Question

我将2个String值从Client.java发送到OutputStream中，如下所示：

outputStream.write(username.getText().getBytes());
outputStream.write(password.getText().getBytes());

在Server.java中，当我读取inputStream时，我试图将每个值分开：

inputStream = s.getInputStream(); byte[]username = new byte[20]; inputStream.read(username); String user = new String(username); System.out.println("username = "+user);

我逻辑地得到：usernamepassword作为控制台输出。我想做的是：

     String usr = new String(user);
     String pass = new String(password);

有没有比在outputStream String中添加分隔符更好的方法呢？

Answer 1

您需要分隔两个字符串值，以便读者知道一个字符串的结束位置和下一个字符串的开头。该分隔符的实际内容由您自行决定。

在写出实际字节之前，您可以使用固定宽度的整数写出字符串的字节长度。然后，读者可以先读取长度，然后再读取指定的字节数：

DataOutputStream dos = new DataOutputStream(outputStream);
byte[] bytes;
int len;

bytes = username.getText().getBytes(StandardCharsets.UTF_8);
len = bytes.length;
dos.writeInt(len);
dos.write(bytes, 0, len);

bytes = password.getText().getBytes(StandardCharsets.UTF_8);
len = bytes.length;
dos.writeInt(len);
dos.write(bytes, 0, len);

inputStream = s.getInputStream();
DataInputStream dis = new DataInputStream(inputStream);
byte[] bytes;
int len;

len = dis.readInt();
bytes = new byte[len];
dis.readFully(bytes);
String username = new String(bytes, StandardCharsets.UTF_8);

len = dis.readInt();
bytes = new byte[len];
dis.readFully(bytes);
String password = new String(bytes, StandardCharsets.UTF_8);

或者，DataOutputStream和DataInputStream可以直接写入/读取String值，在内部为您处理上述逻辑（使用short代替int } for length value）：

DataOutputStream dos = new DataOutputStream(outputStream);
dos.writeUTF(username.getText());
dos.writeUTF(password.getText());

inputStream = s.getInputStream();
DataInputStream dis = new DataInputStream(inputStream);

String username = dis.readUTF();
String password = dis.readUTF();

您可以写出一个永远不会出现在字符串值本身中的唯一字符序列，例如换行符或控制字符（甚至是空终止符）。然后，读者可以读取字节，直到遇到该序列：

OutputStreamWriter writer = new OutputStreamWriter(outputStream, StandardCharsets.UTF_8); 
String s;

s = username.getText();
writer.write(s, 0, s.length());
writer.write(10);

s = password.getText();
writer.write(s, 0, s.length());
writer.write(10);

inputStream = s.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));

String username = reader.readLine();
String password = reader.readLine();

可替换地：

OutputStreamWriter writer = new OutputStreamWriter(outputStream, StandardCharsets.UTF_8); 
String s;

s = username.getText();
writer.write(s, 0, s.length());
writer.write(0);

s = password.getText();
writer.write(s, 0, s.length());
writer.write(0);

inputStream = s.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
StringBuilder sb = new StringBuilder();
int ch;

do
{
    ch = reader.read();
    if (ch <= 0) break;
    sb.append((char)ch);
}
while (true);
String username = sb.toString();

sb.setLength(0);
do
{
    ch = reader.read();
    if (ch <= 0) break;
    sb.append((char)ch);
}
while (true);
String password = sb.toString();

Answer 2

我会选择DataOutputStream进行写作，DataInputStream进行阅读。有了这些，你可以在每个String之前写一个整数值来知道文本的长度，如下所示：

DataOutputStream dos = new DataOutputStream(outputStream);
dos.writeInt(username.getText().length());
dos.write(username.getText().getBytes());
dos.writeInt(password.getText().length());
dos.write(password.getText().getBytes());

然后，在服务器端：

DataInputStream dis = new DataInputStream(inputStream);
int length = 0; // will be used to store the length of each text

length = bytesRead = dis.readInt(); // Read the length of the first text
byte[] usernameBuffer = new byte[length];
dis.read(usernameBuffer);
String username = new String(usernameBuffer);

// Now reading the other text
length = dis.readInt(); // Read the length of the second text
byte[] passwordBuffer = new byte[length];
dis.read(passwordBuffer);
String password = new String(passwordBuffer);

Java - 发送到OustputStream的两个字符串之间的差异

2 个答案: