FileItem.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.t2framework.confeito.apache.commons.fileupload;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;

/**
 * <p>
 * This class represents a file or form item that was received within a
 * <code>multipart/form-data</code> POST request.
 * 
 * <p>
 * After retrieving an instance of this class from a
 * {@link org.t2framework.confeito.apache.commons.fileupload.FileUpload
 * FileUpload} instance (see
 * {@link org.t2framework.confeito.apache.commons.fileupload.FileUpload #parseRequest(javax.servlet.http.HttpServletRequest)}
 * ), you may either request all contents of the file at once using
 * {@link #get()} or request an {@link java.io.InputStream InputStream} with
 * {@link #getInputStream()} and process the file without attempting to load it
 * into memory, which may come handy with large files.
 * 
 * <p>
 * While this interface does not extend <code>javax.activation.DataSource</code>
 * per se (to avoid a seldom used dependency), several of the defined methods
 * are specifically defined with the same signatures as methods in that
 * interface. This allows an implementation of this interface to also implement
 * <code>javax.activation.DataSource</code> with minimal additional work.
 * 
 * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
 * @author <a href="mailto:sean@informage.net">Sean Legassick</a>
 * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
 * @author <a href="mailto:martinc@apache.org">Martin Cooper</a>
 * 
 * @version $Id: FileItem.java 578253 2007-09-21 20:13:14Z jochen $
 */
public interface FileItem extends Serializable {

	// ------------------------------- Methods from javax.activation.DataSource

	/**
	 * Returns an {@link java.io.InputStream InputStream} that can be used to
	 * retrieve the contents of the file.
	 * 
	 * @return An {@link java.io.InputStream InputStream} that can be used to
	 *         retrieve the contents of the file.
	 * 
	 * @throws IOException
	 *             if an error occurs.
	 */
	InputStream getInputStream() throws IOException;

	/**
	 * Returns the content type passed by the browser or <code>null</code> if
	 * not defined.
	 * 
	 * @return The content type passed by the browser or <code>null</code> if
	 *         not defined.
	 */
	String getContentType();

	/**
	 * Returns the original filename in the client's filesystem, 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 filename in the client's filesystem.
	 */
	String getName();

	// ------------------------------------------------------- FileItem methods

	/**
	 * Provides a hint as to whether or not the file contents will be read from
	 * memory.
	 * 
	 * @return <code>true</code> if the file contents will be read from memory;
	 *         <code>false</code> otherwise.
	 */
	boolean isInMemory();

	/**
	 * Returns the size of the file item.
	 * 
	 * @return The size of the file item, in bytes.
	 */
	long getSize();

	/**
	 * Returns the contents of the file item as an array of bytes.
	 * 
	 * @return The contents of the file item as an array of bytes.
	 */
	byte[] get();

	/**
	 * Returns the contents of the file item as a String, using the specified
	 * encoding. This method uses {@link #get()} to retrieve the contents of the
	 * item.
	 * 
	 * @param encoding
	 *            The character encoding to use.
	 * 
	 * @return The contents of the item, as a string.
	 * 
	 * @throws UnsupportedEncodingException
	 *             if the requested character encoding is not available.
	 */
	String getString(String encoding) throws UnsupportedEncodingException;

	/**
	 * Returns the contents of the file item as a String, using the default
	 * character encoding. This method uses {@link #get()} to retrieve the
	 * contents of the item.
	 * 
	 * @return The contents of the item, as a string.
	 */
	String getString();

	/**
	 * A convenience method to write an uploaded item to disk. The client code
	 * is not concerned with whether or not the item is stored in memory, or on
	 * disk in a temporary location. They just want to write the uploaded item
	 * to a file.
	 * <p>
	 * This method is not guaranteed to succeed if called more than once for the
	 * same item. This allows a particular implementation to use, for example,
	 * file renaming, where possible, rather than copying all of the underlying
	 * data, thus gaining a significant performance benefit.
	 * 
	 * @param file
	 *            The <code>File</code> into which the uploaded item should be
	 *            stored.
	 * 
	 * @throws Exception
	 *             if an error occurs.
	 */
	void write(File file) throws Exception;

	/**
	 * Deletes the underlying storage for a file item, including deleting any
	 * associated temporary disk file. Although this storage will be deleted
	 * automatically when the <code>FileItem</code> instance is garbage
	 * collected, this method can be used to ensure that this is done at an
	 * earlier time, thus preserving system resources.
	 */
	void delete();

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

	/**
	 * Sets the field name used to reference this file item.
	 * 
	 * @param name
	 *            The name of the form field.
	 */
	void setFieldName(String name);

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

	/**
	 * Specifies whether or not a <code>FileItem</code> instance represents a
	 * simple form field.
	 * 
	 * @param state
	 *            <code>true</code> if the instance represents a simple form
	 *            field; <code>false</code> if it represents an uploaded file.
	 */
	void setFormField(boolean state);

	/**
	 * Returns an {@link java.io.OutputStream OutputStream} that can be used for
	 * storing the contents of the file.
	 * 
	 * @return An {@link java.io.OutputStream OutputStream} that can be used for
	 *         storing the contensts of the file.
	 * 
	 * @throws IOException
	 *             if an error occurs.
	 */
	OutputStream getOutputStream() throws IOException;

}