CustomObjectFactory.java

package org.apache.ibatis.submitted.custom_collection_handling;

import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

import org.apache.ibatis.reflection.ReflectionException;
import org.apache.ibatis.reflection.factory.ObjectFactory;

public class CustomObjectFactory implements ObjectFactory {

    private static final long serialVersionUID = -8855120656940914948L;

    public <T> T create(Class<T> type) {
        return create(type, null, null);
    }

    public <T> T create(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
        Class<?> classToCreate = resolveInterface(type);
        @SuppressWarnings("unchecked") // we know types are assignable
        T created = (T) instantiateClass(classToCreate, constructorArgTypes, constructorArgs);
        return created;
    }

    public void setProperties(Properties properties) {
        // no props for default
    }

    private <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) {
        try {
            Constructor<T> constructor;
            if (constructorArgTypes == null || constructorArgs == null) {
                constructor = type.getDeclaredConstructor();
                if (!constructor.isAccessible()) {
                    constructor.setAccessible(true);
                }
                return constructor.newInstance();
            }
            constructor = type.getDeclaredConstructor(constructorArgTypes.toArray(new Class[constructorArgTypes.size()]));
            if (!constructor.isAccessible()) {
                constructor.setAccessible(true);
            }
            return constructor.newInstance(constructorArgs.toArray(new Object[constructorArgs.size()]));
        } catch (Exception e) {
            StringBuilder argTypes = new StringBuilder();
            if (constructorArgTypes != null) {
                for (Class<?> argType : constructorArgTypes) {
                    argTypes.append(argType.getSimpleName());
                    argTypes.append(",");
                }
            }
            StringBuilder argValues = new StringBuilder();
            if (constructorArgs != null) {
                for (Object argValue : constructorArgs) {
                    argValues.append(String.valueOf(argValue));
                    argValues.append(",");
                }
            }
            throw new ReflectionException("Error instantiating " + type + " with invalid types (" + argTypes + ") or values (" + argValues + "). Cause: " + e, e);
        }
    }

    private Class<?> resolveInterface(Class<?> type) {
        Class<?> classToCreate;
        if (type == List.class || type == Collection.class) {
            classToCreate = LinkedList.class;
        } else if (type == Map.class) {
            classToCreate = LinkedHashMap.class;
        } else if (type == SortedSet.class) { // issue #510 Collections Support
            classToCreate = TreeSet.class;
        } else if (type == Set.class) {
            classToCreate = HashSet.class;
        } else {
            classToCreate = type;
        }
        return classToCreate;
    }
    
    public <T> boolean isCollection(Class<T> type) {
      return CustomCollection.class.isAssignableFrom(type);
    }

    @SuppressWarnings("unchecked")
    public <T> T[] createArray(Class<T> type, int size) {
      return (T[]) Array.newInstance(type, size);
    }

}