InvokableIteratorMethod.java

/*
 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Contributors:
 *     bstefanescu
 */
package org.nuxeo.ecm.automation.core.impl;

import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.util.Iterator;
import java.util.Map;

import org.nuxeo.ecm.automation.OperationContext;
import org.nuxeo.ecm.automation.OperationException;
import org.nuxeo.ecm.automation.OperationType;
import org.nuxeo.ecm.automation.OutputCollector;
import org.nuxeo.ecm.automation.core.annotations.OperationMethod;

/**
 * A method proxy which accept as input only iterable inputs. At invocation time it iterates over the input elements and
 * invoke the real method using the current input element as the input.
 * <p>
 * The result is collected into a {@link OutputCollector} as specified by the {@link OperationMethod} annotation.
 * <p>
 * This proxy is used (instead of the default {@link InvokableMethod}) when an operation is defining an output collector
 * in the {@link OperationMethod} annotation so that iterable inputs are automatically handled by the chain executor.
 * <p>
 * This specialized implementation is declaring the same consume type as its non-iterable counterpart. But at runtime it
 * consumes any Iterable of the cosume type.
 * <p>
 * To correctly generate the operation documentation the {@link OperationTypeImpl} is checking if the method is iterable
 * or not through {@link #isIterable()} to declare the correct consume type.
 *
 * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
 */
public class InvokableIteratorMethod extends InvokableMethod {

    @SuppressWarnings("rawtypes")
    protected Class<? extends OutputCollector> collector;

    public InvokableIteratorMethod(OperationType op, Method method, OperationMethod anno) {
        super(op, method, anno);
        collector = anno.collector();
        if (collector == OutputCollector.class) {
            throw new IllegalArgumentException("Not an iterable method");
        }
        // check the collector match the method signature - to early detect invalid
        // operation definitions.
        if (consume == Void.TYPE) {
            throw new IllegalArgumentException("An iterable method must have an argument");
        }
        Type[] ctypes = IterableInputHelper.findCollectorTypes(collector);
        if (!((Class<?>) ctypes[0]).isAssignableFrom(produce)) {
            throw new IllegalArgumentException("The collector used on " + method
                    + " doesn't match the method return type");
        }
        // must modify the produced type to fit the real produced type.
        try {
            produce = (Class<?>) ctypes[1];
        } catch (ArrayIndexOutOfBoundsException e) {
            throw new IllegalStateException("Invalid output collector: " + collector + ". No getOutput method found.");
        }
        // the consumed type is not used in chain compilation so we let it as is
        // for now.
    }

    @Override
    public boolean isIterable() {
        return true;
    }

    @Override
    public int inputMatch(Class<?> in) {
        Class<?> iterableIn = IterableInputHelper.getIterableType(in);
        if (iterableIn != null) {
            return super.inputMatch(iterableIn);
        }
        return 0;
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Override
    protected Object doInvoke(OperationContext ctx, Map<String, Object> args) throws OperationException,
            ReflectiveOperationException {
        Object input = ctx.getInput();
        if (!(input instanceof Iterable)) {
            throw new IllegalStateException("An iterable method was called in a non iterable context");
        }
        OutputCollector list = collector.newInstance();
        Iterable<?> iterable = (Iterable<?>) input;
        Iterator<?> it = iterable.iterator();
        while (it.hasNext()) {
            Object in = it.next();
            // update context to use as input the current entry
            ctx.setInput(in);
            list.collect(ctx, super.doInvoke(ctx, args));
        }
        return list.getOutput();
    }

}