To simplify configuration, SHDP provides a dedicated namespace for most of its components. However, one can opt to configure the beans directly through the usual <bean> definition. For more information about XML Schema-based configuration in Spring, see this appendix in the Spring Framework reference documentation.

To use the SHDP namespace, one just needs to import it inside the configuration:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:hdp="http://www.springframework.org/schema/hadoop"
   xsi:schemaLocation="
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/hadoop
    http://www.springframework.org/schema/hadoop/spring-hadoop.xsd">

   <bean/>

   <hdp:configuration/>
</beans>

Once imported, the namespace elements can be declared simply by using the aforementioned prefix. Note that is possible to change the default namespace, for example from <beans> to <hdp>. This is useful for configuration composed mainly of Hadoop components as it avoids declaring the prefix. To achieve this, simply swap the namespace prefix declarations above:

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans
xmlns="http://www.springframework.org/schema/hadoop"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:beans="http://www.springframework.org/schema/beans"
   xsi:schemaLocation="
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/hadoop http://www.springframework.org/schema/hadoop/spring-hadoop.xsd">

    <beans:bean id ... >

    <configuration ...>

</beans:beans>

For the remainder of this doc, to improve readability, the XML examples may simply refer to the <hdp> namespace without the namespace declaration, where possible.

Annotation based configuration is designed to work via a SpringHadoopConfigurerAdapter which is loosely trying to use same type of dsl language familiar from xml. Within the adapter you need to override configure method which is exposing HadoopConfigConfigurer containing familiar attributes to work with a Hadoop configuration.

import org.springframework.context.annotation.Configuration;
import org.springframework.data.hadoop.config.annotation.EnableHadoop
import org.springframework.data.hadoop.config.annotation.SpringHadoopConfigurerAdapter
import org.springframework.data.hadoop.config.annotation.builders.HadoopConfigConfigurer;

@Configuration
@EnableHadoop
static class Config extends SpringHadoopConfigurerAdapter {

  @Override
  public void configure(HadoopConfigConfigurer config) throws Exception {
    config
      .fileSystemUri("hdfs://localhost:8021");
  }

}

In order to use Hadoop, one needs to first configure it namely by creating a Configuration object. The configuration holds information about the job tracker, the input, output format and the various other parameters of the map reduce job.

In its simplest form, the configuration definition is a one liner:

<hdp:configuration />

The declaration above defines a Configuration bean (to be precise a factory bean of type ConfigurationFactoryBean) named, by default, hadoopConfiguration. The default name is used, by conventions, by the other elements that require a configuration - this leads to simple and very concise configurations as the main components can automatically wire themselves up without requiring any specific configuration.

For scenarios where the defaults need to be tweaked, one can pass in additional configuration files:

<hdp:configuration resources="classpath:/custom-site.xml, classpath:/hq-site.xml">

In this example, two additional Hadoop configuration resources are added to the configuration.

In addition to referencing configuration resources, one can tweak Hadoop settings directly through Java Properties. This can be quite handy when just a few options need to be changed:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:hdp="http://www.springframework.org/schema/hadoop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/hadoop http://www.springframework.org/schema/hadoop/spring-hadoop.xsd">

     <hdp:configuration>
        fs.defaultFS=hdfs://localhost:8020
        hadoop.tmp.dir=/tmp/hadoop
        electric=sea
     </hdp:configuration>
</beans>

One can further customize the settings by avoiding the so called hard-coded values by externalizing them so they can be replaced at runtime, based on the existing environment without touching the configuration:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:hdp="http://www.springframework.org/schema/hadoop"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/hadoop http://www.springframework.org/schema/hadoop/spring-hadoop.xsd">

     <hdp:configuration>
        fs.defaultFS=${hd.fs}
        hadoop.tmp.dir=file://${java.io.tmpdir}
        hangar=${number:18}
     </hdp:configuration>

     <context:property-placeholder location="classpath:hadoop.properties" />
</beans>

Through Spring’s property placeholder support, SpEL and the environment abstraction. one can externalize environment specific properties from the main code base easing the deployment across multiple machines. In the example above, the default file system is replaced based on the properties available in hadoop.properties while the temp dir is determined dynamically through SpEL. Both approaches offer a lot of flexbility in adapting to the running environment - in fact we use this approach extensivly in the Spring for Apache Hadoop test suite to cope with the differences between the different development boxes and the CI server.

Additionally, external Properties files can be loaded, Properties beans (typically declared through Spring’s util namespace). Along with the nested properties declaration, this allows customized configurations to be easily declared:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:hdp="http://www.springframework.org/schema/hadoop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/hadoop http://www.springframework.org/schema/hadoop/spring-hadoop.xsd">

   <!-- merge the local properties, the props bean and the two properties files -->
   <hdp:configuration properties-ref="props" properties-location="cfg-1.properties, cfg-2.properties">
      star=chasing
      captain=eo
   </hdp:configuration>

   <util:properties id="props" location="props.properties"/>
</beans>

When merging several properties, ones defined locally win. In the example above the configuration properties are the primary source, followed by the props bean followed by the external properties file based on their defined order. While it’s not typical for a configuration to refer to so many properties, the example showcases the various options available.

It is possible to create configurations based on existing ones - this allows one to create dedicated configurations, slightly different from the main ones, usable for certain jobs (such as streaming - more on that #hadoop:job:streaming[below]). Simply use the configuration-ref attribute to refer to the parent configuration - all its properties will be inherited and overridden as specified by the child:

<!-- default name is 'hadoopConfiguration' -->
<hdp:configuration>
    fs.defaultFS=${hd.fs}
    hadoop.tmp.dir=file://${java.io.tmpdir}
</hdp:configuration>

<hdp:configuration id="custom" configuration-ref="hadoopConfiguration">
    fs.defaultFS=${custom.hd.fs}
</hdp:configuration>

...

Make sure though that you specify a different name since otherwise, because both definitions will have the same name, the Spring container will interpret this as being the same definition (and will usually consider the last one found).

Another option worth mentioning is register-url-handler which, as the name implies, automatically registers an URL handler in the running VM. This allows urls referrencing hdfs resource (by using the hdfs prefix) to be properly resolved - if the handler is not registered, such an URL will throw an exception since the VM does not know what hdfs means.

Last but not least a reminder that one can mix and match all these options to her preference. In general, consider externalizing Hadoop configuration since it allows easier updates without interfering with the application configuration. When dealing with multiple, similar configurations use configuration composition as it tends to keep the definitions concise, in sync and easy to update.

Spring Boot support is enabled automatically if spring-data-hadoop-boot-2.2.0.RELEASE.jar is found from a classpath. Currently Boot auto-configuration is a little limited and only supports configuring of hadoopConfiguration and fsShell beans.

Configuration properties can be defined using various methods. See a Spring Boot dodumentation for details.

@Grab('org.springframework.data:spring-data-hadoop-boot:2.2.0.RELEASE')

import org.springframework.data.hadoop.fs.FsShell

public class App implements CommandLineRunner {

  @Autowired FsShell shell

  void run(String... args) {
    shell.lsr("/tmp").each() {println "> ${it.path}"}
  }

}

Above example which can be run using Spring Boot CLI shows how auto-configuration ease use of Spring Hadoop. In this example Hadoop configuration and FsShell are configured automatically.