com.jn.langx.io.resource

接口 Resource<E>

类型参数:

E -

所有已知子接口:

WritableResource

所有已知实现类:

AbstractLocatableResource, AbstractResource, ByteArrayResource, ClassFile, ClassPathResource, FileResource, InputStreamResource, ResourceClassFile, UrlResource

public interface Resource<E>

任何的可以 用 input stream 去读的都可以被称为资源。例如： 1. 一个普通文件 2. 一个.class 3. 一个 byte[] 4. 一个 字符串 5. 一个 URL 6. 一个 InputStream Resource只是一个资源的描述，它不代表该资源真实存在，如果不存在 getInputStream()返回为 null

方法概要

限定符和类型	方法和说明
long	contentLength() Determine the content length for this resource.
boolean	exists() Determine whether this resource actually exists in physical form.
InputStream	getInputStream() Return an InputStream for the content of an underlying resource.
E	getRealResource()
boolean	isReadable() Indicate whether non-empty contents of this resource can be read via getInputStream().
ReadableByteChannel	readableChannel() Return a ReadableByteChannel.

方法详细资料

getRealResource

E getRealResource()

getInputStream

InputStream getInputStream()
                    throws IOException

Return an 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 getInputStream() call returns a fresh stream.

返回:

the input stream for the underlying resource (must not be null)

抛出:

FileNotFoundException - if the underlying resource doesn't exist

IOException - if the content stream could not be opened

exists

boolean exists()

Determine whether this resource actually exists in physical form.

This method performs a definitive existence check, whereas the existence of a Resource handle only guarantees a valid descriptor handle.

isReadable

boolean isReadable()

Indicate whether non-empty contents of this resource can be read via getInputStream().

Will be true for typical resource descriptors that exist since it strictly implies exists() semantics as of 5.1. Note that actual content reading may still fail when attempted. However, a value of false is a definitive indication that the resource content cannot be read.

另请参阅:

getInputStream(), exists()

readableChannel

ReadableByteChannel readableChannel()
                             throws IOException

Return a ReadableByteChannel.

It is expected that each call creates a fresh channel.

The default implementation returns Channels.newChannel(InputStream) with the result of getInputStream().

返回:

the byte channel for the underlying resource (must not be null)

抛出:

FileNotFoundException - if the underlying resource doesn't exist

IOException - if the content channel could not be opened

另请参阅:

getInputStream()

contentLength

long contentLength()

Determine the content length for this resource.

抛出:

IOException - if the resource cannot be resolved (in the file system or as some other known physical resource type)