001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel;
018
019
020/**
021 * A pluggable strategy to be able to convert objects <a
022 * href="http://camel.apache.org/type-converter.html">to different
023 * types</a> such as to and from String, InputStream/OutputStream,
024 * Reader/Writer, Document, byte[], ByteBuffer etc
025 */
026public interface TypeConverter {
027
028    Object MISS_VALUE = Void.TYPE;
029
030    /**
031     * Whether the type converter allows returning null as a valid response.
032     * <p/>
033     * By default <tt>null</tt> is not a valid response, returning <tt>false</tt> from this method.
034     */
035    boolean allowNull();
036
037    /**
038     * Converts the value to the specified type
039     *
040     * @param type the requested type
041     * @param value the value to be converted
042     * @return the converted value, or <tt>null</tt> if not possible to convert
043     * @throws TypeConversionException is thrown if error during type conversion
044     */
045    <T> T convertTo(Class<T> type, Object value) throws TypeConversionException;
046
047    /**
048     * Converts the value to the specified type in the context of an exchange
049     * <p/>
050     * Used when conversion requires extra information from the current
051     * exchange (such as encoding).
052     *
053     * @param type the requested type
054     * @param exchange the current exchange
055     * @param value the value to be converted
056     * @return the converted value, or <tt>null</tt> if not possible to convert
057     * @throws TypeConversionException is thrown if error during type conversion
058     */
059    <T> T convertTo(Class<T> type, Exchange exchange, Object value) throws TypeConversionException;
060
061    /**
062     * Converts the value to the specified type
063     *
064     * @param type the requested type
065     * @param value the value to be converted
066     * @return the converted value, is never <tt>null</tt>
067     * @throws TypeConversionException is thrown if error during type conversion
068     * @throws NoTypeConversionAvailableException if no type converters exists to convert to the given type
069     */
070    <T> T mandatoryConvertTo(Class<T> type, Object value) throws TypeConversionException, NoTypeConversionAvailableException;
071
072    /**
073     * Converts the value to the specified type in the context of an exchange
074     * <p/>
075     * Used when conversion requires extra information from the current
076     * exchange (such as encoding).
077     *
078     * @param type the requested type
079     * @param exchange the current exchange
080     * @param value the value to be converted
081     * @return the converted value, is never <tt>null</tt>
082     * @throws TypeConversionException is thrown if error during type conversion
083     * @throws NoTypeConversionAvailableException if no type converters exists to convert to the given type
084     */
085    <T> T mandatoryConvertTo(Class<T> type, Exchange exchange, Object value) throws TypeConversionException, NoTypeConversionAvailableException;
086
087    /**
088     * Tries to convert the value to the specified type,
089     * returning <tt>null</tt> if not possible to convert.
090     * <p/>
091     * This method will <b>not</b> throw an exception if an exception occurred during conversion.
092     *
093     * @param type the requested type
094     * @param value the value to be converted
095     * @return the converted value, or <tt>null</tt> if not possible to convert
096     */
097    <T> T tryConvertTo(Class<T> type, Object value);
098
099    /**
100     * Tries to convert the value to the specified type in the context of an exchange,
101     * returning <tt>null</tt> if not possible to convert.
102     * <p/>
103     * This method will <b>not</b> throw an exception if an exception occurred during conversion.
104     * Converts the value to the specified type in the context of an exchange
105     * <p/>
106     * Used when conversion requires extra information from the current
107     * exchange (such as encoding).
108     *
109     * @param type the requested type
110     * @param exchange the current exchange
111     * @param value the value to be converted
112     * @return the converted value, or <tt>null</tt> if not possible to convert
113     */
114    <T> T tryConvertTo(Class<T> type, Exchange exchange, Object value);
115
116}