DBCursor

java.lang.Object
- com.mongodb.DBCursor

All Implemented Interfaces:

Cursor, Closeable, AutoCloseable, Iterable<DBObject>, Iterator<DBObject>
```
@NotThreadSafe
public class DBCursor
extends Object
implements Cursor, Iterable<DBObject>
```
An iterator over database results. Doing a find() query on a collection returns a DBCursor thus
```
    DBCursor cursor = collection.find(query);
    if(cursor.hasNext()) {
       DBObject obj = cursor.next();
    }
 
```
Warning: Calling toArray or length on a DBCursor will irrevocably turn it into an array. This means that, if the cursor was iterating over ten million results (which it was lazily fetching from the database), suddenly there will be a ten-million element array in memory. Before converting to an array, make sure that there are a reasonable number of results using skip() and limit().
For example, to get an array of the 1000-1100th elements of a cursor, use
```
    List<DBObject> obj = collection.find(query).skip(1000).limit(100).toArray();
 
```
See Mongo.getDB(String) for further information about the effective deprecation of this class.
MongoDB documentation

Read Operations

Constructor Summary

Constructors
Constructor and Description
`DBCursor(DBCollection collection, DBObject query, DBObject fields, ReadPreference readPreference)` Initializes a new database cursor.

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`DBCursor`	`addOption(int option)` Adds a query option.
`DBCursor`	`addSpecial(String name, Object value)` Adds a special operator like $maxScan or $returnKey.
`DBCursor`	`batchSize(int numberOfElements)` Limits the number of elements returned in one batch.
`void`	`close()` Terminates this cursor on the server.
`DBCursor`	`comment(String comment)` Adds a comment to the query to identify queries in the database profiler output.
`DBCursor`	`copy()` Creates a copy of an existing database cursor.
`int`	`count()` Counts the number of objects matching the query.
`DBObject`	`curr()` Returns the element the cursor is at.
`DBObject`	`explain()` Returns an object containing basic information about the execution of the query that created this cursor.
`int`	`getBatchSize()` Gets the batch size.
`Collation`	`getCollation()` Returns the collation options
`DBCollection`	`getCollection()` Gets the collection.
`long`	`getCursorId()` Gets the server's identifier for this Cursor.
`DBDecoderFactory`	`getDecoderFactory()` Gets the decoder factory that creates the decoder this cursor will use to decode objects from MongoDB.
`DBObject`	`getKeysWanted()` Gets the fields to be returned.
`int`	`getLimit()` Gets the query limit.
`int`	`getOptions()` Gets the query options.
`DBObject`	`getQuery()` Gets the query.
`ReadPreference`	`getReadPreference()` Gets the default read preference.
`ServerAddress`	`getServerAddress()` Gets the address of the server that data is pulled from.
`boolean`	`hasNext()` Checks if there is another object available.
`DBCursor`	`hint(DBObject indexKeys)` Informs the database of indexed fields of the collection in order to improve performance.
`DBCursor`	`hint(String indexName)` Informs the database of an indexed field of the collection in order to improve performance.
`int`	`itcount()` For testing only! Iterates cursor and counts objects
`Iterator<DBObject>`	`iterator()` Creates a copy of this cursor object that can be iterated.
`int`	`length()` Pulls back all items into an array and returns the number of objects.
`DBCursor`	`limit(int limit)` Limits the number of elements returned.
`DBCursor`	`max(DBObject max)` Specifies an exclusive upper limit for the index to use in a query.
`DBCursor`	`maxScan(int max)` Limits the number of documents a cursor will return for a query.
`DBCursor`	`maxTime(long maxTime, TimeUnit timeUnit)` Set the maximum execution time for operations on this cursor.
`DBCursor`	`min(DBObject min)` Specifies an inclusive lower limit for the index to use in a query.
`DBObject`	`next()` Returns the object the cursor is at and moves the cursor ahead by one.
`int`	`numSeen()` Returns the number of objects through which the cursor has iterated.
`DBObject`	`one()` Returns the first document that matches the query.
`void`	`remove()`
`DBCursor`	`resetOptions()` Resets the query options.
`DBCursor`	`returnKey()` Forces the cursor to only return fields included in the index.
`DBCursor`	`setCollation(Collation collation)` Sets the collation options
`DBCursor`	`setDecoderFactory(DBDecoderFactory factory)` Sets the factory that will be used create a `DBDecoder` that will be used to decode BSON documents into DBObject instances.
`DBCursor`	`setOptions(int options)` Sets the query option - see Bytes.QUERYOPTION_* for list.
`DBCursor`	`setReadPreference(ReadPreference readPreference)` Sets the read preference for this cursor.
`DBCursor`	`showDiskLoc()` Modifies the documents returned to include references to the on-disk location of each document.
`int`	`size()` Counts the number of objects matching the query this does take limit/skip into consideration
`DBCursor`	`skip(int numberOfElements)` Discards a given number of elements at the beginning of the cursor.
`DBCursor`	`slaveOk()` Deprecated. Replaced with `ReadPreference.secondaryPreferred()`
`DBCursor`	`snapshot()` Use snapshot mode for the query.
`DBCursor`	`sort(DBObject orderBy)` Sorts this cursor's elements.
`List<DBObject>`	`toArray()` Converts this cursor to an array.
`List<DBObject>`	`toArray(int max)` Converts this cursor to an array.
`String`	`toString()`
`DBObject`	`tryNext()` Non blocking check for tailable cursors to see if another object is available.

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

Methods inherited from interface java.util.Iterator
forEachRemaining

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Constructor Detail
  - DBCursor
```
public DBCursor(DBCollection collection,
                DBObject query,
                DBObject fields,
                ReadPreference readPreference)
```
    Initializes a new database cursor.
    
    Parameters:
    
    collection - collection to use
    
    query - the query filter to apply
    
    fields - keys to return from the query
    
    readPreference - the read preference for this query
- Method Detail
  - copy
```
public DBCursor copy()
```
    Creates a copy of an existing database cursor. The new cursor is an iterator, even if the original was an array.
    
    Returns:
    
    the new cursor
  - hasNext
```
public boolean hasNext()
```
    Checks if there is another object available.
    Note: Automatically adds the Bytes.QUERYOPTION_AWAITDATA option to any cursors with the Bytes.QUERYOPTION_TAILABLE option set. For non blocking tailable cursors see tryNext().
    
    Specified by:
    
    hasNext in interface Iterator<DBObject>
    
    Returns:
    
    true if there is another object available
    
    MongoDB documentation
    
    Cursor Batches
  - next
```
public DBObject next()
```
    Returns the object the cursor is at and moves the cursor ahead by one.
    Note: Automatically adds the Bytes.QUERYOPTION_AWAITDATA option to any cursors with the Bytes.QUERYOPTION_TAILABLE option set. For non blocking tailable cursors see tryNext().
    
    Specified by:
    
    next in interface Iterator<DBObject>
    
    Returns:
    
    the next element
    
    MongoDB documentation
    
    Cursor Batches
  - tryNext
```
public DBObject tryNext()
```
    Non blocking check for tailable cursors to see if another object is available.
    Returns the object the cursor is at and moves the cursor ahead by one or return null if no documents is available.
    
    Returns:
    
    the next element or null
    
    Throws:
    
    MongoException - if failed
    
    IllegalArgumentException - if the cursor is not tailable
    
    MongoDB documentation
    
    Cursor Batches
  - curr
```
public DBObject curr()
```
    Returns the element the cursor is at.
    
    Returns:
    
    the current element
  - remove
```
public void remove()
```
    Specified by:
    
    remove in interface Iterator<DBObject>
  - addOption
```
public DBCursor addOption(int option)
```
    Adds a query option. See Bytes.QUERYOPTION_* for list.
    
    Parameters:
    
    option - the option to be added
    
    Returns:
    
    this so calls can be chained
    
    See Also:
    
    Bytes
    
    MongoDB documentation
    
    Query Flags
  - setOptions
```
public DBCursor setOptions(int options)
```
    Sets the query option - see Bytes.QUERYOPTION_* for list.
    
    Parameters:
    
    options - the bitmask of options
    
    Returns:
    
    this so calls can be chained
    
    See Also:
    
    Bytes
    
    MongoDB documentation
    
    Query Flags
  - resetOptions
```
public DBCursor resetOptions()
```
    Resets the query options.
    
    Returns:
    
    this so calls can be chained
    
    MongoDB documentation
    
    Query Flags
  - getOptions
```
public int getOptions()
```
    Gets the query options.
    
    Returns:
    
    the bitmask of options
    
    MongoDB documentation
    
    Query Flags
  - getLimit
```
public int getLimit()
```
    Gets the query limit.
    
    Returns:
    
    the limit, or 0 if no limit is set
  - getBatchSize
```
public int getBatchSize()
```
    Gets the batch size.
    
    Returns:
    
    the batch size
  - addSpecial
```
public DBCursor addSpecial(String name,
                           Object value)
```
    Adds a special operator like $maxScan or $returnKey. For example:
```
    addSpecial("$returnKey", 1)
    addSpecial("$maxScan", 100)
 
```
    Parameters:
    
    name - the name of the special query operator
    
    value - the value of the special query operator
    
    Returns:
    
    this so calls can be chained
    
    MongoDB documentation
    
    Special Operators
  - comment
```
public DBCursor comment(String comment)
```
    Adds a comment to the query to identify queries in the database profiler output.
    
    Parameters:
    
    comment - the comment that is to appear in the profiler output
    
    Returns:
    
    this so calls can be chained
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    $comment
  - maxScan
```
public DBCursor maxScan(int max)
```
    Limits the number of documents a cursor will return for a query.
    
    Parameters:
    
    max - the maximum number of documents to return
    
    Returns:
    
    this so calls can be chained
    
    Since:
    
    2.12
    
    See Also:
    
    limit(int)
    
    MongoDB documentation
    
    $maxScan
  - max
```
public DBCursor max(DBObject max)
```
    Specifies an exclusive upper limit for the index to use in a query.
    
    Parameters:
    
    max - a document specifying the fields, and the upper bound values for those fields
    
    Returns:
    
    this so calls can be chained
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    $max
  - min
```
public DBCursor min(DBObject min)
```
    Specifies an inclusive lower limit for the index to use in a query.
    
    Parameters:
    
    min - a document specifying the fields, and the lower bound values for those fields
    
    Returns:
    
    this so calls can be chained
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    $min
  - returnKey
```
public DBCursor returnKey()
```
    Forces the cursor to only return fields included in the index.
    
    Returns:
    
    this so calls can be chained
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    $returnKey
  - showDiskLoc
```
public DBCursor showDiskLoc()
```
    Modifies the documents returned to include references to the on-disk location of each document. The location will be returned in a property named $diskLoc
    
    Returns:
    
    this so calls can be chained
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    $showDiskLoc
  - hint
```
public DBCursor hint(DBObject indexKeys)
```
    Informs the database of indexed fields of the collection in order to improve performance.
    
    Parameters:
    
    indexKeys - a DBObject with fields and direction
    
    Returns:
    
    same DBCursor for chaining operations
    
    MongoDB documentation
    
    $hint
  - hint
```
public DBCursor hint(String indexName)
```
    Informs the database of an indexed field of the collection in order to improve performance.
    
    Parameters:
    
    indexName - the name of an index
    
    Returns:
    
    same DBCursor for chaining operations
    
    MongoDB documentation
    
    $hint
  - maxTime
```
public DBCursor maxTime(long maxTime,
                        TimeUnit timeUnit)
```
    Set the maximum execution time for operations on this cursor.
    
    Parameters:
    
    maxTime - the maximum time that the server will allow the query to run, before killing the operation. A non-zero value requires a server version >= 2.6
    
    timeUnit - the time unit
    
    Returns:
    
    same DBCursor for chaining operations
    
    Since:
    
    2.12.0
    
    MongoDB documentation
    
    $maxTimeMS
    
    Since server release
    
    2.6
  - snapshot
```
public DBCursor snapshot()
```
    Use snapshot mode for the query. Snapshot mode prevents the cursor from returning a document more than once because an intervening write operation results in a move of the document. Even in snapshot mode, documents inserted or deleted during the lifetime of the cursor may or may not be returned. Currently, snapshot mode may not be used with sorting or explicit hints.
    
    Returns:
    
    this so calls can be chained
    
    See Also:
    
    sort(DBObject), hint(DBObject)
    
    MongoDB documentation
    
    $snapshot
  - explain
```
public DBObject explain()
```
    Returns an object containing basic information about the execution of the query that created this cursor. This creates a DBObject with a number of fields, including but not limited to:
    - cursor: cursor type
    - nScanned: number of records examined by the database for this query
    - n: the number of records that the database returned
    - millis: how long it took the database to execute the query
    Returns:
    
    a DBObject containing the explain output for this DBCursor's query
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    Explain Output
  - sort
```
public DBCursor sort(DBObject orderBy)
```
    Sorts this cursor's elements. This method must be called before getting any object from the cursor.
    
    Parameters:
    
    orderBy - the fields by which to sort
    
    Returns:
    
    a cursor pointing to the first element of the sorted results
  - limit
```
public DBCursor limit(int limit)
```
    Limits the number of elements returned. Note: parameter limit should be positive, although a negative value is supported for legacy reason. Passing a negative value will call batchSize(int) which is the preferred method.
    
    Parameters:
    
    limit - the number of elements to return
    
    Returns:
    
    a cursor to iterate the results
    
    MongoDB documentation
    
    Limit
  - batchSize
```
public DBCursor batchSize(int numberOfElements)
```
    Limits the number of elements returned in one batch. A cursor typically fetches a batch of result objects and store them locally.
    
    If batchSize is positive, it represents the size of each batch of objects retrieved. It can be adjusted to optimize performance and limit data transfer.
    
    If batchSize is negative, it will limit of number objects returned, that fit within the max batch size limit (usually 4MB), and cursor will be closed. For example if batchSize is -10, then the server will return a maximum of 10 documents and as many as can fit in 4MB, then close the cursor. Note that this feature is different from limit() in that documents must fit within a maximum size, and it removes the need to send a request to close the cursor server-side.
    
    Parameters:
    
    numberOfElements - the number of elements to return in a batch
    
    Returns:
    
    this so calls can be chained
  - skip
```
public DBCursor skip(int numberOfElements)
```
    Discards a given number of elements at the beginning of the cursor.
    
    Parameters:
    
    numberOfElements - the number of elements to skip
    
    Returns:
    
    a cursor pointing to the new first element of the results
    
    Throws:
    
    IllegalStateException - if the cursor has started to be iterated through
  - getCursorId
```
public long getCursorId()
```
    Description copied from interface: Cursor
    
    Gets the server's identifier for this Cursor.
    
    Specified by:
    
    getCursorId in interface Cursor
    
    Returns:
    
    the cursor's ID, or 0 if there is no active cursor.
  - numSeen
```
public int numSeen()
```
    Returns the number of objects through which the cursor has iterated.
    
    Returns:
    
    the number of objects seen
  - close
```
public void close()
```
    Description copied from interface: Cursor
    
    Terminates this cursor on the server.
    
    Specified by:
    
    close in interface Cursor
    
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
  - slaveOk
```
@Deprecated
public DBCursor slaveOk()
```
    Deprecated. Replaced with ReadPreference.secondaryPreferred()
    
    Declare that this query can run on a secondary server.
    
    Returns:
    
    a copy of the same cursor (for chaining)
    
    See Also:
    
    ReadPreference.secondaryPreferred()
  - iterator
```
public Iterator<DBObject> iterator()
```
    Creates a copy of this cursor object that can be iterated. Note: - you can iterate the DBCursor itself without calling this method - no actual data is getting copied.
    
    Note that use of this method does not let you call close the underlying cursor in the case of either an exception or an early break. The preferred method of iteration is to use DBCursor as an Iterator, so that you can call close() on it in a finally block.
    
    Specified by:
    
    iterator in interface Iterable<DBObject>
    
    Returns:
    
    an iterator
  - toArray
```
public List<DBObject> toArray()
```
    Converts this cursor to an array.
    
    Returns:
    
    an array of elements
    
    Throws:
    
    MongoException - if failed
  - toArray
```
public List<DBObject> toArray(int max)
```
    Converts this cursor to an array.
    
    Parameters:
    
    max - the maximum number of objects to return
    
    Returns:
    
    an array of objects
    
    Throws:
    
    MongoException - if failed
  - count
```
public int count()
```
    Counts the number of objects matching the query. This does not take limit/skip into consideration, and does initiate a call to the server.
    
    Returns:
    
    the number of objects
    
    Throws:
    
    MongoException - if the operation failed
    
    See Also:
    
    size()
  - one
```
public DBObject one()
```
    Returns the first document that matches the query.
    
    Returns:
    
    the first matching document
    
    Since:
    
    2.12
  - length
```
public int length()
```
    Pulls back all items into an array and returns the number of objects. Note: this can be resource intensive.
    
    Returns:
    
    the number of elements in the array
    
    Throws:
    
    MongoException - if failed
    
    See Also:
    
    count(), size()
  - itcount
```
public int itcount()
```
    For testing only! Iterates cursor and counts objects
    
    Returns:
    
    num objects
    
    Throws:
    
    MongoException - if failed
    
    See Also:
    
    count()
  - size
```
public int size()
```
    Counts the number of objects matching the query this does take limit/skip into consideration
    
    Returns:
    
    the number of objects
    
    Throws:
    
    MongoException - if the operation failed
    
    See Also:
    
    count()
  - getKeysWanted
```
public DBObject getKeysWanted()
```
    Gets the fields to be returned.
    
    Returns:
    
    the field selector that cursor used
  - getQuery
```
public DBObject getQuery()
```
    Gets the query.
    
    Returns:
    
    the query that cursor used
  - getCollection
```
public DBCollection getCollection()
```
    Gets the collection.
    
    Returns:
    
    the collection that data is pulled from
  - getServerAddress
```
public ServerAddress getServerAddress()
```
    Description copied from interface: Cursor
    
    Gets the address of the server that data is pulled from. Note that this information may not be available until hasNext() or next() is called.
    
    Specified by:
    
    getServerAddress in interface Cursor
    
    Returns:
    
    the address of the server that data is pulled from
  - setReadPreference
```
public DBCursor setReadPreference(ReadPreference readPreference)
```
    Sets the read preference for this cursor. See the documentation for ReadPreference for more information.
    
    Parameters:
    
    readPreference - read preference to use
    
    Returns:
    
    this so calls can be chained
  - getReadPreference
```
public ReadPreference getReadPreference()
```
    Gets the default read preference.
    
    Returns:
    
    the readPreference used by this cursor
  - getCollation
```
public Collation getCollation()
```
    Returns the collation options
    
    Returns:
    
    the collation options
    
    Since:
    
    3.4
    
    Since server release
    
    3.4
  - setCollation
```
public DBCursor setCollation(Collation collation)
```
    Sets the collation options
    A null value represents the server default.
    
    Parameters:
    
    collation - the collation options to use
    
    Returns:
    
    this
    
    Since:
    
    3.4
    
    Since server release
    
    3.4
  - setDecoderFactory
```
public DBCursor setDecoderFactory(DBDecoderFactory factory)
```
    Sets the factory that will be used create a DBDecoder that will be used to decode BSON documents into DBObject instances.
    
    Parameters:
    
    factory - the DBDecoderFactory
    
    Returns:
    
    this so calls can be chained
  - getDecoderFactory
```
public DBDecoderFactory getDecoderFactory()
```
    Gets the decoder factory that creates the decoder this cursor will use to decode objects from MongoDB.
    
    Returns:
    
    the decoder factory.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class DBCursor

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Iterator

Methods inherited from interface java.lang.Iterable

Constructor Detail

DBCursor

Method Detail

copy

hasNext

next

tryNext

curr

remove

addOption

setOptions

resetOptions

getOptions

getLimit

getBatchSize

addSpecial

comment

maxScan

max

min

returnKey

showDiskLoc

hint

hint

maxTime

snapshot

explain

sort

limit

batchSize

skip

getCursorId

numSeen

close

slaveOk

iterator

toArray

toArray

count

one

length

itcount

size

getKeysWanted

getQuery

getCollection

getServerAddress

setReadPreference

getReadPreference

getCollation

setCollation

setDecoderFactory

getDecoderFactory

toString