Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/**
 * 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.
 */

import java.lang.reflect.Array;

import java.util.List;
import java.util.Map;

public class Main {
    /**
     * Searches a map for a given key. The key can be a regular map key, or a
     * simple expression of the form:
     * 
     * <ul>
     * <li>foo.bar (will lookup 'foo', and then 'bar' in a potential nested map)
     * </li>
     * <li>foo.bar[0].baz (will lookup 'foo', then 'bar' in a potential nested
     * map, then pick the first element in case it is a list/array and then pick
     * 'baz' from the potential map at that position).
     * </ul>
     * 
     * @param map
     *            the map to search in
     * @param key
     *            the key to resolve
     * @return the object in the map with the given key/expression. Or null if
     *         it does not exist.
     */
    public static Object find(Map<?, ?> map, String key) {
        if (map == null || key == null) {
            return null;
        }
        final Object result = map.get(key);
        if (result == null) {
            return find(map, key, 0);
        }
        return result;
    }

    private static Object find(Map<?, ?> map, String key, int fromIndex) {
        final int indexOfDot = key.indexOf('.', fromIndex);
        final int indexOfBracket = key.indexOf('[', fromIndex);
        int indexOfEndBracket = -1;
        int arrayIndex = -1;

        boolean hasDot = indexOfDot != -1;
        boolean hasBracket = indexOfBracket != -1;

        if (hasBracket) {
            // also check that there is an end-bracket
            indexOfEndBracket = key.indexOf("]", indexOfBracket);
            hasBracket = indexOfEndBracket != -1;
            if (hasBracket) {
                final String indexString = key.substring(indexOfBracket + 1, indexOfEndBracket);
                try {
                    arrayIndex = Integer.parseInt(indexString);
                } catch (NumberFormatException e) {
                    // not a valid array/list index
                    hasBracket = false;
                }
            }
        }

        if (hasDot && hasBracket) {
            if (indexOfDot > indexOfBracket) {
                hasDot = false;
            } else {
                hasBracket = false;
            }
        }

        if (hasDot) {
            final String prefix = key.substring(0, indexOfDot);
            final Object nestedObject = map.get(prefix);
            if (nestedObject == null) {
                return find(map, key, indexOfDot + 1);
            }
            if (nestedObject instanceof Map) {
                final String remainingPart = key.substring(indexOfDot + 1);
                @SuppressWarnings("unchecked")
                final Map<String, ?> nestedMap = (Map<String, ?>) nestedObject;
                return find(nestedMap, remainingPart);
            }
        }

        if (hasBracket) {
            final String prefix = key.substring(0, indexOfBracket);
            final Object nestedObject = map.get(prefix);
            if (nestedObject == null) {
                return find(map, key, indexOfBracket + 1);
            }

            String remainingPart = key.substring(indexOfEndBracket + 1);

            try {
                final Object valueAtIndex;
                if (nestedObject instanceof List) {
                    valueAtIndex = ((List<?>) nestedObject).get(arrayIndex);
                } else if (nestedObject.getClass().isArray()) {
                    valueAtIndex = Array.get(nestedObject, arrayIndex);
                } else {
                    // no way to extract from a non-array and non-list
                    valueAtIndex = null;
                }

                if (valueAtIndex != null) {
                    if (remainingPart.startsWith(".")) {
                        remainingPart = remainingPart.substring(1);
                    }

                    if (remainingPart.isEmpty()) {
                        return valueAtIndex;
                    }

                    if (valueAtIndex instanceof Map) {
                        @SuppressWarnings("unchecked")
                        final Map<String, ?> nestedMap = (Map<String, ?>) valueAtIndex;
                        return find(nestedMap, remainingPart);
                    } else {
                        // not traversing any further. Should we want to add
                        // support for double-sided arrays, we could do it here.
                    }
                }

            } catch (IndexOutOfBoundsException e) {
                return null;
            }
        }

        return null;
    }
}