BufferedMOTableModel (SNMP4J-AgentX 2.7.1-SNAPSHOT)

java.lang.Object
- org.snmp4j.agent.mo.BufferedMOTableModel<R>

All Implemented Interfaces:

org.snmp4j.agent.mo.MOTableModel<R>

Direct Known Subclasses:

BufferedMOMutableTableModel
```
public abstract class BufferedMOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
extends Object
implements org.snmp4j.agent.mo.MOTableModel<R>
```
The BufferedMOTableModel is a read-only table model that dynamically loads data from an backend as needed. The internal buffer holds up to getMaxBufferSize() rows fetched from the backend. Rows are removed from the buffer either when they are older than getBufferTimeoutNanoSeconds() or if the maximum number of buffered rows is reached.
The MOTableRowFactory is needed to create table rows from the backend plain row data.

Since:

2.2

Author:

Frank Fock

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected class`	`BufferedMOTableModel.BufferedMOTableRow<R extends org.snmp4j.agent.mo.MOTableRow>` The BufferedMOTableRow is a wrapper class that holds additional information for the buffering.
`protected class`	`BufferedMOTableModel.RowBufferIterator` The RowBufferIterator implements the iterator needed by the `MOTableModel` to traverse the model's rows.

Field Summary

Fields
Modifier and Type	Field and Description
`protected List<BufferedMOTableModel.BufferedMOTableRow<R>>`	`bufferedChunksList`
`protected SortedMap<org.snmp4j.smi.OID,BufferedMOTableModel.BufferedMOTableRow<R>>`	`bufferedRows`
`protected long`	`bufferHits` The number of rows that were read from the buffer without backend access.
`protected long`	`bufferMisses` The number of rows that were read from the backend, because they were not found or not valid in the buffer.
`protected long`	`bufferTimeoutNanoSeconds` The timeout for buffered rows in 10^-9 seconds.
`protected int`	`chunkSize` The number of rows that are fetched with `fetchNextRows(org.snmp4j.smi.OID, int)` consecutively to minimize the number of backend read operations.
`protected int`	`columnCount` The number of columns in this table model.
`protected BufferedMOTableModel.BufferedMOTableRow<R>`	`firstRow`
`protected BufferedMOTableModel.BufferedMOTableRow<R>`	`lastRow`
`protected int`	`maxBufferSize` The maximum number of rows in the buffer.
`protected org.snmp4j.agent.mo.MOTableRowFactory<R>`	`rowFactory`

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`BufferedMOTableModel(org.snmp4j.agent.mo.MOTableRowFactory<R> rowFactory)` Creates a BufferedMOTableModel with the specified `MOTableRowFactory`.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`protected int`	`cleanupBuffer()` Removes any rows from the buffer that exceed the buffer's size limit (FIFO).
`abstract boolean`	`containsRow(org.snmp4j.smi.OID index)`
`protected abstract List<R>`	`fetchNextRows(org.snmp4j.smi.OID lowerBound, int chunkSize)` Fetches a list of rows from the backend source.
`protected abstract org.snmp4j.smi.Variable[]`	`fetchRow(org.snmp4j.smi.OID index)` Fetches the specified row from the backend source.
`abstract org.snmp4j.smi.OID`	`firstIndex()`
`R`	`firstRow()`
`long`	`getBufferHits()` Returns the number of row accesses that were served by the buffer.
`long`	`getBufferMisses()` The number of row accesses that could not be served from the buffer and thus needed backend processing.
`long`	`getBufferTimeoutNanoSeconds()` Gets the timeout nano-seconds for buffered rows.
`int`	`getChunkSize()` Returns the chunk size for GETNEXT like buffer fetching with the `fetchNextRows(org.snmp4j.smi.OID, int)` operation.
`int`	`getColumnCount()`
`protected BufferedMOTableModel.BufferedMOTableRow<R>`	`getFirstBufferRow()` Gets the first row from the buffer or the backend if not available from the buffer.
`protected BufferedMOTableModel.BufferedMOTableRow<R>`	`getLastBufferRow()` Gets the last row from the buffer or the backend if not available from the buffer.
`int`	`getMaxBufferSize()` Returns the maximum number of rows in the buffer.
`R`	`getRow(org.snmp4j.smi.OID index)`
`protected R`	`getRow(org.snmp4j.smi.OID index, boolean putRowIntoBuffer)` Gets a row from the internal buffer or the backend and puts it into the buffer if specified.
`abstract int`	`getRowCount()`
`<F extends org.snmp4j.agent.mo.MOTableRowFactory<R>> F`	`getRowFactory()`
`protected BufferedMOTableModel.BufferedMOTableRow<R>`	`getRowFromBuffer(org.snmp4j.smi.OID index)` Gets a row from the buffer.
`protected boolean`	`isRowValid(long lastRefreshNanoTime)` Tests if the given timestamp (in nano seconds as retrieved from `System.nanoTime()`) denotes a valid row.
`Iterator<R>`	`iterator()`
`abstract org.snmp4j.smi.OID`	`lastIndex()`
`R`	`lastRow()`
`R`	`removeRow(org.snmp4j.smi.OID index)` Removes a row from the table.
`void`	`resetBuffer()` Removes all rows from the internal buffer.
`void`	`setBufferTimeoutNanoSeconds(long bufferTimeoutNanoSeconds)` Sets the timeout nano-seconds for buffered rows.
`void`	`setChunkSize(int chunkSize)` Sets the chunk size for GETNEXT like buffer fetching with the `fetchNextRows(org.snmp4j.smi.OID, int)` operation.
`void`	`setMaxBufferSize(int maxBufferSize)` Sets the maximum number of rows in the buffer.
`<F extends org.snmp4j.agent.mo.MOTableRowFactory<R>> void`	`setRowFactory(F rowFactory)` Sets the factory instance to be used for creating rows for this model.
`Iterator<R>`	`tailIterator(org.snmp4j.smi.OID lowerBound)`
`String`	`toString()`
`protected BufferedMOTableModel.BufferedMOTableRow<R>`	`updateBuffer(List<R> newBufferRows, BufferedMOTableModel.BufferedMOTableRow<R> predecessor)` Updates the internal buffer with a list of consecutive rows.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.snmp4j.agent.mo.MOTableModel
isEmpty

- Field Detail
  - bufferedRows
```
protected final SortedMap<org.snmp4j.smi.OID,BufferedMOTableModel.BufferedMOTableRow<R extends org.snmp4j.agent.mo.MOTableRow>> bufferedRows
```
  - bufferedChunksList
```
protected final List<BufferedMOTableModel.BufferedMOTableRow<R extends org.snmp4j.agent.mo.MOTableRow>> bufferedChunksList
```
  - firstRow
```
protected BufferedMOTableModel.BufferedMOTableRow<R extends org.snmp4j.agent.mo.MOTableRow> firstRow
```
  - lastRow
```
protected BufferedMOTableModel.BufferedMOTableRow<R extends org.snmp4j.agent.mo.MOTableRow> lastRow
```
  - rowFactory
```
protected org.snmp4j.agent.mo.MOTableRowFactory<R extends org.snmp4j.agent.mo.MOTableRow> rowFactory
```
  - columnCount
```
protected int columnCount
```
    The number of columns in this table model.
  - bufferTimeoutNanoSeconds
```
protected long bufferTimeoutNanoSeconds
```
    The timeout for buffered rows in 10^-9 seconds.
  - chunkSize
```
protected int chunkSize
```
    The number of rows that are fetched with fetchNextRows(org.snmp4j.smi.OID, int) consecutively to minimize the number of backend read operations.
  - maxBufferSize
```
protected int maxBufferSize
```
    The maximum number of rows in the buffer. While requests processing the actual upper bound of the buffer might be the sum of getMaxBufferSize() and getChunkSize().
  - bufferHits
```
protected long bufferHits
```
    The number of rows that were read from the buffer without backend access.
  - bufferMisses
```
protected long bufferMisses
```
    The number of rows that were read from the backend, because they were not found or not valid in the buffer.
- Constructor Detail
  - BufferedMOTableModel
```
protected BufferedMOTableModel(org.snmp4j.agent.mo.MOTableRowFactory<R> rowFactory)
```
    Creates a BufferedMOTableModel with the specified MOTableRowFactory.
    
    Parameters:
    
    rowFactory - the row factory to be used to create rows from backend data.
- Method Detail
  - setRowFactory
```
public <F extends org.snmp4j.agent.mo.MOTableRowFactory<R>> void setRowFactory(F rowFactory)
```
    Sets the factory instance to be used for creating rows for this model.
    
    Type Parameters:
    
    F - the MOTableRowFactory class creating rows of type R.
    
    Parameters:
    
    rowFactory - a MOTableRowFactory instance or null to disable row creation.
  - getRowFactory
```
public <F extends org.snmp4j.agent.mo.MOTableRowFactory<R>> F getRowFactory()
```
  - getBufferTimeoutNanoSeconds
```
public long getBufferTimeoutNanoSeconds()
```
    Gets the timeout nano-seconds for buffered rows.
    
    Returns:
    
    the number of nano-seconds after which an buffered row is invalidated and removed from the buffer.
  - setBufferTimeoutNanoSeconds
```
public void setBufferTimeoutNanoSeconds(long bufferTimeoutNanoSeconds)
```
    Sets the timeout nano-seconds for buffered rows.
    
    Parameters:
    
    bufferTimeoutNanoSeconds - the number of nano-seconds after which an buffered row is invalidated and removed from the buffer.
  - getMaxBufferSize
```
public int getMaxBufferSize()
```
    Returns the maximum number of rows in the buffer.
    
    Returns:
    
    the size of the row buffer.
  - setMaxBufferSize
```
public void setMaxBufferSize(int maxBufferSize)
```
    Sets the maximum number of rows in the buffer. The default is
    
    Parameters:
    
    maxBufferSize - the size of the row buffer.
  - getChunkSize
```
public int getChunkSize()
```
    Returns the chunk size for GETNEXT like buffer fetching with the fetchNextRows(org.snmp4j.smi.OID, int) operation. The default is 10.
    
    Returns:
    
    the chunk size for consecutive row fetching from the backend.
  - setChunkSize
```
public void setChunkSize(int chunkSize)
```
    Sets the chunk size for GETNEXT like buffer fetching with the fetchNextRows(org.snmp4j.smi.OID, int) operation. The default is 10.
    
    Parameters:
    
    chunkSize - the chunk size for consecutive row fetching from the backend.
  - getColumnCount
```
public int getColumnCount()
```
    Specified by:
    
    getColumnCount in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - getRowCount
```
public abstract int getRowCount()
```
    Specified by:
    
    getRowCount in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - containsRow
```
public abstract boolean containsRow(org.snmp4j.smi.OID index)
```
    Specified by:
    
    containsRow in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - getRow
```
public R getRow(org.snmp4j.smi.OID index)
```
    Specified by:
    
    getRow in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - getRow
```
protected R getRow(org.snmp4j.smi.OID index,
                   boolean putRowIntoBuffer)
```
    Gets a row from the internal buffer or the backend and puts it into the buffer if specified.
    
    Parameters:
    
    index - the index of the target row.
    
    putRowIntoBuffer - if true then the fetched row (not from the buffer) will be put into the buffer.
    
    Returns:
    
    the row with the given index or null if it does not exist.
  - iterator
```
public Iterator<R> iterator()
```
    Specified by:
    
    iterator in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - tailIterator
```
public Iterator<R> tailIterator(org.snmp4j.smi.OID lowerBound)
```
    Specified by:
    
    tailIterator in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - lastIndex
```
public abstract org.snmp4j.smi.OID lastIndex()
```
    Specified by:
    
    lastIndex in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - firstIndex
```
public abstract org.snmp4j.smi.OID firstIndex()
```
    Specified by:
    
    firstIndex in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - firstRow
```
public R firstRow()
```
    Specified by:
    
    firstRow in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - getFirstBufferRow
```
protected BufferedMOTableModel.BufferedMOTableRow<R> getFirstBufferRow()
```
    Gets the first row from the buffer or the backend if not available from the buffer.
    
    Returns:
    
    the first row as buffered row.
  - lastRow
```
public R lastRow()
```
    Specified by:
    
    lastRow in interface org.snmp4j.agent.mo.MOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>
  - getLastBufferRow
```
protected BufferedMOTableModel.BufferedMOTableRow<R> getLastBufferRow()
```
    Gets the last row from the buffer or the backend if not available from the buffer.
    
    Returns:
    
    the last row as buffered row.
  - isRowValid
```
protected boolean isRowValid(long lastRefreshNanoTime)
```
    Tests if the given timestamp (in nano seconds as retrieved from System.nanoTime()) denotes a valid row.
    
    Parameters:
    
    lastRefreshNanoTime - the last refresh timestamp from a buffered row.
    
    Returns:
    
    true if (System.nanoTime() - lastRefreshNanoTime < bufferTimeoutNanoSeconds)
  - getRowFromBuffer
```
protected BufferedMOTableModel.BufferedMOTableRow<R> getRowFromBuffer(org.snmp4j.smi.OID index)
```
    Gets a row from the buffer.
    
    Parameters:
    
    index - the index of the target row.
    
    Returns:
    
    null if a row with the given index is not buffered (or no longer valid) and the buffered row with that index if that row could be found and is still valid.
  - fetchRow
```
protected abstract org.snmp4j.smi.Variable[] fetchRow(org.snmp4j.smi.OID index)
```
    Fetches the specified row from the backend source.
    
    Parameters:
    
    index - the rows index OID value.
    
    Returns:
    
    the values of the fetched row or null if the row does not exists.
  - fetchNextRows
```
protected abstract List<R> fetchNextRows(org.snmp4j.smi.OID lowerBound,
                                         int chunkSize)
```
    Fetches a list of rows from the backend source.
    
    Parameters:
    
    lowerBound - the lower bound index (inclusive) of the first row to return.
    
    chunkSize - the maximum number of rows to return. Less rows may be returned even if there are more available.
    
    Returns:
    
    a list of rows fetched from the backend. If the last element of the returned list is null, no more rows are available at the source.
  - removeRow
```
public R removeRow(org.snmp4j.smi.OID index)
```
    Removes a row from the table. By default this method throws a UnsupportedOperationException.
    
    Parameters:
    
    index - the index of the target row.
    
    Returns:
    
    the removed row and null if such a row does not exist.
  - updateBuffer
```
protected BufferedMOTableModel.BufferedMOTableRow<R> updateBuffer(List<R> newBufferRows,
                                                                  BufferedMOTableModel.BufferedMOTableRow<R> predecessor)
```
    Updates the internal buffer with a list of consecutive rows.
    
    Parameters:
    
    newBufferRows - a list of rows which must be in lexicographic order (regarding their index values) and without holes.
    
    predecessor - the preceding row of the buffer area that needs to be updated.
    
    Returns:
    
    the buffer row of the first row in the list. As buffer rows are linked by BufferedMOTableModel.BufferedMOTableRow.getNextRow() the buffered rows can be fully traversed by using that first row.
  - cleanupBuffer
```
protected int cleanupBuffer()
```
    Removes any rows from the buffer that exceed the buffer's size limit (FIFO).
    
    Returns:
    
    the number of rows actually removed from the buffer.
  - getBufferHits
```
public long getBufferHits()
```
    Returns the number of row accesses that were served by the buffer.
    
    Returns:
    
    the number of row accesses through the buffered.
  - getBufferMisses
```
public long getBufferMisses()
```
    The number of row accesses that could not be served from the buffer and thus needed backend processing.
    
    Returns:
    
    the number of buffer misses.
  - resetBuffer
```
public void resetBuffer()
```
    Removes all rows from the internal buffer. This method is synchronized to ensure a consistent buffer. It can be used to force a full buffer refresh.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class BufferedMOTableModel<R extends org.snmp4j.agent.mo.MOTableRow>

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface org.snmp4j.agent.mo.MOTableModel

Field Detail

bufferedRows

bufferedChunksList

firstRow

lastRow

rowFactory

columnCount

bufferTimeoutNanoSeconds

chunkSize

maxBufferSize

bufferHits

bufferMisses

Constructor Detail

BufferedMOTableModel

Method Detail

setRowFactory

getRowFactory

getBufferTimeoutNanoSeconds

setBufferTimeoutNanoSeconds

getMaxBufferSize

setMaxBufferSize

getChunkSize

setChunkSize

getColumnCount

getRowCount

containsRow

getRow

getRow

iterator

tailIterator

lastIndex

firstIndex

firstRow

getFirstBufferRow

lastRow

getLastBufferRow

isRowValid

getRowFromBuffer

fetchRow

fetchNextRows

removeRow

updateBuffer

cleanupBuffer

getBufferHits

getBufferMisses

resetBuffer

toString