camel

最近项目里会用到camel，近期会写一篇文章来总结camel中的一些常用的‘知识点’。

总结一下。

1 from

from("file://C:\\Users\\xxx\\documents\\camel?fileName=b.txt").routeId("routeId")
        .log(LoggingLevel.DEBUG,"lalala ${id} ${body}")
        .inOnly("direct:BBB")
        .log(LoggingLevel.DEBUG,"--------"+"${body}"+"processing ${id}");
一直会监听这个路径下的b.txt文件。

2 camel 设置打印log

3 bean processor

类似拦截器，对exchange进行一些处理

如果在bean，processor中有调用exchange.get()方法，读取exchange中的流，之后需要重新set进去才行，否则，之后exchange中的内容为null。

做了一个简单的demo，就了解到这些基本的方法作用，其他的再慢慢探索，还是很枯燥的。

4 onException

捕捉camel route中产生的异常

http://people.apache.org/~dkulp/camel/exception-clause.html

网页中有比较详细的例子可参考。

5 streamCaching

stream缓存，因为stream类型的数据只能读一次。from Camel 2.0 缓存默认不可用。

6 marsh unmarsh

marsh bean转xml

unmarsh xml转bean

7 setExchangePattern(待完成)

可参考 https://examples.javacodegeeks.com/enterprise-java/apache-camel/apache-camel-exchange-example/

http://www.catchmycity.com/tutorial/apache-camel-difference-between-exchangepattern-inout-and-exchangepattern-inonly-in-apache-camel_101

InOnly

InOut request-reply

Not all camel endpoints support INOUT. The JMS endpoint supports it but the file endpoint does not.

Unfortunately this is indeed not well documented.

8 setProperty

setProperty在route中传递， setHeader在exchange中传递。

Similar to message headers, but they last for the duration of the entire exchange.

可参考 http://camel.465427.n5.nabble.com/Camel-Java-DSL-setProperty-behaviour-td5718226.html

9 choice

.choice()
                .when().simple("${body} == 'test inout'").setBody(simple("one")).endChoice()
                .when().simple("${body} == 'aaa'").setBody(simple("two")).endChoice()
                .end()

可参考 https://cleverbuilder.com/articles/camel-choice-when/

10 doTry() doCatch(xx.class)

处理异常，类似java try catch

11 multicast() split()

multicast

The Multicast allows to route the same message to a number of endpoints and process them in a different way. The main difference between the Multicast and Splitter is that Splitter will split the message into several pieces but the Multicast will not modify the request message.

可参考 http://people.apache.org/~dkulp/camel/multicast.html

split

The Splitter from the EIP Pattern allows you split a message into a number of pieces and process them individually

可参考 http://camel.apache.org/splitter.html

12 SEDA indirect vm

可参考 http://camel.apache.org/how-do-the-direct-event-seda-and-vm-endpoints-compare.html

https://cleverbuilder.com/articles/camel-direct-vm-seda/

Component Type Within same CamelContext Within same JVM

Direct Synchronous Yes No

Direct-VM Synchronous Yes Yes

SEDA Asynchronous Yes No

VM Asynchronous Yes Yes

Component	Type	Within same CamelContext	Within same JVM
Direct	Synchronous	Yes	No
Direct-VM	Synchronous	Yes	Yes
SEDA	Asynchronous	Yes	No
VM	Asynchronous	Yes	Yes

13 recipientList

使用recipientList可以创建动态的接收者。

example

from("direct:a").recipientList(header("myHeader").tokenize(","));

myHeader = {'direct:a','direct:b'}

14 camel 打印exchange信息到控制台

解决 DEBUG ProducerCache                  - >>>> Endpoint[direct:start] Exchange[Message: 01234567890123456789... [Body clipped after 20 chars, total length is 1000]]
参考 http://camel.apache.org/how-do-i-set-the-max-chars-when-debug-logging-messages-in-camel.html 设置camelContext信息输出长度。
endpoint.getxxx 参考下图输出body信息。