Commons JXPath example source code file (ValueUtils.java)

This example Commons JXPath source code file (ValueUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons JXPath tags/keywords

bean, cannot, cannot, class, collection, collection, exception, indexedpropertydescriptor, javabean, jxpathexception, jxpathexception, list, method, object, object, propertydescriptor, reflection, util

The Commons JXPath ValueUtils.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.jxpath.util;

import java.beans.IndexedPropertyDescriptor;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.commons.jxpath.Container;
import org.apache.commons.jxpath.DynamicPropertyHandler;
import org.apache.commons.jxpath.JXPathException;

/**
 * Collection and property access utilities.
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 670728 $ $Date: 2008-06-23 15:12:44 -0500 (Mon, 23 Jun 2008) $
 */
public class ValueUtils {
    private static Map dynamicPropertyHandlerMap = new HashMap();
    private static final int UNKNOWN_LENGTH_MAX_COUNT = 16000;

    /**
     * Returns true if the object is an array or a Collection.
     * @param value to test
     * @return boolean
     */
    public static boolean isCollection(Object value) {
        value = getValue(value);
        if (value == null) {
            return false;
        }
        if (value.getClass().isArray()) {
            return true;
        }
        if (value instanceof Collection) {
            return true;
        }
        return false;
    }

    /**
     * Returns 1 if the type is a collection,
     * -1 if it is definitely not
     * and 0 if it may be a collection in some cases.
     * @param clazz to test
     * @return int
     */
    public static int getCollectionHint(Class clazz) {
        if (clazz.isArray()) {
            return 1;
        }

        if (Collection.class.isAssignableFrom(clazz)) {
            return 1;
        }

        if (clazz.isPrimitive()) {
            return -1;
        }

        if (clazz.isInterface()) {
            return 0;
        }

        if (Modifier.isFinal(clazz.getModifiers())) {
            return -1;
        }

        return 0;
    }

    /**
     * If there is a regular non-indexed read method for this property,
     * uses this method to obtain the collection and then returns its
     * length.
     * Otherwise, attempts to guess the length of the collection by
     * calling the indexed get method repeatedly.  The method is supposed
     * to throw an exception if the index is out of bounds.
     * @param object collection
     * @param pd IndexedPropertyDescriptor
     * @return int
     */
    public static int getIndexedPropertyLength(Object object,
            IndexedPropertyDescriptor pd) {
        if (pd.getReadMethod() != null) {
            return getLength(getValue(object, pd));
        }

        Method readMethod = pd.getIndexedReadMethod();
        if (readMethod == null) {
            throw new JXPathException(
                "No indexed read method for property " + pd.getName());
        }

        for (int i = 0; i < UNKNOWN_LENGTH_MAX_COUNT; i++) {
            try {
                readMethod.invoke(object, new Object[] { new Integer(i)});
            }
            catch (Throwable t) {
                return i;
            }
        }

        throw new JXPathException(
            "Cannot determine the length of the indexed property "
                + pd.getName());
    }

    /**
     * Returns the length of the supplied collection. If the supplied object
     * is not a collection, returns 1. If collection is null, returns 0.
     * @param collection to check
     * @return int
     */
    public static int getLength(Object collection) {
        if (collection == null) {
            return 0;
        }
        collection = getValue(collection);
        if (collection.getClass().isArray()) {
            return Array.getLength(collection);
        }
        if (collection instanceof Collection) {
            return ((Collection) collection).size();
        }
        return 1;
    }

    /**
     * Returns an iterator for the supplied collection. If the argument
     * is null, returns an empty iterator. If the argument is not
     * a collection, returns an iterator that produces just that one object.
     * @param collection to iterate
     * @return Iterator
     */
    public static Iterator iterate(Object collection) {
        if (collection == null) {
            return Collections.EMPTY_LIST.iterator();
        }
        if (collection.getClass().isArray()) {
            int length = Array.getLength(collection);
            if (length == 0) {
                return Collections.EMPTY_LIST.iterator();
            }
            ArrayList list = new ArrayList();
            for (int i = 0; i < length; i++) {
                list.add(Array.get(collection, i));
            }
            return list.iterator();
        }
        if (collection instanceof Collection) {
            return ((Collection) collection).iterator();
        }
        return Collections.singletonList(collection).iterator();
    }

    /**
     * Grows the collection if necessary to the specified size. Returns
     * the new, expanded collection.
     * @param collection to expand
     * @param size desired size
     * @return collection or array
     */
    public static Object expandCollection(Object collection, int size) {
        if (collection == null) {
            return null;
        }
        if (size < getLength(collection)) {
            throw new JXPathException("adjustment of " + collection
                    + " to size " + size + " is not an expansion");
        }
        if (collection.getClass().isArray()) {
            Object bigger =
                Array.newInstance(
                    collection.getClass().getComponentType(),
                    size);
            System.arraycopy(
                collection,
                0,
                bigger,
                0,
                Array.getLength(collection));
            return bigger;
        }
        if (collection instanceof Collection) {
            while (((Collection) collection).size() < size) {
                ((Collection) collection).add(null);
            }
            return collection;
        }
        throw new JXPathException(
            "Cannot turn "
                + collection.getClass().getName()
                + " into a collection of size "
                + size);
    }

    /**
     * Remove the index'th element from the supplied collection.
     * @param collection to edit
     * @param index int
     * @return the resulting collection
     */
    public static Object remove(Object collection, int index) {
        collection = getValue(collection);
        if (collection == null) {
            return null;
        }
        if (index >= getLength(collection)) {
            throw new JXPathException("No such element at index " + index);
        }
        if (collection.getClass().isArray()) {
            int length = Array.getLength(collection);
            Object smaller =
                Array.newInstance(
                    collection.getClass().getComponentType(),
                    length - 1);
            if (index > 0) {
                System.arraycopy(collection, 0, smaller, 0, index);
            }
            if (index < length - 1) {
                System.arraycopy(
                    collection,
                    index + 1,
                    smaller,
                    index,
                    length - index - 1);
            }
            return smaller;
        }
        if (collection instanceof List) {
            int size = ((List) collection).size();
            if (index < size) {
                ((List) collection).remove(index);
            }
            return collection;
        }
        if (collection instanceof Collection) {
            Iterator it = ((Collection) collection).iterator();
            for (int i = 0; i < index; i++) {
                if (!it.hasNext()) {
                    break;
                }
                it.next();
            }
            if (it.hasNext()) {
                it.next();
                it.remove();
            }
            return collection;
        }
        throw new JXPathException(
            "Cannot remove "
                + collection.getClass().getName()
                + "["
                + index
                + "]");
    }

    /**
     * Returns the index'th element of the supplied collection.
     * @param collection to read
     * @param index int
     * @return collection[index]
     */
    public static Object getValue(Object collection, int index) {
        collection = getValue(collection);
        Object value = collection;
        if (collection != null) {
            if (collection.getClass().isArray()) {
                if (index < 0 || index >= Array.getLength(collection)) {
                    return null;
                }
                value = Array.get(collection, index);
            }
            else if (collection instanceof List) {
                if (index < 0 || index >= ((List) collection).size()) {
                    return null;
                }
                value = ((List) collection).get(index);
            }
            else if (collection instanceof Collection) {
                int i = 0;
                Iterator it = ((Collection) collection).iterator();
                for (; i < index; i++) {
                    it.next();
                }
                if (it.hasNext()) {
                    value = it.next();
                }
                else {
                    value = null;
                }
            }
        }
        return value;
    }

    /**
     * Modifies the index'th element of the supplied collection.
     * Converts the value to the required type if necessary.
     * @param collection to edit
     * @param index to replace
     * @param value new value
     */
    public static void setValue(Object collection, int index, Object value) {
        collection = getValue(collection);
        if (collection != null) {
            if (collection.getClass().isArray()) {
                Array.set(
                    collection,
                    index,
                    convert(value, collection.getClass().getComponentType()));
            }
            else if (collection instanceof List) {
                ((List) collection).set(index, value);
            }
            else if (collection instanceof Collection) {
                throw new UnsupportedOperationException(
                        "Cannot set value of an element of a "
                                + collection.getClass().getName());
            }
        }
    }

    /**
     * Returns the value of the bean's property represented by
     * the supplied property descriptor.
     * @param bean to read
     * @param propertyDescriptor indicating what to read
     * @return Object value
     */
    public static Object getValue(Object bean,
            PropertyDescriptor propertyDescriptor) {
        Object value;
        try {
            Method method =
                getAccessibleMethod(propertyDescriptor.getReadMethod());
            if (method == null) {
                throw new JXPathException("No read method");
            }
            value = method.invoke(bean, new Object[0]);
        }
        catch (Exception ex) {
            throw new JXPathException(
                "Cannot access property: "
                    + (bean == null ? "null" : bean.getClass().getName())
                    + "."
                    + propertyDescriptor.getName(),
                ex);
        }
        return value;
    }

    /**
     * Modifies the value of the bean's property represented by
     * the supplied property descriptor.
     * @param bean to read
     * @param propertyDescriptor indicating what to read
     * @param value to set
     */
    public static void setValue(Object bean,
            PropertyDescriptor propertyDescriptor, Object value) {
        try {
            Method method =
                getAccessibleMethod(propertyDescriptor.getWriteMethod());
            if (method == null) {
                throw new JXPathException("No write method");
            }
            value = convert(value, propertyDescriptor.getPropertyType());
            method.invoke(bean, new Object[] { value });
        }
        catch (Exception ex) {
            throw new JXPathException(
                "Cannot modify property: "
                    + (bean == null ? "null" : bean.getClass().getName())
                    + "."
                    + propertyDescriptor.getName(),
                ex);
        }
    }

    /**
     * Convert value to type.
     * @param value Object
     * @param type destination
     * @return conversion result
     */
    private static Object convert(Object value, Class type) {
        try {
            return TypeUtils.convert(value, type);
        }
        catch (Exception ex) {
            throw new JXPathException(
                "Cannot convert value of class "
                    + (value == null ? "null" : value.getClass().getName())
                    + " to type "
                    + type,
                ex);
        }
    }

    /**
     * Returns the index'th element of the bean's property represented by
     * the supplied property descriptor.
     * @param bean to read
     * @param propertyDescriptor indicating what to read
     * @param index int
     * @return Object
     */
    public static Object getValue(Object bean,
            PropertyDescriptor propertyDescriptor, int index) {
        if (propertyDescriptor instanceof IndexedPropertyDescriptor) {
            try {
                IndexedPropertyDescriptor ipd =
                    (IndexedPropertyDescriptor) propertyDescriptor;
                Method method = ipd.getIndexedReadMethod();
                if (method != null) {
                    return method.invoke(
                        bean,
                        new Object[] { new Integer(index)});
                }
            }
            catch (InvocationTargetException ex) {
                Throwable t = ex.getTargetException();
                if (t instanceof IndexOutOfBoundsException) {
                    return null;
                }
                throw new JXPathException(
                    "Cannot access property: " + propertyDescriptor.getName(),
                    t);
            }
            catch (Throwable ex) {
                throw new JXPathException(
                    "Cannot access property: " + propertyDescriptor.getName(),
                    ex);
            }
        }

        // We will fall through if there is no indexed read

        return getValue(getValue(bean, propertyDescriptor), index);
    }

    /**
     * Modifies the index'th element of the bean's property represented by
     * the supplied property descriptor. Converts the value to the required
     * type if necessary.
     * @param bean to edit
     * @param propertyDescriptor indicating what to set
     * @param index int
     * @param value to set
     */
    public static void setValue(Object bean,
            PropertyDescriptor propertyDescriptor, int index, Object value) {
        if (propertyDescriptor instanceof IndexedPropertyDescriptor) {
            try {
                IndexedPropertyDescriptor ipd =
                    (IndexedPropertyDescriptor) propertyDescriptor;
                Method method = ipd.getIndexedWriteMethod();
                if (method != null) {
                    method.invoke(
                        bean,
                        new Object[] {
                            new Integer(index),
                            convert(value, ipd.getIndexedPropertyType())});
                    return;
                }
            }
            catch (Exception ex) {
                throw new RuntimeException(
                    "Cannot access property: "
                        + propertyDescriptor.getName()
                        + ", "
                        + ex.getMessage());
            }
        }
        // We will fall through if there is no indexed read
        Object collection = getValue(bean, propertyDescriptor);
        if (isCollection(collection)) {
            setValue(collection, index, value);
        }
        else if (index == 0) {
            setValue(bean, propertyDescriptor, value);
        }
        else {
            throw new RuntimeException(
                "Not a collection: " + propertyDescriptor.getName());
        }
    }

    /**
     * If the parameter is a container, opens the container and
     * return the contents.  The method is recursive.
     * @param object to read
     * @return Object
     */
    public static Object getValue(Object object) {
        while (object instanceof Container) {
            object = ((Container) object).getValue();
        }
        return object;
    }

    /**
     * Returns a shared instance of the dynamic property handler class
     * returned by <code>getDynamicPropertyHandlerClass().
     * @param clazz to handle
     * @return DynamicPropertyHandler
     */
    public static DynamicPropertyHandler getDynamicPropertyHandler(Class clazz) {
        DynamicPropertyHandler handler =
            (DynamicPropertyHandler) dynamicPropertyHandlerMap.get(clazz);
        if (handler == null) {
            try {
                handler = (DynamicPropertyHandler) clazz.newInstance();
            }
            catch (Exception ex) {
                throw new JXPathException(
                    "Cannot allocate dynamic property handler of class "
                        + clazz.getName(),
                    ex);
            }
            dynamicPropertyHandlerMap.put(clazz, handler);
        }
        return handler;
    }

    // -------------------------------------------------------- Private Methods
    //
    //  The rest of the code in this file was copied FROM
    //  org.apache.commons.beanutils.PropertyUtil. We don't want to introduce
    //  a dependency on BeanUtils yet - DP.
    //

    /**
     * Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified Method.  If no such method
     * can be found, return <code>null.
     *
     * @param method The method that we wish to call
     * @return Method
     */
    public static Method getAccessibleMethod(Method method) {

        // Make sure we have a method to check
        if (method == null) {
            return (null);
        }

        // If the requested method is not public we cannot call it
        if (!Modifier.isPublic(method.getModifiers())) {
            return (null);
        }

        // If the declaring class is public, we are done
        Class clazz = method.getDeclaringClass();
        if (Modifier.isPublic(clazz.getModifiers())) {
            return (method);
        }

        String name = method.getName();
        Class[] parameterTypes = method.getParameterTypes();
        while (clazz != null) {
            // Check the implemented interfaces and subinterfaces
            Method aMethod = getAccessibleMethodFromInterfaceNest(clazz,
                    name, parameterTypes);
            if (aMethod != null) {
                return aMethod;
            }

            clazz = clazz.getSuperclass();
            if (clazz != null && Modifier.isPublic(clazz.getModifiers())) {
                try {
                    return clazz.getDeclaredMethod(name, parameterTypes);
                }
                catch (NoSuchMethodException e) { //NOPMD
                    //ignore
                }
            }
        }
        return null;
    }

    /**
     * Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified method, by scanning through
     * all implemented interfaces and subinterfaces.  If no such Method
     * can be found, return <code>null.
     *
     * @param clazz Parent class for the interfaces to be checked
     * @param methodName Method name of the method we wish to call
     * @param parameterTypes The parameter type signatures
     * @return Method
     */
    private static Method getAccessibleMethodFromInterfaceNest(Class clazz,
            String methodName, Class[] parameterTypes) {

        Method method = null;

        // Check the implemented interfaces of the parent class
        Class[] interfaces = clazz.getInterfaces();
        for (int i = 0; i < interfaces.length; i++) {

            // Is this interface public?
            if (!Modifier.isPublic(interfaces[i].getModifiers())) {
                continue;
            }

            // Does the method exist on this interface?
            try {
                method =
                    interfaces[i].getDeclaredMethod(methodName, parameterTypes);
            }
            catch (NoSuchMethodException e) { //NOPMD
                //ignore
            }
            if (method != null) {
                break;
            }

            // Recursively check our parent interfaces
            method =
                getAccessibleMethodFromInterfaceNest(
                    interfaces[i],
                    methodName,
                    parameterTypes);
            if (method != null) {
                break;
            }
        }

        // Return whatever we have found
        return (method);
    }
}