Java-IO_NIO_AIO-优快云博客

本文链接：https://blog.youkuaiyun.com/sf2gis2/article/details/52853166

Java-IO_NIO_AIO

sf2gis@163.com

2016年4月5日

1目标：从与外部进行各种输入输出。

2原理：将外部数据作为字节流（stream）或字符流（reader）读入数据。

原始的数据流称为节点流，经过包装后的节点流称为处理流。处理流增加了缓冲和便捷操作。

3流程：读取流：打开文件，读取数据，关闭文件。写入流：打开文件，写入数据，关闭文件。

3.1 读取流：打开文件，读取数据，关闭文件。

BufferedReaderbr=new BufferedReader(new FileReader("aaa.txt"));

String strRead;

while((strRead=br.readLine())!=null){

System.out.println(strRead);

}

br.close();

3.2 写入流：打开文件，写入数据，关闭文件。

PrintWriterpw=new PrintWriter(new FileWriter("ccc.xx"));

pw.println("thisis string to print writer");

pw.println("123");

pw.close();

3.3 示例：读取文件后打印出来。写入数据到指定文件。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

//read from reader

BufferedReaderbr=new BufferedReader(new FileReader("aaa.txt"));

String strRead;

while((strRead=br.readLine())!=null){

System.out.println(strRead);

}

br.close();

//write to writer

PrintWriterpw=new PrintWriter(new FileWriter("ccc.xx"));

pw.println("thisis string to print writer");

pw.println("123");

pw.close();

}

//结果

this is file.

这是文件。

END

//aaa.txt

this is file.

这是文件。

END

//ccc.xx

this is string to printwriter

123

4方法：文件File，操作文件和目录

示例：创建一个新文件，并显示路径、名称。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

Filef=new File("aaa.txt");

BooleanbNew=f.createNewFile();

System.out.println("AbsolutePath="+f.getAbsolutePath()+",name="+f.getName()+",createnew="+bNew);

}

//结果

AbsolutePath=/home/sf/test/workspace/Client/aaa.txt,name=aaa.txt,createnew=true

4.1 使用文件过滤器FilenameFileter，返回指定的文件和路径

FilenameFilter 接口的accept()方法接受name和dir参数，添加过滤逻辑，得到能够返回true的文件和路径。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

File f = new File(".");

// {//all files and paths

// String[] arrName = f.list();

// for (String name : arrName) {

// System.out.println(name);

// }

{//filter .txt files and folders

String[] arrName = f.list(new FilenameFilter(){

@Override

public boolean accept(File dir, String name) {

// TODO Auto-generated method stub

return name.endsWith(".txt") ||new File(name).isDirectory();

}

});

for (String name : arrName) {

System.out.println(name);

}

//结果，过滤掉.xx文件

.settings

aaa.txt

src

bbb.txt

bin

5方法：字节流Stream处理8位Byte类型的IO，字符流Reader处理16位char类型的IO。

参考：http://www.51testing.com/html/85/258885-811659.html

http://blog.youkuaiyun.com/xiadasong007/article/details/4776913

5.1 区别与联系：Stream和Reader提供了基本相同的功能及子类，只是输入格式不同。两者使用InputStreamReader和OutputStreamWrite进行适配。

5.2 方法：字节流Stream，InputStream，OutputStream等

目标：提供基本字节流的IO及针对不同设备的特殊IO。

原理：jvm读写IO设备，以字节流的形式输出输出。

方法：将byte数组输入或输出

参考：http://www.runoob.com/java/java-files-io.html

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

//read from stream

FileInputStream fi=newFileInputStream("aaa.txt");

byte[] buff=new byte[100];

int iReaded=0;

while((iReaded=fi.read(buff))>0){

System.out.println(new String(buff,0,iReaded)+",readed="+iReaded);

}

fi.close();

//write to stream

FileOutputStream fo=newFileOutputStream("bbb.txt");

fo.write("abcxx".getBytes());

fo.close();

System.out.println("Write to Steam=bbb.txtabcxx");

}

//结果

this is file.

这是文件。

END

,readed=34

Write to Steam=bbb.txt abcxx

//aaa.txt

this is file.

这是文件。

END

//bbb.txt

abcxx

5.3 方法：字符流Reader，Writer

5.3.1目标：提供基于字符流的IO。

5.3.2原理：将字节流、字符串等解析为字符。

5.3.3流程：参见流程：读取流：打开文件，读取数据，关闭文件。写入流：打开文件，写入数据，关闭文件。

5.3.4方法：与Stream相似的子类。

缓冲字符流：BufferedReader。增加readLine()实用功能。

BufferedReader in = newBufferedReader(new InputStreamReader(conn.getInputStream()));

String strLine=null;

while((strLine=in.readLine())!=null){

strResult+=strLine;

}

System.out.println("response="+strResult);

用户输入：Scanner（替代BufferReader）。

6方法：系统标准流重定向System.setIn(),setOut(),setErr()。

参考：http://www.169it.com/tech-qa-java/article-16154326677047614285.html

示例：标准输出重定向到文件，然后再重定向到console。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

//redirect to file

PrintStream ps=new PrintStream(new FileOutputStream("ccc.xx"));

PrintStream stdout=System.out;

System.setOut(ps);

System.out.println("System.out.println() is printinghere.");

ps.close();

System.setOut(stdout);

System.out.println("System.out.println() is printinghere.2");

}

//结果

System.out.println() isprinting here.2

//ccc.xx

System.out.println() isprinting here.

7方法：进程IO

进程Process具有标准输出、输出、错误流，可以用于交互。

示例：运行进程javac，获得输出的错误信息。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

Process p=Runtime.getRuntime().exec("javac");

BufferedReader br=new BufferedReader(newInputStreamReader(p.getErrorStream()));

String buff =null;

while((buff= br.readLine())!=null){

System.out.println(buff);

}

//结果

Usage: javac <options><source files>

where possible optionsinclude:

-g Generate all debugginginfo

-g:none Generate no debugging info

-g:{lines,vars,source} Generate only some debugging info

-nowarn Generate no warnings

-verbose Output messages about whatthe compiler is doing

-deprecation Output source locations wheredeprecated APIs are used

-classpath <path> Specify where to find user classfiles and annotation processors

-cp <path> Specify where to find userclass files and annotation processors

-sourcepath <path> Specify where to find input sourcefiles

-bootclasspath <path> Override location of bootstrap classfiles

-extdirs <dirs> Override location of installedextensions

-endorseddirs <dirs> Override location of endorsed standardspath

-proc:{none,only} Control whether annotation processingand/or compilation is done.

-processor<class1>[,<class2>,<class3>...] Names of the annotationprocessors to run; bypasses default discovery process

-processorpath <path> Specify where to find annotationprocessors

-d <directory> Specify where to place generatedclass files

-s <directory> Specify where to place generatedsource files

-implicit:{none,class} Specify whether or not to generate classfiles for implicitly referenced files

-encoding <encoding> Specify character encoding used bysource files

-source <release> Provide source compatibility withspecified release

-target <release> Generate class files for specific VMversion

-version Version information

-help Print a synopsis ofstandard options

-Akey[=value] Options to pass to annotationprocessors

-X Print a synopsis ofnonstandard options

-J<flag> Pass <flag> directlyto the runtime system

-Werror Terminate compilation ifwarnings occur

@<filename> Read options and filenames fromfile

8方法：文件任意访问RandomAccessFile

设置文件位置seek（pos）。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

RandomAccessFile ra=newRandomAccessFile("aaa.txt","r");

ra.seek(5);

String strRead;

while((strRead=ra.readLine())!=null){

System.out.println("readed="+newString(strRead.getBytes("UTF-8"),"UTF-8"));

}

ra.close();

}

//结果

readed=is file.

readed=END

//aaa.txt

this is file.

END

9方法：序列化

9.1 目标：将内存中的对象持久化到硬盘或网络上。

9.2 原理：将对象按字节流读写。

9.3 流程：实现Serialize接口（仅作为标识，无需实现任何方法）。使用ObjectOutputStream、ObjectInputStream读写。

参考：http://www.myexception.cn/j2se/318778.html

9.3.1实现Serialization接口：仅作为标识，无需实现任何方法。

class Person implementsSerializable{

9.3.2序列化到文件：ObjectOutputStream。

ObjectOutputStreamop=new ObjectOutputStream(new FileOutputStream("s.txt"));

op.writeObject(p1);

op.writeObject(p2);

op.writeObject(null);//thisis a flag for termination of file

op.close();

9.3.3从文件反序列化到对象：ObjectInputStream。

ObjectInputStreamip=new ObjectInputStream(new FileInputStream("s.txt"));

Object obj;

while((obj=ip.readObject())!=null){

Personp=(Person)obj;

System.out.println("readobj="+p.getName()+","+p.getAge());

}

ip.close();

9.3.4示例：写入两个对象+null结束标识，然后顺序读出。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException,ClassNotFoundException {

// TODO Auto-generated method stub

//write

Person p1=new Person();

p1.setName("a1");

p1.setAge(12);

Person p2=new Person();

p2.setName("ass");

p2.setAge(55);

ObjectOutputStreamop=new ObjectOutputStream(new FileOutputStream("s.txt"));

op.writeObject(p1);

op.writeObject(p2);

op.writeObject(null);//thisis a flag for termination of file

op.close();

//read

ObjectInputStreamip=new ObjectInputStream(new FileInputStream("s.txt"));

Object obj;

while((obj=ip.readObject())!=null){

Person p=(Person)obj;

System.out.println("readobj="+p.getName()+","+p.getAge());

}

ip.close();

}

class Person implements Serializable{

private String name;

private int age;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

//结果

read obj=a1,12

read obj=ass,55

9.4 方法：定义不序列化的数据transient。

示例：male为transient，将不进行序列化，读取时使用默认值。

//Client.java

private transient int age

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException,ClassNotFoundException {

// TODO Auto-generated method stub

//write

Person p1=new Person();

p1.setName("a1");

p1.setAge(12);

p1.setMale(true);

Person p2=new Person();

p2.setName("ass");

p2.setAge(55);

p2.setMale(true);

ObjectOutputStream op=new ObjectOutputStream(newFileOutputStream("s.txt"));

op.writeObject(p1);

op.writeObject(p2);

op.writeObject(null);//this is a flag for termination offile

op.close();

//read

ObjectInputStream ip=new ObjectInputStream(newFileInputStream("s.txt"));

Object obj;

while((obj=ip.readObject())!=null){

Person p=(Person)obj;

System.out.println("readobj="+p.getName()+","+p.getAge()+","+p.isMale());

}

ip.close();

}

class Person implementsSerializable{

private String name;

private int age;

privatetransient boolean male;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public boolean isMale() {

return male;

}

public void setMale(boolean male) {

this.male = male;

}

//结果：不带transient时，male全部为true,带有transient时，male为默认值false。

read obj=a1,12,false

read obj=ass,55,false

9.5 方法：自定义对象内部的序列化方法

9.5.1目标：自定义对象内部序列化的方法

9.5.2原是：实现Externalizable接口的序列化读写方法。

9.5.3流程：实现Externalizable接口，使用ObjectOutputStream、ObjectInputStream读写。

9.5.3.1 实现Externalizable接口：自定义如何处理对象内部数据的序列化。

publicvoid writeExternal(ObjectOutput out) throws IOException {

publicvoid readExternal(ObjectInput in) throws IOException, ClassNotFoundException {

9.5.3.2 使用ObjectOutputStream、ObjectInputStream读写。

//write

ObjectOutputStreamout=new ObjectOutputStream(new FileOutputStream("s.txt"));

out.writeObject(stu1);

out.writeObject(stu2);

out.writeObject(null);

out.close();

//read

ObjectInputStreamin=new ObjectInputStream(new FileInputStream("s.txt"));

Object obj;

while((obj=in.readObject())!=null){

Student stu=(Student)obj;

System.out.println("read="+stu.getName()+",age="+stu.getAge()+",score="+stu.getScore());

}

in.close();

9.5.3.3 示例：将score，age两个属性在序列化时反转。

//Client.java

import java.io.*;

public class Client {

public static void main(String[] args) throws IOException, ClassNotFoundException{

// TODO Auto-generated method stub

Student stu1=new Student();

stu1.setName("s1");

stu1.setAge(10);

stu1.setScore(5);

Student stu2=new Student();

stu2.setName("s2");

stu2.setAge(12);

stu2.setScore(5);

//write

ObjectOutputStreamout=new ObjectOutputStream(new FileOutputStream("s.txt"));

out.writeObject(stu1);

out.writeObject(stu2);

out.writeObject(null);

out.close();

//read

ObjectInputStreamin=new ObjectInputStream(new FileInputStream("s.txt"));

Object obj;

while((obj=in.readObject())!=null){

Student stu=(Student)obj;

System.out.println("read="+stu.getName()+",age="+stu.getAge()+",score="+stu.getScore());

}

in.close();

}

class Student implements Externalizable{

public Student() {

super();

// TODO Auto-generated constructor stub

}

private String name;

private int age;

private int score;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public int getScore() {

return score;

}

public void setScore(int score) {

this.score = score;

}

@Override

publicvoid writeExternal(ObjectOutput out) throws IOException {

// TODO Auto-generated method stub

out.writeObject(name);

out.writeInt(score);//first write score

out.writeInt(age);

}

@Override

publicvoid readExternal(ObjectInput in) throws IOException, ClassNotFoundException {

// TODO Auto-generated method stub

this.name=(String)(in.readObject());

this.age=in.readInt();//first read as age

this.score=in.readInt();

}

//结果：

read=s1,age=5,score=10

read=s2,age=5,score=12

10 方法：类的版本标识servialVersionUID

10.1 目标：区分类的不同版本。

10.2 原理：相同的servialVersionUID表示类的版本相同。

默认是1L，通过IDE的警告可以生成64位long数字。

参考：http://www.cnblogs.com/guanghuiqq/archive/2012/07/18/2597036.html

10.3 流程：实现Serialization接口，添加servialVersionUID属性。

class Student implements Serializable{

privatestatic final long serialVersionUID = 5092187866910248456L;

11 方法：NIO（new io）

11.1 目标：IO的升级版，使用内存映射文件处理IO，提高速度。

11.2 原理：内存映射文件使用channel表示，使用buffer作为缓冲。

11.3 流程：创建流，获取channel，读取buff，关闭资源。

11.3.1创建流：与基于IO相同。

FileInputStreamin=new FileInputStream("aaa.txt");

11.3.2获取channel：从IO中获取相应的channel。

FileChannelc=in.getChannel();

11.3.3读取buff：从channel中读取到buff。

while(c.read(buff)!=-1){

11.3.4关闭资源：关闭IO。

in.close();

11.3.5示例：读取指定文件中的内容。

//Client.java

import java.io.*;

import java.nio.*;

import java.nio.channels.*;

public class Client {

public static void main(String[] args) throws IOException,ClassNotFoundException {

// TODO Auto-generated method stub

FileInputStreamin=new FileInputStream("aaa.txt");

FileChannelc=in.getChannel();

ByteBuffer buff=ByteBuffer.allocate(100);

while(c.read(buff)!=-1){

System.out.println(new String(buff.array()));

}

in.close();

}

//结果

this is file.

END

//aaa.txt

this is file.

END

11.4 方法：channel,buffer,selector

参考：http://www.iteye.com/magazines/132-Java-NIO

11.4.1内存映射通道channel：通道，用于表示一段内存映射文件，由JVM管理进行内存映射。由IO获取。

11.4.2缓冲区buffer：与通道交互，用于读写内存映射文件到内存。有多种类型的buff。

为了便于操作，提供了容量capacity,当前位置position，最大使用位置limit。自定义标记mark（），转到mark位置reset（）,。请求内存allocate()。读写翻转flip()，位置复位clear（）。

11.4.3字符集charset：常用字符串GBK，UTF-8，ISO-8859-1。

11.4.4文件锁FileLock：FileChannel的lock（）/tryLock()。

11.4.5选择器Selector：单线程轮询提供模拟AIO。

多个非阻塞式的的channel集合，注册后使用SelectionKey表示（包含所有感兴趣的事件、附加对象及相关属性）建立连接的channel。

11.4.5.1 流程：服务器：配置服务端通道和选择器，轮询（select（），可连接：连接后读写。可读：读写）。

客户端：配置客户端通道和选择器，轮询（select（），可连接：连接后读写。可读：读写）。

11.4.5.1.1 配置服务端通道和选择器：

Selector sel=Selector.open();

ServerSocketChannel serChannel=ServerSocketChannel.open();

serChannel.bind(newInetSocketAddress("127.0.0.1",35536));

serChannel.configureBlocking(false);

serChannel.register(sel, SelectionKey.OP_ACCEPT);

11.4.5.1.2 轮询：select（）检查当前的连接状态，如果可连接，则连接后读写。可读：读写。

if(sk.isAcceptable()){

ServerSocketChannelserver=(ServerSocketChannel)sk.channel();

SocketChannel client=server.accept();

client.configureBlocking(false);

//write

client.write(ByteBuffer.wrap(new String("this isserver.").getBytes()));

client.register(sel,SelectionKey.OP_READ);

System.out.println("ServerAccepted.");

}

if(sk.isReadable()){

SocketChannel sc=(SocketChannel)(sk.channel());

ByteBufferbuff=ByteBuffer.allocate(1024);

sc.read(buff);

String content=new String(buff.array());

System.out.println("read="+content);

sk.interestOps(SelectionKey.OP_READ);

System.out.println("ServerReaded.");

}

11.4.5.2 示例：Selector模拟AIO。

//Server.java

package lee;

import java.io.*;

import java.net.*;

import java.nio.ByteBuffer;

import java.nio.channels.*;

import java.util.Iterator;

public class Server {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

Selector sel=Selector.open();

ServerSocketChannel serChannel=ServerSocketChannel.open();

serChannel.bind(new InetSocketAddress("127.0.0.1",35536));

serChannel.configureBlocking(false);

serChannel.register(sel, SelectionKey.OP_ACCEPT);

while(true){

System.out.println("Server iswaiting...");

sel.select();

Iterator<SelectionKey>it=sel.selectedKeys().iterator();

while(it.hasNext()){

SelectionKey sk=it.next();

it.remove();

if(sk.isAcceptable()){

ServerSocketChannelserver=(ServerSocketChannel)sk.channel();

SocketChannel client=server.accept();

client.configureBlocking(false);

//write

client.write(ByteBuffer.wrap(newString("this is server.").getBytes()));

client.register(sel,SelectionKey.OP_READ);

System.out.println("ServerAccepted.");

}

if(sk.isReadable()){

SocketChannelsc=(SocketChannel)(sk.channel());

ByteBufferbuff=ByteBuffer.allocate(1024);

sc.read(buff);

String content=new String(buff.array());

System.out.println("read="+content);

sk.interestOps(SelectionKey.OP_READ);

System.out.println("ServerReaded.");

}

//Client.java

package lee;

import java.io.*;

import java.net.*;

import java.nio.ByteBuffer;

importjava.nio.channels.SelectionKey;

importjava.nio.channels.Selector;

importjava.nio.channels.SocketChannel;

import java.util.Iterator;

import java.util.Scanner;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

SocketChannel channel = SocketChannel.open();

channel.configureBlocking(false);

Selector sel = Selector.open();

channel.connect(newInetSocketAddress("127.0.0.1", 35536));

channel.register(sel, SelectionKey.OP_CONNECT);

while (true) {

sel.select();

Iterator<SelectionKey> it =sel.selectedKeys().iterator();

while (it.hasNext()) {

SelectionKey sk = it.next();

it.remove();

if (sk.isConnectable()) {

SocketChannel client = (SocketChannel)sk.channel();

client.configureBlocking(false);

if (client.isConnectionPending()) {

client.finishConnect();

}

// write,need a thread to writ alone

Scanner in = new Scanner(System.in);

while (in.hasNext()) {

String strInput = in.nextLine();

client.write(ByteBuffer.wrap(strInput.getBytes()));

}

in.close();

client.register(sel, SelectionKey.OP_READ);

}

if (sk.isReadable()) {

SocketChannel sc = (SocketChannel)(sk.channel());

ByteBuffer buff =ByteBuffer.allocate(1024);

sc.read(buff);

String content = newString(buff.array());

System.out.println("read=" +content);

}

//结果：Client端

aaa

ccc

//结果：Server端

Server is waiting...

Server Accepted.

Server is waiting...

read=aaa

Server Readed.

Server is waiting...

read=ccc

Server Readed.

Server is waiting...

11.4.5.3 示例：Selector服务端和客户端多次交互。

//Server.java

package lee;

import java.io.*;

import java.net.*;

import java.nio.ByteBuffer;

import java.nio.channels.*;

import java.util.Iterator;

public class Server {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

Selector sel=Selector.open();

ServerSocketChannel serChannel=ServerSocketChannel.open();

serChannel.bind(newInetSocketAddress("127.0.0.1",35536));

serChannel.configureBlocking(false);

serChannel.register(sel, SelectionKey.OP_ACCEPT);

while(true){

System.out.println("Server iswaiting...");

sel.select();

Iterator<SelectionKey>it=sel.selectedKeys().iterator();

while(it.hasNext()){

SelectionKey sk=it.next();

it.remove();

if(sk.isAcceptable()){

ServerSocketChannel server=(ServerSocketChannel)sk.channel();

SocketChannel client=server.accept();

client.configureBlocking(false);

//write

client.write(ByteBuffer.wrap(newString("this is server.").getBytes()));

client.register(sel,SelectionKey.OP_READ);

System.out.println("ServerAccepted.");

}

if(sk.isReadable()){

SocketChannelsc=(SocketChannel)(sk.channel());

sc.write(ByteBuffer.wrap(newString("this is server 2.").getBytes()));

ByteBufferbuff=ByteBuffer.allocate(1024);

sc.read(buff);

String content=new String(buff.array());

System.out.println("read="+content);

sk.interestOps(SelectionKey.OP_READ);

System.out.println("ServerReaded.");

}

//Client.java

package lee;

import java.io.*;

import java.net.*;

import java.nio.ByteBuffer;

importjava.nio.channels.SelectionKey;

importjava.nio.channels.Selector;

importjava.nio.channels.SocketChannel;

import java.util.Iterator;

import java.util.Scanner;

public class Client {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

SocketChannel channel = SocketChannel.open();

channel.configureBlocking(false);

Selector sel = Selector.open();

channel.connect(newInetSocketAddress("127.0.0.1", 35536));

channel.register(sel, SelectionKey.OP_CONNECT);

while (true) {

sel.select();

Iterator<SelectionKey> it =sel.selectedKeys().iterator();

while (it.hasNext()) {

SelectionKey sk = it.next();

it.remove();

if (sk.isConnectable()) {

final SocketChannel client =(SocketChannel) sk.channel();

client.configureBlocking(false);

if (client.isConnectionPending()) {

client.finishConnect();

}

// write,need a thread to writ alone

Thread t0=new Thread(new Runnable(){

@Override

public void run() {

// TODO Auto-generated methodstub

Scanner in = newScanner(System.in);

while (in.hasNext()) {

String strInput =in.nextLine();

try {

client.write(ByteBuffer.wrap(strInput.getBytes()));

} catch (IOException e){

// TODOAuto-generated catch block

e.printStackTrace();

}

in.close();

}

});

t0.start();

client.register(sel, SelectionKey.OP_READ);

}

if (sk.isReadable()) {

SocketChannel sc = (SocketChannel)(sk.channel());

ByteBuffer buff =ByteBuffer.allocate(1024);

sc.read(buff);

String content = newString(buff.array());

System.out.println("read=" +content);

}

//结果：Client端

read=this is server.

aaa

read=this is server 2.

//结果：Server端

Server is waiting...

Server Accepted.

Server is waiting...

read=aaa_

12 方法： AIO（NIO.2）

12.1 目标：NIO的升级，增加了路径、文件的快捷操作类，增加异步处理方法。

12.2 原理：多线程IO。

12.3 流程：

12.4 方法：Paths、Files

路径操作：Path表示路径，Paths为快捷路径处理类。

文件操作：Files为快捷文件处理类，walkFileTree()可以浏览文件树，FileVisitor为文件或路径的处理类，可以处理文件（访问、访问失败）或路径（路径访问前、后）。

示例：使用Path和Files浏览目录和文件。

//Client.java

import java.io.*;

import java.nio.file.*;

importjava.nio.file.attribute.BasicFileAttributes;

public class Client {

public static void main(String[] args) throws IOException,ClassNotFoundException {

// TODO Auto-generated method stub

Pathpath=Paths.get(".");

System.out.println(path.getNameCount()+":"+path.toAbsolutePath());

Files.walkFileTree(path,new SimpleFileVisitor<Path>(){

@Override

publicFileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throwsIOException {

// TODO Auto-generated method stub

System.out.println("preVisitDirectory="+dir);

return super.preVisitDirectory(dir, attrs);

}

@Override

publicFileVisitResult visitFile(Path file, BasicFileAttributes attrs) throwsIOException {

// TODO Auto-generated method stub

System.out.println("visitFile="+file);

return super.visitFile(file, attrs);

}

@Override

publicFileVisitResult visitFileFailed(Path file, IOException exc) throws IOException{

// TODO Auto-generated method stub

System.out.println("visitFileFailed="+file);

return super.visitFileFailed(file, exc);

}

@Override

publicFileVisitResult postVisitDirectory(Path dir, IOException exc) throwsIOException {

// TODO Auto-generated method stub

System.out.println("postVisitDirectory="+dir);

return super.postVisitDirectory(dir, exc);

}

});

}

//结果

1:/home/sf/test/workspace/Client/.

preVisitDirectory=.

visitFile=./.project

preVisitDirectory=./.settings

visitFile=./.settings/org.eclipse.jdt.core.prefs

postVisitDirectory=./.settings

visitFile=./aaa.txt

preVisitDirectory=./src

visitFile=./src/Client.java

postVisitDirectory=./src

visitFile=./.classpath

preVisitDirectory=./bin

visitFile=./bin/Client$1.class

visitFile=./bin/Client.class

postVisitDirectory=./bin

visitFile=./aaa.txt~

postVisitDirectory=.