java.lang.NumberFormatException:Integer.parseInt中为null
好的,下面是我在创建一个简单的TFTP(普通文件传输协议)程序时使用的两个类。我正在运行此程序的服务器实例和客户端实例。我试图做到的是: 客户机连接到服务器并发送它所需的特定文件的消息。服务器定位文件并发送响应(1或0…1表示文件存在,0表示文件不存在)。然后服务器将文件的内容发送到客户端应用程序。我试图发送的文件只是简单的文本文件 现在,我能够接收到客户端想要的文本文件的名称,但是当我返回响应时,我没有得到任何返回。下面是服务器和客户端都运行的方法 这是服务器实例java.lang.NumberFormatException:Integer.parseInt中为null,java,number-formatting,Java,Number Formatting,好的,下面是我在创建一个简单的TFTP(普通文件传输协议)程序时使用的两个类。我正在运行此程序的服务器实例和客户端实例。我试图做到的是: 客户机连接到服务器并发送它所需的特定文件的消息。服务器定位文件并发送响应(1或0…1表示文件存在,0表示文件不存在)。然后服务器将文件的内容发送到客户端应用程序。我试图发送的文件只是简单的文本文件 现在,我能够接收到客户端想要的文本文件的名称,但是当我返回响应时,我没有得到任何返回。下面是服务器和客户端都运行的方法 这是服务器实例 SwingUtilities
SwingUtilities.invokeLater(new Runnable(){
public void run(){
String fileRequest = UDPReceiver(SERVER_PORT_NUMBER);
outputArea.append("\n" + "File Requested: " + fileRequest + "\n");
outputArea.append("Determining if file exists...\n");
String checkFile = SHARED_DIR + "\\" + fileRequest;
outputArea.append("Checking location: " + checkFile + "\n");
boolean check = fileCheck(checkFile);
if(check == true){
outputArea.append("File location verified..." + "\n");
outputArea.append("Initiating transfer...." + "\n\n");
UDPSender(CLIENT_HOSTNAME, CLIENT_PORT_NUMBER, "1");
}
else{
outputArea.append("File does not exist..." + "\n");
outputArea.append("Exiting run..." + "\n");
}
}
});
客户端实例
SwingUtilities.invokeLater(new Runnable(){
public void run(){
UDPSender(SERVER_HOSTNAME, SERVER_PORT_NUMBER, FILE_REQUEST);
String message = UDPReceiver(CLIENT_PORT_NUMBER);
outputArea.append("\n\n" + message + "\n");
if(message == "1"){
// File exists
outputArea.append("\n");
outputArea.append("File verified..." + "\n");
outputArea.append("Transfer initiated..." + "\n");
}
else{
// File doesn't exist
outputArea.append("\n");
outputArea.append("File does not exist..." + "\n");
outputArea.append("Terminating connection...");
}
}
});
以下是发送方和接收方方法
private void UDPSender(String hostname, String port, String message){
DatagramSocket socket = null;
try{
// Create a datagram socket, look for the first available port
socket = new DatagramSocket();
outputArea.append("Using local port: " + socket.getLocalPort() + "\n");
ByteArrayOutputStream bOut = new ByteArrayOutputStream();
PrintStream pOut = new PrintStream(bOut);
pOut.print(message);
// Convert printstream to byte array
byte[] bArray = bOut.toByteArray();
// Create a DatagramPacket, containing a maximum buffer of 256 bytes
DatagramPacket packet = new DatagramPacket(bArray, bArray.length);
outputArea.append("Looking for hostname " + hostname + "\n");
// Get the InetAddress object
InetAddress remote_addr = InetAddress.getByName(hostname);
// Check its IP Number
outputArea.append("Hostname has IP Address = " + remote_addr.getHostAddress() + "\n");
// Configure the DatagramPacket
packet.setAddress(remote_addr);
packet.setPort(Integer.parseInt(port));
// Send the packet
socket.send(packet);
outputArea.append("Packet sent at: " + new Date() + "\n");
// Display packet information
outputArea.append("Sent by: " + remote_addr.getHostAddress() + "\n");
outputArea.append("Sent from: " + packet.getPort() + "\n");
socket.close();
}
catch(UnknownHostException ue){
outputArea.append("Unknown host: " + hostname + "\n");
outputArea.append("Unknown host: " + ue + "\n");
}
catch(IOException e){
outputArea.append("Error: " + e + "\n");
}
}
private String UDPReceiver(String portNum){
String message = "";
DatagramSocket socket = null;
try{
// Create a DatagramSocket
socket = new DatagramSocket(Integer.parseInt(portNum));
outputArea.append("Listening on local port " + socket.getLocalPort() + "\n");
// Create a DatagramPacket, containing a maximum buffer of 256 bytes
DatagramPacket packet = new DatagramPacket(new byte[256], 256);
// Receive a packet - remember by default this is a blocking operation
socket.receive(packet);
outputArea.append("Packet received at " + new Date() + "\n");
// Display packet information
InetAddress remote_addr = packet.getAddress();
outputArea.append("Sender: " + remote_addr.getHostAddress() + "\n");
outputArea.append("From Port: " + packet.getPort() + "\n");
CLIENT_HOSTNAME = remote_addr.getHostAddress();
//CLIENT_PORT_NUMBER = Integer.toString(packet.getPort());
// Display packet contents, by reading from byte array
ByteArrayInputStream bin = new ByteArrayInputStream(packet.getData());
// Display only up to the length of the original UDP packet
for(int i = 0; i < packet.getLength(); i++){
int data = bin.read();
if(data == -1){
break;
}
else{
message = message + (char)data;
//outputArea.append(Character.toString((char)data));
}
}
socket.close();
return message;
}
catch(IOException e){
outputArea.append("Error: " + e + "\n");
message = "Error: " + e;
return message;
}
}
但我不知道这有什么问题
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:454)
at java.lang.Integer.parseInt(Integer.java:527)
at tftp_gui.main.UDPReceiver(main.java:508)
at tftp_gui.main.access$800(main.java:20)
at tftp_gui.main$10.run(main.java:374)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:721)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:691)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
您的方法是错误的,因为它需要打开客户端端口,无论如何,您的特殊问题是,当找不到文件时,您没有返回结果: 检查:
if(check == true){
outputArea.append("File location verified..." + "\n");
outputArea.append("Initiating transfer...." + "\n\n");
UDPSender(CLIENT_HOSTNAME, CLIENT_PORT_NUMBER, "1");
}
else {
outputArea.append("File does not exist..." + "\n");
outputArea.append("Exiting run..." + "\n");
UDPSender(CLIENT_HOSTNAME, CLIENT_PORT_NUMBER, "0"); // here you should send 0
}
此外,这里还有一个小问题:if(message==“1”)
它应该看起来像if(“1”。equals(message))
您的错误是可以自我解释的-您没有声明正确的客户端端口号或服务器端口号,以下是我用于测试的内容:
private final static String SERVER_PORT_NUMBER = "1234";
private static String CLIENT_HOSTNAME;
private static final String CLIENT_PORT_NUMBER = "2345";
private static final String FILE_REQUEST = "a.txt";
private static final String SHARED_DIR = "d:/";
private static final String SERVER_HOSTNAME = "localhost";
我明白。我只是忘了把那部分放进去。我用来测试这个的文件实际上就在那里。但是,我确实将代码放入了程序中,但仍然没有收到任何响应。@jwebster我已经测试了您的代码,发现了一些小错误,但整个发送-接收部分工作正常
private final static String SERVER_PORT_NUMBER = "1234";
private static String CLIENT_HOSTNAME;
private static final String CLIENT_PORT_NUMBER = "2345";
private static final String FILE_REQUEST = "a.txt";
private static final String SHARED_DIR = "d:/";
private static final String SERVER_HOSTNAME = "localhost";