Package 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:
Frank Fock, Jochen Katz
See Also:

  • Field Details

  • Constructor Details

    • AbstractVariable

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

  • Method Details

    • 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 BERInputStream.
      Specified by:
      decodeBER in interface BERSerializable
      Parameters:
      inputStream - an BERInputStream 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 BERInputStream. 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 less than 128 for regular SMI objects and a value greater or equal than 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:

    • 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