Module org.snmp4j.agent
Package org.snmp4j.agent.mo.snmp

Class RowCount

  • All Implemented Interfaces:
    Cloneable, Comparable<org.snmp4j.smi.Variable>, org.snmp4j.asn1.BERSerializable, org.snmp4j.smi.Variable
    public class RowCount
extends Object
implements org.snmp4j.smi.Variable
    The RowCount class implements a Variable that counts the rows of a table and returns the number of rows as value. This class is a dynamic Variable, which means it needs to be cloned when serialized. When cloned, a Gauge32 instance with the row count of the source table will be created.
    Since:
    3.2.1
    Author:
    Frank Fock

    • Field Summary

      • Fields inherited from interface org.snmp4j.smi.Variable

        serialVersionUID

    • Constructor Summary

      Constructors 
      Constructor Description
      RowCount()
      Creates a RowCount which returns zero always.
      RowCount​(MOTable moTable)
      Creates a row counting Gauge32 variable for the specified MOTable.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      Object clone()
      Clones this variable.
      int compareTo​(org.snmp4j.smi.Variable o)  
      void decodeBER​(org.snmp4j.asn1.BERInputStream inputStream)
      Decodes a Variable from an InputStream.
      void encodeBER​(OutputStream outputStream)
      Encodes a Variable to an OutputStream.
      void fromSubIndex​(org.snmp4j.smi.OID subIndex, boolean impliedLength)
      Sets the value of this Variable from the supplied (sub-)index.
      int getBERLength()
      Returns the length of this BERSerializable object 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).
      int getSyntax()
      Gets the ASN.1 syntax identifier value of this SNMP variable.
      String getSyntaxString()
      Gets a textual description of this Variable.
      long getValue()
      Gets the number of rows in the associated table as unsigned long value.
      boolean isDynamic()
      Indicates whether this variable is dynamic.
      boolean isException()
      Checks whether this variable represents an exception like noSuchObject, noSuchInstance, and endOfMibView.
      int toInt()
      Returns an integer representation of this variable if such a representation exists.
      long toLong()
      Returns a long representation of this variable if such a representation exists.
      org.snmp4j.smi.OID toSubIndex​(boolean impliedLength)
      Converts the value of this Variable to a (sub-)index value.

      • Methods inherited from interface org.snmp4j.smi.Variable

        equals, hashCode, toString

    • Constructor Detail

      • RowCount

        public RowCount()
        Creates a RowCount which returns zero always.

      • RowCount

        public RowCount​(MOTable moTable)
        Creates a row counting Gauge32 variable for the specified MOTable.
        Parameters:
        moTable - a table instance whose rows should be counted by this variable.

    • Method Detail

      • getValue

        public long getValue()
        Gets the number of rows in the associated table as unsigned long value.
        Returns:
        the number of rows in the associated table (greater or equal to zero). Zero is returned if a null table is associated.

      • compareTo

        public int compareTo​(org.snmp4j.smi.Variable o)
        Specified by:
        compareTo in interface Comparable<org.snmp4j.smi.Variable>
        Specified by:
        compareTo in interface org.snmp4j.smi.Variable

      • clone

        public Object clone()
        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 org.snmp4j.smi.Variable
        Overrides:
        clone in class Object
        Returns:
        a new instance of this Variable with the same value.

      • getSyntax

        public int getSyntax()
        Gets the ASN.1 syntax identifier value of this SNMP variable.
        Specified by:
        getSyntax in interface org.snmp4j.smi.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 org.snmp4j.smi.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

      • toInt

        public int toInt()
        Returns an integer representation of this variable if such a representation exists.
        Specified by:
        toInt in interface org.snmp4j.smi.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.

      • toLong

        public long toLong()
        Returns a long representation of this variable if such a representation exists.
        Specified by:
        toLong in interface org.snmp4j.smi.Variable
        Returns:
        a long value.
        Throws:
        UnsupportedOperationException - if a long representation does not exists for this Variable.

      • getSyntaxString

        public String getSyntaxString()
        Gets a textual description of this Variable.
        Specified by:
        getSyntaxString in interface org.snmp4j.smi.Variable
        Returns:
        a textual description like 'Integer32' as used in the Structure of Management Information (SMI) modules. '?' is returned if the syntax is unknown.

      • toSubIndex

        public org.snmp4j.smi.OID toSubIndex​(boolean impliedLength)
        Converts the value of this Variable to a (sub-)index value.
        Specified by:
        toSubIndex in interface org.snmp4j.smi.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.

      • fromSubIndex

        public void fromSubIndex​(org.snmp4j.smi.OID subIndex,
                         boolean impliedLength)
        Sets the value of this Variable from the supplied (sub-)index.
        Specified by:
        fromSubIndex in interface org.snmp4j.smi.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.

      • isDynamic

        public boolean isDynamic()
        Indicates whether this variable is dynamic. If a variable is dynamic, precautions have to be taken when a Variable is serialized using BER encoding, because between determining the length with getBERLength() for encoding enclosing SEQUENCES and the actual encoding of the Variable itself with encodeBER(java.io.OutputStream) changes to the value need to be blocked by synchronization. In order to ensure proper synchronization if a Variable is dynamic, modifications of the variables content need to synchronize on the Variable instance. This can be achieved for the standard SMI Variable implementations for example by 
            public static modifyVariable(Integer32 variable, int value)
      synchronize(variable) {
        variable.setValue(value);
      }
    }
        Specified by:
        isDynamic in interface org.snmp4j.smi.Variable
        Returns:
        true because the variable might change its value between two calls to getBERLength() and encodeBER(java.io.OutputStream).

      • getBERLength

        public int getBERLength()
        Returns the length of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).
        Specified by:
        getBERLength in interface org.snmp4j.asn1.BERSerializable
        Returns:
        the BER encoded length of this variable.

      • getBERPayloadLength

        public int getBERPayloadLength()
        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 org.snmp4j.asn1.BERSerializable
        Returns:
        the BER encoded length of this variable.

      • decodeBER

        public void decodeBER​(org.snmp4j.asn1.BERInputStream inputStream)
               throws IOException
        Decodes a Variable from an InputStream.
        Specified by:
        decodeBER in interface org.snmp4j.asn1.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 void encodeBER​(OutputStream outputStream)
               throws IOException
        Encodes a Variable to an OutputStream.
        Specified by:
        encodeBER in interface org.snmp4j.asn1.BERSerializable
        Parameters:
        outputStream - an OutputStream.
        Throws:
        IOException - if an error occurs while writing to the stream.