org.apache.axiom.util.activation.DataSourceUtils 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 org.apache.axiom.util.activation;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import org.apache.axiom.ext.activation.SizeAwareDataSource;
/**
* Contains utility methods to work with {@link DataSource} objects.
*/
public class DataSourceUtils {
private static final Class byteArrayDataSourceClass;
static {
Class clazz;
try {
clazz = Class.forName("javax.mail.util.ByteArrayDataSource");
} catch (ClassNotFoundException e) {
clazz = null;
}
byteArrayDataSourceClass = clazz;
}
/**
* Determine the size of the data represented by a {@link DataSource} object.
* The method will try to determine the size without reading the data source.
* It will do so by looking for the {@link SizeAwareDataSource} interface. In addition, it
* supports some other well known data source implementations for which it is possible to
* get the size of the data without reading it.
*
* As noted in the documentation of the {@link SizeAwareDataSource}, the returned value
* may be an estimation that is not 100% accurate, and code using this method must be prepared
* to receive more or less data from the data source.
*
* @param ds the data source
* @return (an estimation of) the size of the data or -1 if the size is unknown
*/
public static long getSize(DataSource ds) {
if (ds instanceof SizeAwareDataSource) {
return ((SizeAwareDataSource)ds).getSize();
} else if (byteArrayDataSourceClass != null && byteArrayDataSourceClass.isInstance(ds)) {
// Special optimization for JavaMail's ByteArrayDataSource (Axiom's ByteArrayDataSource
// already implements SizeAwareDataSource and doesn't need further optimization):
// we know that ByteArrayInputStream#available() directly returns the size of the
// data source.
try {
return ((ByteArrayInputStream)ds.getInputStream()).available();
} catch (IOException ex) {
// We will never get here...
return -1;
}
} else if (ds instanceof FileDataSource) {
// Special optimization for FileDataSources: no need to open and read the file
// to know its size!
return ((FileDataSource)ds).getFile().length();
} else {
return -1;
}
}
}