com.sun.mail.util.logging.SeverityComparator Maven / Gradle / Ivy
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* Copyright (c) 2013-2015 Jason Mehrens. All rights reserved.
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package com.sun.mail.util.logging;
import java.io.Serializable;
import java.util.Comparator;
import java.util.logging.Level;
import java.util.logging.LogRecord;
/**
* Orders log records by level, thrown, sequence, and time.
*
* This comparator orders LogRecords by how severely each is attributed to
* failures in a program. The primary ordering is determined by the use of the
* logging API throughout a program by specifying a level to each log message.
* The secondary ordering is determined at runtime by the type of errors and
* exceptions generated by the program. The remaining ordering assumes that
* older log records are less severe than newer log records.
*
*
* The following LogRecord properties determine severity ordering:
*
* - The natural comparison of the LogRecord
* {@linkplain Level#intValue level}.
*
- The expected recovery order of {@linkplain LogRecord#getThrown() thrown}
* property of a LogRecord and its cause chain. This ordering is derived from
* the JLS 11.5 The Exception Hierarchy. This is performed by
* {@linkplain #apply(java.lang.Throwable) finding} the throwable that best
* describes the entire cause chain. Once a specific throwable of each chain is
* identified it is then ranked lowest to highest by the following rules:
*
*
* - All LogRecords with a {@code Throwable} defined as
* "{@link #isNormal(java.lang.Throwable) normal occurrence}".
*
- All LogRecords that do not have a thrown object.
*
- All checked exceptions. This is any class that is assignable to the
* {@code java.lang.Throwable} class and is not a
* {@code java.lang.RuntimeException} or a {@code java.lang.Error}.
*
- All unchecked exceptions. This is all {@code java.lang.RuntimeException}
* objects.
*
- All errors that indicate a serious problem. This is all
* {@code java.lang.Error} objects.
*
* - The natural comparison of the LogRecord
* {@linkplain LogRecord#getSequenceNumber() sequence}.
*
- The natural comparison of the LogRecord
* {@linkplain LogRecord#getMillis() millis}.
*
*
* @author Jason Mehrens
* @since JavaMail 1.5.2
*/
public class SeverityComparator implements Comparator, Serializable {
/**
* The generated serial version UID.
*/
private static final long serialVersionUID = -2620442245251791965L;
/**
* A single instance that is shared among the logging package.
*/
private static final SeverityComparator INSTANCE = new SeverityComparator();
/**
* A shared instance of a SeverityComparator. This is package private so the
* public API is not polluted with more methods.
*
* @return a shared instance of a SeverityComparator.
*/
static SeverityComparator getInstance() {
return INSTANCE;
}
/**
* Identifies a single throwable that best describes the given throwable and
* the entire {@linkplain Throwable#getCause() cause} chain. This method can
* be overridden to change the behavior of
* {@link #compare(java.util.logging.LogRecord, java.util.logging.LogRecord)}.
*
* @param chain the throwable or null.
* @return null if null was given, otherwise the throwable that best
* describes the entire chain.
* @see #isNormal(java.lang.Throwable)
*/
public Throwable apply(final Throwable chain) {
//Matches the j.u.f.UnaryOperator interface.
int limit = 0;
Throwable root = chain;
Throwable high = null;
Throwable normal = null;
for (Throwable cause = chain; cause != null; cause = cause.getCause()) {
root = cause; //Find the deepest cause.
//Find the deepest nomral occurrance.
if (isNormal(cause)) {
normal = cause;
}
//Find the deepest error that happened before a normal occurance.
if (normal == null && cause instanceof Error) {
high = cause;
}
//Deal with excessive cause chains and cyclic throwables.
if (++limit == (1 << 16)) {
break; //Give up.
}
}
return high != null ? high : normal != null ? normal : root;
}
/**
* {@link #apply(java.lang.Throwable) Reduces} each throwable chain argument
* then compare each throwable result.
*
* @param tc1 the first throwable chain or null.
* @param tc2 the second throwable chain or null.
* @return a negative integer, zero, or a positive integer as the first
* argument is less than, equal to, or greater than the second.
* @see #apply(java.lang.Throwable)
* @see #compareThrowable(java.lang.Throwable, java.lang.Throwable)
*/
public final int applyThenCompare(Throwable tc1, Throwable tc2) {
return tc1 == tc2 ? 0 : compareThrowable(apply(tc1), apply(tc2));
}
/**
* Compares two throwable objects or null. This method does not
* {@link #apply(java.lang.Throwable) reduce} each argument before
* comparing. This is method can be overridden to change the behavior of
* {@linkplain #compare(LogRecord, LogRecord)}.
*
* @param t1 the first throwable or null.
* @param t2 the second throwable or null.
* @return a negative integer, zero, or a positive integer as the first
* argument is less than, equal to, or greater than the second.
* @see #isNormal(java.lang.Throwable)
*/
public int compareThrowable(final Throwable t1, final Throwable t2) {
if (t1 == t2) { //Reflexive test including null.
return 0;
} else {
//Only one or the other is null at this point.
//Force normal occurrence to be lower than null.
if (t1 == null) {
return isNormal(t2) ? 1 : -1;
} else {
if (t2 == null) {
return isNormal(t1) ? -1 : 1;
}
}
//From this point on neither are null.
//Follow the shortcut if we can.
if (t1.getClass() == t2.getClass()) {
return 0;
}
//Ensure normal occurrence flow control is ordered low.
if (isNormal(t1)) {
return isNormal(t2) ? 0 : -1;
} else {
if (isNormal(t2)) {
return 1;
}
}
//Rank the two unidenticial throwables using the rules from
//JLS 11.5 The Exception Hierarchy.
if (t1 instanceof Error) {
return t2 instanceof Error ? 0 : 1;
} else if (t1 instanceof RuntimeException) {
return t2 instanceof Error ? -1
: t2 instanceof RuntimeException ? 0 : 1;
} else {
return t2 instanceof Error
|| t2 instanceof RuntimeException ? -1 : 0;
}
}
}
/**
* Compares two log records based on severity.
*
* @param o1 the first log record.
* @param o2 the second log record.
* @return a negative integer, zero, or a positive integer as the first
* argument is less than, equal to, or greater than the second.
* @throws NullPointerException if either argument is null.
*/
public int compare(final LogRecord o1, final LogRecord o2) {
if (o1 == null || o2 == null) { //Don't allow null.
throw new NullPointerException(toString(o1, o2));
}
/**
* LogRecords are mutable so a reflexive relationship test is a safety
* requirement.
*/
if (o1 == o2) {
return 0;
}
int cmp = compare(o1.getLevel(), o2.getLevel());
if (cmp == 0) {
cmp = applyThenCompare(o1.getThrown(), o2.getThrown());
if (cmp == 0) {
cmp = compare(o1.getSequenceNumber(), o2.getSequenceNumber());
if (cmp == 0) {
cmp = compare(o1.getMillis(), o2.getMillis());
}
}
}
return cmp;
}
/**
* Determines if the given object is also a comparator and it imposes the
* same ordering as this comparator.
*
* @param o the reference object with which to compare.
* @return true if this object equal to the argument; false otherwise.
*/
@Override
public boolean equals(final Object o) {
return o == null ? false : o.getClass() == getClass();
}
/**
* Returns a hash code value for the object.
*
* @return Returns a hash code value for the object.
*/
@Override
public int hashCode() {
return 31 * getClass().hashCode();
}
/**
* Determines if the given throwable instance is "normal occurrence". This
* is any checked or unchecked exception with 'Interrupt' in the class name
* or ancestral class name. Any {@code java.lang.ThreadDeath} object or
* subclasses.
*
* This method can be overridden to change the behavior of the
* {@linkplain #apply(java.lang.Throwable)} method.
*
* @param t a throwable or null.
* @return true the given throwable is a "normal occurrence".
*/
public boolean isNormal(final Throwable t) {
if (t == null) { //This is only needed when called directly.
return false;
}
/**
* Use the class names to avoid loading more classes.
*/
final Class root = Throwable.class;
final Class error = Error.class;
for (Class c = t.getClass(); c != root; c = c.getSuperclass()) {
if (error.isAssignableFrom(c)) {
if (c.getName().equals("java.lang.ThreadDeath")) {
return true;
}
} else {
//Interrupt, Interrupted or Interruption.
if (c.getName().contains("Interrupt")) {
return true;
}
}
}
return false;
}
/**
* Compare two level objects.
*
* @param a the first level.
* @param b the second level.
* @return a negative integer, zero, or a positive integer as the first
* argument is less than, equal to, or greater than the second.
*/
private int compare(final Level a, final Level b) {
return a == b ? 0 : compare(a.intValue(), b.intValue());
}
/**
* Outline the message create string.
*
* @param o1 argument one.
* @param o2 argument two.
* @return the message string.
*/
private static String toString(final Object o1, final Object o2) {
return o1 + ", " + o2;
}
/**
* Compare two longs. Can be removed when JDK 1.7 is required.
*
* @param x the first long.
* @param y the second long.
* @return a negative integer, zero, or a positive integer as the first
* argument is less than, equal to, or greater than the second.
*/
private int compare(final long x, final long y) {
return x < y ? -1 : x > y ? 1 : 0;
}
}