http://netty.io/netty-all/: Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients. (The Netty Project) 
/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project 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.
 */

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.

/**
 * 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 io.netty.util.internal.logging;

import java.text.MessageFormat;
import java.util.HashSet;
import java.util.Set;

// 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.




For example,



MessageFormatter.format("Hi {}.", "there")




will return the string "Hi there.".


The {} pair is called the formatting anchor. It serves to designate
the location where arguments need to be substituted within the message
pattern.


In case your message contains the '{' or the '}' character, you do not have
to do anything special unless the '}' character immediately follows '{'. For
example,



MessageFormatter.format("Set {1,2,3} is not equal to {}.", "1,2");




will return the string "Set {1,2,3} is not equal to 1,2.".




If for whatever reason you need to place the string "{}" in the message
without its formatting anchor 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,



MessageFormatter.format("Set \\{} is not equal to {}.", "1,2");




will return the string "Set {} is not equal to 1,2.".




The escaping behavior just described can be overridden by escaping the escape
character '\'. Calling



MessageFormatter.format("File name is C:\\\\{}.", "file.zip");




will return the string "File name is C:\file.zip".



 The formatting conventions are different than those of MessageFormat which ships with the Java platform. This is justified by the fact that SLF4J's implementation is 10 times faster than that of MessageFormat. This local performance difference is both measurable and significant in the larger context of the complete logging processing chain. 


 See also format(String, Object), format(String, Object, Object) and arrayFormat(String, Object[]) methods for more details. 
/**
 * Formats messages according to very simple substitution rules. Substitutions
 * can be made 1, 2 or more arguments.
 * <p/>
 * <p/>
 * For example,
 * <p/>
 * <pre>
 * MessageFormatter.format(&quot;Hi {}.&quot;, &quot;there&quot;)
 * </pre>
 * <p/>
 * 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,
 * <p/>
 * <pre>
 * MessageFormatter.format(&quot;Set {1,2,3} is not equal to {}.&quot;, &quot;1,2&quot;);
 * </pre>
 * <p/>
 * will return the string "Set {1,2,3} is not equal to 1,2.".
 * <p/>
 * <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,
 * <p/>
 * <pre>
 * MessageFormatter.format(&quot;Set \\{} is not equal to {}.&quot;, &quot;1,2&quot;);
 * </pre>
 * <p/>
 * will return the string "Set {} is not equal to 1,2.".
 * <p/>
 * <p/>
 * The escaping behavior just described can be overridden by escaping the escape
 * character '\'. Calling
 * <p/>
 * <pre>
 * MessageFormatter.format(&quot;File name is C:\\\\{}.&quot;, &quot;file.zip&quot;);
 * </pre>
 * <p/>
 * will return the string "File name is C:\file.zip".
 * <p/>
 * <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/>
 * <p/>
 * See also {@link #format(String, Object)},
 * {@link #format(String, Object, Object)} and
 * {@link #arrayFormat(String, Object[])} methods for more details.
 */
final class MessageFormatter {
    private static final String DELIM_STR = "{}";
    private static final char ESCAPE_CHAR = '\\';

    
Performs single argument substitution for the 'messagePattern' passed as
parameter.


For example,



MessageFormatter.format("Hi {}.", "there");




will return the string "Hi there.".



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

    
Performs a two argument substitution for the 'messagePattern' passed as
parameter.


For example,



MessageFormatter.format("Hi {}. My name is {}.", "Alice", "Bob");




will return the string "Hi Alice. My name is Bob.".

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

    
Same principle as the format(String, Object) and format(String, Object, Object) methods except that any number of arguments can be passed in an array. 
Params:
  • messagePattern – The message pattern which will be parsed and formatted
  • argArray –       An array of arguments to be substituted in place of formatting
                      anchors
Returns:The formatted message
/**
     * 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
     */
    static FormattingTuple arrayFormat(final String messagePattern,
                                       final Object[] argArray) {
        if (argArray == null || argArray.length == 0) {
            return new FormattingTuple(messagePattern, null);
        }

        int lastArrIdx = argArray.length - 1;
        Object lastEntry = argArray[lastArrIdx];
        Throwable throwable = lastEntry instanceof Throwable? (Throwable) lastEntry : null;

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

        int j = messagePattern.indexOf(DELIM_STR);
        if (j == -1) {
            // this is a simple string
            return new FormattingTuple(messagePattern, throwable);
        }

        StringBuilder sbuf = new StringBuilder(messagePattern.length() + 50);
        int i = 0;
        int L = 0;
        do {
            boolean notEscaped = j == 0 || messagePattern.charAt(j - 1) != ESCAPE_CHAR;
            if (notEscaped) {
                // normal case
                sbuf.append(messagePattern, i, j);
            } else {
                sbuf.append(messagePattern, i, j - 1);
                // check that escape char is not is escaped: "abc x:\\{}"
                notEscaped = j >= 2 && messagePattern.charAt(j - 2) == ESCAPE_CHAR;
            }

            i = j + 2;
            if (notEscaped) {
                deeplyAppendParameter(sbuf, argArray[L], null);
                L++;
                if (L > lastArrIdx) {
                    break;
                }
            } else {
                sbuf.append(DELIM_STR);
            }
            j = messagePattern.indexOf(DELIM_STR, i);
        } while (j != -1);

        // append the characters following the last {} pair.
        sbuf.append(messagePattern, i, messagePattern.length());
        return new FormattingTuple(sbuf.toString(), L <= lastArrIdx? throwable : null);
    }

    // special treatment of array values was suggested by 'lizongbo'
    private static void deeplyAppendParameter(StringBuilder sbuf, Object o,
                                              Set<Object[]> seenSet) {
        if (o == null) {
            sbuf.append("null");
            return;
        }
        Class<?> objClass = o.getClass();
        if (!objClass.isArray()) {
            if (Number.class.isAssignableFrom(objClass)) {
                // Prevent String instantiation for some number types
                if (objClass == Long.class) {
                    sbuf.append(((Long) o).longValue());
                } else if (objClass == Integer.class || objClass == Short.class || objClass == Byte.class) {
                    sbuf.append(((Number) o).intValue());
                } else if (objClass == Double.class) {
                    sbuf.append(((Double) o).doubleValue());
                } else if (objClass == Float.class) {
                    sbuf.append(((Float) o).floatValue());
                } else {
                    safeObjectAppend(sbuf, o);
                }
            } else {
                safeObjectAppend(sbuf, o);
            }
        } else {
            // check for primitive array types because they
            // unfortunately cannot be cast to Object[]
            sbuf.append('[');
            if (objClass == boolean[].class) {
                booleanArrayAppend(sbuf, (boolean[]) o);
            } else if (objClass == byte[].class) {
                byteArrayAppend(sbuf, (byte[]) o);
            } else if (objClass == char[].class) {
                charArrayAppend(sbuf, (char[]) o);
            } else if (objClass == short[].class) {
                shortArrayAppend(sbuf, (short[]) o);
            } else if (objClass == int[].class) {
                intArrayAppend(sbuf, (int[]) o);
            } else if (objClass == long[].class) {
                longArrayAppend(sbuf, (long[]) o);
            } else if (objClass == float[].class) {
                floatArrayAppend(sbuf, (float[]) o);
            } else if (objClass == double[].class) {
                doubleArrayAppend(sbuf, (double[]) o);
            } else {
                objectArrayAppend(sbuf, (Object[]) o, seenSet);
            }
            sbuf.append(']');
        }
    }

    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, Set<Object[]> seenSet) {
        if (a.length == 0) {
            return;
        }
        if (seenSet == null) {
            seenSet = new HashSet<Object[]>(a.length);
        }
        if (seenSet.add(a)) {
            deeplyAppendParameter(sbuf, a[0], seenSet);
            for (int i = 1; i < a.length; i++) {
                sbuf.append(", ");
                deeplyAppendParameter(sbuf, a[i], seenSet);
            }
            // allow repeats in siblings
            seenSet.remove(a);
        } else {
            sbuf.append("...");
        }
    }

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

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

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

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

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

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

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

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

    private MessageFormatter() {
    }
}