adding first bit of file docos
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Iwein Fuld
125
spring-integration-reference/src/file.xml
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125
spring-integration-reference/src/file.xml
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<chapter id="files">
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<title>Dealing with Files</title>
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<section id="file-intro">
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<title>Introduction</title>
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<para>
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Spring Integration File extends the Spring Integration Core with
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dedicated
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vocabulary to deal with reading, writing and transforming
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files.
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There is a namespace that enables elements that define channel
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adapters dedicated to files and support for transformers that
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transform files into strings or byte arrays.
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</para>
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<para>
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This section will explain the workings of
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<classname>PollableFileSource</classname>
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,
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<classname>FileWritingMessageConsumer
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</classname>
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and how to configure them as
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<emphasis>beans</emphasis>
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. Also the support for dealing with files through file specific
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implementations of
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<interfacename>Transformer</interfacename>
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will be discussed. Finally the file specific namespace will be
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discussed.
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</para>
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</section>
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<section id="file-reading">
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<title>Reading Files</title>
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<para>
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A
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<classname>PollableFileSource</classname>
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can be used to consume files from the filesystem. This is an
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implementation of
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<interfacename>PollableSource</interfacename>
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that creates messages from a file system directory.
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<programlisting language="xml"><![CDATA[<bean id="pollableFileSource" class="org.springframework.integration.file.PollableFileSource"
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p:inputDirectory="file:${input.directory.property}"/>]]></programlisting>
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</para>
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<para>
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To prevent creating messages for certain files, you may supply a
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{@link FileListFilter}. By default, an
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<classname>AcceptOnceFileListFilter
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</classname>
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is used. This filter ensures files are picked up only once from the
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directory.
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<programlisting language="xml"><![CDATA[<bean id="pollableFileSource" class="org.springframework.integration.file.PollableFileSource"
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p:inputDirectory="file:${input.directory.property}"
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p:filter-ref="customFilterBean"/>]]></programlisting>
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</para>
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<para>
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A common problem with reading files is that a file may be detected
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before it is ready. The default
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<classname>AcceptOnceFileListFilter
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</classname>
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does
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not prevent this. In most cases, this can be prevented if the
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file-writing process renames each file as soon as it is ready for
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reading. A pattern-matching filter that accepts only files that are
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ready (e.g. based on a known suffix), composed with the default
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<classname>AcceptOnceFileListFilter
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</classname>
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allows for this.
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<programlisting language="xml"><![CDATA[ <bean id="pollableFileSource" class="org.springframework.integration.file.PollableFileSource"
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p:inputDirectory="file:${input.directory.property}"
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p:filter-ref="compositeFilter"/>
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<bean id="compositeFilter" class="org.springframework.integration.file.CompositeFileListFilter">
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<constructor-arg>
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<list>
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<bean class="org.springframework.integration.file.AcceptOnceFileListFilter" />
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<bean class="org.springframework.integration.file.PatternMatchingFileListFilter">
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<constructor-arg value="^test.*$"/>
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</bean>
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</list>
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</constructor-arg>
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</bean>]]></programlisting>
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</para>
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<para>
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The configuration can be simplified using the file specific
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namespace. To do this use the following template.
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<programlisting language="xml"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
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<beans xmlns="http://www.springframework.org/schema/beans"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xmlns:integration="http://www.springframework.org/schema/integration"
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xmlns:file="http://www.springframework.org/schema/integration/file"
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xsi:schemaLocation="http://www.springframework.org/schema/beans
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http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
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http://www.springframework.org/schema/integration
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http://www.springframework.org/schema/integration/spring-integration-1.0.xsd
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http://www.springframework.org/schema/integration/file
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http://www.springframework.org/schema/integration/file/spring-integration-file-1.0.xsd">
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</beans>]]></programlisting>
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Within this namespace you can reduce the PollableFileSource and wrap
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it in a InboundChannelAdapter like this:
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<programlisting language="xml">
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<![CDATA[ <file:inbound-channel-adapter id="filesIn"
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directory="file:${input.directory.property}"/> (1)
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<file:inbound-channel-adapter id="filesIn"
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directory="file:${java.io.tmpdir}/spring-integration-samples/input"
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filter="customFilterBean" /> (2)
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<file:inbound-channel-adapter id="filesIn"
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directory="file:${java.io.tmpdir}/spring-integration-samples/input"
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filename-pattern="^test.*$" /> (3)
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]]>
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</programlisting>
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</para>
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</section>
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<section id="file-writing">
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<title>Writing files</title>
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<para>
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<!-- paragraph with the basics -->
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</para>
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<para>
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<!-- extra configuration options -->
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</para>
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<para>
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<!-- namespace support -->
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</para>
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</section>
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</chapter>
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