com.wl4g.component.common.resource.StreamResource Maven / Gradle / Ivy
/*
* Copyright 2017 ~ 2025 the original author or authors.
*
* Licensed 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 com.wl4g.component.common.resource;
/**
* Retention of upstream license agreement statement:
* Thank you very much spring framework, We fully comply with and support the open license
* agreement of spring. The purpose of migration is to solve the problem
* that these elegant API programs can still be easily used without running
* in the spring environment.
*
* Copyright 2002-2017 the original author or authors.
*
* Licensed 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.
*/
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URL;
/**
* Interface for a resource descriptor that abstracts from the actual type of
* underlying resource, such as a file or class path resource.
*
*
* An InputStream can be opened for every resource if it exists in physical
* form, but a URL or File handle can just be returned for certain resources.
* The actual behavior is implementation-specific.
*
* @author Juergen Hoeller
* @since 28.12.2003
* @see #getInputStream()
* @see #getURL()
* @see #getURI()
* @see #getFile()
* @see WritableStreamResource
* @see ContextResource
* @see UrlStreamResource
* @see ClassPathStreamResource
* @see FileStreamResource
* @see PathResource
* @see ByteArrayResource
* @see StreamResource
*/
public interface StreamResource {
/**
* Return an {@link InputStream} for the content of an underlying resource.
*
* It is expected that each call creates a fresh stream.
*
* This requirement is particularly important when you consider an API such
* as JavaMail, which needs to be able to read the stream multiple times
* when creating mail attachments. For such a use case, it is
* required that each {@code getInputStream()} call returns a fresh
* stream.
*
* @return the input stream for the underlying resource (must not be
* {@code null})
* @throws java.io.FileNotFoundException
* if the underlying resource doesn't exist
* @throws IOException
* if the content stream could not be opened
*/
InputStream getInputStream() throws IOException;
/**
* Determine whether this resource actually exists in physical form.
*
* This method performs a definitive existence check, whereas the existence
* of a {@code Resource} handle only guarantees a valid descriptor handle.
*/
boolean exists();
/**
* Indicate whether the contents of this resource can be read via
* {@link #getInputStream()}.
*
* Will be {@code true} for typical resource descriptors; note that actual
* content reading may still fail when attempted. However, a value of
* {@code false} is a definitive indication that the resource content cannot
* be read.
*
* @see #getInputStream()
*/
boolean isReadable();
/**
* Indicate whether this resource represents a handle with an open stream.
* If {@code true}, the InputStream cannot be read multiple times, and must
* be read and closed to avoid resource leaks.
*
* Will be {@code false} for typical resource descriptors.
*/
boolean isOpen();
/**
* Return a URL handle for this resource.
*
* @throws IOException
* if the resource cannot be resolved as URL, i.e. if the
* resource is not available as descriptor
*/
URL getURL() throws IOException;
/**
* Return a URI handle for this resource.
*
* @throws IOException
* if the resource cannot be resolved as URI, i.e. if the
* resource is not available as descriptor
* @since 2.5
*/
URI getURI() throws IOException;
/**
* Return a File handle for this resource.
*
* @throws java.io.FileNotFoundException
* if the resource cannot be resolved as absolute file path,
* i.e. if the resource is not available in a file system
* @throws IOException
* in case of general resolution/reading failures
* @see #getInputStream()
*/
File getFile() throws IOException;
/**
* Determine the content length for this resource.
*
* @throws IOException
* if the resource cannot be resolved (in the file system or as
* some other known physical resource type)
*/
long contentLength() throws IOException;
/**
* Determine the last-modified timestamp for this resource.
*
* @throws IOException
* if the resource cannot be resolved (in the file system or as
* some other known physical resource type)
*/
long lastModified() throws IOException;
/**
* Create a resource relative to this resource.
*
* @param relativePath
* the relative path (relative to this resource)
* @return the resource handle for the relative resource
* @throws IOException
* if the relative resource cannot be determined
*/
StreamResource createRelative(String relativePath) throws IOException;
/**
* Determine a filename for this resource, i.e. typically the last part of
* the path: for example, "myfile.txt".
*
* Returns {@code null} if this type of resource does not have a filename.
*/
String getFilename();
/**
* Return a description for this resource, to be used for error output when
* working with the resource.
*
* Implementations are also encouraged to return this value from their
* {@code toString} method.
*
* @see Object#toString()
*/
String getDescription();
}