Generic Enum converter for iBatis

My goal was to create a simple, extensible Enum converter that would work with

iBatis. This seems like a trivial problem, but took me a while to find a proper solution. There were some additional preconditions:
* all given Enums are jaxb generated objects – but any standard Java Enum should work
* conversion was 1-to-1, no special conditions and processing The example Enum for this problem looks like this one (copy&paste from jaxb generated source):

@XmlType(name ="ServiceType") 
@XmlEnum
public enum ServiceType {

    @XmlEnumValue("stationary")
    STATIONARY("stationary"),
    @XmlEnumValue("mobile")
    MOBILE("mobile");
    private final String value;

    ServiceType(String v) {
        value = v;
    }

    public String value() {
        return value;
    }

    public static ServiceType fromValue(String v) {
        for (ServiceType c: ServiceType.values()) {
            if (c.value.equals(v)) {
                return c;
            }
        }
        throw new IllegalArgumentException(v);
    }

}

“No big deal”, you say. I beg to differ. What I wanted to achieve was a simple construction which would look like this when used for another Enum (CommonEnumTypeHandler is the name of my generic converter):

public class ServiceTypeHandler extends CommonEnumTypeHandler { }

Unfortunately due to the fact, that Java does not have reified generics, which is described in

multiple places, I had to stick with passing through a Class type of my enum. So it looks like this:

public class ServiceTypeHandler extends CommonEnumTypeHandler {

    public ServiceTypeHandler() {
        super(ServiceType.class);
    }
}

My final class has to look like this one below:

import java.sql.SQLException;

import com.ibatis.sqlmap.client.extensions.ParameterSetter;
import com.ibatis.sqlmap.client.extensions.ResultGetter;
import com.ibatis.sqlmap.client.extensions.TypeHandlerCallback;

public abstract class CommonEnumTypeHandler implements TypeHandlerCallback {

    Class enumClass;

    public CommonEnumTypeHandler(Class clazz) {
        this.enumClass = clazz;
    }

    public void setParameter(ParameterSetter ps, Object o) throws SQLException {
        if (o.getClass().isAssignableFrom(enumClass)) {
            ps.setString(((T) o).name().toUpperCase());
        } else
            throw new SQLException("Excpected " + enumClass + " object than: " + o);
    }

    public Object getResult(ResultGetter rs) throws SQLException {
        Object o = valueOf(rs.getString());
        if (o == null)
            throw new SQLException("Unknown parameter type: " + rs.getString());
        return o;
    }

    public Object valueOf(String s) {
        return Enum.valueOf(enumClass, s.toUpperCase());
    }
}

 

You May Also Like

Sonar Gerrit Plugin Release

I am happy to announce a first release of my Sonar Gerrit plugin. This plugin reports Sonar violations on your patchsets to your Gerrit server. Sonar analyses full project, but only files included in patchset are commented on Gerrit. Please forward to project page for installation instructions. This plugin is intended to use with Gerrit Trigger plugin for Jenkins CI server. Together they provide a great tool for automatic static code analysis.I am happy to announce a first release of my Sonar Gerrit plugin. This plugin reports Sonar violations on your patchsets to your Gerrit server. Sonar analyses full project, but only files included in patchset are commented on Gerrit. Please forward to project page for installation instructions. This plugin is intended to use with Gerrit Trigger plugin for Jenkins CI server. Together they provide a great tool for automatic static code analysis.