| /* |
| * Copyright (c) OSGi Alliance (2012, 2014). All Rights Reserved. |
| * |
| * 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 org.osgi.dto; |
| |
| import java.lang.reflect.Array; |
| import java.lang.reflect.Field; |
| import java.lang.reflect.Modifier; |
| import java.util.IdentityHashMap; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * Super type for Data Transfer Objects. |
| * |
| * <p> |
| * A Data Transfer Object (DTO) is easily serializable having only public fields |
| * of primitive types and their wrapper classes, Strings, and DTOs. List, Set, |
| * Map and array aggregates may also be used. The aggregates must only hold |
| * objects of the listed types or aggregates. |
| * |
| * <p> |
| * The object graph from a Data Transfer Object must be a tree to simplify |
| * serialization and deserialization. |
| * |
| * @author $Id$ |
| * @NotThreadSafe |
| */ |
| public abstract class DTO { |
| |
| /** |
| * Return a string representation of this DTO suitable for use when |
| * debugging. |
| * |
| * <p> |
| * The format of the string representation is not specified and subject to |
| * change. |
| * |
| * @return A string representation of this DTO suitable for use when |
| * debugging. |
| */ |
| @Override |
| public String toString() { |
| return appendValue(new StringBuilder(), new IdentityHashMap<Object, String>(), "#", this).toString(); |
| } |
| |
| /** |
| * Append the specified DTO's string representation to the specified |
| * StringBuilder. |
| * |
| * @param result StringBuilder to which the string representation is |
| * appended. |
| * @param objectRefs References to "seen" objects. |
| * @param refpath The reference path of the specified DTO. |
| * @param dto The DTO whose string representation is to be appended. |
| * @return The specified StringBuilder. |
| */ |
| private static StringBuilder appendDTO(final StringBuilder result, final Map<Object, String> objectRefs, final String refpath, final DTO dto) { |
| result.append("{"); |
| String delim = ""; |
| for (Field field : dto.getClass().getFields()) { |
| if (Modifier.isStatic(field.getModifiers())) { |
| continue; |
| } |
| result.append(delim); |
| final String name = field.getName(); |
| appendString(result, name); |
| result.append(":"); |
| Object value = null; |
| try { |
| value = field.get(dto); |
| } catch (IllegalAccessException e) { |
| // use null value; |
| } |
| appendValue(result, objectRefs, refpath + "/" + name, value); |
| delim = ", "; |
| } |
| result.append("}"); |
| return result; |
| } |
| |
| /** |
| * Append the specified value's string representation to the specified |
| * StringBuilder. |
| * |
| * <p> |
| * This method handles cycles in the object graph, using path-based |
| * references, even though the specification requires the object graph from |
| * a DTO to be a tree. |
| * |
| * @param result StringBuilder to which the string representation is |
| * appended. |
| * @param objectRefs References to "seen" objects. |
| * @param refpath The reference path of the specified value. |
| * @param value The object whose string representation is to be appended. |
| * @return The specified StringBuilder. |
| */ |
| private static StringBuilder appendValue(final StringBuilder result, final Map<Object, String> objectRefs, final String refpath, final Object value) { |
| if (value == null) { |
| return result.append("null"); |
| } |
| // Simple Java types |
| if (value instanceof String || value instanceof Character) { |
| return appendString(result, compress(value.toString())); |
| } |
| if (value instanceof Number || value instanceof Boolean) { |
| return result.append(value.toString()); |
| } |
| |
| // Complex types |
| final String path = objectRefs.get(value); |
| if (path != null) { |
| result.append("{\"$ref\":"); |
| appendString(result, path); |
| result.append("}"); |
| return result; |
| } |
| objectRefs.put(value, refpath); |
| |
| if (value instanceof DTO) { |
| return appendDTO(result, objectRefs, refpath, (DTO) value); |
| } |
| if (value instanceof Map) { |
| return appendMap(result, objectRefs, refpath, (Map<?, ?>) value); |
| } |
| if (value instanceof List || value instanceof Set) { |
| return appendIterable(result, objectRefs, refpath, (Iterable<?>) value); |
| } |
| if (value.getClass().isArray()) { |
| return appendArray(result, objectRefs, refpath, value); |
| } |
| return appendString(result, compress(value.toString())); |
| } |
| |
| /** |
| * Append the specified array's string representation to the specified |
| * StringBuilder. |
| * |
| * @param result StringBuilder to which the string representation is |
| * appended. |
| * @param objectRefs References to "seen" objects. |
| * @param refpath The reference path of the specified array. |
| * @param array The array whose string representation is to be appended. |
| * @return The specified StringBuilder. |
| */ |
| private static StringBuilder appendArray(final StringBuilder result, final Map<Object, String> objectRefs, final String refpath, final Object array) { |
| result.append("["); |
| final int length = Array.getLength(array); |
| for (int i = 0; i < length; i++) { |
| if (i > 0) { |
| result.append(","); |
| } |
| appendValue(result, objectRefs, refpath + "/" + i, Array.get(array, i)); |
| } |
| result.append("]"); |
| return result; |
| } |
| |
| /** |
| * Append the specified iterable's string representation to the specified |
| * StringBuilder. |
| * |
| * @param result StringBuilder to which the string representation is |
| * appended. |
| * @param objectRefs References to "seen" objects. |
| * @param refpath The reference path of the specified list. |
| * @param iterable The iterable whose string representation is to be |
| * appended. |
| * @return The specified StringBuilder. |
| */ |
| private static StringBuilder appendIterable(final StringBuilder result, final Map<Object, String> objectRefs, final String refpath, final Iterable<?> iterable) { |
| result.append("["); |
| int i = 0; |
| for (Object item : iterable) { |
| if (i > 0) { |
| result.append(","); |
| } |
| appendValue(result, objectRefs, refpath + "/" + i, item); |
| i++; |
| } |
| result.append("]"); |
| return result; |
| } |
| |
| /** |
| * Append the specified map's string representation to the specified |
| * StringBuilder. |
| * |
| * @param result StringBuilder to which the string representation is |
| * appended. |
| * @param objectRefs References to "seen" objects. |
| * @param refpath The reference path of the specified map. |
| * @param map The map whose string representation is to be appended. |
| * @return The specified StringBuilder. |
| */ |
| private static StringBuilder appendMap(final StringBuilder result, final Map<Object, String> objectRefs, final String refpath, final Map<?, ?> map) { |
| result.append("{"); |
| String delim = ""; |
| for (Map.Entry<?, ?> entry : map.entrySet()) { |
| result.append(delim); |
| final String name = String.valueOf(entry.getKey()); |
| appendString(result, name); |
| result.append(":"); |
| final Object value = entry.getValue(); |
| appendValue(result, objectRefs, refpath + "/" + name, value); |
| delim = ", "; |
| } |
| result.append("}"); |
| return result; |
| } |
| |
| /** |
| * Append the specified string to the specified StringBuilder. |
| * |
| * @param result StringBuilder to which the string is appended. |
| * @param string The string to be appended. |
| * @return The specified StringBuilder. |
| */ |
| private static StringBuilder appendString(final StringBuilder result, final CharSequence string) { |
| result.append("\""); |
| int i = result.length(); |
| result.append(string); |
| while (i < result.length()) { // escape if necessary |
| char c = result.charAt(i); |
| if ((c == '"') || (c == '\\')) { |
| result.insert(i, '\\'); |
| i = i + 2; |
| continue; |
| } |
| if (c < 0x20) { |
| result.insert(i + 1, Integer.toHexString(c | 0x10000)); |
| result.replace(i, i + 2, "\\u"); |
| i = i + 6; |
| continue; |
| } |
| i++; |
| } |
| result.append("\""); |
| return result; |
| } |
| |
| /** |
| * Compress, in length, the specified string. |
| * |
| * @param in The string to potentially compress. |
| * @return The string compressed, if necessary. |
| */ |
| private static CharSequence compress(final CharSequence in) { |
| final int length = in.length(); |
| if (length <= 21) { |
| return in; |
| } |
| StringBuilder result = new StringBuilder(21); |
| result.append(in, 0, 9); |
| result.append("..."); |
| result.append(in, length - 9, length); |
| return result; |
| } |
| } |