Java example source code file (ImmutableDescriptor.java)
The ImmutableDescriptor.java Java example source code/*
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* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
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* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package javax.management;
import com.sun.jmx.mbeanserver.Util;
import java.io.InvalidObjectException;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
/**
* An immutable descriptor.
* @since 1.6
*/
public class ImmutableDescriptor implements Descriptor {
private static final long serialVersionUID = 8853308591080540165L;
/**
* The names of the fields in this ImmutableDescriptor with their
* original case. The names must be in alphabetical order as determined
* by {@link String#CASE_INSENSITIVE_ORDER}.
*/
private final String[] names;
/**
* The values of the fields in this ImmutableDescriptor. The
* elements in this array match the corresponding elements in the
* {@code names} array.
*/
private final Object[] values;
private transient int hashCode = -1;
/**
* An empty descriptor.
*/
public static final ImmutableDescriptor EMPTY_DESCRIPTOR =
new ImmutableDescriptor();
/**
* Construct a descriptor containing the given fields and values.
*
* @throws IllegalArgumentException if either array is null, or
* if the arrays have different sizes, or
* if a field name is null or empty, or if the same field name
* appears more than once.
*/
public ImmutableDescriptor(String[] fieldNames, Object[] fieldValues) {
this(makeMap(fieldNames, fieldValues));
}
/**
* Construct a descriptor containing the given fields. Each String
* must be of the form {@code fieldName=fieldValue}. The field name
* ends at the first {@code =} character; for example if the String
* is {@code a=b=c} then the field name is {@code a} and its value
* is {@code b=c}.
*
* @throws IllegalArgumentException if the parameter is null, or
* if a field name is empty, or if the same field name appears
* more than once, or if one of the strings does not contain
* an {@code =} character.
*/
public ImmutableDescriptor(String... fields) {
this(makeMap(fields));
}
/**
* <p>Construct a descriptor where the names and values of the fields
* are the keys and values of the given Map.</p>
*
* @throws IllegalArgumentException if the parameter is null, or
* if a field name is null or empty, or if the same field name appears
* more than once (which can happen because field names are not case
* sensitive).
*/
public ImmutableDescriptor(Map<String, ?> fields) {
if (fields == null)
throw new IllegalArgumentException("Null Map");
SortedMap<String, Object> map =
new TreeMap<String, Object>(String.CASE_INSENSITIVE_ORDER);
for (Map.Entry<String, ?> entry : fields.entrySet()) {
String name = entry.getKey();
if (name == null || name.equals(""))
throw new IllegalArgumentException("Empty or null field name");
if (map.containsKey(name))
throw new IllegalArgumentException("Duplicate name: " + name);
map.put(name, entry.getValue());
}
int size = map.size();
this.names = map.keySet().toArray(new String[size]);
this.values = map.values().toArray(new Object[size]);
}
/**
* This method can replace a deserialized instance of this
* class with another instance. For example, it might replace
* a deserialized empty ImmutableDescriptor with
* {@link #EMPTY_DESCRIPTOR}.
*
* @return the replacement object, which may be {@code this}.
*
* @throws InvalidObjectException if the read object has invalid fields.
*/
private Object readResolve() throws InvalidObjectException {
boolean bad = false;
if (names == null || values == null || names.length != values.length)
bad = true;
if (!bad) {
if (names.length == 0 && getClass() == ImmutableDescriptor.class)
return EMPTY_DESCRIPTOR;
final Comparator<String> compare = String.CASE_INSENSITIVE_ORDER;
String lastName = ""; // also catches illegal null name
for (int i = 0; i < names.length; i++) {
if (names[i] == null ||
compare.compare(lastName, names[i]) >= 0) {
bad = true;
break;
}
lastName = names[i];
}
}
if (bad)
throw new InvalidObjectException("Bad names or values");
return this;
}
private static SortedMap<String, ?> makeMap(String[] fieldNames,
Object[] fieldValues) {
if (fieldNames == null || fieldValues == null)
throw new IllegalArgumentException("Null array parameter");
if (fieldNames.length != fieldValues.length)
throw new IllegalArgumentException("Different size arrays");
SortedMap<String, Object> map =
new TreeMap<String, Object>(String.CASE_INSENSITIVE_ORDER);
for (int i = 0; i < fieldNames.length; i++) {
String name = fieldNames[i];
if (name == null || name.equals(""))
throw new IllegalArgumentException("Empty or null field name");
Object old = map.put(name, fieldValues[i]);
if (old != null) {
throw new IllegalArgumentException("Duplicate field name: " +
name);
}
}
return map;
}
private static SortedMap<String, ?> makeMap(String[] fields) {
if (fields == null)
throw new IllegalArgumentException("Null fields parameter");
String[] fieldNames = new String[fields.length];
String[] fieldValues = new String[fields.length];
for (int i = 0; i < fields.length; i++) {
String field = fields[i];
int eq = field.indexOf('=');
if (eq < 0) {
throw new IllegalArgumentException("Missing = character: " +
field);
}
fieldNames[i] = field.substring(0, eq);
// makeMap will catch the case where the name is empty
fieldValues[i] = field.substring(eq + 1);
}
return makeMap(fieldNames, fieldValues);
}
/**
* <p>Return an {@code ImmutableDescriptor} whose contents are the union of
* the given descriptors. Every field name that appears in any of
* the descriptors will appear in the result with the
* value that it has when the method is called. Subsequent changes
* to any of the descriptors do not affect the ImmutableDescriptor
* returned here.</p>
*
* <p>In the simplest case, there is only one descriptor and the
* returned {@code ImmutableDescriptor} is a copy of its fields at the
* time this method is called:</p>
*
* <pre>
* Descriptor d = something();
* ImmutableDescriptor copy = ImmutableDescriptor.union(d);
* </pre>
*
* @param descriptors the descriptors to be combined. Any of the
* descriptors can be null, in which case it is skipped.
*
* @return an {@code ImmutableDescriptor} that is the union of the given
* descriptors. The returned object may be identical to one of the
* input descriptors if it is an ImmutableDescriptor that contains all of
* the required fields.
*
* @throws IllegalArgumentException if two Descriptors contain the
* same field name with different associated values. Primitive array
* values are considered the same if they are of the same type with
* the same elements. Object array values are considered the same if
* {@link Arrays#deepEquals(Object[],Object[])} returns true.
*/
public static ImmutableDescriptor union(Descriptor... descriptors) {
// Optimize the case where exactly one Descriptor is non-Empty
// and it is immutable - we can just return it.
int index = findNonEmpty(descriptors, 0);
if (index < 0)
return EMPTY_DESCRIPTOR;
if (descriptors[index] instanceof ImmutableDescriptor
&& findNonEmpty(descriptors, index + 1) < 0)
return (ImmutableDescriptor) descriptors[index];
Map<String, Object> map =
new TreeMap<String, Object>(String.CASE_INSENSITIVE_ORDER);
ImmutableDescriptor biggestImmutable = EMPTY_DESCRIPTOR;
for (Descriptor d : descriptors) {
if (d != null) {
String[] names;
if (d instanceof ImmutableDescriptor) {
ImmutableDescriptor id = (ImmutableDescriptor) d;
names = id.names;
if (id.getClass() == ImmutableDescriptor.class
&& names.length > biggestImmutable.names.length)
biggestImmutable = id;
} else
names = d.getFieldNames();
for (String n : names) {
Object v = d.getFieldValue(n);
Object old = map.put(n, v);
if (old != null) {
boolean equal;
if (old.getClass().isArray()) {
equal = Arrays.deepEquals(new Object[] {old},
new Object[] {v});
} else
equal = old.equals(v);
if (!equal) {
final String msg =
"Inconsistent values for descriptor field " +
n + ": " + old + " :: " + v;
throw new IllegalArgumentException(msg);
}
}
}
}
}
if (biggestImmutable.names.length == map.size())
return biggestImmutable;
return new ImmutableDescriptor(map);
}
private static boolean isEmpty(Descriptor d) {
if (d == null)
return true;
else if (d instanceof ImmutableDescriptor)
return ((ImmutableDescriptor) d).names.length == 0;
else
return (d.getFieldNames().length == 0);
}
private static int findNonEmpty(Descriptor[] ds, int start) {
for (int i = start; i < ds.length; i++) {
if (!isEmpty(ds[i]))
return i;
}
return -1;
}
private int fieldIndex(String name) {
return Arrays.binarySearch(names, name, String.CASE_INSENSITIVE_ORDER);
}
public final Object getFieldValue(String fieldName) {
checkIllegalFieldName(fieldName);
int i = fieldIndex(fieldName);
if (i < 0)
return null;
Object v = values[i];
if (v == null || !v.getClass().isArray())
return v;
if (v instanceof Object[])
return ((Object[]) v).clone();
// clone the primitive array, could use an 8-way if/else here
int len = Array.getLength(v);
Object a = Array.newInstance(v.getClass().getComponentType(), len);
System.arraycopy(v, 0, a, 0, len);
return a;
}
public final String[] getFields() {
String[] result = new String[names.length];
for (int i = 0; i < result.length; i++) {
Object value = values[i];
if (value == null)
value = "";
else if (!(value instanceof String))
value = "(" + value + ")";
result[i] = names[i] + "=" + value;
}
return result;
}
public final Object[] getFieldValues(String... fieldNames) {
if (fieldNames == null)
return values.clone();
Object[] result = new Object[fieldNames.length];
for (int i = 0; i < fieldNames.length; i++) {
String name = fieldNames[i];
if (name != null && !name.equals(""))
result[i] = getFieldValue(name);
}
return result;
}
public final String[] getFieldNames() {
return names.clone();
}
/**
* Compares this descriptor to the given object. The objects are equal if
* the given object is also a Descriptor, and if the two Descriptors have
* the same field names (possibly differing in case) and the same
* associated values. The respective values for a field in the two
* Descriptors are equal if the following conditions hold:
*
* <ul>
* <li>If one value is null then the other must be too.
* <li>If one value is a primitive array then the other must be a primitive
* array of the same type with the same elements.</li>
* <li>If one value is an object array then the other must be too and
* {@link Arrays#deepEquals(Object[],Object[])} must return true.</li>
* <li>Otherwise {@link Object#equals(Object)} must return true.
* </ul>
*
* @param o the object to compare with.
*
* @return {@code true} if the objects are the same; {@code false}
* otherwise.
*
*/
// Note: this Javadoc is copied from javax.management.Descriptor
// due to 6369229.
@Override
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Descriptor))
return false;
String[] onames;
if (o instanceof ImmutableDescriptor) {
onames = ((ImmutableDescriptor) o).names;
} else {
onames = ((Descriptor) o).getFieldNames();
Arrays.sort(onames, String.CASE_INSENSITIVE_ORDER);
}
if (names.length != onames.length)
return false;
for (int i = 0; i < names.length; i++) {
if (!names[i].equalsIgnoreCase(onames[i]))
return false;
}
Object[] ovalues;
if (o instanceof ImmutableDescriptor)
ovalues = ((ImmutableDescriptor) o).values;
else
ovalues = ((Descriptor) o).getFieldValues(onames);
return Arrays.deepEquals(values, ovalues);
}
/**
* <p>Returns the hash code value for this descriptor. The hash
* code is computed as the sum of the hash codes for each field in
* the descriptor. The hash code of a field with name {@code n}
* and value {@code v} is {@code n.toLowerCase().hashCode() ^ h}.
* Here {@code h} is the hash code of {@code v}, computed as
* follows:</p>
*
* <ul>
* <li>If {@code v} is null then {@code h} is 0.
* <li>If {@code v} is a primitive array then {@code h} is computed using
* the appropriate overloading of {@code java.util.Arrays.hashCode}.</li>
* <li>If {@code v} is an object array then {@code h} is computed using
* {@link Arrays#deepHashCode(Object[])}.</li>
* <li>Otherwise {@code h} is {@code v.hashCode()}.
* </ul>
*
* @return A hash code value for this object.
*
*/
// Note: this Javadoc is copied from javax.management.Descriptor
// due to 6369229.
@Override
public int hashCode() {
if (hashCode == -1) {
hashCode = Util.hashCode(names, values);
}
return hashCode;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder("{");
for (int i = 0; i < names.length; i++) {
if (i > 0)
sb.append(", ");
sb.append(names[i]).append("=");
Object v = values[i];
if (v != null && v.getClass().isArray()) {
String s = Arrays.deepToString(new Object[] {v});
s = s.substring(1, s.length() - 1); // remove [...]
v = s;
}
sb.append(String.valueOf(v));
}
return sb.append("}").toString();
}
/**
* Returns true if all of the fields have legal values given their
* names. This method always returns true, but a subclass can
* override it to return false when appropriate.
*
* @return true if the values are legal.
*
* @exception RuntimeOperationsException if the validity checking fails.
* The method returns false if the descriptor is not valid, but throws
* this exception if the attempt to determine validity fails.
*/
public boolean isValid() {
return true;
}
/**
* <p>Returns a descriptor which is equal to this descriptor.
* Changes to the returned descriptor will have no effect on this
* descriptor, and vice versa.</p>
*
* <p>This method returns the object on which it is called.
* A subclass can override it
* to return another object provided the contract is respected.
*
* @exception RuntimeOperationsException for illegal value for field Names
* or field Values.
* If the descriptor construction fails for any reason, this exception will
* be thrown.
*/
@Override
public Descriptor clone() {
return this;
}
/**
* This operation is unsupported since this class is immutable. If
* this call would change a mutable descriptor with the same contents,
* then a {@link RuntimeOperationsException} wrapping an
* {@link UnsupportedOperationException} is thrown. Otherwise,
* the behavior is the same as it would be for a mutable descriptor:
* either an exception is thrown because of illegal parameters, or
* there is no effect.
*/
public final void setFields(String[] fieldNames, Object[] fieldValues)
throws RuntimeOperationsException {
if (fieldNames == null || fieldValues == null)
illegal("Null argument");
if (fieldNames.length != fieldValues.length)
illegal("Different array sizes");
for (int i = 0; i < fieldNames.length; i++)
checkIllegalFieldName(fieldNames[i]);
for (int i = 0; i < fieldNames.length; i++)
setField(fieldNames[i], fieldValues[i]);
}
/**
* This operation is unsupported since this class is immutable. If
* this call would change a mutable descriptor with the same contents,
* then a {@link RuntimeOperationsException} wrapping an
* {@link UnsupportedOperationException} is thrown. Otherwise,
* the behavior is the same as it would be for a mutable descriptor:
* either an exception is thrown because of illegal parameters, or
* there is no effect.
*/
public final void setField(String fieldName, Object fieldValue)
throws RuntimeOperationsException {
checkIllegalFieldName(fieldName);
int i = fieldIndex(fieldName);
if (i < 0)
unsupported();
Object value = values[i];
if ((value == null) ?
(fieldValue != null) :
!value.equals(fieldValue))
unsupported();
}
/**
* Removes a field from the descriptor.
*
* @param fieldName String name of the field to be removed.
* If the field name is illegal or the field is not found,
* no exception is thrown.
*
* @exception RuntimeOperationsException if a field of the given name
* exists and the descriptor is immutable. The wrapped exception will
* be an {@link UnsupportedOperationException}.
*/
public final void removeField(String fieldName) {
if (fieldName != null && fieldIndex(fieldName) >= 0)
unsupported();
}
static Descriptor nonNullDescriptor(Descriptor d) {
if (d == null)
return EMPTY_DESCRIPTOR;
else
return d;
}
private static void checkIllegalFieldName(String name) {
if (name == null || name.equals(""))
illegal("Null or empty field name");
}
private static void unsupported() {
UnsupportedOperationException uoe =
new UnsupportedOperationException("Descriptor is read-only");
throw new RuntimeOperationsException(uoe);
}
private static void illegal(String message) {
IllegalArgumentException iae = new IllegalArgumentException(message);
throw new RuntimeOperationsException(iae);
}
}
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