Java example source code file (BasicAttribute.java)
The BasicAttribute.java Java example source code/*
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*
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* 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.naming.directory;
import java.util.Vector;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.lang.reflect.Array;
import javax.naming.NamingException;
import javax.naming.NamingEnumeration;
import javax.naming.OperationNotSupportedException;
/**
* This class provides a basic implementation of the <tt>Attribute interface.
*<p>
* This implementation does not support the schema methods
* <tt>getAttributeDefinition() and getAttributeSyntaxDefinition().
* They simply throw <tt>OperationNotSupportedException.
* Subclasses of <tt>BasicAttribute should override these methods if they
* support them.
*<p>
* The <tt>BasicAttribute class by default uses Object.equals() to
* determine equality of attribute values when testing for equality or
* when searching for values, <em>except when the value is an array.
* For an array, each element of the array is checked using <tt>Object.equals().
* Subclasses of <tt>BasicAttribute can make use of schema information
* when doing similar equality checks by overriding methods
* in which such use of schema is meaningful.
* Similarly, the <tt>BasicAttribute class by default returns the values passed to its
* constructor and/or manipulated using the add/remove methods.
* Subclasses of <tt>BasicAttribute can override get() and getAll()
* to get the values dynamically from the directory (or implement
* the <tt>Attribute interface directly instead of subclassing BasicAttribute).
*<p>
* Note that updates to <tt>BasicAttribute (such as adding or removing a value)
* does not affect the corresponding representation of the attribute
* in the directory. Updates to the directory can only be effected
* using operations in the <tt>DirContext interface.
*<p>
* A <tt>BasicAttribute instance is not synchronized against concurrent
* multithreaded access. Multiple threads trying to access and modify a
* <tt>BasicAttribute should lock the object.
*
* @author Rosanna Lee
* @author Scott Seligman
* @since 1.3
*/
public class BasicAttribute implements Attribute {
/**
* Holds the attribute's id. It is initialized by the public constructor and
* cannot be null unless methods in BasicAttribute that use attrID
* have been overridden.
* @serial
*/
protected String attrID;
/**
* Holds the attribute's values. Initialized by public constructors.
* Cannot be null unless methods in BasicAttribute that use
* values have been overridden.
*/
protected transient Vector<Object> values;
/**
* A flag for recording whether this attribute's values are ordered.
* @serial
*/
protected boolean ordered = false;
@SuppressWarnings("unchecked")
public Object clone() {
BasicAttribute attr;
try {
attr = (BasicAttribute)super.clone();
} catch (CloneNotSupportedException e) {
attr = new BasicAttribute(attrID, ordered);
}
attr.values = (Vector<Object>)values.clone();
return attr;
}
/**
* Determines whether obj is equal to this attribute.
* Two attributes are equal if their attribute-ids, syntaxes
* and values are equal.
* If the attribute values are unordered, the order that the values were added
* are irrelevant. If the attribute values are ordered, then the
* order the values must match.
* If obj is null or not an Attribute, false is returned.
*<p>
* By default <tt>Object.equals() is used when comparing the attribute
* id and its values except when a value is an array. For an array,
* each element of the array is checked using <tt>Object.equals().
* A subclass may override this to make
* use of schema syntax information and matching rules,
* which define what it means for two attributes to be equal.
* How and whether a subclass makes
* use of the schema information is determined by the subclass.
* If a subclass overrides <tt>equals(), it should also override
* <tt>hashCode()
* such that two attributes that are equal have the same hash code.
*
* @param obj The possibly null object to check.
* @return true if obj is equal to this attribute; false otherwise.
* @see #hashCode
* @see #contains
*/
public boolean equals(Object obj) {
if ((obj != null) && (obj instanceof Attribute)) {
Attribute target = (Attribute)obj;
// Check order first
if (isOrdered() != target.isOrdered()) {
return false;
}
int len;
if (attrID.equals(target.getID()) &&
(len=size()) == target.size()) {
try {
if (isOrdered()) {
// Go through both list of values
for (int i = 0; i < len; i++) {
if (!valueEquals(get(i), target.get(i))) {
return false;
}
}
} else {
// order is not relevant; check for existence
Enumeration<?> theirs = target.getAll();
while (theirs.hasMoreElements()) {
if (find(theirs.nextElement()) < 0)
return false;
}
}
} catch (NamingException e) {
return false;
}
return true;
}
}
return false;
}
/**
* Calculates the hash code of this attribute.
*<p>
* The hash code is computed by adding the hash code of
* the attribute's id and that of all of its values except for
* values that are arrays.
* For an array, the hash code of each element of the array is summed.
* If a subclass overrides <tt>hashCode(), it should override
* <tt>equals()
* as well so that two attributes that are equal have the same hash code.
*
* @return an int representing the hash code of this attribute.
* @see #equals
*/
public int hashCode() {
int hash = attrID.hashCode();
int num = values.size();
Object val;
for (int i = 0; i < num; i ++) {
val = values.elementAt(i);
if (val != null) {
if (val.getClass().isArray()) {
Object it;
int len = Array.getLength(val);
for (int j = 0 ; j < len ; j++) {
it = Array.get(val, j);
if (it != null) {
hash += it.hashCode();
}
}
} else {
hash += val.hashCode();
}
}
}
return hash;
}
/**
* Generates the string representation of this attribute.
* The string consists of the attribute's id and its values.
* This string is meant for debugging and not meant to be
* interpreted programmatically.
* @return The non-null string representation of this attribute.
*/
public String toString() {
StringBuffer answer = new StringBuffer(attrID + ": ");
if (values.size() == 0) {
answer.append("No values");
} else {
boolean start = true;
for (Enumeration<Object> e = values.elements(); e.hasMoreElements(); ) {
if (!start)
answer.append(", ");
answer.append(e.nextElement());
start = false;
}
}
return answer.toString();
}
/**
* Constructs a new instance of an unordered attribute with no value.
*
* @param id The attribute's id. It cannot be null.
*/
public BasicAttribute(String id) {
this(id, false);
}
/**
* Constructs a new instance of an unordered attribute with a single value.
*
* @param id The attribute's id. It cannot be null.
* @param value The attribute's value. If null, a null
* value is added to the attribute.
*/
public BasicAttribute(String id, Object value) {
this(id, value, false);
}
/**
* Constructs a new instance of a possibly ordered attribute with no value.
*
* @param id The attribute's id. It cannot be null.
* @param ordered true means the attribute's values will be ordered;
* false otherwise.
*/
public BasicAttribute(String id, boolean ordered) {
attrID = id;
values = new Vector<>();
this.ordered = ordered;
}
/**
* Constructs a new instance of a possibly ordered attribute with a
* single value.
*
* @param id The attribute's id. It cannot be null.
* @param value The attribute's value. If null, a null
* value is added to the attribute.
* @param ordered true means the attribute's values will be ordered;
* false otherwise.
*/
public BasicAttribute(String id, Object value, boolean ordered) {
this(id, ordered);
values.addElement(value);
}
/**
* Retrieves an enumeration of this attribute's values.
*<p>
* By default, the values returned are those passed to the
* constructor and/or manipulated using the add/replace/remove methods.
* A subclass may override this to retrieve the values dynamically
* from the directory.
*/
public NamingEnumeration<?> getAll() throws NamingException {
return new ValuesEnumImpl();
}
/**
* Retrieves one of this attribute's values.
*<p>
* By default, the value returned is one of those passed to the
* constructor and/or manipulated using the add/replace/remove methods.
* A subclass may override this to retrieve the value dynamically
* from the directory.
*/
public Object get() throws NamingException {
if (values.size() == 0) {
throw new
NoSuchElementException("Attribute " + getID() + " has no value");
} else {
return values.elementAt(0);
}
}
public int size() {
return values.size();
}
public String getID() {
return attrID;
}
/**
* Determines whether a value is in this attribute.
*<p>
* By default,
* <tt>Object.equals() is used when comparing attrVal
* with this attribute's values except when <tt>attrVal is an array.
* For an array, each element of the array is checked using
* <tt>Object.equals().
* A subclass may use schema information to determine equality.
*/
public boolean contains(Object attrVal) {
return (find(attrVal) >= 0);
}
// For finding first element that has a null in JDK1.1 Vector.
// In the Java 2 platform, can just replace this with Vector.indexOf(target);
private int find(Object target) {
Class<?> cl;
if (target == null) {
int ct = values.size();
for (int i = 0 ; i < ct ; i++) {
if (values.elementAt(i) == null)
return i;
}
} else if ((cl=target.getClass()).isArray()) {
int ct = values.size();
Object it;
for (int i = 0 ; i < ct ; i++) {
it = values.elementAt(i);
if (it != null && cl == it.getClass()
&& arrayEquals(target, it))
return i;
}
} else {
return values.indexOf(target, 0);
}
return -1; // not found
}
/**
* Determines whether two attribute values are equal.
* Use arrayEquals for arrays and <tt>Object.equals() otherwise.
*/
private static boolean valueEquals(Object obj1, Object obj2) {
if (obj1 == obj2) {
return true; // object references are equal
}
if (obj1 == null) {
return false; // obj2 was not false
}
if (obj1.getClass().isArray() &&
obj2.getClass().isArray()) {
return arrayEquals(obj1, obj2);
}
return (obj1.equals(obj2));
}
/**
* Determines whether two arrays are equal by comparing each of their
* elements using <tt>Object.equals().
*/
private static boolean arrayEquals(Object a1, Object a2) {
int len;
if ((len = Array.getLength(a1)) != Array.getLength(a2))
return false;
for (int j = 0; j < len; j++) {
Object i1 = Array.get(a1, j);
Object i2 = Array.get(a2, j);
if (i1 == null || i2 == null) {
if (i1 != i2)
return false;
} else if (!i1.equals(i2)) {
return false;
}
}
return true;
}
/**
* Adds a new value to this attribute.
*<p>
* By default, <tt>Object.equals() is used when comparing attrVal
* with this attribute's values except when <tt>attrVal is an array.
* For an array, each element of the array is checked using
* <tt>Object.equals().
* A subclass may use schema information to determine equality.
*/
public boolean add(Object attrVal) {
if (isOrdered() || (find(attrVal) < 0)) {
values.addElement(attrVal);
return true;
} else {
return false;
}
}
/**
* Removes a specified value from this attribute.
*<p>
* By default, <tt>Object.equals() is used when comparing attrVal
* with this attribute's values except when <tt>attrVal is an array.
* For an array, each element of the array is checked using
* <tt>Object.equals().
* A subclass may use schema information to determine equality.
*/
public boolean remove(Object attrval) {
// For the Java 2 platform, can just use "return removeElement(attrval);"
// Need to do the following to handle null case
int i = find(attrval);
if (i >= 0) {
values.removeElementAt(i);
return true;
}
return false;
}
public void clear() {
values.setSize(0);
}
// ---- ordering methods
public boolean isOrdered() {
return ordered;
}
public Object get(int ix) throws NamingException {
return values.elementAt(ix);
}
public Object remove(int ix) {
Object answer = values.elementAt(ix);
values.removeElementAt(ix);
return answer;
}
public void add(int ix, Object attrVal) {
if (!isOrdered() && contains(attrVal)) {
throw new IllegalStateException(
"Cannot add duplicate to unordered attribute");
}
values.insertElementAt(attrVal, ix);
}
public Object set(int ix, Object attrVal) {
if (!isOrdered() && contains(attrVal)) {
throw new IllegalStateException(
"Cannot add duplicate to unordered attribute");
}
Object answer = values.elementAt(ix);
values.setElementAt(attrVal, ix);
return answer;
}
// ----------------- Schema methods
/**
* Retrieves the syntax definition associated with this attribute.
*<p>
* This method by default throws OperationNotSupportedException. A subclass
* should override this method if it supports schema.
*/
public DirContext getAttributeSyntaxDefinition() throws NamingException {
throw new OperationNotSupportedException("attribute syntax");
}
/**
* Retrieves this attribute's schema definition.
*<p>
* This method by default throws OperationNotSupportedException. A subclass
* should override this method if it supports schema.
*/
public DirContext getAttributeDefinition() throws NamingException {
throw new OperationNotSupportedException("attribute definition");
}
// ---- serialization methods
/**
* Overridden to avoid exposing implementation details
* @serialData Default field (the attribute ID -- a String),
* followed by the number of values (an int), and the
* individual values.
*/
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
s.defaultWriteObject(); // write out the attrID
s.writeInt(values.size());
for (int i = 0; i < values.size(); i++) {
s.writeObject(values.elementAt(i));
}
}
/**
* Overridden to avoid exposing implementation details.
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject(); // read in the attrID
int n = s.readInt(); // number of values
values = new Vector<>(n);
while (--n >= 0) {
values.addElement(s.readObject());
}
}
class ValuesEnumImpl implements NamingEnumeration<Object> {
Enumeration<Object> list;
ValuesEnumImpl() {
list = values.elements();
}
public boolean hasMoreElements() {
return list.hasMoreElements();
}
public Object nextElement() {
return(list.nextElement());
}
public Object next() throws NamingException {
return list.nextElement();
}
public boolean hasMore() throws NamingException {
return list.hasMoreElements();
}
public void close() throws NamingException {
list = null;
}
}
/**
* Use serialVersionUID from JNDI 1.1.1 for interoperability.
*/
private static final long serialVersionUID = 6743528196119291326L;
}
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