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Pentaho Documentation

Create job entry plugins

Parent article

A job entry implements a logical task in ETL control flow. Job entries are executed in sequence, each job entry generating a boolean result that can be used for conditional branching in the job sequence.

Sample job entry workflow

This section explains the architecture and programming concepts for creating your own PDI job entry plugin. We recommended that you open and refer to the Sample job entry plugin section while following these instructions.

A job entry plugin integrates with PDI by implementing two distinct Java interfaces. Each interface represents a set of responsibilities performed by a PDI job. Each of the interfaces has a base class that implements the bulk of the interface in order to simplify plugin development.

All job entry interfaces and corresponding base classes are part of the org.pentaho.di.job.entry package.

Java InterfaceBase ClassMain Responsibilities
JobEntryInterfaceJobEntryBase
  • Maintain job entry settings
  • Serialize job entry settings
  • Provide access to dialog class
  • Execute job entry task
JobEntryDialogInterfaceJobEntryDialog
  • Job entry settings dialog

Implementing a job entry

This section explains the job entry interface.

JobEntryInterface is the main Java interface that a plugin implements.

Java Interfaceorg.pentaho.di.job.entry.JobEntryInterface
Base classorg.pentaho.di.job.entry.JobEntryBase
Keep track of job entry settings

The implementing class keeps track of job entry settings using private fields with corresponding get and set methods. The dialog class implementing JobEntryDialogInterface uses these methods to copy the user supplied configuration in and out of the dialog box.

  • public Object clone()

    This method is called when a job entry is duplicated in the PDI client (Spoon). It returns a deep copy of the job entry object. It is essential that the implementing class creates proper deep copies if the job entry configuration is stored in modifiable objects, such as lists or custom helper objects.

Serialize job entry settings

The plugin serializes its settings to both XML and a PDI repository.

  • public String getXML()

    This method is called by PDI whenever a job entry serializes its settings to XML. It is called when saving a job in the PDI client. The method returns an XML string containing the serialized settings. The string contains a series of XML tags, one tag per setting. The helper class, org.pentaho.di.core.xml.XMLHandler, constructs the XML string.

  • public void loadXML()

    This method is called by PDI whenever a job entry reads its settings from XML. The XML node containing the job entry settings is passed in as an argument. Again, the helper class, org.pentaho.di.core.xml.XMLHandler, is used to read the settings from the XML node.

  • public void saveRep()

    This method is called by PDI whenever a job entry saves its settings to a PDI repository. The repository object passed in as the first argument provides a convenient set of methods for serializing job entry settings. When calling repository serialization methods, job id and job entry id are required. The job id is passed in to saveRep() as an argument, and the job entry id can be obtained by a call to getObjectId() inherited from the base class.

  • public void loadRep()

    This method is called by PDI whenever a job entry reads its configuration from a PDI repository. The job entry id given in the arguments is used as the identifier when using the repositories serialization methods. When developing plugins, make sure the serialization code is in synch with the settings available from the job entry dialog. When testing a plugin in the PDI client, PDI internally saves and loads a copy of the job before it is executed.

Provide the name of the dialog class

PDI needs to know which class takes care of the settings dialog box for the job entry. The interface method getDialogClassName() returns the name of the class implementing the JobEntryDialogInterface.

Provide information about possible outcomes

A job entry may support up to three types of outgoing hops: True, False, and Unconditional. Sometimes it does not make sense to support all three. For instance, if the job entry performs a task that does not produce a boolean outcome, like the dummy job entry, it may make sense to suppress the True and False outgoing hops. There are other job entries, which carry an inherent boolean outcome, such as the File Exists job entry. It may make sense in such cases to suppress the unconditional outgoing hop.

The job entry plugin class must implement two methods to indicate to PDI which outgoing hops it supports.

  • public boolean evaluates()

    This method returns true if the job entry supports the True and False outgoing hops. If the job entry does not support distinct outcomes, it returns false.

  • public boolean isUnconditional()

    This method returns true if the job entry supports the unconditional outgoing hop. If the job entry does not support the unconditional hop, it returns false.

Execute the Job entry task

The class implementing JobEntryInterface executes the actual job entry task.

  • public Result execute()

    The execute() method is called by PDI when it is time for the job entry to execute its logic. The arguments are a result object, which is passed in from the previously executed job entry, and an integer number indicating the distance of the job entry from the start entry of the job. The job entry should execute its configured task and report back on the outcome. A job entry does that by calling specified methods on the passed in result object.

  • prev_result.setNrErrors()

    The job entry indicates whether it has encountered any errors during execution. If there are errors, setNrErrors calls with the number of errors encountered. Typically, this is 1. If there are no errors, setNrErrors is called with an argument of zero (0).

  • prev_result.setResult()

    The job entry must indicate the outcome of the task. This value determines which output hops follow next. If a job entry does not support evaluation, it need not call prev_result.setResult().

Finally, the passed in prev_result object is returned.

Interface with the PDI plugin system

The class implementing JobEntryInterface must be annotated with the JobEntry Java annotation. Supply the following annotation attributes:

AttributeDescription
idA globally unique ID for the job entry
imageThe resource location for the png icon image of the job entry
nameA short label for the job entry
descriptionA longer description for the job entry
categoryDescriptionThe category the entry should appear under in the PDI job entry tree. For example General, Utility, File Management, etc.
i18nPackageNameIf the i18nPackageName attribute is supplied in the annotation attributes, the values of name, description, and categoryDescription are interpreted as i18n keys relative to the message bundle contained in given package. The keys may be supplied in the extended form i18n:<packagename> key to specify a package that is different from the package given in the i18nPackageName attribute.

Please refer to the Sample job entry plugin for a complete implementation example.

Implementing the job entry settings dialog box

This section explains how to implement the settings dialog of a job entry plugin

JobEntryDialogInterface is the Java interface that implements the settings dialog of a job entry plugin.

Java Interfaceorg.pentaho.di.job.entry.JobEntryDialogInterface
Base classorg.pentaho.di.ui.job.entry.JobEntryDialog
Maintain the dialog for job entry settings

The dialog class is responsible for constructing and opening the settings dialog for the job entry. When you open the job entry settings in Spoon, the system instantiates the dialog class passing in the JobEntryInterface object and calling the open() method on the dialog. SWT is the native windowing environment of Spoon and the framework used for implementing job entry dialogs.

  • public JobEntryInterface open()

    This method returns only after the dialog has been confirmed or cancelled. The method must conform to these rules:

    • If the dialog is confirmed
      • The JobEntryInterface object must be updated to reflect the new settings
      • If you changed any settings, the Changed flag of the JobEntryInterface object must be set to true
      • open() returns the JobEntryInterface object
    • If the dialog is cancelled
      • The JobEntryInterface object must not be changed
      • The Changed flag of theJobEntryInterface object must be set to the value it had at the time the dialog opened
      • open() must return null

The JobEntryInterface object has an internal Changed flag that is accessible using hasChanged() and setChanged(). Spoon decides whether the job has unsaved changes based on the Changed flag, so it is important for the dialog to set the flag appropriately.

Additionally, the job entry dialog must make sure that the job entry name is not set to be empty. The dialog may be confirmed only after a non-empty name is set.

The sample job entry plugin project has an implementation of the dialog class that is consistent with these rules and is a good basis for creating your own dialogs.

Logging in job entries

A job entry interacts with the PDI logging system by using the logging methods inherited from JobEntryBase.

These methods are used to issue log lines to the PDI logging system on different severity levels. Multi-argument versions of the methods are available to do some basic formatting, which is equivalent to a call to MessageFormat.format(message, arguments).

  • public void logMinimal()
  • public void logBasic()
  • public void logDetailed()
  • public void logDebug()
  • public void logRowlevel()
  • public void logError()

These methods query the logging level. They are often used to guard sections of code, that should only be executed with elevated logging settings.

  • public boolean isBasic()
  • public boolean isDetailed()
  • public boolean isDebug()
  • public boolean isRowLevel()

Job entries should log the this information at specified levels:

Log LevelLog Information Content
MinimalOnly information that is interesting at a very high-level, for example job Started or Ended jobs. Individual job entries do not log anything at this level.
BasicInformation that may be interesting to you during regular ETL operation
DetailedPrepared SQL or other query statements, resource allocation and initialization like opening files or connections
DebugAnything that may be useful in debugging job entries
Row LevelAnything that may be helpful in debugging problems at the level of individual rows and values
ErrorFatal errors that abort the job

Deploying job entry plugins

To deploy your plugin, perform the following steps:

Procedure

  1. Create a JAR file containing your plugin classes and resources

  2. Create a new folder, give it a meaningful name, and place your JAR file inside the folder

  3. Place the plugin folder you just created in a specific location for PDI to find.

    Depending on how you use PDI, you need to copy the plugin folder to one or more locations as per the following list:
    • Deploying to the PDI client (Spoon) or Carte:
      1. Copy the plugin folder into this location: design-tools/data-integration/plugins/jobentries
      2. Restart the PDI client. After restarting the PDI client, the new job entry is available for use.
    • Deploying to Pentaho Server for Data Integration :
      1. Copy the plugin folder to this location: server/pentaho-server/pentaho-solutions/system/kettle/plugins/jobentries
      2. Restart the server. After restarting the Pentaho Server, the plugin is available to the server.
    • Deploying to Pentaho Server for Business Analytics
      1. Copy the plugin folder to this location: server/pentaho-server/pentaho-solutions/system/kettle/plugins/jobentries
      2. Restart the server. After restarting the Pentaho Server, the plugin is available to the server.

Sample job entry plugin

The sample job entry plugin project is designed to show a minimal functional implementation of a job entry plugin that you can use as a basis to develop your own custom job entries.

The sample job entry plugin functionality lets you manually configure which outcome to generate. This screen shot shows the job entry configuration dialog and outgoing hops.Job entry configuration dialog

Procedure

  1. Obtain the sample plugin source.

    The plugin source is available in the download package. Download the package and unzip it. The job entry plugin resides in the kettle-sdk-jobentry-plugin folder.

  2. Configure the build by opening kettle-sdk-jobentry-plugin/build/build.properties and setting the kettle-dir property to the base directory of your PDI installation.

  3. Build and deploy.

    You may choose to build and deploy the plugin from the command line, or work with the Eclipse IDE instead. Both options are described below.
    • Build and deploy from the command line:

      The plugin is built using Apache Ant. Build and deploy the plugin from the command line by invoking the install target from the build directory.

      kettle-sdk-jobentry-plugin $ cd build
      build $ ant install

      The install target compiles the source, creates a JAR file, creates a plugin folder, and copies the plugin folder into the plugins/jobentries directory of your PDI installation.

    • Build and deploy from Eclipse:
      • Import the plugin sources into Eclipse:
        1. From the menu, select File Import Existing Projects Into Workspace.
        2. Browse to the kettle-sdk-jobentry-plugin folder and choose the project to be imported.
      • To build and install the plugin, follow these steps:
        1. Open the Ant view in Eclipse by selecting Window Show View from the main menu and select Ant.

          You may have to select Other Ant if you have not used the Ant view before.

        2. Drag the file build/build.xml from your project into the Ant view, and execute the install target by double-clicking it.
        3. After the plugin has been deployed, restart the PDI client (Spoon).
  4. Open the PDI client, and verify that the new job entry is available as "Demo" in the Conditions section.

Exploring more job entries

PDI sources provide example implementations of job entries. Each PDI core job entry is located in a sub-package of org.pentaho.di.job.entries found in the engine/src folder. The corresponding dialog class is located in org.pentaho.di.ui.job.entries found in the ui/src folder.

For example, these are the classes that make up the File Exists job entry:

  • org.pentaho.di.job.entries.fileexists.JobEntryFileExists
  • org.pentaho.di.ui.job.entries.fileexists.JobEntryFileExistsDialog

The dialog classes of the core PDI job entries are located in a different package and source folder. They are also assembled into a separate JAR file. This allows PDI to load the UI-related jar file when launching the PDI client (Spoon) and avoid loading the UI-related jar when it is not needed.