Java I/O 扩展

Java I/O 扩展

NIO

NIO

输入

输出

内存映射文件

一切皆文件

Channel

Buffer

Channel

Channel

Channel

InputStream

OutputStream

map()

块

Buffer

Channel

Buffer

Buffer

Channel

Channel

Buffer

Channel

Buffer

Buffer

java.nio.ByteBuffer

Buffer

CharBuffer

ShortBuffer

ByteBuffer

ByteBuffer

// Allocates a new buffer.
static XxxBuffer allocate(int capacity);

ByteBuffer

MappedByteBuffer

Channel

MappedByteBuffer

Channel

map()

int capacity()

int  remaining()

int  limit()

int  position()

Buffer   position(int newPosition)

Buffer   reset()

Buffer   clear()

Buffer   flip()

封存

Buffer

put()

get()

相对

绝对

/**
* @author jifang
* @since 16/1/9下午8:31.
*/
public class BufferTest {

@Test
public void client() {
ByteBuffer buffer = ByteBuffer.allocate(64);
displayBufferInfo(buffer, "init");

buffer.put((byte) 'a');
buffer.put((byte) 'b');
buffer.put((byte) 'c');
displayBufferInfo(buffer, "after put");

buffer.flip();
displayBufferInfo(buffer, "after flip");
System.out.println((char) buffer.get());
displayBufferInfo(buffer, "after a get");

buffer.clear();
displayBufferInfo(buffer, "after clear");
// 依然可以访问到数据
System.out.println((char) buffer.get(2));
}

private void displayBufferInfo(Buffer buffer, String msg) {
System.out.println("---------" + msg + "-----------");
System.out.println("position: " + buffer.position());
System.out.println("limit: " + buffer.limit());
System.out.println("capacity: " + buffer.capacity());
}
}

allocate()

ByteBuffer

allocateDirect()

DirectByteBuffer

DirectByteBuffer

DirectByteBuffer

DirectByteBuffer

ByteBuffer

allocateDirect(int capacity)

ByteBuffer

DirectByteBuffer

Channel

Buffer

Buffer

Channel

Channel

java.nio.channels.Channel

Channel

Buffer

Channel

Buffer

FileChannel

DatagramChannel

Pipe.SinkChannel

Pipe.SourceChannel

SelectableChannel

SocketChannel

ServerSocketChannel

Channel

InputStream

OutputStream

getChannel()

Channel

Channel

FileInputStream

FileOutputStream

FileChannel

PipedInputStream

PipedOutputStream

Pipe.SourceChannel

Pipe.SinkChannel

Channel

MappedByteBuffer    map(FileChannel.MapMode mode, long position, long size)

read()

write()

map()

ByteBuffer

/**
* @author jifang
* @since 16/1/9下午10:55.
*/
public class ChannelTest {
private CharsetDecoder decoder = Charset.forName("utf-8").newDecoder();

@Test
public void client() throws IOException {
try (FileChannel inChannel = new FileInputStream("save.txt").getChannel();
FileChannel outChannel = new FileOutputStream("attach.txt").getChannel()) {
MappedByteBuffer buffer = inChannel.map(FileChannel.MapMode.READ_ONLY, 0,
new File("save.txt").length());
displayBufferInfo(buffer, "init buffer");

// 将Buffer内容一次写入另一文件的Channel
outChannel.write(buffer);
buffer.flip();
// 解码CharBuffer之后输出
System.out.println(decoder.decode(buffer));
}
}

// ...
}

Charset

java.nio.charset.Charset

Charset

Charset

availableCharsets()

/**
* @author jifang
* @since 16/1/10下午4:32.
*/
public class CharsetLearn {

@Test
public void testGetAllCharsets() {
SortedMap<String, Charset> charsetMap = Charset.availableCharsets();
for (Map.Entry<String, Charset> charset : charsetMap.entrySet()) {
System.out.println(charset.getKey() + " aliases -> " + charset.getValue().aliases() + " chaset -> " + charset.getValue());
}
}
}

UTF-8

unicode-1-1-utf-8

UTF8

forName()

@Test
public void testGetCharset() {
Charset utf8 = Charset.forName("UTF-8");
Charset unicode11 = Charset.forName("unicode-1-1-utf-8");
System.out.println(utf8.name());
System.out.println(unicode11.name());
System.out.println(unicode11 == utf8);
}

StandardCharsets

@Test
public void testGetCharset() {
// 使用UTF-8属性
Charset utf8 = StandardCharsets.UTF_8;
Charset unicode11 = Charset.forName("unicode-1-1-utf-8");
System.out.println(utf8.name());
System.out.println(unicode11.name());
System.out.println(unicode11 == utf8);
}

Charset

decode()

encode()

ByteBuffer

CharBuffer

ByteBuffer   encode(CharBuffer cb)

ByteBuffer   encode(String str)

CharBuffer   decode(ByteBuffer bb)

Charset

newDecoder()

newEncoder()

CharsetDecoder

CharsetEncoder

encode

decode

@Test
public void testDecodeEncode() throws IOException {
File inFile = new File("save.txt");
FileChannel in = new FileInputStream(inFile).getChannel();

MappedByteBuffer byteBuffer = in.map(FileChannel.MapMode.READ_ONLY, 0, inFile.length());
// Charset utf8 = Charset.forName("UTF-8");
Charset utf8 = StandardCharsets.UTF_8;

// 解码
// CharBuffer charBuffer = utf8.decode(byteBuffer);
CharBuffer charBuffer = utf8.newDecoder().decode(byteBuffer);
System.out.println(charBuffer);

// 编码
// ByteBuffer encoded = utf8.encode(charBuffer);
ByteBuffer encoded = utf8.newEncoder().encode(charBuffer);
byte[] bytes = new byte[(int) inFile.length()];
encoded.get(bytes);
for (int i = 0; i < bytes.length; ++i) {
System.out.print(bytes[i]);
}
System.out.println();

}

getBytes(String charset)

使用

WatchService

监控文件变化

Path

register

WatchKey    register(WatchService watcher, WatchEvent.Kind<?>... events);
WatchKey    register(WatchService watcher, WatchEvent.Kind<?>[] events, WatchEvent.Modifier... modifiers);

Path

Watchable

register

Watchable

WatchService

Path

WatchService

FileSystem

WatchService

WatchService service = FileSystems.getDefault().newWatchService();

register

WatchService

WatchKey poll()

WatchKey poll(long timeout, TimeUnit unit)

WatchKey take()

WatchKey

WatchEvent

List<WatchEvent<?>>  pollEvents()

boolean  reset()

WatchEvent

T    context()

int  count()

WatchEvent.Kind<T>   kind()

/**
* @author jifang
* @since 16/1/10下午8:00.
*/
public class ChangeWatcher {

public static void main(String[] args) {
watch("/Users/jifang/");
}

public static void watch(String directory) {
try {
WatchService service = FileSystems.getDefault().newWatchService();
Paths.get(directory).register(service,
StandardWatchEventKinds.ENTRY_CREATE,
StandardWatchEventKinds.ENTRY_DELETE,
StandardWatchEventKinds.ENTRY_MODIFY);
while (true) {
WatchKey key = service.take();
for (WatchEvent event : key.pollEvents()) {
System.out.println(event.context() + " 文件发生了 " + event.kind() + " 事件!");
}

if (!key.reset()) {
break;
}
}
} catch (IOException | InterruptedException e) {
throw new RuntimeException(e);
}
}
}

WatchService

Guava IO

commons-io

Guava

commons-io

pom.xml

<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>19.0</version>
</dependency>

URL.openConnection()

IOStream

public static String getHtml(String url) {
if (StringUtils.isBlank(url)) {
return null;
}
try {
return Resources.toString(new URL(url), StandardCharsets.UTF_8);
} catch (IOException e) {
LOGGER.error("getHtml error url = {}", url, e);
throw new RuntimeException(e);
}
}

Resources

readLines(URL url, Charset charset, LineProcessor<T> callback)

public static List<String> processUrl(String url, final String regexp) {
try {
return Resources.readLines(new URL(url), StandardCharsets.UTF_8, new LineProcessor<List<String>>() {

private Pattern pattern = Pattern.compile(regexp);
private List<String> strings = new ArrayList<>();

@Override
public boolean processLine(String line) throws IOException {
Matcher matcher = pattern.matcher(line);
while (matcher.find()) {
strings.add(matcher.group());
}
return true;
}

@Override
public List<String> getResult() {
return strings;
}
});
} catch (IOException e) {
LOGGER.error("processUrl error, url = {}, regexp = {}", url, regexp, e);
throw new RuntimeException(e);
}
}

源

汇

Files

Resources

Java IO 简化

InputStream/OutputStream

Readable/Appendable

Writer

Appendable

Reader

Readable

com.google.common.io.ByteStreams

com.google.common.io.CharStreams

static long  copy(Readable/InputStream from, Appendable/OutputStream to)

static byte[]    toByteArray(InputStream in)

static int   read(InputStream in, byte[] b, int off, int len)

static ByteArrayDataInput    newDataInput(byte[] bytes, int start)

static String    toString(Readable r)

/**
* 一行代码读取文件内容
*
* @throws IOException
*/
@Test
public void getFileContent() throws IOException {
FileReader reader = new FileReader("save.txt");
System.out.println(CharStreams.toString(reader));
}

ByteStreams

CharStreams

Guava源与汇

ByteSource

CharSource

ByteSink

CharSink

InputStream/OutputStream

Reader/Writer

/**
* @author jifang
* @since 16/1/11下午4:39.
*/
public class SourceSinkTest {

@Test
public void fileSinkSource() throws IOException {
File file = new File("save.txt");
CharSink sink = Files.asCharSink(file, StandardCharsets.UTF_8);
sink.write("- 你好吗?\n- 我很好.");

CharSource source = Files.asCharSource(file, StandardCharsets.UTF_8);
System.out.println(source.read());
}

@Test
public void netSource() throws IOException {
CharSource source = Resources.asCharSource(new URL("http://www.sun.com"), StandardCharsets.UTF_8);
System.out.println(source.readFirstLine());
}
}

获取源与汇

Files.asByteSource(File)

Files.asByteSink(File file, FileWriteMode... modes)

Resources.asByteSource(URL url)

ByteSource.wrap(byte[] b)

ByteSource.concat(ByteSource... sources)

Files.asCharSource(File file, Charset charset)

Files.asCharSink(File file, Charset charset, FileWriteMode... modes)

Resources.asCharSource(URL url, Charset charset)

CharSource.wrap(CharSequence charSequence)

CharSource.concat(CharSource... sources)

ByteSource.asCharSource(Charset charset)

ByteSink.asCharSink(Charset charset)

使用源与汇

CharSource

String    read()

long copyTo(CharSink/Appendable to)

@Test
public void saveHtmlFileChar() throws IOException {
CharSource source = Resources.asCharSource(new URL("http://www.google.com"), StandardCharsets.UTF_8);
source.copyTo(Files.asCharSink(new File("save1.html"), StandardCharsets.UTF_8));
}

@Test
public void saveHtmlFileByte() throws IOException {
ByteSource source = Resources.asByteSource(new URL("http://www.google.com"));
//source.copyTo(new FileOutputStream("save2.html"));
source.copyTo(Files.asByteSink(new File("save2.html")));
}

Files与Resources

Files

Resources

URL

File

ByteSource

CharSource

Resources

static void  copy(URL from, OutputStream to)

static URL   getResource(String resourceName)

static List<String>  readLines(URL url, Charset charset)

static <T> T readLines(URL url, Charset charset, LineProcessor<T> callback)

static byte[]    toByteArray(URL url)

static String    toString(URL url, Charset charset)

Files

static void  append(CharSequence from, File to, Charset charset)

static void  copy(File from, Charset charset, Appendable to)

static void  copy(File from, File to)

static void  copy(File from, OutputStream to)

static File  createTempDir()

static MappedByteBuffer  map(File file, FileChannel.MapMode mode, long size)

FileChannel.map(java.nio.channels.FileChannel.MapMode, long, long)

static void  move(File from, File to)

static <T> T readBytes(File file, ByteProcessor<T> processor)

static String    readFirstLine(File file, Charset charset)

static List<String>  readLines(File file, Charset charset)

static <T> T readLines(File file, Charset charset, LineProcessor<T> callback)

static byte[]    toByteArray(File file)

static String    toString(File file, Charset charset)

static void  touch(File file)

static void  write(byte[] from, File to)

static void  write(CharSequence from, File to, Charset charset)