Hello World 예제

이 예제는 간단하지만 PDI의 몇 가지 기본적인 내용들에 대해서는 설명이 될 것이다.

• Spoon을 사용하는 방법

• Transformations

• Step 과 Hop

• 미리 선언된 변수들

• Spoon을 통한 미리보기와 실행

• Pan 툴을 이용한 터미널에서 Transformation 실행하기

Overview

인물정보를 가지고 있는 CSV 파일을 XML파일로 변환하되 여기에 각 인물마다 인삿말을 더하는 작업을 한다고 해보자.

아래의 CSV파일의 내용이다.

위의 CSV는 아래와 같은 XML이 될 것이다.

이렇게 이름에 인삿말을 더해 파일을 생성하는 것이 첫 번째 Transformation의 목표다.
Transformation은 Hop으로 연결된 Step으로 이루어진다. 이러한 Step과 Hop은 데이터의 흐름을 나타낸다. 따라서 Transformation 은 데이터 흐름 지향적(data-flow oriented) 이라고 할 수 있다.

환경 준비

Transformation 을 하기전에 먼저 개발하기 편한 위치에 Tutorial 폴더를 만들자. 여기에 이번 튜토리얼의 모든 파일을 저장할 것이다. 위에서 본 CSV파일을 list.csv 이름으로 폴더에 저장하자.

Transformation 과정

이 작업은 3개의 subtask로 나눠서 수행될 것이다.

1. Transformation 생성

2. Step과 Hop을 이용해 Transformation의 뼈대를 구성

3. 행동 순서대로 각 Step을 설정

Transformation 생성

1. 새 파일 를 클릭하고 Transformation 을 선택한다. 아니면 파일 메뉴를 클릭하고 새로 만들기 를 선택한 후 Transformation 을 선택해도 된다. 또 다른 방법으로 Ctrl-N 단축키를 눌러도 된다.

2. 왼쪽의 뷰 네비게이터에서 Transformation 1 을 더블클릭하거나 우클릭 후 설정 메뉴를 선택한다. 아니면 Ctrl+T 단축키를 누른다.

3. Transformation 프로퍼티를 설정할 수 있는 윈도우가 나타난다. 우선은 Transformation 이름과 설명란에만 내용을 입력하고 확인 을 누른다.

4. Tutorial폴더에 hello 라는 이름으로 Transformation을 저장하자.  hello.ktr 파일 생성될 것이다.

Constructing the skeleton of the Transformation using Steps and Hops

A Step is the minimal unit inside a Transformation. A wide variety of Steps are available, grouped into categories like Input and Output, among others. Each Step is designed to accomplish a specific function, such as reading a parameter or normalizing a dataset.

A Hop is a graphical representation of data flowing between two Steps, with an origin and a destination. The data that flows through that Hop constitutes the Output Data of the origin Step, and the Input Data of the destination Step. A Hop has only one origin and one destination, but more than one Hop could leave a Step. When that happens, the Output Data can be copied or distributed to every destination. Likewise, more than one Hop can reach a Step. In those instances, the Step has to have the ability to merge the Input from the different Steps in order to create the Output.

A Transformation has to do the following:

• Read the CSV file

• Build the greetings

• Save the greetings in the XML file

For each of these items you'll use a different Step, according to the next diagram:

Open

In this example, the correspondence between tasks and Steps is one-to-one because the Transformation is very simple. It isn't always that way, though.

Here's how to start the Transformation:

1. To the left of the workspace is the Steps Palette. Select the Input category.

2. Drag the CSV file onto the workspace on the right.

3. Select the Scripting category.

4. Drag the Modified JavaScript Value icon to the workspace.

5. Select the Output category.

6. Drag the XML Output icon to the workspace.

Now you will link the CSV file input with the Modified Java Script Value by creating a Hop:

1. Select the first Step.

2. Hold the Shift key and drag the icon onto the second Step.

3. Link the Modified Java Script Value with the XML Output via this same process.

Open

Specifying Step behavior

Every Step has a configuration window. These windows vary according to the functionality of the Steps and the category to which they belong. However, Step Name is always a representative name inside the Transformation - this doesn't change among Step configurations. Step Description allows you to clarify the purpose of the Step.

Configuring the CSV file input Step

1. Double-click on the CSV file input Step.

2. The configuration window belonging to this kind of Step will appear. Here you'll indicate the location, format and content of the input file.

3. Replace the default name with one that is more representative of this Step's function. In this case, type in name list.

4. In the Filename field, type the name and location of the input file.

5. Click Get Fields to add the list of column names of the input file to the grid. By default, the Step assumes that the file has headers (the Header row present checkbox is checked).

6. The grid has now the names of the columns of your file: last_name and name, and should look like this:
   

7. Switch lazy conversion off

8. Click Preview to ensure that the file will be read as expected. A window showing data from the file will appear.

9. Click OK to finish defining the Step CSV file input.

Configuring the Modified JavaScript Value Step

1. Double-click on the Modified JavaScript Value Step.

2. The Step configuration window will appear. This is different from the previous Step config window in that it allows you to write JavaScript code. You will use it to build the message "Hello, " concatenated with each of the names.

3. Name this Step Greetings.

4. The main area of the configuration window is for coding. To the left, there is a tree with a set of available functions that you can use in the code. In particular, the last two branches have the input and output fields, ready to use in the code. In this example there are two fields: last_name and name. Write the following code:

   var msg = 'Hello, ' + name.getString() + "!";

5. At the bottom you can type any variable created in the code. In this case, you have created a variable named msg. Since you need to send this message to the output file, you have to write the variable name in the grid. This should be the result:
   

6. Click OK to finish configuring Step Modified Script Value.

7. Select the Step you just configured. In order to check that the new field will leave this Step, you will now see the Input and Output Fields. Input Fields are the data columns that reach a Step. Output Fields are the data columns that leave a Step. There are Steps that simply transform the input data. In this case, the input and output fields are usually the same. There are Steps, however, that add fields to the Output - Calculator, for example. There are other Steps that filter or combine data causing that the Output has less fields that the Input - Group by, for example.

8. Right-click the Step to bring up a context menu.

9. Select Show Input Fields. You'll see that the Input Fields are last_name and name, which come from the CSV file input Step.

10. Select Show Output Fields. You'll see that not only do you have the existing fields, but also the new msg field.