Package org.apache.sis.xml

Class NilReason

java.lang.Object

org.apache.sis.xml.NilReason

All Implemented Interfaces:

Serializable

public final class NilReason
extends Object
implements Serializable

Explanation for a missing XML element. The nil reason can be parsed and formatted as a string using the valueOf(String) and toString() methods respectively. The string can be either a URI or an enumeration value described below. More specifically, NilReason can be:

• One of the predefined INAPPLICABLE, MISSING, TEMPLATE, UNKNOWN or WITHHELD enumeration values.
• The OTHER enumeration value, or a new enumeration value formatted as "other:" concatenated with a brief textual explanation.
• A URI which should refer to a resource which describes the reason for the exception.

NilReason is used in a number of XML elements where it is necessary to permit one of the above values as an alternative to the primary element.

Immutability and thread safety

This final class is immutable and thus inherently thread-safe.

Since:

0.3

Version:

0.4

Author:

Martin Desruisseaux (Geomatys)

See Also:

• NilObject
• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final NilReason	INAPPLICABLE	There is no value.
static final NilReason	MISSING	The correct value is not readily available to the sender of this data.
static final NilReason	OTHER	Other reason without explanation.
static final NilReason	TEMPLATE	The value will be available later.
static final NilReason	UNKNOWN	The correct value is not known to, and not computable by, the sender of this data.
static final NilReason	WITHHELD	The value is not divulged.

Method Summary

Modifier and Type	Method	Description
<T> T	createNilObject(Class<T> type)	Returns an object of the given type which is nil for the reason represented by this instance.
boolean	equals(Object other)	Compares this NilReason with the specified object for equality.
static NilReason	forObject(Object object)	If the given object is nil, returns the reason why it does not contain information.
String	getOtherExplanation()	If this NilReason is an enumeration of kind OTHER, returns the explanation text.
URI	getURI()	If the explanation of this NilReason is referenced by a URI, returns that URI.
int	hashCode()	Returns a hash code value for this NilReason.
String	toString()	Returns the GML string representation of this NilReason.
static NilReason	valueOf(String reason)	Parses the given nil reason.
static NilReason[]	values()	Returns an array containing every instances of this type that have not yet been garbage collected.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

INAPPLICABLE

public static final NilReason INAPPLICABLE

There is no value.

The string representation is "inapplicable". Other properties (explanation and URI) are null.

MISSING

public static final NilReason MISSING

The correct value is not readily available to the sender of this data. Furthermore, a correct value may not exist.

The string representation is "missing". Other properties (explanation and URI) are null.

TEMPLATE

public static final NilReason TEMPLATE

The value will be available later.

The string representation is "template". Other properties (explanation and URI) are null.

UNKNOWN

public static final NilReason UNKNOWN

The correct value is not known to, and not computable by, the sender of this data. However, a correct value probably exists.

The string representation is "unknown". Other properties (explanation and URI) are null.

WITHHELD

public static final NilReason WITHHELD

The value is not divulged.

The string representation is "withheld". Other properties (explanation and URI) are null.

OTHER

public static final NilReason OTHER

Other reason without explanation. The string representation of this constant is "other". The explanation property is an empty string, and the URI is null.

Providing an explanation

Users are encouraged to use the valueOf(String) method instead of this constant, in order to provide a brief explanation. The string representation for valueOf(…) is "other:explanation" where explanation is a string of two or more characters with no included spaces.

When testing if a NilReason instance is any kind of "other" reason, users should test if getOtherExplanation() != null instead than comparing the reference against this constant.

Method Details

values

public static NilReason[] values()

Returns an array containing every instances of this type that have not yet been garbage collected. The first elements of the returned array are the constants defined in this class, in declaration order. All other elements are the instances created by the valueOf(String) method, in no particular order.

Returns:

an array containing the instances of NilReason.

valueOf

public static NilReason valueOf(String reason)
                         throws URISyntaxException

Parses the given nil reason. This method accepts the following cases:

• If the given argument is one of the "inapplicable", "missing", "template", "unknown", "withheld" or "other" strings (ignoring cases and leading/trailing spaces), then the corresponding predefined constant is returned.
• Otherwise if the given argument is "other:" followed by an explanation text, then an instance for that explanation is returned. More specifically:
  • Space characters and ISO controls are silently omitted.
  • If the remaining string has less than two characters, then the OTHER constant is returned.
• Otherwise this method attempts to parse the given argument as a URI. Such URI should refer to a resource which describes the reason for the exception.

This method returns existing instances when possible.

Parameters:

reason - the reason why an element is not present.

Returns:

the reason as a NilReason object.

Throws:

URISyntaxException - if the given string is not one of the predefined enumeration values and cannot be parsed as a URI.

getOtherExplanation

public String getOtherExplanation()

If this NilReason is an enumeration of kind OTHER, returns the explanation text. Otherwise returns null. If non-null, then the explanation is a string without whitespace.

Note that in the special case where this nil reason is the OTHER instance itself, then this method returns an empty string. For all other cases, the string contains at least two characters.

Returns:

the explanation, or null if this NilReason is not of kind OTHER.

getURI

public URI getURI()

If the explanation of this NilReason is referenced by a URI, returns that URI. Otherwise returns null. The URI and the other explanation attributes are mutually exclusive.

Returns:

the URI, or null if the explanation of this NilReason is not referenced by a URI.

toString

public String toString()

Returns the GML string representation of this NilReason. The returned string is a simple enumeration value (e.g. "inapplicable") if this NilReason is one of the predefined constants, or a string of the form "other:explanation", or a URI.

Overrides:

toString in class Object

Returns:

the GML string representation of this NilReason.

hashCode

public int hashCode()

Returns a hash code value for this NilReason.

Overrides:

hashCode in class Object

equals

public boolean equals(Object other)

Compares this NilReason with the specified object for equality.

Overrides:

equals in class Object

Parameters:

other - the object to compare with this NilReason.

createNilObject

public <T> T createNilObject(Class<T> type)

Returns an object of the given type which is nil for the reason represented by this instance. The type argument can be one of the following cases:

• An interface: in such case, this method returns an object which implement the given interface together with the NilObject and LenientComparable interfaces:
  • The NilObject.getNilReason() method will return this NilReason instance.
  • The equals(…) and hashCode() methods behave as documented in LenientComparable.
  • The toString() method is unspecified (may contain debugging information).
  • All other methods return an empty collections, empty arrays, null, NaN, 0 or false, in this preference order, depending on the method return type.
• One of Boolean, Byte, Short, Integer, Long, Float, Double or String types: in such case, this method returns a specific instance which will be recognized as "nil" by the XML marshaller.

Type Parameters:

T - the compile-time type of the type argument.

Parameters:

type - the object type as an interface (usually a GeoAPI one) or one of the special types.

Returns:

an NilObject of the given type.

Throws:

IllegalArgumentException - if the given type is not a supported type.

forObject

public static NilReason forObject(Object object)

If the given object is nil, returns the reason why it does not contain information. This method performs the following choices:

• If the given object implements the NilObject interface, then this method delegates to the NilObject.getNilReason() method.
• Otherwise if the given object is one of the Boolean, Byte, Short, Integer, Long, Float, Double or String instances returned by createNilObject(Class), then this method returns the associated reason.
• Otherwise this method returns null.

Parameters:

object - the object for which to get the NilReason, or null.

Returns:

the reason why the given object contains no information, or null if the given object is not nil.

Since:

0.4

See Also:

• NilObject.getNilReason()