org.snmp4j.smi

Class AbstractVariable

java.lang.Object

org.snmp4j.smi.AbstractVariable

All Implemented Interfaces:

Serializable, Cloneable, Comparable<Variable>, BERSerializable, Variable

Direct Known Subclasses:

Counter64, Integer32, Null, OctetString, OID, SMIAddress, UnsignedInteger32, VariantVariable

public abstract class AbstractVariable
extends Object
implements Variable, Serializable

The Variable abstract class is the base class for all SNMP variables.

All derived classes need to be registered with their SMI BER type in the smisyntaxes.propertiesso that the createFromBER(BERInputStream inputStream) method is able to decode a variable from a BER encoded stream.

To register additional syntaxes, set the system property SMISYNTAXES_PROPERTIES before decoding a Variable for the first time. The path of the property file must be accessible from the classpath and it has to be specified relative to the Variable class.

Since:

1.8

Version:

1.8

Author:

Jochen Katz & Frank Fock

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	SMISYNTAXES_PROPERTIES

Constructor Summary

Constructors

Constructor and Description
AbstractVariable() The abstract Variable class serves as the base class for all specific SNMP syntax types.

Method Summary

Methods

Modifier and Type	Method and Description
abstract Object	clone() Clones this variable.
abstract int	compareTo(Variable o)
static Variable	createFromBER(BERInputStream inputStream) Creates a Variable from a BER encoded InputStream.
static Variable	createFromSyntax(int smiSyntax) Creates a Variable from the supplied SMI syntax identifier.
abstract void	decodeBER(BERInputStream inputStream) Decodes a Variable from an InputStream.
abstract void	encodeBER(OutputStream outputStream) Encodes a Variable to an OutputStream.
static boolean	equal(AbstractVariable a, AbstractVariable b) Tests if two variables have the same value.
abstract boolean	equals(Object o)
abstract void	fromSubIndex(OID subIndex, boolean impliedLength) Sets the value of this Variable from the supplied (sub-)index.
abstract int	getBERLength() Returns the length of this Variable in bytes when encoded according to the Basic Encoding Rules (BER).
int	getBERPayloadLength() Returns the length of the payload of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).
abstract int	getSyntax() Gets the ASN.1 syntax identifier value of this SNMP variable.
static int	getSyntaxFromString(String syntaxString) Returns the BER syntax ID for the supplied syntax string (as returned by getSyntaxString(int)).
String	getSyntaxString() Gets a textual description of this Variable.
static String	getSyntaxString(int syntax) Gets a textual description of the supplied syntax type.
abstract int	hashCode()
boolean	isDynamic() Indicates whether this variable is dynamic, which means that it might change its value while it is being (BER) serialized.
boolean	isException() Checks whether this variable represents an exception like noSuchObject, noSuchInstance, and endOfMibView.
abstract int	toInt() Returns an integer representation of this variable if such a representation exists.
abstract long	toLong() Returns a long representation of this variable if such a representation exists.
abstract String	toString() Gets a string representation of the variable.
abstract OID	toSubIndex(boolean impliedLength) Converts the value of this Variable to a (sub-)index value.

Methods inherited from class java.lang.Object

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

Field Detail

SMISYNTAXES_PROPERTIES

public static final String SMISYNTAXES_PROPERTIES

See Also:

Constant Field Values

Constructor Detail

AbstractVariable

public AbstractVariable()

The abstract Variable class serves as the base class for all specific SNMP syntax types.

Method Detail

equals

public abstract boolean equals(Object o)

Specified by:

equals in interface Variable

Overrides:

equals in class Object

compareTo

public abstract int compareTo(Variable o)

Specified by:

compareTo in interface Comparable<Variable>

Specified by:

compareTo in interface Variable

hashCode

public abstract int hashCode()

Specified by:

hashCode in interface Variable

Overrides:

hashCode in class Object

getBERLength

public abstract int getBERLength()

Returns the length of this Variable in bytes when encoded according to the Basic Encoding Rules (BER).

Specified by:

getBERLength in interface BERSerializable

Returns:

the BER encoded length of this variable.

getBERPayloadLength

public int getBERPayloadLength()

Description copied from interface: BERSerializable

Returns the length of the payload of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).

Specified by:

getBERPayloadLength in interface BERSerializable

Returns:

the BER encoded length of this variable.

decodeBER

public abstract void decodeBER(BERInputStream inputStream)
                        throws IOException

Decodes a Variable from an InputStream.

Specified by:

decodeBER in interface BERSerializable

Parameters:

inputStream - an InputStream containing a BER encoded byte stream.

Throws:

IOException - if the stream could not be decoded by using BER rules.

encodeBER

public abstract void encodeBER(OutputStream outputStream)
                        throws IOException

Encodes a Variable to an OutputStream.

Specified by:

encodeBER in interface BERSerializable

Parameters:

outputStream - an OutputStream.

Throws:

IOException - if an error occurs while writing to the stream.

createFromBER

public static Variable createFromBER(BERInputStream inputStream)
                              throws IOException

Creates a Variable from a BER encoded InputStream. Subclasses of Variable are registered using the properties file smisyntaxes.properties in this package. The properties are read when this method is called first.

Parameters:

inputStream - an BERInputStream containing a BER encoded byte stream.

Returns:

an instance of a subclass of Variable.

Throws:

IOException - if the inputStream is not properly BER encoded.

createFromSyntax

public static Variable createFromSyntax(int smiSyntax)

Creates a Variable from the supplied SMI syntax identifier. Subclasses of Variable are registered using the properties file smisyntaxes.properties in this package. The properties are read when this method is called for the first time.

Parameters:

smiSyntax - an SMI syntax identifier of the registered types, which is typically defined by SMIConstants.

Returns:

a Variable variable instance of the supplied SMI syntax.

getSyntax

public abstract int getSyntax()

Gets the ASN.1 syntax identifier value of this SNMP variable.

Specified by:

getSyntax in interface Variable

Returns:

an integer value < 128 for regular SMI objects and a value >= 128 for exception values like noSuchObject, noSuchInstance, and endOfMibView.

isException

public boolean isException()

Checks whether this variable represents an exception like noSuchObject, noSuchInstance, and endOfMibView.

Specified by:

isException in interface Variable

Returns:

true if the syntax of this variable is an instance of Null and its syntax equals one of the following:

• SMIConstants.EXCEPTION_NO_SUCH_OBJECT
• SMIConstants.EXCEPTION_NO_SUCH_INSTANCE
• SMIConstants.EXCEPTION_END_OF_MIB_VIEW

toString

public abstract String toString()

Gets a string representation of the variable.

Specified by:

toString in interface Variable

Overrides:

toString in class Object

Returns:

a string representation of the variable's value.

toInt

public abstract int toInt()

Returns an integer representation of this variable if such a representation exists.

Specified by:

toInt in interface Variable

Returns:

an integer value (if the native representation of this variable would be a long, then the long value will be casted to int).

Throws:

UnsupportedOperationException - if an integer representation does not exists for this Variable.

Since:

1.7

toLong

public abstract long toLong()

Returns a long representation of this variable if such a representation exists.

Specified by:

toLong in interface Variable

Returns:

a long value.

Throws:

UnsupportedOperationException - if a long representation does not exists for this Variable.

Since:

1.7

clone

public abstract Object clone()

Description copied from interface: Variable

Clones this variable. Cloning can be used by the SNMP4J API to better support concurrency by creating a clone for internal processing. The content of this object is independent to the content of the clone. Thus, changes to the clone will have no effect to this object.

Specified by:

clone in interface Variable

Overrides:

clone in class Object

Returns:

a new instance of this Variable with the same value.

getSyntaxString

public static String getSyntaxString(int syntax)

Gets a textual description of the supplied syntax type.

Parameters:

syntax - the BER code of the syntax.

Returns:

a textual description like 'Integer32' for syntax as used in the Structure of Management Information (SMI) modules. '?' is returned if the supplied syntax is unknown.

getSyntaxString

public final String getSyntaxString()

Gets a textual description of this Variable.

Specified by:

getSyntaxString in interface Variable

Returns:

a textual description like 'Integer32' as used in the Structure of Management Information (SMI) modules. '?' is returned if the syntax is unknown.

Since:

1.7

getSyntaxFromString

public static int getSyntaxFromString(String syntaxString)

Returns the BER syntax ID for the supplied syntax string (as returned by getSyntaxString(int)).

Parameters:

syntaxString - the textual representation of the syntax.

Returns:

the corresponding BER ID.

Since:

1.6

toSubIndex

public abstract OID toSubIndex(boolean impliedLength)

Converts the value of this Variable to a (sub-)index value.

Specified by:

toSubIndex in interface Variable

Parameters:

impliedLength - specifies if the sub-index has an implied length. This parameter applies to variable length variables only (e.g. OctetString and OID). For other variables it has no effect.

Returns:

an OID that represents this value as an (sub-)index.

Throws:

UnsupportedOperationException - if this variable cannot be used in an index.

Since:

1.7

fromSubIndex

public abstract void fromSubIndex(OID subIndex,
                boolean impliedLength)

Sets the value of this Variable from the supplied (sub-)index.

Specified by:

fromSubIndex in interface Variable

Parameters:

subIndex - the sub-index OID.

impliedLength - specifies if the sub-index has an implied length. This parameter applies to variable length variables only (e.g. OctetString and OID). For other variables it has no effect.

Throws:

UnsupportedOperationException - if this variable cannot be used in an index.

Since:

1.7

isDynamic

public boolean isDynamic()

Indicates whether this variable is dynamic, which means that it might change its value while it is being (BER) serialized. If a variable is dynamic, it will be cloned on-the-fly when it is added to a PDU with PDU.add(VariableBinding). By cloning the value, it is ensured that there are no inconsistent changes between determining the length with getBERLength() for encoding enclosing SEQUENCES and the actual encoding of the Variable itself with encodeBER(java.io.OutputStream).

Specified by:

isDynamic in interface Variable

Returns:

false by default. Derived classes may override this if implementing dynamic Variable instances.

Since:

1.8

equal

public static boolean equal(AbstractVariable a,
            AbstractVariable b)

Tests if two variables have the same value.

Parameters:

a - a variable.

b - another variable.

Returns:

true if a == null) ? (b == null) : a.equals(b).

Since:

2.0