foreach 内部的骡子变压器

Question

我正在使用 Mule 3.5。我在 foreach 标签内使用 bean-builder-transformer 时遇到问题。这是我的第一次测试：

<flow name="mule.activity">
<poll doc:name="Poll">
<fixed-frequency-scheduler frequency="10000"/>
<db:select config-ref="JSDB" doc:name="Database">
<db:parameterized-query><![CDATA[SELECT * FROM ACTIVITY WHERE rownum <= 6]]></db:parameterized-query>
</db:select>
</poll>
<foreach doc:name="For Each">
<logger message="start id #[payload.'ID']" level="DEBUG" category="mule.activity" doc:name="log" />
</foreach>

这是日志：

[2015-03-18 16:29:23,165] DEBUG: start id 1363230
[2015-03-18 16:29:23,165] DEBUG: start id 1363231
[2015-03-18 16:29:23,165] DEBUG: start id 1363232
[2015-03-18 16:29:23,165] DEBUG: start id 1363233
[2015-03-18 16:29:23,166] DEBUG: start id 1363236
[2015-03-18 16:29:23,166] DEBUG: start id 1363237

一切正常

现在我在 foreach 标签内添加一个 bean-builder-transformer：

<foreach doc:name="For Each">

<logger message="start payload: #[payload]" level="DEBUG" category="mule.activity" doc:name="log" />
<logger message="start id #[payload.'ID']" level="DEBUG" category="mule.activity" doc:name="log" />

<bean-builder-transformer beanClass="com.jsolutions.mule.IO">
<bean-property property-name="bean_prop_1" evaluator="map-payload" expression="TABLE_FIELD_1" optional="true" />
<bean-property property-name="bean_prop_2" evaluator="map-payload" expression="TABLE_FIELD_2" optional="true" />
... (map all query fields except ID)
</bean-builder-transformer>

<logger message="end payload: #[payload]" level="DEBUG" category="mule.activity" doc:name="log" />
<logger
message="end id #[payload.'ID']" level="DEBUG" category="mule.activity" doc:name="log" />

<!-- use the message in order to call a ws service -->
</foreach>

这是日志：

[2015-03-19 10:08:28,668] DEBUG: start payload: {FIELD_1=004369951, ID=1363230}
[2015-03-19 10:08:28,676] DEBUG: start id 1363230
[2015-03-19 10:08:28,684] DEBUG: end payload: com.jsolutions.mule.IO@67231ee8
[2015-03-19 10:08:28,687] DEBUG: end id null
[2015-03-19 10:08:28,688] DEBUG: start payload: {FIELD_1=004369951, ID=1363231}
[2015-03-19 10:08:28,688] DEBUG: start id null
[2015-03-19 10:08:28,690] DEBUG: end payload: com.jsolutions.mule.IO@2bc6e9f1
[2015-03-19 10:08:28,690] DEBUG: end id null
[2015-03-19 10:08:28,691] DEBUG: start payload: {FIELD_1=004369951, ID=1363232}
[2015-03-19 10:08:28,691] DEBUG: start id null
[2015-03-19 10:08:28,692] DEBUG: end payload: com.jsolutions.mule.IO@1028e3ab
[2015-03-19 10:08:28,692] DEBUG: end id null
[2015-03-19 10:08:28,693] DEBUG: start payload: {FIELD_1=TO3925878, ID=1363233}
[2015-03-19 10:08:28,693] DEBUG: start id null
[2015-03-19 10:08:28,694] DEBUG: end payload: com.jsolutions.mule.IO@6c7af7d6
[2015-03-19 10:08:28,695] DEBUG: end id null
[2015-03-19 10:08:28,695] DEBUG: start payload: {FIELD_1=TS7066322, ID=1363236}
[2015-03-19 10:08:28,695] DEBUG: start id null
[2015-03-19 10:08:28,697] DEBUG: end payload: com.jsolutions.mule.IO@7d253a3d
[2015-03-19 10:08:28,697] DEBUG: end id null
[2015-03-19 10:08:28,698] DEBUG: start payload: {FIELD_1=022245675, ID=1363237}
[2015-03-19 10:08:28,698] DEBUG: start id null
[2015-03-19 10:08:28,699] DEBUG: end payload: com.jsolutions.mule.IO@1712bafb
[2015-03-19 10:08:28,700] DEBUG: end id null

我不明白为什么，第一次迭代后，id总是"null" ... 提前感谢您的回复。

Answer 1

假设起始有效载荷是一个映射（根据问题下的评论，这仍然是待定的），使用以下表达式检索 ID：

#[message.payload.ID]

的确，虽然在大多数情况下直接使用 payload 访问消息有效负载是可行的，但在某些情况下它不起作用。使用 message.payload 一直有效。

foreach 内部的骡子变压器

mule transformer inside foreach

mule