001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.hadoop.fs;
019
020 import java.io.FileNotFoundException;
021 import java.io.IOException;
022 import java.util.EnumSet;
023
024 import org.apache.hadoop.HadoopIllegalArgumentException;
025 import org.apache.hadoop.classification.InterfaceAudience;
026 import org.apache.hadoop.classification.InterfaceStability;
027
028 /****************************************************************
029 * CreateFlag specifies the file create semantic. Users can combine flags like: <br>
030 * <code>
031 * EnumSet.of(CreateFlag.CREATE, CreateFlag.APPEND)
032 * <code>
033 * <p>
034 *
035 * Use the CreateFlag as follows:
036 * <ol>
037 * <li> CREATE - to create a file if it does not exist,
038 * else throw FileAlreadyExists.</li>
039 * <li> APPEND - to append to a file if it exists,
040 * else throw FileNotFoundException.</li>
041 * <li> OVERWRITE - to truncate a file if it exists,
042 * else throw FileNotFoundException.</li>
043 * <li> CREATE|APPEND - to create a file if it does not exist,
044 * else append to an existing file.</li>
045 * <li> CREATE|OVERWRITE - to create a file if it does not exist,
046 * else overwrite an existing file.</li>
047 * </ol>
048 *
049 * Following combination is not valid and will result in
050 * {@link HadoopIllegalArgumentException}:
051 * <ol>
052 * <li> APPEND|OVERWRITE</li>
053 * <li> CREATE|APPEND|OVERWRITE</li>
054 * </ol>
055 *****************************************************************/
056 @InterfaceAudience.Public
057 @InterfaceStability.Evolving
058 public enum CreateFlag {
059
060 /**
061 * Create a file. See javadoc for more description
062 * already exists
063 */
064 CREATE((short) 0x01),
065
066 /**
067 * Truncate/overwrite a file. Same as POSIX O_TRUNC. See javadoc for description.
068 */
069 OVERWRITE((short) 0x02),
070
071 /**
072 * Append to a file. See javadoc for more description.
073 */
074 APPEND((short) 0x04);
075
076 private final short mode;
077
078 private CreateFlag(short mode) {
079 this.mode = mode;
080 }
081
082 short getMode() {
083 return mode;
084 }
085
086 /**
087 * Validate the CreateFlag and throw exception if it is invalid
088 * @param flag set of CreateFlag
089 * @throws HadoopIllegalArgumentException if the CreateFlag is invalid
090 */
091 public static void validate(EnumSet<CreateFlag> flag) {
092 if (flag == null || flag.isEmpty()) {
093 throw new HadoopIllegalArgumentException(flag
094 + " does not specify any options");
095 }
096 final boolean append = flag.contains(APPEND);
097 final boolean overwrite = flag.contains(OVERWRITE);
098
099 // Both append and overwrite is an error
100 if (append && overwrite) {
101 throw new HadoopIllegalArgumentException(
102 flag + "Both append and overwrite options cannot be enabled.");
103 }
104 }
105
106 /**
107 * Validate the CreateFlag for create operation
108 * @param path Object representing the path; usually String or {@link Path}
109 * @param pathExists pass true if the path exists in the file system
110 * @param flag set of CreateFlag
111 * @throws IOException on error
112 * @throws HadoopIllegalArgumentException if the CreateFlag is invalid
113 */
114 public static void validate(Object path, boolean pathExists,
115 EnumSet<CreateFlag> flag) throws IOException {
116 validate(flag);
117 final boolean append = flag.contains(APPEND);
118 final boolean overwrite = flag.contains(OVERWRITE);
119 if (pathExists) {
120 if (!(append || overwrite)) {
121 throw new FileAlreadyExistsException("File already exists: "
122 + path.toString()
123 + ". Append or overwrite option must be specified in " + flag);
124 }
125 } else if (!flag.contains(CREATE)) {
126 throw new FileNotFoundException("Non existing file: " + path.toString()
127 + ". Create option is not specified in " + flag);
128 }
129 }
130 }