java.util.logging.Formatter Maven / Gradle / Ivy

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.
 */

package java.util.logging;

import java.text.MessageFormat;
import java.util.ResourceBundle;

/**
 * {@code Formatter} objects are used to format {@link LogRecord} objects into a
 * string representation. Head and tail strings are sometimes used to wrap a set
 * of records. The {@code getHead} and {@code getTail} methods are used for this
 * purpose.
 */
public abstract class Formatter {

    /**
     * Constructs a {@code Formatter} object.
     */
    protected Formatter() {
    }

    /**
     * Converts a {@link LogRecord} object into a string representation. The
     * resulted string is usually localized and includes the message field of
     * the record.
     *
     * @param r
     *            the log record to be formatted into a string.
     * @return the formatted string.
     */
    public abstract String format(LogRecord r);

    /**
     * Formats a {@code LogRecord} object into a localized string
     * representation. This is a convenience method for subclasses of {@code
     * Formatter}.
     * 
     * The message string is firstly localized using the {@code ResourceBundle}
     * object associated with the supplied {@code LogRecord}.
     * 
     * Notice : if message contains "{0", then java.text.MessageFormat is used.
     * Otherwise no formatting is performed.
     *
     * @param r
     *            the log record to be formatted.
     * @return the string resulted from the formatting.
     */
    public String formatMessage(LogRecord r) {
        String pattern = r.getMessage();
        ResourceBundle rb = null;
        // try to localize the message string first
        if ((rb = r.getResourceBundle()) != null) {
            try {
                pattern = rb.getString(pattern);
            } catch (Exception e) {
                pattern = r.getMessage();
            }
        }
        if (pattern != null) {
            Object[] params = r.getParameters();
            /*
             * if the message contains "{0", use java.text.MessageFormat to
             * format the string
             */
            if (pattern.indexOf("{0") >= 0 && params != null && params.length > 0) {
                try {
                    pattern = MessageFormat.format(pattern, params);
                } catch (IllegalArgumentException e) {
                    pattern = r.getMessage();
                }
            }
        }
        return pattern;
    }

    /**
     * Gets the head string used to wrap a set of log records. This base class
     * always returns an empty string.
     *
     * @param h
     *            the target handler.
     * @return the head string used to wrap a set of log records, empty in this
     *         implementation.
     */
    public String getHead(Handler h) {
        return "";
    }

    /**
     * Gets the tail string used to wrap a set of log records. This base class
     * always returns the empty string.
     *
     * @param h
     *            the target handler.
     * @return the tail string used to wrap a set of log records, empty in this
     *         implementation.
     */
    public String getTail(Handler h) {
        return "";
    }
}