ToStringHelper xref

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    1   /**
    2    * Copyright (c) 2004-2011 QOS.ch
    3    * All rights reserved.
    4    *
    5    * Permission is hereby granted, free  of charge, to any person obtaining
    6    * a  copy  of this  software  and  associated  documentation files  (the
    7    * "Software"), to  deal in  the Software without  restriction, including
    8    * without limitation  the rights to  use, copy, modify,  merge, publish,
    9    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
    10   * permit persons to whom the Software  is furnished to do so, subject to
    11   * the following conditions:
    12   *
    13   * The  above  copyright  notice  and  this permission  notice  shall  be
    14   * included in all copies or substantial portions of the Software.
    15   *
    16   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
    17   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
    18   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
    19   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
    20   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
    21   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
    22   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    23   *
    24   */
    25  package org.slf4j.instrumentation;
    26
    27  import java.util.Map;
    28  import java.util.WeakHashMap;
    29
    30  public class ToStringHelper {
    31
    32  	/**
    33  	 * Prefix to use at the start of the representation. Always used.
    34  	 */
    35  	private static final String ARRAY_PREFIX = "[";
    36
    37  	/**
    38  	 * Suffix to use at the end of the representation. Always used.
    39  	 */
    40  	private static final String ARRAY_SUFFIX = "]";
    41
    42  	/**
    43  	 * String separating each element when rendering an array. To be compatible
    44  	 * with lists comma-space is used.
    45  	 */
    46
    47  	private static final String ELEMENT_SEPARATOR = ", ";
    48
    49  	/**
    50  	 * unrenderableClasses is essentially a Set of Class objects which has for
    51  	 * some reason failed to render properly when invoked through a toString
    52  	 * method call. To avoid memory leaks a data structure using weak references
    53  	 * is needed, but unfortunately the runtime library does not contain a
    54  	 * WeakHashSet class, so the behavior is emulated with a WeakHashmap with
    55  	 * the class as the key, and a Long containing the value of
    56  	 * System.currentTimeMilis when an instance of the class failed to render.
    57  	 */
    58
    59  	final static Map<Class<?>, Object> unrenderableClasses = new WeakHashMap<Class<?>, Object>();
    60
    61  	/**
    62  	 * Returns o.toString() unless it throws an exception (which causes it to be
    63  	 * stored in unrenderableClasses) or already was present in
    64  	 * unrenderableClasses. If so, the same string is returned as would have
    65  	 * been returned by Object.toString(). Arrays get special treatment as they
    66  	 * don't have usable toString methods.
    67  	 *
    68  	 * @param o
    69  	 *            incoming object to render.
    70  	 * @return
    71  	 */
    72
    73  	public static String render(Object o) {
    74  		if (o == null) {
    75  			return String.valueOf(o);
    76  		}
    77  		Class<?> objectClass = o.getClass();
    78
    79  		if (unrenderableClasses.containsKey(objectClass) == false) {
    80  			try {
    81  				if (objectClass.isArray()) {
    82  					return renderArray(o, objectClass).toString();
    83  				} else {
    84  					return o.toString();
    85  				}
    86  			} catch (Exception e) {
    87  				Long now = new Long(System.currentTimeMillis());
    88
    89  				System.err.println("Disabling exception throwing class "
    90  						+ objectClass.getName() + ", " + e.getMessage());
    91
    92  				unrenderableClasses.put(objectClass, now);
    93  			}
    94  		}
    95  		String name = o.getClass().getName();
    96  		return name + "@" + Integer.toHexString(o.hashCode());
    97  	}
    98
    99  	/**
    100 	 * renderArray returns an array similar to a List. If the array type is an
    101 	 * object they are rendered with "render(object)" for each. If the array
    102 	 * type is a primitive each element is added directly to the string buffer
    103 	 * collecting the result.
    104 	 *
    105 	 * @param o
    106 	 * @param objectClass
    107 	 * @return
    108 	 */
    109 	private static StringBuffer renderArray(Object o, Class<?> objectClass) {
    110 		Class<?> componentType = objectClass.getComponentType();
    111 		StringBuffer sb = new StringBuffer(ARRAY_PREFIX);
    112
    113 		if (componentType.isPrimitive() == false) {
    114 			Object[] oa = (Object[]) o;
    115 			for (int i = 0; i < oa.length; i++) {
    116 				if (i > 0) {
    117 					sb.append(ELEMENT_SEPARATOR);
    118 				}
    119 				sb.append(render(oa[i]));
    120 			}
    121 		} else {
    122 			if (Boolean.TYPE.equals(componentType)) {
    123 				boolean[] ba = (boolean[]) o;
    124 				for (int i = 0; i < ba.length; i++) {
    125 					if (i > 0) {
    126 						sb.append(ELEMENT_SEPARATOR);
    127 					}
    128 					sb.append(ba[i]);
    129 				}
    130 			} else if (Integer.TYPE.equals(componentType)) {
    131 				int[] ia = (int[]) o;
    132 				for (int i = 0; i < ia.length; i++) {
    133 					if (i > 0) {
    134 						sb.append(ELEMENT_SEPARATOR);
    135 					}
    136 					sb.append(ia[i]);
    137 				}
    138
    139 			} else if (Long.TYPE.equals(componentType)) {
    140 				long[] ia = (long[]) o;
    141 				for (int i = 0; i < ia.length; i++) {
    142 					if (i > 0) {
    143 						sb.append(ELEMENT_SEPARATOR);
    144 					}
    145 					sb.append(ia[i]);
    146 				}
    147 			} else if (Double.TYPE.equals(componentType)) {
    148 				double[] ia = (double[]) o;
    149 				for (int i = 0; i < ia.length; i++) {
    150 					if (i > 0) {
    151 						sb.append(ELEMENT_SEPARATOR);
    152 					}
    153 					sb.append(ia[i]);
    154 				}
    155 			} else if (Float.TYPE.equals(componentType)) {
    156 				float[] ia = (float[]) o;
    157 				for (int i = 0; i < ia.length; i++) {
    158 					if (i > 0) {
    159 						sb.append(ELEMENT_SEPARATOR);
    160 					}
    161 					sb.append(ia[i]);
    162 				}
    163 			} else if (Character.TYPE.equals(componentType)) {
    164 				char[] ia = (char[]) o;
    165 				for (int i = 0; i < ia.length; i++) {
    166 					if (i > 0) {
    167 						sb.append(ELEMENT_SEPARATOR);
    168 					}
    169 					sb.append(ia[i]);
    170 				}
    171 			} else if (Short.TYPE.equals(componentType)) {
    172 				short[] ia = (short[]) o;
    173 				for (int i = 0; i < ia.length; i++) {
    174 					if (i > 0) {
    175 						sb.append(ELEMENT_SEPARATOR);
    176 					}
    177 					sb.append(ia[i]);
    178 				}
    179 			} else if (Byte.TYPE.equals(componentType)) {
    180 				byte[] ia = (byte[]) o;
    181 				for (int i = 0; i < ia.length; i++) {
    182 					if (i > 0) {
    183 						sb.append(ELEMENT_SEPARATOR);
    184 					}
    185 					sb.append(ia[i]);
    186 				}
    187 			}
    188 		}
    189 		sb.append(ARRAY_SUFFIX);
    190 		return sb;
    191 	}
    192 }