一.对象序列化:
1.对象流:
ObjectInputStream 和 ObjectOutputStream
2.作用:
ObjectOutputSteam:内存中的对象-->存储中的文件,通过网络传输出去
ObjectInputStream:存储中的文件,通过网络传输出去-->内存中的对象
3.对象的序列化机制:
对象序列化机制允许把内存中的java对象转换成平台无关的二进制流,从而允许把这种二进制流持久地保存在磁盘上,或通过网络将这种二进制流传输到另外一个网络节点。//当其他程序获取了这种二进制流,就可以恢复成原来的java对象
4.序列化和反序列化过程:
代码实现:
public static void main(String[] args) throws IOException, ClassNotFoundException {//创建对象流ObjectOutputStream oos = new ObjectOutputStream( new FileOutputStream("object.txt"));//字符串序列化oos.writeObject("北京欢迎你!");oos.flush();System.out.println("***************************************");//对象序列化Person p = new Person("tom",20);oos.writeObject(p);oos.flush();oos.close();System.out.println("***************************************");//反序列化:把对象从文件或数据库中读取到内存中ObjectInputStream ois = new ObjectInputStream(new FileInputStream("object.txt"));Object o = ois.readObject();System.out.println(o);Object o1 = ois.readObject();System.out.println(o1);ois.close(); }
5.实现序列化的对象所属的类需要满足:
1)需要实现接口:Serializable
2)当前类提供一个全局常量:SerialVersionUid
3)除了当前类需要实现Serializable接口之外,还需要保证其内部所有属性也必须是可序列化的
补充:ObjectOutputStream和ObjectInputStream不能序列化static和transient修饰的成员变量
二.随机存取文件流:
1.随机存取文件流:RandomAccessFile
2.使用说明:
1)RandomAccessFile直接继承于java.lang.Object类,实现了数据读取和输出
2)RandomAccessFile即可以是输入流又可以是输出流
3)RandomAccessFile作为输出流时,写出文件如果不存在,则在执行过程中自动创建,
如果写出的文件存在,则会对原文件内容进行覆盖
4)可以通过相关的操作,实现RandomAccessFile"插入"数据的效果。seek(int pos)
3.典型代码:
@Test public void test() throws IOException {RandomAccessFile acf1 = new RandomAccessFile("cat.jpg", "r");RandomAccessFile acf2 = new RandomAccessFile("cat3.jpg", "rw");byte[] bute = new byte[1024];int len;while ((len = acf1.read(bute)) != -1) {acf2.write(bute, 0, len);}acf1.close();acf2.close();}@Test public void test2() throws IOException {RandomAccessFile acf1 = new RandomAccessFile("hello1.txt", "rw");acf1.seek(3);acf1.write("xyz".getBytes());acf1.close();}@Test public void test3() throws IOException {/*使用 RandomAccessFile 实现插入功能*/RandomAccessFile acf1 = new RandomAccessFile("h.txt", "rw");acf1.seek(3);StringBuilder sb = new StringBuilder((int)new File("h.txt").length());//把剩余内容存到StringBuilder对象byte[] bute = new byte[1024];int len;while ((len = acf1.read(bute)) != -1) {sb.append(new String(bute,0,len));}//把指针从写指到3acf1.seek(3);acf1.write("xyz".getBytes());acf1.write(sb.toString().getBytes());acf1.close();}
三.网络传输:
1.实现网络通信需要解决的两个问题
1)如何准确地定位网络上一台或多台主机:定位主机上的特定应用
2)找到主机后如何可靠高效地进行数据传输
2.网络通信的两个要素:
1)对应问题一:ip和端口号
2)对应问题二:提供网络通信协议:TCP/IP参考模型(应用层,传输层,网络层,物理+数据链路层)
3.通信要素一:ip和端口号
1)ip的理解
》ip:唯一标识Internet上计算机(通信实体)
》在java 中使用InetAddress类代表ip
》ip分类:ipv4和ipv6 ;万维网和局域网
》域名:www.baidu.com ,www.jd.com
2)InetAddress类:
2.1 实例化
getByName(String host),getLocalHost()
2.2 常用方法
getHostName() /getHostAddress()
3.端口号:正在计算机上运行的进程
要求:不同的进程不同的端口号
范围:被规定为一个正整数 0-65535
端口号与ip地址组合得出一个网络套接字:Socket
4.通信要素二:网络通信协议:
1)分类模型
2)TCP和UDP的区别
TCP协议:使用协议前建立TCP连接,形成传输通道,传输前使用三次握手方式,点对点通信,是可靠的;在连接中可进行大数据量的传输;传输完毕,需释放已建立的连接,效率低
UDP协议:将数据,源,目的封装成数据包,不需要建立连接,每个数据报的大小限制在64k内;
发送不管对方是否准备好,接收方收到也不确认,故是不可靠的;可以广播发送;发送数据结束时,无需释放资源,开销小,速度快
5.代码实例:
1)IP地址代码实例:
public class InetAddressTest {public static void main(String[] args) throws UnknownHostException {//根据ip地址创建ip地址对象InetAddress ina1 =InetAddress.getByName("192.168.1.1");System.out.println(ina1);//根据域名创建ip地址对象InetAddress ina2= InetAddress.getByName("www.baidu.com");System.out.println(ina2);byte[] address = ina1.getAddress();System.out.println(ina1.getHostName());System.out.println(ina1.getHostAddress());System.out.println(ina2.getHostName());System.out.println(ina2.getHostAddress());} }
2)TCP代码实例:
public class Tcp1Test { //发送信息@Testpublic void test() throws IOException {Socket clent = new Socket(InetAddress.getByName("127.0.0.1"),8899);OutputStream outputStream = clent.getOutputStream();outputStream.write("我是客户端".getBytes());outputStream.close();clent.close();}@Testpublic void test2() throws IOException {ServerSocket server =new ServerSocket(8899);Socket accept = server.accept();InputStream inputStream = accept.getInputStream();ByteArrayOutputStream byteout =new ByteArrayOutputStream();byte[] buffer =new byte[20];int len;while((len=inputStream.read(buffer))!=-1){byteout.write(buffer,0,len);System.out.println(byteout.toString());}server.close();inputStream.close();byteout.close();}}
public class Tcp2Test {//发送文件@Testpublic void test1() throws IOException {InetAddress inet= InetAddress.getByName("127.0.0.1");Socket clent =new Socket(inet,8851);OutputStream outputStream = clent.getOutputStream();FileInputStream fis= new FileInputStream("leaf.jpg");byte[] buffer= new byte[10];int len;while((len=fis.read(buffer))!=-1){outputStream.write(buffer,0,len);}fis.close();outputStream.close();clent.close();}@Testpublic void test2() throws IOException {ServerSocket server =new ServerSocket(8851);Socket accept = server.accept();InputStream inputStream = accept.getInputStream();FileOutputStream fos=new FileOutputStream("leaf2.jpg");byte[] bufferr = new byte[10];int len;while((len=inputStream.read(bufferr))!=-1){fos.write(bufferr,0,len);}fos.close();inputStream.close();server.close();}}
public class Tcp3Test {//发送文件,服务器返回信息@Testpublic void test() throws IOException {InetAddress inet = InetAddress.getByName("127.0.0.1");Socket client =new Socket(inet,7788);OutputStream outputStream = client.getOutputStream();//从本地读取文件并发送到服务器FileInputStream fis =new FileInputStream("leaf.jpg");byte[] buffer =new byte[20];int len;while((len=fis.read(buffer))!=-1){outputStream.write(buffer,0,len);}//关闭数据输出client.shutdownOutput();//接受服务器发送的信息,并输出到控制台InputStream inputStream = client.getInputStream();ByteArrayOutputStream bos =new ByteArrayOutputStream();byte[] bu =new byte[20];int len1;while((len1=inputStream.read(bu))!=-1){bos.write(bu,0,len1);}System.out.println(bos.toString());fis.close();outputStream.close();client.close();}@Testpublic void test2() throws IOException {ServerSocket server = new ServerSocket(7788);Socket accept = server.accept();InputStream inputStream = accept.getInputStream();//接受客户端发送文件并存到本地FileOutputStream fos= new FileOutputStream("leaf3.jpg");byte[] buff =new byte[20];int len;while((len=inputStream.read(buff))!=-1){fos.write(buff,0,len);}//给客户端发送已接收消息OutputStream outputStream = accept.getOutputStream();outputStream.write("图片已收到,谢谢".getBytes());fos.close();inputStream.close();server.close();outputStream.close();}}
3)UDP代码实例:
public class UdpTest {@Testpublic void test() throws IOException {//发送端DatagramSocket socket =new DatagramSocket();InetAddress inet =InetAddress.getLocalHost();String str="我是udp方式发送的数据";byte[] buff = str.getBytes();DatagramPacket packet =new DatagramPacket(buff,0,buff.length,inet,8890);socket.send(packet);socket.close();}@Testpublic void test2() throws IOException {//接收者DatagramSocket socket =new DatagramSocket(8890);byte[] buffer =new byte[100];DatagramPacket packet =new DatagramPacket(buffer,0,buffer.length);socket.receive(packet);System.out.println(new String(packet.getData(),0,packet.getLength()));} }
4)URL代码实例:
public class UrlTest {@Testpublic void test() throws MalformedURLException {//获取url对象URL url =new URL("http://localhost:8080/examples/leaf.jpg");//url 主要方法System.out.println(url.getProtocol());//获取协议System.out.println(url.getHost());//获取主机System.out.println(url.getPort());//获取端口System.out.println(url.getQuery());//获取查询内容}@Testpublic void test2() throws IOException {//服务器下载图片 URL url =new URL("http://localhost:8080/examples/leaf.jpg");HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();urlConnection.connect();InputStream inputStream = urlConnection.getInputStream();byte[] buffer =new byte[20];int len;FileOutputStream fos =new FileOutputStream("leafdown.jpg");while((len=inputStream.read(buffer))!=-1){fos.write(buffer,0,len);}inputStream.close();fos.close();urlConnection.disconnect();} }