# Data Convertors and Validators

Column converters as well as validators can be provided via client plugins. See Creating Client Plugins for more information on how to create client plugins.

## Column Converters

In order to build a column converter, the plugin class implementing the IClientPlugin interface (see [Implement the Plugin Interface](https://docs.servoy.com/reference/extension-dev/serverside)) also needs to implement the interface [IColumnConverterProvider](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/plugins/IColumnConverterProvider.html) to produce [ITypedColumnConverter](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/ITypedColumnConverter.html) instances in the getColumnConverters() method.

Note that IColumnConverter is considered to be deprecated, therefore in getColumnConverters() method do return an [ITypedColumnConverter](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/ITypedColumnConverter.html) array.

A column converter class implementing the [ITypedColumnConverter](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/ITypedColumnConverter.html) interface has to implement the following three methods that will be displayed in the Conversion tab:

* convertFromObject(): Converts from dataprovider value to db value
* convertToObject(): Converts from db value to dataprovider value
* getToObjectType(): The dataprovider data type (so the resulting type of the convertToObject()), being one of the IColumnTypes constants: TEXT, INTEGER, NUMBER, DATETIME or MEDIA

A column converter class can define properties in the getDefaultProperties() method, which will be displayed in the Conversion tab as well.

The column types that the column converter supports are to be specified in the getSupportedColumnTypes() method.

For an example of a column converter, see the NrToJodaConverter class in the example given on Providing UI Converters from Plugins page.

All the implemented custom column converters must be returned by the getColumnConverters() method of the plugin class implementing the [IColumnConverterProvider](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/plugins/IColumnConverterProvider.html) interface, so that they become available within Servoy Developer.

## Column Validators

In order to build a column validator, the plugin class implementing the IClientPlugin interface (see [Implement the Plugin Interface](https://docs.servoy.com/reference/extension-dev/serverside)) also needs to implement the interface [IColumnValidatorProvider](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/plugins/IColumnValidatorProvider.html) to produce [IColumnValidator](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/IColumnValidator.html) instances in the getColumnValidators() method.

The validation rule of an [IColumnValidator](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/IColumnValidator.html) is defined in the validate() method.

An [IColumnValidator](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/IColumnValidator.html) can also define properties in the getDefaultProperties() method, whose values will be set by the developer in UI, in the Validation tab.

The column types that the validator supports are specified in the getSupportedColumnTypes() method.

All the implemented custom column validators must be returned by the getColumnValidators() method of the plugin class implementing the [IColumnValidatorProvider](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/plugins/IColumnValidatorProvider.html) interface, so that they become available within Servoy Developer.

New implementations should be returning an instance of the [IColumnValidator2](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/IColumnValidator2.html) which extends IColumnValidator which adds public void validate(Map\<String, String> props, Object value, String dataprovider, IRecordMarkers recordMarkers, Object state); method that works with the new validation framework: [Data/Record/Column validation](https://docs.servoy.com/guides/develop/programming-guide/working-with-data/data-rec-column-validation)

As an example how the new [IColumnValidator2](https://developer.servoy.com/docs/public-api/2024/com/servoy/j2db/dataprocessing/IColumnValidator2.html) interface works look here (see also below the example)

**Example**

This is an example of validating the size of a column of type TEXT or MEDIA. The validation rule is that the size must be lower or equal to the value given by the developer by setting the length property in the Validation tab.

```java
import java.util.Map;
import com.servoy.j2db.dataprocessing.IColumnValidator2;
import com.servoy.j2db.dataprocessing.IValidationObject;
import com.servoy.j2db.persistence.IColumnTypes;
import com.servoy.j2db.util.ILogLevel;
import com.servoy.j2db.util.Utils;
@SuppressWarnings("nls")
public class NumberRangeValidator implements IColumnValidator2
{
 private static final String FROM_PROPERTY = "from";
 private static final String TO_PROPERTY = "to";

 public Map<String, String> getDefaultProperties()
 {
     Map<String, String> props = new java.util.LinkedHashMap<>();
     props.put(FROM_PROPERTY, "");
     props.put(TO_PROPERTY, "");
     return props;
 }

 public String getName()
 {
     return "servoy.NumberRangeValidator";
 }
 public int[] getSupportedColumnTypes()
 {
     return new int[] { IColumnTypes.INTEGER, IColumnTypes.NUMBER };
 }
 /**
 * IColumnValidator2 interface with the new IRecordMarkers, if given then the error is reported on that instead of throwing an exception.
 */ 
 @Override
 public void validate(Map<String, String> props, Object value, String dataprovider, IRecordMarkers recordMarkers, Object state)
 {
     if (value == null || value.toString().trim().length() == 0) return;
     double from = Utils.getAsDouble(props.get(FROM_PROPERTY));
     double to = Utils.getAsDouble(props.get(TO_PROPERTY));
     double val = Utils.getAsDouble(value);
     if (val < from || val > to)
     {
         if (validationObject != null)
            recordMarkers.report("i18n:servoy.validator.range", dataprovider, ILogLevel.ERROR, state, new Object[] { value, dataprovider, Double.valueOf(from), Double.valueOf(to) });
         else throw new IllegalArgumentException();
     }
 }
 
 // the old validate method of IColumnValidator interface, just call the IColumnValidator2 valdiate method with null.
 public void validate(Map<String, String> props, Object arg) throws IllegalArgumentException
 {
     validate(props, arg, null, null, null);
 }
}
```