FileItemInput.java

/*
 * 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 org.apache.commons.fileupload2.core;

import java.io.IOException;
import java.io.InputStream;

/**
 * Provides access to a file or form item that was received within a {@code multipart/form-data} POST request.
 * <p>
 * The items contents are retrieved by calling {@link #getInputStream()}.
 * </p>
 * <p>
 * Instances of this class are created by accessing the iterator, returned by {@link AbstractFileUpload#getItemIterator(RequestContext)}.
 * </p>
 * <p>
 * <em>Note</em>: There is an interaction between the iterator and its associated instances of {@link FileItemInput}: By invoking
 * {@link java.util.Iterator#hasNext()} on the iterator, you discard all data, which hasn't been read so far from the previous data.
 * </p>
 */
public interface FileItemInput extends FileItemHeadersProvider<FileItemInput> {

    /**
     * This exception is thrown, if an attempt is made to read data from the {@link InputStream}, which has been returned by
     * {@link FileItemInput#getInputStream()}, after {@link java.util.Iterator#hasNext()} has been invoked on the iterator, which created the
     * {@link FileItemInput}.
     */
    class ItemSkippedException extends FileUploadException {

        /**
         * The exceptions serial version UID, which is being used when serializing an exception instance.
         */
        private static final long serialVersionUID = 2;

        /**
         * Constructs an instance with a given detail message.
         *
         * @param message The detail message (which is saved for later retrieval by the {@link #getMessage()} method)
         */
        ItemSkippedException(final String message) {
            super(message);
        }

    }

    /**
     * Gets the content type passed by the browser or {@code null} if not defined.
     *
     * @return The content type passed by the browser or {@code null} if not defined.
     */
    String getContentType();

    /**
     * Gets the name of the field in the multipart form corresponding to this file item.
     *
     * @return The name of the form field.
     */
    String getFieldName();

    /**
     * Opens an {@link InputStream}, which allows to read the items contents.
     *
     * @return The input stream, from which the items data may be read.
     * @throws IllegalStateException The method was already invoked on this item. It is not possible to recreate the data stream.
     * @throws IOException           An I/O error occurred.
     * @see ItemSkippedException
     */
    InputStream getInputStream() throws IOException;

    /**
     * Gets the original file name in the client's file system, as provided by the browser (or other client software). In most cases, this will be the base file
     * name, without path information. However, some clients, such as the Opera browser, do include path information.
     *
     * @return The original file name in the client's file system.
     */
    String getName();

    /**
     * Tests whether or not a {@code FileItem} instance represents a simple form field.
     *
     * @return {@code true} if the instance represents a simple form field; {@code false} if it represents an uploaded file.
     */
    boolean isFormField();

}