javax.mail.internet.UniqueValue Maven / Gradle / Ivy
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package javax.mail.internet;
import java.net.*;
import javax.mail.Session;
/**
* This is a utility class that generates unique values. The generated
* String contains only US-ASCII characters and hence is safe for use
* in RFC822 headers.
*
* This is a package private class.
*
* @author John Mani
* @author Max Spivak
* @author Bill Shannon
*/
class UniqueValue {
/**
* A global unique number, to ensure uniqueness of generated strings.
*/
private static int id = 0;
/**
* Get a unique value for use in a multipart boundary string.
*
* This implementation generates it by concatenating a global
* part number, a newly created object's hashCode(),
* and the current time (in milliseconds).
*/
public static String getUniqueBoundaryValue() {
StringBuffer s = new StringBuffer();
// Unique string is ----=_Part__.
s.append("----=_Part_").append(getUniqueId()).append("_").
append(s.hashCode()).append('.').
append(System.currentTimeMillis());
return s.toString();
}
/**
* Get a unique value for use in a Message-ID.
*
* This implementation generates it by concatenating a newly
* created object's hashCode(), a global ID
* (incremented on every use), the current
* time (in milliseconds), the string "JavaMail", and
* this user's local address generated by
* InternetAddress.getLocalAddress().
* (The address defaults to "javamailuser@localhost" if
* getLocalAddress() returns null.)
*
* @param ssn Session object used to get the local address
* @see javax.mail.internet.InternetAddress
*/
public static String getUniqueMessageIDValue(Session ssn) {
String suffix = null;
InternetAddress addr = InternetAddress.getLocalAddress(ssn);
if (addr != null)
suffix = addr.getAddress();
else {
suffix = "javamailuser@localhost"; // worst-case default
}
StringBuffer s = new StringBuffer();
// Unique string is ...JavaMail.
s.append(s.hashCode()).append('.').append(getUniqueId()).append('.').
append(System.currentTimeMillis()).append('.').
append("JavaMail.").
append(suffix);
return s.toString();
}
/**
* Ensure ID is unique by synchronizing access.
* XXX - Could use AtomicInteger.getAndIncrement() in J2SE 5.0.
*/
private static synchronized int getUniqueId() {
return id++;
}
}