====== Spring Batch ======

===== Execute with Test Resources =====
To execute a Spring Batch programm with test resource using Maven the ''exec.classpathScope'' needs to be set on the ''mvn'' command.

  mvn exec:java -Dexec.classpathScope="test"

===== Output =====

==== No Output ====
Sometimes there is nothing to be written as there is no output. A NoopItemWriter can be created like this:

<sxh java>
public class NoopItemWriter<T> implements ItemWriter<T> {
    
    @Override
    public void write(List<? extends T> items) throws Exception {
        // nothing to do here
    }

}
</sxh>

The item writer is added to the launch context file.

<code><beans:bean id="itemWriter" class="one.time.util.NoopItemWriter" /></code>


===== Input =====

==== Declare Comment Lines ====
Depending on the system and file comments may start with very different characters. These can be specified in the item writer (if it is supported by the implementation) like this:

<sxh xml>
<beans:property name="comments">
    <beans:array value-type="java.lang.String">
        <beans:value>#</beans:value>
        <beans:value>;</beans:value>
        <beans:value>!</beans:value>
    </beans:array>
</beans:property>
</sxh>

==== Skipping Empty Lines ====
The default reader implementation does not skip empty lines. There is a reader implementation from Robert Kasanicky where empty lines are treated as comments.

The implementation can be found {{::extflatfileitemreader.java|here}}.

==== Skipping First Lines ====
CSV files often start with the column names. Generally these must be skipped when processing the file. If you are using the [[http://docs.spring.io/spring-batch/apidocs/org/springframework/batch/item/file/FlatFileItemReader.html | FlatFileItemReader]] you can just add a property to your itemReader bean like this:

  <beans:property name="linesToSkip" value="1" />


==== CSV File Input ====
Reading a delimited file with Spring Batch is a combination of using a file item reader, line mapper and line tokenizer.

<sxh xml;title: Example>
<beans:bean id="itemReader" class="one.time.util.ExtFlatFileItemReader">
	    <beans:property name="linesToSkip" value="1" />
		<beans:property name="resource" value="${data.location}" />
		<beans:property name="lineMapper">
		    
			<beans:bean class="org.springframework.batch.item.file.mapping.DefaultLineMapper">
				<beans:property name="lineTokenizer">
					<beans:bean class="org.springframework.batch.item.file.transform.DelimitedLineTokenizer">
                                            <!-- field delimiter of your csv file -->
					    <beans:property name="delimiter" value="," />
                                                <!-- property names of your bean , the order of the names is important -->
						<beans:property name="names" value="id,street,housenumber" />
					</beans:bean>
				</beans:property>
				<beans:property name="fieldSetMapper">
                                        <!-- the fields are mapped to properties of your bean -->
					<beans:bean class="org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper">
                                                <!-- the model your data is mapped to -->
						<beans:property name="targetType" value="my.model.Location" />
					</beans:bean>
				</beans:property>
			</beans:bean>
			
		</beans:property>
</beans:bean>
</sxh>

==== Tab Delimited Values ====
To declare the tab character as a delimiter "\t" cannot be specified. Instead use the Java constant from the Spring framework.

<sxh xml>
  <beans:property name="lineTokenizer">
    <beans:bean class="org.springframework.batch.item.file.transform.DelimitedLineTokenizer">
      <!-- field delimiter of your csv file -->
      <beans:property name="delimiter">
        <util:constant static-field="org.springframework.batch.item.file.transform.DelimitedLineTokenizer.DELIMITER_TAB"/>
      </beans:property>
    </beans:bean>
  </beans:property>
</sxh>

Don't forget to add the namespance to the head of the xml file.

<sxh xml>
<beans:beans xmlns:beans="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jdbc="http://www.springframework.org/schema/jdbc"
	xmlns:batch="http://www.springframework.org/schema/batch"
	xmlns:util="http://www.springframework.org/schema/util"
	xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="
          http://www.springframework.org/schema/batch http://www.springframework.org/schema/batch/spring-batch-2.2.xsd
          http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
          http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd
          http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
          http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd">
</sxh>



===== Create Jar with Dependencies =====
To embed all dependencies and create an executable jar the pom.xml must be extended by the maven-assenbly-plugin.

<sxh xml>
    <build>
		<plugins>
			<plugin>
				<artifactId>maven-assembly-plugin</artifactId>
				<configuration>
					<archive>
						<manifest>
							<mainClass>
								org.springframework.batch.core.launch.support.CommandLineJobRunner
							</mainClass>
						</manifest>
					</archive>
					<descriptorRefs>
						<descriptorRef>jar-with-dependencies</descriptorRef>
					</descriptorRefs>
				</configuration>
			</plugin>
		</plugins>
	</build>
</sxh>

Create the jar with executing the following line on the command line

  mvn clean compile assembly:single
  
Execute the program with

  java -jar program-jar-with-dependencies.jar launch-context.xml jobid

{{tag>devel java}}