Spring Integration-文件适配器

Question

I'm newbie to Spring, I am writing a file adapter which reads file from the input folder and move the files to output folder. I played with the following examples but there are some points that are not clear to me.

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:integration="http://www.springframework.org/schema/integration"
xmlns:file="http://www.springframework.org/schema/integration/file"
xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/integration
        http://www.springframework.org/schema/integration/spring-integration.xsd
        http://www.springframework.org/schema/integration/file
        http://www.springframework.org/schema/integration/file/spring-integration-file.xsd">

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"/>

<file:inbound-channel-adapter id="filesIn"
                              directory="C:\Users\my\Desktop\files\in"
                              filename-regex="[a-z]+.txt">
    <integration:poller id="poller" fixed-delay="5000"/>
</file:inbound-channel-adapter>

<file:file-to-string-transformer input-channel="filesIn" output-channel="strings"/>

<integration:channel id="strings"/> 

<integration:service-activator input-channel="strings"
                               output-channel="filesOut"
                               ref="handler"/>

<file:outbound-channel-adapter id="filesOut" directory="C:\Users\my\Desktop\files\out"/>

<bean id="handler" class="org.springframework.integration.samples.filecopy.Handler"/>

I have few more questions regarding the above file.

1. I don't have a clear idea about the <integration:channel id="strings"/> tag. Why its just string. What are the other possible values which can be used instead strings .
2. As I tested input-channel of the integration:service-activator and output-channel of the file-to-string-transformer has nothing to do with <integration:channel id="strings"/> is it correct?

3. handler bean which is used in integration:service-activator has 3 methods.

    public class Handler { public String handleString(String input) { System.out.println("Copying text: " + input); return input.toUpperCase(); } public File handleFile(File input) { System.out.println("Copying file: " + input.getAbsolutePath()); return input; } public byte[] handleBytes(byte[] input) { System.out.println("Copying " + input.length + " bytes ..."); return new String(input).toUpperCase().getBytes(); } } 

   And currently it fires only one method which is handleString(String whichTakesString) is it because of the <integration:service-activator input-channel="strings" ? How can I call the other methods, what is the way to do it. I tried to figure this out many ways but still no chance.

Answer 1

First of all it looks like you haven't got enough theoretical knowledges, so consider to read the books: EIP Book , Spring Integration in Action .

In general MessageChannel is a concept to carry messages between services via loosely-coupling manner.

strings is just a bean name and it can be any value. <integration:channel> is just a custom tag, which produces a MessageChannel in the end. To be more comfortable with that you should to read the Reference Manual .

Since you use <file:file-to-string-transformer> , the result of this component will be String file representation.

Your <service-activator> invokes handleString method of your Handler because the runtime payload argument type resolution.

To make it worked with other methods you should use appropriate transformer ( <file:file-to-bytes-transformer> ) or don't use it at all - the <file:inbound-channel-adapter> produces File object as payload for resulting message.