Sander_M Sander_M - 23 days ago 10
Java Question

Univocity - Is it possible to parse a file to a runtime generated bean/class?

I am using univocity to parse some files to javabeans. These beans are compiled classes. However I wish to generate these classes during runtime and then parse the files to the at runtime generated classes.

Full code is here: gist

A snippet of the code that uses the Univocity library:

private static void parseBean(final Class<?> dynamicClass) throws FileNotFoundException {
@SuppressWarnings("unchecked")
final BeanListProcessor<?> rowProcessor = new BeanListProcessor<Class<?>>((Class<Class<?>>) dynamicClass);

final CsvParserSettings parserSettings = new CsvParserSettings();
parserSettings.setProcessor(rowProcessor);
parserSettings.setHeaderExtractionEnabled(false);
parserSettings.getFormat().setDelimiter('|');
parserSettings.setEmptyValue("");
parserSettings.setNullValue("");

final CsvParser parser = new CsvParser(parserSettings);
parser.parse(new FileReader("src/main/resources/person.csv"));

final List<?> beans = rowProcessor.getBeans();
for (final Object domain : beans) {
final Domain domainImpl = (Domain) domain;
System.out.println("Person id is: " + domainImpl.getIdentifier());
System.out.println("Person name is: " + domainImpl.getColumnByIndex(1));
System.out.println();
}
}


The file looks like this:

0|Eric
1|Maria


All the values seems to be null, so something is going wrong when parsing the file and mapping it to the bean...

Person id is: null
Person name is: null


Is it possible to parse files to runtime generated beans/classes using the Univocity library?

Answer

The problem here is that your code is not generating the @Parsed annotations correctly. Check this:

    Object o = dynamicClass.newInstance();
    Field f = dynamicClass.getDeclaredField("id");
    f.setAccessible(true);
    java.lang.annotation.Annotation[] annotations = f.getAnnotations();
    System.out.println(Arrays.toString(annotations));

You will get an empty annotation array. I've fixed your code to generate the annotations properly:

Change your addAnnotation method to this:

private static void addAnnotation(final CtClass clazz, final String fieldName, final String annotationName, String member, int memberValue) throws Exception {
    final ClassFile cfile = clazz.getClassFile();
    final ConstPool cpool = cfile.getConstPool();
    final CtField cfield = clazz.getField(fieldName);

    final AnnotationsAttribute attr = new AnnotationsAttribute(cpool, AnnotationsAttribute.visibleTag);
    final Annotation annot = new Annotation(annotationName, cpool);
    annot.addMemberValue(member, new IntegerMemberValue(cpool, memberValue));
    attr.addAnnotation(annot);
    cfield.getFieldInfo().addAttribute(attr);
}

And call it like this:

addAnnotation(cc, "id", "com.univocity.parsers.annotations.Parsed","index", 0);

With this change, I can parse a sample input such as this:

parser.parse(new StringReader("0|John|12-04-1986"));

And will get the following output:

Person id is: 0
Person name is: John

Hope this helps.

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