MessageFormatter.java

/**
 * Copyright (c) 2004-2011 QOS.ch
 * All rights reserved.
 *
 * Permission is hereby granted, free  of charge, to any person obtaining
 * a  copy  of this  software  and  associated  documentation files  (the
 * "Software"), to  deal in  the Software without  restriction, including
 * without limitation  the rights to  use, copy, modify,  merge, publish,
 * distribute,  sublicense, and/or sell  copies of  the Software,  and to
 * permit persons to whom the Software  is furnished to do so, subject to
 * the following conditions:
 *
 * The  above  copyright  notice  and  this permission  notice  shall  be
 * included in all copies or substantial portions of the Software.
 *
 * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
 * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
 * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */
package org.slf4j.helpers;

import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Map;

// contributors: lizongbo: proposed special treatment of array parameter values
// Joern Huxhorn: pointed out double[] omission, suggested deep array copy
/**
 * Formats messages according to very simple substitution rules. Substitutions
 * can be made 1, 2 or more arguments.
 * 
 * <p>
 * For example,
 * 
 * <pre>
 * MessageFormatter.format(&quot;Hi {}.&quot;, &quot;there&quot;)
 * </pre>
 * 
 * will return the string "Hi there.".
 * <p>
 * The {} pair is called the <em>formatting anchor</em>. It serves to designate
 * the location where arguments need to be substituted within the message
 * pattern.
 * <p>
 * In case your message contains the '{' or the '}' character, you do not have
 * to do anything special unless the '}' character immediately follows '{'. For
 * example,
 * 
 * <pre>
 * MessageFormatter.format(&quot;Set {1,2,3} is not equal to {}.&quot;, &quot;1,2&quot;);
 * </pre>
 * 
 * will return the string "Set {1,2,3} is not equal to 1,2.".
 * 
 * <p>
 * If for whatever reason you need to place the string "{}" in the message
 * without its <em>formatting anchor</em> meaning, then you need to escape the
 * '{' character with '\', that is the backslash character. Only the '{'
 * character should be escaped. There is no need to escape the '}' character.
 * For example,
 * 
 * <pre>
 * MessageFormatter.format(&quot;Set \\{} is not equal to {}.&quot;, &quot;1,2&quot;);
 * </pre>
 * 
 * will return the string "Set {} is not equal to 1,2.".
 * 
 * <p>
 * The escaping behavior just described can be overridden by escaping the escape
 * character '\'. Calling
 * 
 * <pre>
 * MessageFormatter.format(&quot;File name is C:\\\\{}.&quot;, &quot;file.zip&quot;);
 * </pre>
 * 
 * will return the string "File name is C:\file.zip".
 * 
 * <p>
 * The formatting conventions are different than those of {@link MessageFormat}
 * which ships with the Java platform. This is justified by the fact that
 * SLF4J's implementation is 10 times faster than that of {@link MessageFormat}.
 * This local performance difference is both measurable and significant in the
 * larger context of the complete logging processing chain.
 * 
 * <p>
 * See also {@link #format(String, Object)},
 * {@link #format(String, Object, Object)} and
 * {@link #arrayFormat(String, Object[])} methods for more details.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @author Joern Huxhorn
 */
final public class MessageFormatter {
  static final char DELIM_START = '{';
  static final char DELIM_STOP = '}';
  static final String DELIM_STR = "{}";
  private static final char ESCAPE_CHAR = '\\';

  /**
   * Performs single argument substitution for the 'messagePattern' passed as
   * parameter.
   * <p>
   * For example,
   * 
   * <pre>
   * MessageFormatter.format(&quot;Hi {}.&quot;, &quot;there&quot;);
   * </pre>
   * 
   * will return the string "Hi there.".
   * <p>
   * 
   * @param messagePattern
   *          The message pattern which will be parsed and formatted
   * @param argument
   *          The argument to be substituted in place of the formatting anchor
   * @return The formatted message
   */
  final public static FormattingTuple format(String messagePattern, Object arg) {
    return arrayFormat(messagePattern, new Object[] { arg });
  }

  /**
   * 
   * Performs a two argument substitution for the 'messagePattern' passed as
   * parameter.
   * <p>
   * For example,
   * 
   * <pre>
   * MessageFormatter.format(&quot;Hi {}. My name is {}.&quot;, &quot;Alice&quot;, &quot;Bob&quot;);
   * </pre>
   * 
   * will return the string "Hi Alice. My name is Bob.".
   * 
   * @param messagePattern
   *          The message pattern which will be parsed and formatted
   * @param arg1
   *          The argument to be substituted in place of the first formatting
   *          anchor
   * @param arg2
   *          The argument to be substituted in place of the second formatting
   *          anchor
   * @return The formatted message
   */
  final public static FormattingTuple format(final String messagePattern,
      Object arg1, Object arg2) {
    return arrayFormat(messagePattern, new Object[] { arg1, arg2 });
  }

  static final Throwable getThrowableCandidate(Object[] argArray) {
    if (argArray == null || argArray.length == 0) {
      return null;
    }

    final Object lastEntry = argArray[argArray.length - 1];
    if (lastEntry instanceof Throwable) {
      return (Throwable) lastEntry;
    }
    return null;
  }

  /**
   * Same principle as the {@link #format(String, Object)} and
   * {@link #format(String, Object, Object)} methods except that any number of
   * arguments can be passed in an array.
   * 
   * @param messagePattern
   *          The message pattern which will be parsed and formatted
   * @param argArray
   *          An array of arguments to be substituted in place of formatting
   *          anchors
   * @return The formatted message
   */
  final public static FormattingTuple arrayFormat(final String messagePattern,
      final Object[] argArray) {

    Throwable throwableCandidate = getThrowableCandidate(argArray);

    if (messagePattern == null) {
      return new FormattingTuple(null, argArray, throwableCandidate);
    }

    if (argArray == null) {
      return new FormattingTuple(messagePattern);
    }

    int i = 0;
    int j;
    // use string builder for better multicore performance 
    StringBuilder sbuf = new StringBuilder(messagePattern.length() + 50);

    int L;
    for (L = 0; L < argArray.length; L++) {

      j = messagePattern.indexOf(DELIM_STR, i);

      if (j == -1) {
        // no more variables
        if (i == 0) { // this is a simple string
          return new FormattingTuple(messagePattern, argArray,
              throwableCandidate);
        } else { // add the tail string which contains no variables and return
          // the result.
          sbuf.append(messagePattern.substring(i, messagePattern.length()));
          return new FormattingTuple(sbuf.toString(), argArray,
              throwableCandidate);
        }
      } else {
        if (isEscapedDelimeter(messagePattern, j)) {
          if (!isDoubleEscaped(messagePattern, j)) {
            L--; // DELIM_START was escaped, thus should not be incremented
            sbuf.append(messagePattern.substring(i, j - 1));
            sbuf.append(DELIM_START);
            i = j + 1;
          } else {
            // The escape character preceding the delimiter start is
            // itself escaped: "abc x:\\{}"
            // we have to consume one backward slash
            sbuf.append(messagePattern.substring(i, j - 1));
            deeplyAppendParameter(sbuf, argArray[L], new HashMap<Object[], Object>());
            i = j + 2;
          }
        } else {
          // normal case
          sbuf.append(messagePattern.substring(i, j));
          deeplyAppendParameter(sbuf, argArray[L], new HashMap<Object[], Object>());
          i = j + 2;
        }
      }
    }
    // append the characters following the last {} pair.
    sbuf.append(messagePattern.substring(i, messagePattern.length()));
    if (L < argArray.length - 1) {
      return new FormattingTuple(sbuf.toString(), argArray, throwableCandidate);
    } else {
      return new FormattingTuple(sbuf.toString(), argArray, null);
    }
  }

  final static boolean isEscapedDelimeter(String messagePattern,
      int delimeterStartIndex) {

    if (delimeterStartIndex == 0) {
      return false;
    }
    char potentialEscape = messagePattern.charAt(delimeterStartIndex - 1);
    if (potentialEscape == ESCAPE_CHAR) {
      return true;
    } else {
      return false;
    }
  }

  final static boolean isDoubleEscaped(String messagePattern,
      int delimeterStartIndex) {
    if (delimeterStartIndex >= 2
        && messagePattern.charAt(delimeterStartIndex - 2) == ESCAPE_CHAR) {
      return true;
    } else {
      return false;
    }
  }

  // special treatment of array values was suggested by 'lizongbo'
  private static void deeplyAppendParameter(StringBuilder sbuf, Object o,
      Map<Object[], Object> seenMap) {
    if (o == null) {
      sbuf.append("null");
      return;
    }
    if (!o.getClass().isArray()) {
      safeObjectAppend(sbuf, o);
    } else {
      // check for primitive array types because they
      // unfortunately cannot be cast to Object[]
      if (o instanceof boolean[]) {
        booleanArrayAppend(sbuf, (boolean[]) o);
      } else if (o instanceof byte[]) {
        byteArrayAppend(sbuf, (byte[]) o);
      } else if (o instanceof char[]) {
        charArrayAppend(sbuf, (char[]) o);
      } else if (o instanceof short[]) {
        shortArrayAppend(sbuf, (short[]) o);
      } else if (o instanceof int[]) {
        intArrayAppend(sbuf, (int[]) o);
      } else if (o instanceof long[]) {
        longArrayAppend(sbuf, (long[]) o);
      } else if (o instanceof float[]) {
        floatArrayAppend(sbuf, (float[]) o);
      } else if (o instanceof double[]) {
        doubleArrayAppend(sbuf, (double[]) o);
      } else {
        objectArrayAppend(sbuf, (Object[]) o, seenMap);
      }
    }
  }

  private static void safeObjectAppend(StringBuilder sbuf, Object o) {
    try {
      String oAsString = o.toString();
      sbuf.append(oAsString);
    } catch (Throwable t) {
      System.err
          .println("SLF4J: Failed toString() invocation on an object of type ["
              + o.getClass().getName() + "]");
      t.printStackTrace();
      sbuf.append("[FAILED toString()]");
    }

  }

  private static void objectArrayAppend(StringBuilder sbuf, Object[] a,
      Map<Object[], Object> seenMap) {
    sbuf.append('[');
    if (!seenMap.containsKey(a)) {
      seenMap.put(a, null);
      final int len = a.length;
      for (int i = 0; i < len; i++) {
        deeplyAppendParameter(sbuf, a[i], seenMap);
        if (i != len - 1)
          sbuf.append(", ");
      }
      // allow repeats in siblings
      seenMap.remove(a);
    } else {
      sbuf.append("...");
    }
    sbuf.append(']');
  }

  private static void booleanArrayAppend(StringBuilder sbuf, boolean[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void byteArrayAppend(StringBuilder sbuf, byte[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void charArrayAppend(StringBuilder sbuf, char[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void shortArrayAppend(StringBuilder sbuf, short[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void intArrayAppend(StringBuilder sbuf, int[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void longArrayAppend(StringBuilder sbuf, long[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void floatArrayAppend(StringBuilder sbuf, float[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }

  private static void doubleArrayAppend(StringBuilder sbuf, double[] a) {
    sbuf.append('[');
    final int len = a.length;
    for (int i = 0; i < len; i++) {
      sbuf.append(a[i]);
      if (i != len - 1)
        sbuf.append(", ");
    }
    sbuf.append(']');
  }
}