计算机在线考试系统 附源码和文档

package edu.exam.online.professional.utils; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import java.net.NetworkInterface; import java.nio.ByteBuffer; import java.util.Date; import java.util.Enumeration; import java.util.Random; import java.util.concurrent.atomic.AtomicInteger; import java.util.logging.Level; /** * A globally unique identifier for objects. * <p>Consists of 12 bytes, divided as follows: * <blockquote><pre> * <table border="1"> * <tr><td>0</td><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td><td>6</td> * <td>7</td><td>8</td><td>9</td><td>10</td><td>11</td></tr> * <tr><td colspan="4">time</td><td colspan="3">machine</td> * <td colspan="2">pid</td><td colspan="3">inc</td></tr> * </table> * </pre></blockquote> * * @guodandan objectids */ public class ObjectId implements Comparable<ObjectId>, java.io.Serializable { private static final long serialVersionUID = -4415279469780082174L; public static Logger log = LogManager.getLogger(ObjectId.class.getName()); /** * Gets a new object id. * * @return the new id */ public static ObjectId get() { return new ObjectId(); } /** * Checks if a string could be an <code>ObjectId</code>. * * @return whether the string could be an object id */ public static boolean isValid(String s) { if (s == null) return false; final int len = s.length(); if (len != 24) return false; for (int i = 0; i < len; i++) { char c = s.charAt(i); if (c >= '0' && c <= '9') continue; if (c >= 'a' && c <= 'f') continue; if (c >= 'A' && c <= 'F') continue; return false; } return true; } /** * Turn an object into an <code>ObjectId</code>, if possible. * Strings will be converted into <code>ObjectId</code>s, if possible, and <code>ObjectId</code>s will * be cast and returned. Passing in <code>null</code> returns <code>null</code>. * * @param o the object to convert * @return an <code>ObjectId</code> if it can be massaged, null otherwise */ public static ObjectId massageToObjectId(Object o) { if (o == null) return null; if (o instanceof ObjectId) return (ObjectId) o; if (o instanceof String) { String s = o.toString(); if (isValid(s)) return new ObjectId(s); } return null; } public ObjectId(Date time) { this(time, _genmachine, _nextInc.getAndIncrement()); } public ObjectId(Date time, int inc) { this(time, _genmachine, inc); } public ObjectId(Date time, int machine, int inc) { _time = (int) (time.getTime() / 1000); _machine = machine; _inc = inc; _new = false; } /** * Creates a new instance from a string. * * @param s the string to convert * @throws IllegalArgumentException if the string is not a valid id */ public ObjectId(String s) { this(s, false); } public ObjectId(String s, boolean babble) { if (!isValid(s)) throw new IllegalArgumentException("invalid ObjectId [" + s + "]"); if (babble) s = babbleToMongod(s); byte b[] = new byte[12]; for (int i = 0; i < b.length; i++) { b[i] = (byte) Integer.parseInt(s.substring(i * 2, i * 2 + 2), 16); } ByteBuffer bb = ByteBuffer.wrap(b); _time = bb.getInt(); _machine = bb.getInt(); _inc = bb.getInt(); _new = false; } public ObjectId(byte[] b) { if (b.length != 12) throw new IllegalArgumentException("need 12 bytes"); ByteBuffer bb = ByteBuffer.wrap(b); _time = bb.getInt(); _machine = bb.getInt(); _inc = bb.getInt(); _new = false; } /** * Creates an ObjectId * * @param time time in seconds * @param machine machine ID * @param inc incremental value */ public ObjectId(int time, int machine, int inc) { _time = time; _machine = machine; _inc = inc; _new = false; } /** * Create a new object id. */ public ObjectId() { _time = (int) (System.currentTimeMillis() / 1000); _machine = _genmachine; _inc = _nextInc.getAndIncrement(); _new = true; } public int hashCode() { int x = _time; x += (_machine * 111); x += (_inc * 17); return x; } public boolean equals(Object o) { if (this == o) return true; ObjectId other = massageToObjectId(o); if (other == null) return false; return _time == other._time && _machine == other._machine && _inc == other._inc; } public String toStringBabble() { return babbleToMongod(toStringMongod()); } public String toStringMongod() { byte b[] = toByteArray(); StringBuilder buf = new StringBuilder(24); for (int i = 0; i < b.length; i++) { int x = b[i] & 0xFF; String s = Integer.toHexString(x); if (s.length() == 1) buf.append("0"); buf.append(s); } return buf.toString(); } public byte[] toByteArray() { byte b[] = new byte[12]; ByteBuffer bb = ByteBuffer.wrap(b); // by default BB is big endian like we need bb.putInt(_time); bb.putInt(_machine); bb.putInt(_inc); return b; } static String _pos(String s, int p) { return s.substring(p * 2, (p * 2) + 2); } public static String babbleToMongod(String b) { if (!isValid(b)) throw new IllegalArgumentException("invalid object id: " + b); StringBuilder buf = new StringBuilder(24); for (int i = 7; i >= 0; i--) buf.append(_pos(b, i)); for (int i = 11; i >= 8; i--) buf.append(_pos(b, i)); return buf.toString(); } public String toString() { return toStringMongod(); } int _compareUnsigned(int i, int j) { long li = 0xFFFFFFFFL; li = i & li; long lj = 0xFFFFFFFFL; lj = j & lj; long diff = li - lj; if (diff < Integer.MIN_VALUE) return Integer.MIN_VALUE; if (diff > Integer.MAX_VALUE) return Integer.MAX_VALUE; return (int) diff; } public int compareTo(ObjectId id) { if (id == null) return -1; int x = _compareUnsigned(_time, id._time); if (x != 0) return x; x = _compareUnsigned(_machine, id._machine); if (x != 0) return x; return _compareUnsigned(_inc, id._inc); } public int getMachine() { return _machine; } /** * Gets the time of this ID, in milliseconds */ public long getTime() { return _time * 1000L; } /** * Gets the time of this ID, in seconds */ public int getTimeSecond() { return _time; } public int getInc() { return _inc; } public int _time() { return _time; } public int _machine() { return _machine; } public int _inc() { return _inc; } public boolean isNew() { return _new; } public void notNew() { _new = false; } /** * Gets the generated machine ID, identifying the machine / process / class loader */ public static int getGenMachineId() { return _genmachine; } /** * Gets the current value of the auto increment */ public static int g