Runtime components : Core components : Formatters : Tasks : Handling binary message : Adding your own FormatElement
  
Adding your own FormatElement
The Built-in FormatElementsprovide a set of format elements. But they cannot cover all the requirements in your application development.
To add a format element
1 Add the class name into the class table of format component:
<?xml version="1.0"?>
<btt.xml>
  <kColl id="components">
    <kColl id="format">
      <field id="initializer"
value="com.ibm.btt.format.FormatInitializer" />
      <field id="extFile" value="format.xml" />
      <kColl id="classTable">
        <field id="myFormat" value="com.mycompany.format.MyFormatElement" />
      </kColl>
    </kColl>
  </kColl>
</btt.xml>
2 Create a Java class com.mycompany.format.MyFormatElement.
This class needs to be a subclass of com.ibm.btt.format.CompositeFormat, com.ibm.btt.format.FieldFormat or com.ibm.btt.format.BaseDecorator. Any class in package com.ibm.btt.format.impl is not intended to be subclassed.
3 Create default constructor method for class com.mycompany.format.MyFormatElement.
Every format element can be instantiated by default constructor method.
4 Create get and set methods for the attributes.
Format element can be customized in definition. For example, you can specify encoding attribute for com.ibm.btt.format.impl.StringFormat in the format definition xml tag. If your format element has some attributes to be customized, you need to create get and set methods for them. The methods need to comply with Java Bean specification. When you create the instance of FormatElement, FormatFactory populates your attributes from definition automatically. The attribute can be in simple types such as int, Integer, float, Float, long, Long, double, Double, byte, Byte, char, Character and String, and so on.
5 Override or implement methods from base class in class com.mycompany.format.MyFormatElement. The following table tells which method you should override or implement.
Methods that can be overridden
 
Base ClassDescription
Methods
Override
CompositeFormatSplit the input message into two messages, and return them as an array in length of 2. The first message in the array is the message that should be processed by this format element, and the second message is the remaining message.
Take Message 1FCD2639FE for example: the returned array of Message may be {1FCD, 2639FE}. The first element 1FCD is the Message required by this FormatElement, while the second element 2639FE is the remaining Message.
Translate the data into binary message.
Translate the binary message into data.
Return the children format element of the composite format element. You can call it in extract, format and unformat methods.
public Message[] extract(Message message) throws ExtractException;
YES
public Message format(ReadAdapter dataAdapter) throws FormatException;
YES
public void unformat(Message message, WriteAdapter dataAdapter) throws UnformatException
YES
public List<FormatElement>getChildren ();
NO
FieldFormatSplit the input message into two messages, and returned them as an array in length of 2.
Translate the data into binary message.
Translate the binary message into data.
public Message[] extract(Message message) throws ExtractException;
YES
public Message format(ReadAdapter dataAdapter) throws FormatException;
YES
public void unformat(Message message, WriteAdapter dataAdapter) throws UnformatException
YES
BaseDecoratorSplit the input message into two messages, and returned them as an array in length of 2.
public Message[] extract(Message message) throws ExtractException;
YES
Modify the binary message after execute format method of the decorated format element.
protected Message addDecoration(Message message) throws FormatException;
YES
Modify the binary message before execute unformat method of the decorated format element.
protected Message removeDecoration(Message message) throws UnformatException;
YES
6 Override attribute() method if needed.
protected Map<String, String> attributes();
You can override this method. It returns a Map with both key and value in type of String. The key represents the attribute name and the value represents the attribute value. This method is only used in toString() method of the format element.
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Handling binary message