DefaultDTOModel.java

package org.jboss.capedwarf.common.dto;

import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * Default DTO model.
 *
 * @author <a href="mailto:ales.justin@jboss.org">Ales Justin</a>
 */
public class DefaultDTOModel<U extends Serializable> implements DTOModel<U> {
    private Class<U> entityClass;
    private boolean needsClassName;
    private Method idMethod;

    private Class<?> dto;
    private Map<Method, Method> properties;
    private Map<String, ValueConverter> converters;

    public DefaultDTOModel(Class<U> entityClass) {
        if (entityClass == null)
            throw new IllegalArgumentException("Null entity class");

        this.entityClass = entityClass;
        init();
    }

    private void init() {
        DTOClass dtoc = entityClass.getAnnotation(DTOClass.class);
        if (dtoc == null)
            throw new IllegalArgumentException("No such DTOClass: " + entityClass);
        this.dto = dtoc.value();

        needsClassName = dtoc.needsClassName();
        try {
            idMethod = entityClass.getMethod("getId");
            if (idMethod.getReturnType() != Long.class)
                idMethod = null; // ignore non Long id
        } catch (Throwable ignored) {
        }

        try {
            properties = new HashMap<Method, Method>();
            converters = new HashMap<String, ValueConverter>();

            resolve(entityClass);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private void resolve(Class<?> clazz) throws Exception {
        Method[] methods = clazz.getMethods();
        for (Method m : methods) {
            DTOProperty dtop = m.getAnnotation(DTOProperty.class);
            if (dtop != null) {
                String name = m.getName();
                if (name.startsWith("get") == false && name.startsWith("is") == false)
                    throw new IllegalArgumentException("Not a getter method: " + m);

                if (converters.containsKey(name) == false) {
                    String dp = dtop.property();
                    String pn;
                    if (dp != null && dp.length() > 0) {
                        pn = dp;
                    } else {
                        if (name.startsWith("is"))
                            pn = "set" + name.substring(2); // is
                        else
                            pn = "s" + name.substring(1); //get
                    }
                    Method dtoM = dto.getMethod(pn);
                    properties.put(m, dtoM);

                    ValueConverter vc = getVC(dtop);
                    converters.put(name, vc);
                }
            }
        }
    }

    private ValueConverter getVC(DTOProperty dtop) throws Exception {
        Class<? extends ValueConverter> vcc = dtop.converter();
        if (vcc == NoopValueConverter.class)
            return NoopValueConverter.INSTANCE;
        else if (vcc == StringValueConverter.class)
            return StringValueConverter.INSTANCE;

        return vcc.newInstance();
    }

    @SuppressWarnings({"unchecked"})
    public Object toDTO(U entity) {
        try {
            Object dtoInstance = dto.newInstance();

            if (dtoInstance instanceof Identity) {
                Identity identity = (Identity) dtoInstance;
                if (needsClassName)
                    identity.setClassName(entityClass.getName());
                if (idMethod != null)
                    identity.setId((Long) idMethod.invoke(entity));
            }

            for (Method key : properties.keySet()) {
                Method dtoProperty = properties.get(key);
                ValueConverter vc = converters.get(key.getName());
                Object value = vc.convert(key.invoke(entity));
                dtoProperty.invoke(dtoInstance, value);
            }
            return dtoInstance;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}