象 - 评估的根对象是应用程序上下文，因此您可以执行诸如引用其他 bean 上的属性之类的操作

are initialization time SpEL expressions - they are evaluated during context initialization. There is no Message object yet - the root object for the evaluation is the application context, so you can do things like referencing properties on other beans

 <property name="bId" value="#{somebean.foo}" />

这些类型的表达之间存在很大差异.

There's a big difference between these types of expressions.

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