Examples of com.sleepycat.db.DatabaseEntry

com.sleepycat.db.DatabaseEntry
Encodes database key and data items as a byte array.
Storage and retrieval for the {@link com.sleepycat.db.Database Database} and {@link com.sleepycat.db.Cursor Cursor} methodsare based on key/data pairs. Both key and data items are represented by DatabaseEntry objects. Key and data byte arrays may refer to arrays of zero length up to arrays of essentially unlimited length.
The DatabaseEntry class provides simple access to an underlying object whose elements can be examined or changed. DatabaseEntry objects can be subclassed, providing a way to associate with it additional data or references to other structures.
Access to DatabaseEntry objects is not re-entrant. In particular, if multiple threads simultaneously access the same DatabaseEntry object using {@link com.sleepycat.db.Database Database} or {@link com.sleepycat.db.Cursor Cursor} methods, the results are undefined.
DatabaseEntry objects may be used in conjunction with the object mapping support provided in the {@link com.sleepycat.bind} package.

Input and Output Parameters

DatabaseEntry objects are used for both input data (when writing to a database or specifying a search parameter) and output data (when reading from a database). For certain methods, one parameter may be an input parameter and another may be an output parameter. For example, the {@link Database#get} method has an input key parameter and an outputdata parameter. The documentation for each method describes whether its parameters are input or output parameters.
For DatabaseEntry input parameters, the caller is responsible for initializing the data array of the DatabaseEntry. For DatabaseEntry output parameters, the method called will initialize the data array.
For DatabaseEntry output parameters, by default the method called will reuse the byte array in the DatabaseEntry, if the data returned fits in the byte array. This behavior can be configured with {@link #setReuseBuffer} or {@link #setUserBuffer}. If an entry is configured to reuse the byte array (the default behavior), the length of the underlying byte array should not be used to determine the amount of data returned each time the entry is used as an output parameter, rather the {@link #getSize}call should be used. If an entry is configured to not reuse the byte array, a new array is allocated each time the entry is used as an output parameter, so the application can safely keep a reference to the byte array returned by {@link #getData} without danger that the array will be overwritten ina subsequent call.

Offset and Size Properties

By default the Offset property is zero and the Size property is the length of the byte array. However, to allow for optimizations involving the partial use of a byte array, the Offset and Size may be set to non-default values.
For DatabaseEntry output parameters, the Size will always be set to the length of the returned data and the Offset will always be set to zero.
However, for DatabaseEntry input parameters the Offset and Size are set to non-default values by the built-in tuple and serial bindings. For example, with a tuple or serial binding the byte array is grown dynamically as data is output, and the Size is set to the number of bytes actually used. For a serial binding, the Offset is set to a non-zero value in order to implement an optimization having to do with the serialization stream header.
Therefore, for output DatabaseEntry parameters the application can assume that the Offset is zero and the Size is the length of the byte array. However, for input DatabaseEntry parameters the application should not make this assumption. In general, it is safest for the application to always honor the Size and Offset properties, rather than assuming they have default values.

Partial Offset and Length Properties

By default the specified data (byte array, offset and size) corresponds to the full stored key or data item. Optionally, the Partial property can be set to true, and the PartialOffset and PartialLength properties are used to specify the portion of the key or data item to be read or written. For details, see the {@link #setPartial(int,int,boolean)} method.
Note that the Partial properties are set only by the caller. They will never be set by a Database or Cursor method, nor will they every be set by bindings. Therefore, the application can assume that the Partial properties are not set, unless the application itself sets them explicitly.

        Dbc cursor = null;
        List<String> list = new ArrayList<String>();


        try {
            try {
                DatabaseEntry key = new DatabaseEntry(new byte[0]);
                DatabaseEntry data = new DatabaseEntry((byte[]) null);


                data.setPartial(true);


                cursor = files.cursor(txn, flags);


                if (cursor.get(key, data,
                               DbConstants.DB_SET_RANGE | flags) != DbConstants.DB_NOTFOUND)

View Full Code Here

    /* -- Implement DbDatabase -- */


    /** {@inheritDoc} */
    public byte[] get(DbTransaction txn, byte[] key, boolean forUpdate) {
  try {
      DatabaseEntry valueEntry = new DatabaseEntry();
      OperationStatus status = db.get(
    BdbTransaction.getBdbTxn(txn), new DatabaseEntry(key),
    valueEntry, forUpdate ? LockMode.RMW : null);
      if (status == SUCCESS) {
    return convertData(valueEntry.getData());
      } else if (status == NOTFOUND) {
    return null;
      } else {
    throw new DbDatabaseException("Operation failed: " + status);
      }

View Full Code Here

    }


    /** {@inheritDoc} */
    public void markForUpdate(DbTransaction txn, byte[] key) {
  try {
      DatabaseEntry valueEntry = new DatabaseEntry();
      /* Ignore value by truncating to zero bytes */
      valueEntry.setPartial(0, 0, true);
      OperationStatus status = db.get(
    BdbTransaction.getBdbTxn(txn), new DatabaseEntry(key),
    valueEntry, LockMode.RMW);
      if (status != SUCCESS && status != NOTFOUND) {
    throw new DbDatabaseException("Operation failed: " + status);
      }
  } catch (DatabaseException e) {

View Full Code Here


    /** {@inheritDoc} */
    public void put(DbTransaction txn, byte[] key, byte[] value) {
  try {
      OperationStatus status = db.put(
    BdbTransaction.getBdbTxn(txn), new DatabaseEntry(key),
    new DatabaseEntry(value));
      if (status != SUCCESS) {
    throw new DbDatabaseException("Operation failed: " + status);
      }
  } catch (DatabaseException e) {
      throw BdbEnvironment.convertException(e, true);

View Full Code Here

    public boolean putNoOverwrite(
  DbTransaction txn, byte[] key, byte[] value)
    {
  try {
      OperationStatus status = db.putNoOverwrite(
    BdbTransaction.getBdbTxn(txn), new DatabaseEntry(key),
    new DatabaseEntry(value));
      if (status == SUCCESS) {
    return true;
      } else if (status == KEYEXIST) {
    return false;
      } else {

View Full Code Here


    /** {@inheritDoc} */
    public boolean delete(DbTransaction txn, byte[] key) {
  try {
      OperationStatus status = db.delete(
    BdbTransaction.getBdbTxn(txn), new DatabaseEntry(key));
      if (status == SUCCESS) {
    return true;
      } else if (status == NOTFOUND) {
    return false;
      } else {

View Full Code Here

  }
    }


    /** {@inheritDoc} */
    public boolean findNext(byte[] key) {
  DatabaseEntry searchEntry = new DatabaseEntry(key);
  try {
      OperationStatus status =
    cursor.getSearchKeyRange(searchEntry, valueEntry, null);
      if (status == SUCCESS) {
    keyEntry = searchEntry;

View Full Code Here

    }


    /** {@inheritDoc} */
    public boolean putNoOverwrite(byte[] key, byte[] value) {
  try {
      DatabaseEntry putKeyEntry = new DatabaseEntry(key);
      DatabaseEntry putValueEntry = new DatabaseEntry(value);
      OperationStatus status = cursor.putNoOverwrite(
    putKeyEntry, putValueEntry);
      if (status == SUCCESS) {
    isCurrent = true;
    keyEntry = putKeyEntry;

View Full Code Here

        Dbc cursor = null;
        List list = new ArrayList();


        try {
            try {
                DatabaseEntry key = new DatabaseEntry(new byte[0]);
                DatabaseEntry data = new DatabaseEntry((byte[]) null);


                data.setPartial(true);


                cursor = files.cursor(txn, flags);


                if (cursor.get(key, data,
                               DbConstants.DB_SET_RANGE | flags) != DbConstants.DB_NOTFOUND)

View Full Code Here

    public void setUp()
        throws IOException {


        envHome = new File(System.getProperty(SharedTestUtils.DEST_DIR));
        SharedTestUtils.emptyDir(envHome);
        keyEntry = new DatabaseEntry();
        dataEntry = new DatabaseEntry();
    }

View Full Code Here

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Related Classes of com.sleepycat.db.DatabaseEntry

com.sleepycat.bind.serial.StoredClassCatalog

com.sleepycat.bind.serial.test.SerialBindingTest

com.sleepycat.bind.tuple.test.TupleBindingTest

com.sleepycat.bind.tuple.test.TupleFormatTest

com.sleepycat.collections.BlockIterator

com.sleepycat.collections.DataCursor

com.sleepycat.collections.DataView

com.sleepycat.collections.KeyRangeTest

com.sleepycat.collections.test.TransactionTest

com.sleepycat.db.test.DatabaseTest

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Examples of com.sleepycat.db.DatabaseEntry

Input and Output Parameters

Offset and Size Properties

Partial Offset and Length Properties

Related Classes of com.sleepycat.db.DatabaseEntry