ListGetExecutor.java

/*
* Copyright 2016 Nabarun Mondal
* 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.
*
*/


package com.noga.njexl.lang.internal;
import java.util.Arrays;
import java.util.List;
import java.lang.reflect.Array;
/**
 * Specialized executor to get a property from a List or array.
 * @since 2.0
 */
public final class ListGetExecutor extends AbstractExecutor.Get {
    /** The java.lang.reflect.Array.get method used as an active marker in ListGet. */
    private static final java.lang.reflect.Method ARRAY_GET =
            initMarker(Array.class, "get", Object.class, Integer.TYPE);
    /** The java.util.obj.get method used as an active marker in ListGet. */
    private static final java.lang.reflect.Method LIST_GET =
            initMarker(List.class, "get", Integer.TYPE);

    /** The java.lang.String.charAt method used as an active marker in ListGet. */
    private static final java.lang.reflect.Method CHAR_AT =
            initMarker(String.class, "charAt", Integer.TYPE);


    /** The property. */
    private final Integer property;

    /**
     * Creates an instance checking for the List interface or Array capability.
     * @param is the introspector
     * @param clazz the class to introspect
     * @param key the key to use in obj.get(key)
     */
    public ListGetExecutor(Introspector is, Class<?> clazz, Integer key) {
        super(clazz, discover(clazz));
        property = key;
    }

    /** {@inheritDoc} */
    @Override
    public Object getTargetProperty() {
        return property;
    }
    
    /**
     * Get the property from the obj or array.
     * @param obj the List/array.
     * @return obj.get(key)
     */
    @Override
    public Object execute(final Object obj) {
        int inx = property.intValue() ;
        int len =-1;
        if (method == ARRAY_GET) {
            len = Array.getLength(obj);
            if ( inx < 0 ){ inx  = len + inx ; }
            return java.lang.reflect.Array.get(obj,inx );
        }
        if (method == CHAR_AT) {
            len = ((String)obj).length()  ;
            if ( inx < 0 ){ inx  = len + inx ; }
            return ((String)obj).charAt(inx);
        }
        len = ((List<?>) obj).size() ;
        if ( inx < 0 ){ inx  = len + inx ; }
        return ((List<?>) obj).get(inx);
    }

    /** {@inheritDoc} */
    @Override
    public Object tryExecute(final Object obj, Object key) {
        if (obj != null && method != null
            && objectClass.equals(obj.getClass())
            && key instanceof Integer) {
            if (method == ARRAY_GET) {
                return java.lang.reflect.Array.get(obj, ((Integer) key).intValue());
            } else {
                return ((List<?>) obj).get(((Integer) key).intValue());
            }
        }
        return TRY_FAILED;
    }


    /**
     * Finds the method to perform the get on a obj of array.
     * @param clazz the class to introspect
     * @return a marker method, obj.get or array.get
     */
    static java.lang.reflect.Method discover(Class<?> clazz) {
        //return discoverList(false, clazz, property);
        if (clazz.isArray()) {
            return ARRAY_GET;
        }
        if (List.class.isAssignableFrom(clazz)) {
            return LIST_GET;
        }
        if (String.class.isAssignableFrom(clazz)) {
            return CHAR_AT;
        }
        return null;
    }
}