Java example source code file (MessageFormatter.java)

This example Java source code file (MessageFormatter.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

delim_start, delim_stop, delim_str, escape_char, failed, formattingtuple, hashmap, illegalstateexception, messageformatter, object, slf4j, string, stringbuilder, text, throwable, util

The MessageFormatter.java Java example source code

/**
 * 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("Hi {}.", "there")
 * </pre>
 *
 * will return the string "Hi there.".
 * <p>
 * The {} pair is called the <em>formatting anchor. 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("Set {1,2,3} is not equal to {}.", "1,2");
 * </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 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("Set \\{} is not equal to {}.", "1,2");
 * </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("File name is C:\\\\{}.", "file.zip");
 * </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 Gülcü
 * @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("Hi {}.", "there");
     * </pre>
     *
     * 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
     */
    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("Hi {}. My name is {}.", "Alice", "Bob");
     * </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;
    }

    final public static FormattingTuple arrayFormat(final String messagePattern, final Object[] argArray) {
        Throwable throwableCandidate = getThrowableCandidate(argArray);
        Object[] args = argArray;
        if (throwableCandidate != null) {
            args = trimmedCopy(argArray);
        }
        return arrayFormat(messagePattern, args, throwableCandidate);
    }

    private static Object[] trimmedCopy(Object[] argArray) {
        if (argArray == null || argArray.length == 0) {
            throw new IllegalStateException("non-sensical empty or null argument array");
        }
        final int trimemdLen = argArray.length - 1;
        Object[] trimmed = new Object[trimemdLen];
        System.arraycopy(argArray, 0, trimmed, 0, trimemdLen);
        return trimmed;
    }

    final public static FormattingTuple arrayFormat(final String messagePattern, final Object[] argArray, Throwable throwable) {

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

        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, throwable);
                } else { // add the tail string which contains no variables and return
                    // the result.
                    sbuf.append(messagePattern, i, messagePattern.length());
                    return new FormattingTuple(sbuf.toString(), argArray, throwable);
                }
            } else {
                if (isEscapedDelimeter(messagePattern, j)) {
                    if (!isDoubleEscaped(messagePattern, j)) {
                        L--; // DELIM_START was escaped, thus should not be incremented
                        sbuf.append(messagePattern, 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, i, j - 1);
                        deeplyAppendParameter(sbuf, argArray[L], new HashMap<Object[], Object>());
                        i = j + 2;
                    }
                } else {
                    // normal case
                    sbuf.append(messagePattern, i, j);
                    deeplyAppendParameter(sbuf, argArray[L], new HashMap<Object[], Object>());
                    i = j + 2;
                }
            }
        }
        // append the characters following the last {} pair.
        sbuf.append(messagePattern, i, messagePattern.length());
        return new FormattingTuple(sbuf.toString(), argArray, throwable);
    }

    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) {
            Util.report("SLF4J: Failed toString() invocation on an object of type [" + o.getClass().getName() + "]", t);
            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(']');
    }

}