Data stored in CSV-format (Comma Separated Values) can easily be mapped to fields of a plain old java object (POJO) using Java-annotations.

This package provides an implementation for the marshall-api, a generic api for marshalling and unmarshalling data using Java-annotations.

Usage

The Annotated POJO Class

In order to instantiate an Unmarshaller/Marshaller, you will firstly need a Java-class that contains the fields, to which the external data should be mapped to. The marshall-api provides some ready to be used annotations, like

• InputField, used for unmarshalling
• OutputField, used for marshalling

Place this annotations on your fields of the POJO and

provide getter- and setter-methods.

For instance,

public class BeanClass {

    @InputField( position=0 )
    private String description;
    
    @OutputField ( name="comment" )
    private String target_description;
    
    // getter-/setter-methods
}

For the annotations to be recognized, a so called AnnotationInterpreter is needed. The DefaultAnnotationInterpreter provides a default implementation, which can be found in the marshall-api.

Factory-classes are provided to create the CsvUnmarshaller and CsvMarshaller objects, as well as CsvAnnotationInterpreter.

Using the Default Implementation

The easiest way to instantiate the Unmarshaller/Marshaller is through methods provided by the Factory-classes.

For instance,

Unmarshaller<BeanClass> unmarshaller = 
    CsvUnmarshallerFactory
    .createDefaultCsvUnmarshaller( BeanClass.class, new FileReader(...) );

returns an object of CsvUnmarshaller, which was instantiated with the CsvAnnotationInterpreter. Without using the Factory-class you must instantiate an AnnotationInterpreter by yourself, e.g.

// the annotation interpreter
CsvAnnotationInterpreter<T> interpreter = 
    CsvAnnotationInterpreterFactory
    .createDefaultCsvAnnotationInterpreter( annotatedClass );

// the csv unmarshaller
Unmarshaller<T> unmarshaller = new CsvUnmarshaller<T>( interpreter, reader );

Marshalling/Unmarshalling

The Unmarshaller/Marshaller-instance provides methods to read/write the instantiated objects. For instance

• unmarshaller.getAll();, returns a list of T
• marshaller.writeNext(t);, writes an instance t of type T

If you have large csv-files a step by step unmarshalling process would be more appropriate:

• unmarshaller.getNext();

returns the next unmarshalled instance of type T.