org.apache.tools.ant.types.resources.ContentTransformingResource 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
*
* https://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.tools.ant.types.resources;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.types.ResourceCollection;
/**
* A resource that transforms the content of another resource.
*
* Wraps around another resource, delegates all queries (except
* getSize) to that other resource but transforms stream content
* on the fly.
*
* @since Ant 1.8
*/
public abstract class ContentTransformingResource extends ResourceDecorator {
private static final int BUFFER_SIZE = 8192;
/** no arg constructor */
protected ContentTransformingResource() {
}
/**
* Constructor with another resource to wrap.
* @param other the resource to wrap.
*/
protected ContentTransformingResource(final ResourceCollection other) {
super(other);
}
/**
* Get the size of this Resource.
* @return the size, as a long, 0 if the Resource does not exist (for
* compatibility with java.io.File), or UNKNOWN_SIZE if not known.
*/
@Override
public long getSize() {
if (isExists()) {
try (InputStream in = getInputStream()) {
final byte[] buf = new byte[BUFFER_SIZE];
int size = 0;
int readNow;
while ((readNow = in.read(buf, 0, buf.length)) > 0) {
size += readNow;
}
return size;
} catch (final IOException ex) {
throw new BuildException(
"caught exception while reading " + getName(), ex);
}
}
return 0;
}
/**
* Get an InputStream for the Resource.
* @return an InputStream containing this Resource's content.
* @throws IOException if unable to provide the content of this
* Resource as a stream.
* @throws UnsupportedOperationException if InputStreams are not
* supported for this Resource type.
*/
@Override
public InputStream getInputStream() throws IOException {
InputStream in = getResource().getInputStream();
if (in != null) {
in = wrapStream(in);
}
return in;
}
/**
* Get an OutputStream for the Resource.
* @return an OutputStream to which content can be written.
* @throws IOException if unable to provide the content of this
* Resource as a stream.
* @throws UnsupportedOperationException if OutputStreams are not
* supported for this Resource type.
*/
@Override
public OutputStream getOutputStream() throws IOException {
OutputStream out = getResource().getOutputStream();
if (out != null) {
out = wrapStream(out);
}
return out;
}
/**
* Suppress FileProvider, re-implement Appendable
*/
@Override
public T as(final Class clazz) {
if (Appendable.class.isAssignableFrom(clazz)) {
if (isAppendSupported()) {
final Appendable a = getResource().as(Appendable.class);
if (a != null) {
return clazz.cast((Appendable) () -> {
OutputStream out = a.getAppendOutputStream();
return out == null ? null : wrapStream(out);
});
}
}
return null;
}
return FileProvider.class.isAssignableFrom(clazz)
? null : getResource().as(clazz);
}
/**
* Learn whether the transformation performed allows appends.
*
* In general compressed outputs will become invalid if they
* are appended to, for example.
*
* This implementations returns false.
*
* @return boolean false
*/
protected boolean isAppendSupported() {
return false;
}
/**
* Get a content-filtering/transforming InputStream.
*
* @param in InputStream to wrap, will never be null.
* @return a compressed InputStream.
* @throws IOException if there is a problem.
*/
protected abstract InputStream wrapStream(InputStream in)
throws IOException;
/**
* Get a content-filtering/transforming OutputStream.
*
* @param out OutputStream to wrap, will never be null.
* @return a compressed OutputStream.
* @throws IOException if there is a problem.
*/
protected abstract OutputStream wrapStream(OutputStream out)
throws IOException;
}