DB

java.lang.Object
- com.mongodb.DB

```
@ThreadSafe
public class DB
extends Object
```
A thread-safe client view of a logical database in a MongoDB cluster. A DB instance can be achieved from a MongoClient instance using code like:
```
 
 MongoClient mongoClient = new MongoClient();
 DB db = mongoClient.getDB("<db name>");
 
 
```
See Mongo.getDB(String) for further information about the effective deprecation of this class.
See Also:

MongoClient

MongoDB documentation

Database

Constructor Summary

Constructors
Constructor and Description

DB(Mongo mongo, String name)
Constructs a new instance of the DB.

Constructors
Constructor and Description
`DB(Mongo mongo, String name)` Constructs a new instance of the `DB`.

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`void`	`addOption(int option)` Adds the given flag to the default query options.
`WriteResult`	`addUser(String userName, char[] password)` Deprecated. Use `DB.command` to call either the createUser or updateUser command
`WriteResult`	`addUser(String userName, char[] password, boolean readOnly)` Deprecated. Use `DB.command` to call either the createUser or updateUser command
`boolean`	`collectionExists(String collectionName)` Checks to see if a collection with a given name exists on a server.
`CommandResult`	`command(DBObject command)` Executes a database command.
`CommandResult`	`command(DBObject command, DBEncoder encoder)` Executes a database command.
`CommandResult`	`command(DBObject command, ReadPreference readPreference)` Executes the command against the database with the given read preference.
`CommandResult`	`command(DBObject command, ReadPreference readPreference, DBEncoder encoder)` Executes a database command with the selected readPreference, and encodes the command using the given encoder.
`CommandResult`	`command(String command)` Executes a database command.
`CommandResult`	`command(String command, ReadPreference readPreference)` Executes a database command.
`DBCollection`	`createCollection(String collectionName, DBObject options)` Creates a collection with a given name and options.
`DBCollection`	`createView(String viewName, String viewOn, List<? extends DBObject> pipeline)` Creates a view with the given name, backing collection/view name, and aggregation pipeline that defines the view.
`DBCollection`	`createView(String viewName, String viewOn, List<? extends DBObject> pipeline, DBCreateViewOptions options)` Creates a view with the given name, backing collection/view name, aggregation pipeline, and options that defines the view.
`CommandResult`	`doEval(String code, Object... args)` Evaluates JavaScript functions on the database server.
`protected DBCollection`	`doGetCollection(String name)` Gets a collection with a given name.
`void`	`dropDatabase()` Drops this database.
`Object`	`eval(String code, Object... args)` Calls `doEval(java.lang.String, java.lang.Object[])`.
`DBCollection`	`getCollection(String name)` Gets a collection with a given name.
`DBCollection`	`getCollectionFromString(String collectionName)` Returns a collection matching a given string.
`Set<String>`	`getCollectionNames()` Returns a set containing the names of all collections in this database.
`Mongo`	`getMongo()` Gets the Mongo instance
`String`	`getName()` Returns the name of this database.
`int`	`getOptions()` Gets the query options
`ReadConcern`	`getReadConcern()` Get the read concern for this database.
`ReadPreference`	`getReadPreference()` Gets the read preference for this database.
`DB`	`getSisterDB(String name)` Gets another database on same server
`CommandResult`	`getStats()` Helper method for calling a 'dbStats' command.
`WriteConcern`	`getWriteConcern()` Gets the write concern for this database.
`WriteResult`	`removeUser(String userName)` Deprecated. Use `DB.command` to call the dropUser command
`void`	`resetOptions()` Resets the query options.
`void`	`setOptions(int options)` Sets the query options, overwriting previous value.
`void`	`setReadConcern(ReadConcern readConcern)` Sets the read concern for this database.
`void`	`setReadPreference(ReadPreference readPreference)` Sets the read preference for this database.
`void`	`setWriteConcern(WriteConcern writeConcern)` Sets the write concern for this database.
`void`	`slaveOk()` Deprecated. Replaced with `ReadPreference.secondaryPreferred()`
`String`	`toString()`

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

- Constructor Detail
  - DB
```
public DB(Mongo mongo,
          String name)
```
    Constructs a new instance of the DB.
    
    Parameters:
    
    mongo - the mongo instance
    
    name - the database name - must not be empty and cannot contain spaces
- Method Detail
  - getMongo
```
public Mongo getMongo()
```
    Gets the Mongo instance
    
    Returns:
    
    the mongo instance that this database was created from.
  - setReadPreference
```
public void setReadPreference(ReadPreference readPreference)
```
    Sets the read preference for this database. Will be used as default for read operations from any collection in this database. See the documentation for ReadPreference for more information.
    
    Parameters:
    
    readPreference - ReadPreference to use
    
    MongoDB documentation
    
    Read Preference
  - setWriteConcern
```
public void setWriteConcern(WriteConcern writeConcern)
```
    Sets the write concern for this database. It will be used for write operations to any collection in this database. See the documentation for WriteConcern for more information.
    
    Parameters:
    
    writeConcern - WriteConcern to use
    
    MongoDB documentation
    
    Write Concern
  - getReadPreference
```
public ReadPreference getReadPreference()
```
    Gets the read preference for this database.
    
    Returns:
    
    ReadPreference to be used for read operations, if not specified explicitly
    
    MongoDB documentation
    
    Read Preference
  - getWriteConcern
```
public WriteConcern getWriteConcern()
```
    Gets the write concern for this database.
    
    Returns:
    
    WriteConcern to be used for write operations, if not specified explicitly
    
    MongoDB documentation
    
    Write Concern
  - setReadConcern
```
public void setReadConcern(ReadConcern readConcern)
```
    Sets the read concern for this database.
    
    Parameters:
    
    readConcern - the read concern to use for this collection
    
    Since:
    
    3.3
    
    MongoDB documentation
    
    Read Concern
    
    Since server release
    
    3.2
  - getReadConcern
```
public ReadConcern getReadConcern()
```
    Get the read concern for this database.
    
    Returns:
    
    the ReadConcern
    
    Since:
    
    3.3
    
    MongoDB documentation
    
    Read Concern
    
    Since server release
    
    3.2
  - doGetCollection
```
protected DBCollection doGetCollection(String name)
```
    Gets a collection with a given name. If the collection does not exist, a new collection is created.
    
    This class is NOT part of the public API. Be prepared for non-binary compatible changes in minor releases.
    
    Parameters:
    
    name - the name of the collection
    
    Returns:
    
    the collection
  - getCollection
```
public DBCollection getCollection(String name)
```
    Gets a collection with a given name.
    
    Parameters:
    
    name - the name of the collection to return
    
    Returns:
    
    the collection
  - dropDatabase
```
public void dropDatabase()
```
    Drops this database. Removes all data on disk. Use with caution.
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    Drop Database
  - getCollectionFromString
```
public DBCollection getCollectionFromString(String collectionName)
```
    Returns a collection matching a given string.
    
    Parameters:
    
    collectionName - the name of the collection
    
    Returns:
    
    the collection
  - getName
```
public String getName()
```
    Returns the name of this database.
    
    Returns:
    
    the name
  - getCollectionNames
```
public Set<String> getCollectionNames()
```
    Returns a set containing the names of all collections in this database.
    
    Returns:
    
    the names of collections in this database
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    getCollectionNames()
  - createCollection
```
public DBCollection createCollection(String collectionName,
                                     DBObject options)
```
    Creates a collection with a given name and options. If the collection already exists, this throws a CommandFailureException.
    
    Possible options:
    - capped (boolean) - Enables a collection cap. False by default. If enabled, you must specify a size parameter.
    - size (int) - If capped is true, size specifies a maximum size in bytes for the capped collection. When capped is false, you may use size to preallocate space.
    - max (int) - Optional. Specifies a maximum "cap" in number of documents for capped collections. You must also specify size when specifying max.
    Note that if the options parameter is null, the creation will be deferred to when the collection is written to.
    Parameters:
    
    collectionName - the name of the collection to return
    
    options - options
    
    Returns:
    
    the collection
    
    Throws:
    
    MongoCommandException - if the server is unable to create the collection
    
    WriteConcernException - if the WriteConcern specified on this DB could not be satisfied
    
    MongoException - for all other failures
    
    MongoDB documentation
    
    createCollection()
  - createView
```
public DBCollection createView(String viewName,
                               String viewOn,
                               List<? extends DBObject> pipeline)
```
    Creates a view with the given name, backing collection/view name, and aggregation pipeline that defines the view.
    
    Parameters:
    
    viewName - the name of the view to create
    
    viewOn - the backing collection/view for the view
    
    pipeline - the pipeline that defines the view
    
    Returns:
    
    the view as a DBCollection
    
    Throws:
    
    MongoCommandException - if the server is unable to create the collection
    
    WriteConcernException - if the WriteConcern specified on this DB could not be satisfied
    
    MongoException - for all other failures
    
    Since:
    
    3.4
    
    MongoDB documentation
    
    Create Command
    
    Since server release
    
    3.4
  - createView
```
public DBCollection createView(String viewName,
                               String viewOn,
                               List<? extends DBObject> pipeline,
                               DBCreateViewOptions options)
```
    Creates a view with the given name, backing collection/view name, aggregation pipeline, and options that defines the view.
    
    Parameters:
    
    viewName - the name of the view to create
    
    viewOn - the backing collection/view for the view
    
    pipeline - the pipeline that defines the view
    
    options - the options for creating the view
    
    Returns:
    
    the view as a DBCollection
    
    Throws:
    
    MongoCommandException - if the server is unable to create the collection
    
    WriteConcernException - if the WriteConcern specified on this DB could not be satisfied
    
    MongoException - for all other failures
    
    Since:
    
    3.4
    
    MongoDB documentation
    
    Create Command
    
    Since server release
    
    3.4
  - command
```
public CommandResult command(String command)
```
    Executes a database command. This method constructs a simple DBObject using command as the field name and true as its value, and calls command(DBObject, ReadPreference) with the default read preference for the database.
    
    Parameters:
    
    command - command to execute
    
    Returns:
    
    result of command from the database
    
    Throws:
    
    MongoException - if the command failed
    
    MongoDB documentation
    
    Commands
  - command
```
public CommandResult command(DBObject command)
```
    Executes a database command. This method calls command(DBObject, ReadPreference) with the default read preference for the database.
    
    Parameters:
    
    command - DBObject representation of the command to be executed
    
    Returns:
    
    result of the command execution
    
    Throws:
    
    MongoException - if the command failed
    
    MongoDB documentation
    
    Commands
  - command
```
public CommandResult command(DBObject command,
                             DBEncoder encoder)
```
    Executes a database command. This method calls command(DBObject, ReadPreference, DBEncoder) with the default read preference for the database.
    
    Parameters:
    
    command - DBObject representation of the command to be executed
    
    encoder - DBEncoder to be used for command encoding
    
    Returns:
    
    result of the command execution
    
    Throws:
    
    MongoException - if the command failed
    
    MongoDB documentation
    
    Commands
  - command
```
public CommandResult command(DBObject command,
                             ReadPreference readPreference,
                             DBEncoder encoder)
```
    Executes a database command with the selected readPreference, and encodes the command using the given encoder.
    
    Parameters:
    
    command - The DBObject representation the command to be executed
    
    readPreference - Where to execute the command - this will only be applied for a subset of commands
    
    encoder - The DBEncoder that knows how to serialise the command
    
    Returns:
    
    The result of executing the command, success or failure
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    Commands
  - command
```
public CommandResult command(DBObject command,
                             ReadPreference readPreference)
```
    Executes the command against the database with the given read preference.
    
    Parameters:
    
    command - The DBObject representation the command to be executed
    
    readPreference - Where to execute the command - this will only be applied for a subset of commands
    
    Returns:
    
    The result of executing the command, success or failure
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    Commands
  - command
```
public CommandResult command(String command,
                             ReadPreference readPreference)
```
    Executes a database command. This method constructs a simple DBObject and calls command(DBObject, ReadPreference).
    
    Parameters:
    
    command - The name of the command to be executed
    
    readPreference - Where to execute the command - this will only be applied for a subset of commands
    
    Returns:
    
    The result of the command execution
    
    Throws:
    
    MongoException - if the command failed
    
    Since:
    
    2.12
    
    MongoDB documentation
    
    Commands
  - getSisterDB
```
public DB getSisterDB(String name)
```
    Gets another database on same server
    
    Parameters:
    
    name - name of the database
    
    Returns:
    
    the DB for the given name
  - collectionExists
```
public boolean collectionExists(String collectionName)
```
    Checks to see if a collection with a given name exists on a server.
    
    Parameters:
    
    collectionName - a name of the collection to test for existence
    
    Returns:
    
    false if no collection by that name exists, true if a match to an existing collection was found
    
    Throws:
    
    MongoException - if the operation failed
  - doEval
```
public CommandResult doEval(String code,
                            Object... args)
```
    Evaluates JavaScript functions on the database server. This is useful if you need to touch a lot of data lightly, in which case network transfer could be a bottleneck.
    
    Parameters:
    
    code - String representation of JavaScript function
    
    args - arguments to pass to the JavaScript function
    
    Returns:
    
    result of the command execution
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    db.eval()
  - eval
```
public Object eval(String code,
                   Object... args)
```
    Calls doEval(java.lang.String, java.lang.Object[]). If the command is successful, the "retval" field is extracted and returned. Otherwise an exception is thrown.
    
    Parameters:
    
    code - String representation of JavaScript function
    
    args - arguments to pass to the JavaScript function
    
    Returns:
    
    result of the execution
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    db.eval()
  - getStats
```
public CommandResult getStats()
```
    Helper method for calling a 'dbStats' command. It returns storage statistics for a given database.
    
    Returns:
    
    result of the execution
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    Database Stats
  - addUser
```
@Deprecated
public WriteResult addUser(String userName,
                                       char[] password)
```
    Deprecated. Use DB.command to call either the createUser or updateUser command
    
    Adds or updates a user for this database
    
    Parameters:
    
    userName - the user name
    
    password - the password
    
    Returns:
    
    the result of executing this operation
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    Access Control
    
    createUser
    
    updateUser
  - addUser
```
@Deprecated
public WriteResult addUser(String userName,
                                       char[] password,
                                       boolean readOnly)
```
    Deprecated. Use DB.command to call either the createUser or updateUser command
    
    Adds or updates a user for this database
    
    Parameters:
    
    userName - the user name
    
    password - the password
    
    readOnly - if true, user will only be able to read
    
    Returns:
    
    the result of executing this operation
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    Access Control
    
    createUser
    
    updateUser
  - removeUser
```
@Deprecated
public WriteResult removeUser(String userName)
```
    Deprecated. Use DB.command to call the dropUser command
    
    Removes the specified user from the database.
    
    Parameters:
    
    userName - user to be removed
    
    Returns:
    
    the result of executing this operation
    
    Throws:
    
    MongoException - if the operation failed
    
    MongoDB documentation
    
    Access Control
  - slaveOk
```
@Deprecated
public void slaveOk()
```
    Deprecated. Replaced with ReadPreference.secondaryPreferred()
    
    Makes it possible to execute "read" queries on a slave node
    
    See Also:
    
    ReadPreference.secondaryPreferred()
  - addOption
```
public void addOption(int option)
```
    Adds the given flag to the default query options.
    
    Parameters:
    
    option - value to be added
    
    MongoDB documentation
    
    Query Flags
  - setOptions
```
public void setOptions(int options)
```
    Sets the query options, overwriting previous value.
    
    Parameters:
    
    options - bit vector of query options
    
    MongoDB documentation
    
    Query Flags
  - resetOptions
```
public void resetOptions()
```
    Resets the query options.
    
    MongoDB documentation
    
    Query Flags
  - getOptions
```
public int getOptions()
```
    Gets the query options
    
    Returns:
    
    bit vector of query options
    
    MongoDB documentation
    
    Query Flags
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class DB

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DB

Method Detail

getMongo

setReadPreference

setWriteConcern

getReadPreference

getWriteConcern

setReadConcern

getReadConcern

doGetCollection

getCollection

dropDatabase

getCollectionFromString

getName

getCollectionNames

createCollection

createView

createView

command

command

command

command

command

command

getSisterDB

collectionExists

doEval

eval

getStats

addUser

addUser

removeUser

slaveOk

addOption

setOptions

resetOptions

getOptions

toString