java中getById 如果主键字段名不是id 可以嘛 java gethostname

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mob64ca14085c24 2023-11-26 19:36:54

文章标签 TCP UDP InetAddress类聊天 System 文章分类 Java 后端开发

一、InetAddress类

1.1 作用

可以表示互联网协议地址

1.2 常用方法

public static InetAddress getByName(String host)
获得一个InetAddress对象实例；
host可以是主机名或者主机IP地址
public String getHostAddress()
获取当前计算机所在网络中的IP地址
public String getHostName()
获取主机名
getLocalHost()
获取主机名和IP地址

1.3 案例

public class Thread {
    public static void main(String[] args) throws UnknownHostException {
        InetAddress address = InetAddress.getByName("DESKTOP-TSM707T");
        System.out.println(address.getHostName());
        System.out.println(address.getHostAddress());
        System.out.println(address.getLocalHost());
    }
}

结果:
DESKTOP-TSM707T
192.168.16.104
DESKTOP-TSM707T/192.168.16.104

注意:计算机名称可以:
此电脑—>属性—>高级系统设置—>计算机名

二、UDP协议

2.1 特点

客户端与服务端不需要建立链接
发送数据速度较TCP快
发送数据有大小限制

2.2 UDP发送数据步骤

创建客户端Socket对象
将数据打包，包里的数据包括要发送的数据，数据的长度，发送端的IP，端口号，注意数据是以字节流的形式打包的。
发送数据

2.3 UDP发送数据示例

public class Thread {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket =  new DatagramSocket();
        byte[] bytes = "UDP发送端".getBytes();
        InetAddress address = InetAddress.getByName("DESKTOP-TSM707T");
        DatagramPacket packet = new DatagramPacket(bytes, bytes.length, address,8823);
        socket.send(packet);
    }
}

2.4 UDP接收数据步骤

创建带有端口号的服务端Socket对象
创建数据包对象
Socket对象接收发送端发过来的数据包
从包中获取数据
可以不关闭服务端对象

2.5 UDP接受数据示例

public class receive {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket(8823);
        byte[] bytes = new byte[1024];
        DatagramPacket packet = new DatagramPacket(bytes, bytes.length);
        System.out.println("UDP发送端信息已经过来");
        socket.receive(packet);
        byte[] data = packet.getData();
        System.out.println(packet.getAddress().getHostName() + "发送过来的消息是:" + new String(data));
        socket.close();
    }
}

2.6 UDP输出指定路径文件内容

难点是:

怎么将文件中读出的数据打包
用的是BufferedReader类中的readLine()方法获取数据,然后发送
怎么将包中的数据读出
可以在死循环里一直新建包队象，一直等待接受包然后读数据

注意:
UDP接受数据时，新建一个包对象只能接受该包对象大小的数据，只能输出一行！！！！

发送端:

public class send_file {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket();
        FileInputStream inputStream = new FileInputStream("D:a.java");
        int i;
        DatagramPacket packet = null;
        byte[] bytes = new byte[1024];
        InetAddress byName = InetAddress.getByName("MS-20181121ZVTC");
        while ((i = inputStream.read(bytes)) != -1) {
            packet = new DatagramPacket(bytes,1024, byName, 1111);
            socket.send(packet);
            System.out.print(new String(bytes));
        }
        socket.close();
    }

接收端：

public static void main(String[] args) throws IOException {
        FileOutputStream outputStream = new FileOutputStream("D:\\b.java");
        DatagramSocket socket = new DatagramSocket(1111);
        DatagramPacket datagramPacket = null;
        byte[] bytes = new byte[1024];
        while (true){
            datagramPacket = new DatagramPacket(bytes,bytes.length );
            socket.receive(datagramPacket);
            byte[] data = datagramPacket.getData();
            outputStream.write(data);
            System.out.println(new String(data));
        }
    }

2.7 简单UDP聊天

思路:
声明发送端线程和接收端线程，开辟两个聊天室，分别有一个发送端和接收端线程，sleep的作用是确保接收端线程先开启，然后发送端线程再开启。使用InputstreamReader(Syetem.in)从键盘端读取数据。

发送端线程

public class send extends Thread{
    int port;
    send(int port) {
        this.port = port;
    }
    @Override
    public void run() {
        try {
            //创建发送端Socket对象
            DatagramSocket socket = new DatagramSocket();
            //从指定路径读取数据
            InetAddress address = InetAddress.getByName("DESKTOP-TSM707T");
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            byte[] bytes = new byte[1024];
            String str = null;
            DatagramPacket packet;
            while(!(str = in.readLine()).equals("88")) {
                packet = new DatagramPacket(str.getBytes(), str.getBytes().length, address, port);
                socket.send(packet);
            }
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

接收端线程

public class receive extends  Thread{
    int port;
    public receive(int port) {
        this.port = port;
    }
    @Override
    public void run() {
        try {
            DatagramSocket socket = new DatagramSocket(port);
            System.out.println("准备接收数据");
            while (true) {
                byte[] bytes = new byte[1024];
                DatagramPacket packet = new DatagramPacket(bytes, bytes.length);
                socket.receive(packet);
                System.out.println("发送端发来信息:" + new String(packet.getData()));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

聊天窗口1:

public class talkroom {
    public static void main(String[] args) throws InterruptedException {
        receive rec = new receive(4212);
        send se = new send(2424);
        rec.start();
        Thread.sleep(10000);
        se.start();
    }
}

聊天窗口2:

public class talkroom2 {
    public static void main(String[] args) throws InterruptedException {
        receive rec = new receive(2424);
        send se = new send(4212);
        rec.start();
        Thread.sleep(10000);
        se.start();
    }
}

三、TCP协议

3.1 特点

客户端与服务端需要建立链接
不用将数据打包，将数据发送到通道和通过通道获取数据
传输数据速度较UDP慢

3.2 TCP发送数据步骤

创建带有主机IP和端口号的Socket对象
获得输出流
往缓冲区写入数据

3.3 TCP发送数据示例

说明:Socket构造函数第一个参数可以是InetAddress对象，也可以是字符串

public class TCP_text {
    public static void main(String[] args) throws IOException {
        InetAddress address = InetAddress.getByName("DESKTOP-TSM707T");
        Socket socket = new Socket(address, 8984);
        OutputStream out = socket.getOutputStream();
        String str = "TCP发送";
        out.write(str.getBytes());
        socket.close();
    }
}

3.4 TCP接收数据步骤

创建带端口号的ServerSocket对象
创建Socket对象
从通道中获取数据
对数据进行操作

3.5 TCP接收数据示例

public class TCP_receive {
    public static void main(String[] args) throws IOException {
        ServerSocket ser = new ServerSocket(8984);
        System.out.println("准备接收数据");
        Socket socket = ser.accept();
        InputStream in = socket.getInputStream();
        byte[] bytes = new byte[1024];
        int len = 0;
        while((len = in.read(bytes)) != -1) {
            System.out.println(new String(bytes, 0, len));
        }
    }
}

3.5 用TCP发送文件到接收端

思路:利用BuffferedeReader和BufferWriter来封装通过socket对象获得的输入输出流，然后进行操作。

发送端:

public static void main(String[] args) throws IOException {
        InetAddress address = InetAddress.getByName("MS-20181121ZVTC");
        Socket socket = new Socket(address, 1111);
        File file = new File("D:\\a.java");
        BufferedReader re = new BufferedReader(new FileReader(file));
        OutputStream out = socket.getOutputStream();
        BufferedWriter wri = new BufferedWriter(new OutputStreamWriter(out));
        String str = null;
        while((str = re.readLine()) != null) {
            wri.write(str);
            System.out.println(str);
            wri.newLine();
            wri.flush();
        }
        re.close();
        wri.close();
        socket.close();
    }

接收端:

public static void main(String[] args) throws IOException {
            ServerSocket ser = new ServerSocket(1111);
            System.out.println("准备接收数据");
            Socket socket = ser.accept();
            InputStream in = socket.getInputStream();
            BufferedReader re = new BufferedReader(new InputStreamReader(in));
            BufferedWriter wri = new BufferedWriter(new FileWriter("D:\\b.java"));
            String str = null;
            while((str = re.readLine()) != null) {
                System.out.println(str);
                wri.write(str);
                wri.newLine();
                wri.flush();
            }
            re.close();
            wri.close();
        }

注意:

void shutdownInput()
禁用此套接字的输出流。

在客户端使用该方法的作用是告诉服务端不再传输数据

3.6 TCP简单聊天

思路:和上面UDP简单聊天一样

注意:一定要注意参数的名称是否写对，否则会造成传参错误而出不来结果；
客户端线程:

public class Send_Thread extends Thread{
    int port;
    public Send_Thread(int port) {
        this.port = port;
    }
    @Override
    public void run() {
        try {
            InetAddress address = InetAddress.getByName("DESKTOP-TSM707T");
            Socket socket = new Socket(address, port);
            OutputStream out = socket.getOutputStream();
            BufferedWriter buf = new BufferedWriter(new OutputStreamWriter(out));
            BufferedReader re = new BufferedReader(new InputStreamReader(System.in));
            String str = null;
            while(true) {
                str = re.readLine();
                buf.write(str);
                buf.newLine();
                buf.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

服务端线程:

public class Receive_Thread extends Thread {
    int port;

    public Receive_Thread(int port) {
        this.port = port;
    }
    @Override
    public void run() {
        try {
            ServerSocket ser = new ServerSocket(port);
            System.out.println("准备接收数据:");
            Socket socket = ser.accept();
            InputStream in = socket.getInputStream();
            BufferedReader re = new BufferedReader(new InputStreamReader(in));
            while(true) {
                System.out.println(socket.getInetAddress().getHostAddress() + "发来的数据" + re.readLine());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

用户1：

public class room1 {
    public static void main(String[] args) throws InterruptedException {
        Receive_Thread rec = new Receive_Thread(1114);
        Send_Thread se = new Send_Thread(2224);
        rec.start();
        Thread.sleep(10000);
        se.start();
    }
}

用户2:

public class room2 {
    public static void main(String[] args) throws InterruptedException {
        Receive_Thread rec = new Receive_Thread(2224);
        Send_Thread se = new Send_Thread(1114);
        rec.start();
        Thread.sleep(10000);
        se.start();
    }
}

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