我正在尝试构建一个客户端/服务器应用程序,其中客户端向服务器发出命令,并且服务器根据命令执行不同的功能。
我的客户端代码如下:
公共(public)类客户端{
private Socket clientSocket;
private BufferedReader buffer;
private BufferedReader in;
private PrintWriter out;
public Client (String host, int port) throws UnknownHostException, IOException {
this.clientSocket = new Socket (host,port);
this.buffer = new BufferedReader(new InputStreamReader (System.in));
}
public void start () throws IOException {
this.in = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
this.out = new PrintWriter (this.clientSocket.getOutputStream());
while (true ) {
String input = buffer.readLine();
String parser [] = input.trim().split(":");
this.out.println(input);
this.out.flush();
if ("quit".equals(parser[0]) || parser[0] == null)
break;
else if ("create account".equals(parser[0]))
System.out.println(in.readLine());
else if ("upload".equals(parser[0])) {
System.out.println("Here");
File file = new File(parser[1]);
long length = file.length();
byte[] bytes = new byte[1000000];
InputStream in = new FileInputStream(file);
OutputStream out = this.clientSocket.getOutputStream();
int count;
System.out.println("Sending");
while ((count = in.read(bytes)) > 0) {
out.write(bytes, 0, count);
}
out.close();
in.close();
break;
}
}
}
public static void main (String args []) throws UnknownHostException, IOException {
Client client = new Client ("127.0.0.1", 6666);
client.start();
}
}
我的服务器代码如下:
公共(public)类服务器{
public static void main (String args []) throws IOException {
ServerSocket socket = new ServerSocket (6666);
Biblioteca biblioteca = new Biblioteca(); //biblioteca comum a todas as threads
while (true) {
Socket clientSocket = socket.accept();
Thread cliente = new Thread (new Service (clientSocket, biblioteca));
cliente.start();
}
}
}
由于这是一个多客户端服务器,因此我创建了一个运行整个服务器的线程。这是它的代码:
公共(public)类Service实现Runnable{
private Socket clientSocket;
private Biblioteca biblioteca;
public Service (Socket clientSocket, Biblioteca biblioteca) throws IOException {
this.clientSocket = clientSocket;
this.biblioteca = biblioteca;
}
public void run () {
String answer;
try {
BufferedReader in = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(this.clientSocket.getOutputStream());
while (true) {
String s = in.readLine();
String parser [] = s.trim().split(":");
if ("create account".equals(parser[0])) {
this.biblioteca.createAccount(parser[1], parser[2]);
out.println("Conta com email: " + parser[1] + " criada\n");
out.flush();
}
else if ("upload".equals(parser[0])){
InputStream inS = this.clientSocket.getInputStream();
OutputStream outS = new FileOutputStream(new File ("/Users/Jota/Desktop/SDSERVER/test2.xml"));
byte[] bytes = new byte[1000000];
int count;
System.out.println ("Receiving");
while ((count = inS.read(bytes)) > 0) {
outS.write(bytes, 0, count);
}
System.out.println("Received");
outS.close();
inS.close();
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
所以一切都按计划运行,除非我尝试使用“上传”功能。在客户端命令行上,如果我输入类似“upload:/Users/Jota/Desktop/SDMUSICA/encostateamim.mp3”之类的内容,则应该以这种方式解析:parser[0] ==“upload”和parser[1 ] ==“/Users/Jota/Desktop/SDMUSICA/encostateamim.mp3”
问题是我收到以下错误:
java.lang.NullPointerException
at Service.run(Service.java:31)
服务类的第31行是:
String parser [] = s.trim().split(":");
我不明白这里怎么会出现 nullPointerException,有人可以帮助我吗?
最佳答案
因为在 try catch block 中,您只能捕获 IOException。请注意,如果您在 catch 中声明类类型,它只会捕获该类或子类。如果你想捕获所有异常,请声明 Exception ex。
关于java - 处理tcp java socket项目中的异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/59553190/