Package com.mongodb.client.model

Class Projections

java.lang.Object

com.mongodb.client.model.Projections

public final class Projections
extends Object

A factory for projections. A convenient way to use this class is to statically import all of its methods, which allows usage like:

    collection.find().projection(fields(include("x", "y"), excludeId()))
 

Since:

3.0

MongoDB documentation

Projection

Method Summary

Modifier and Type	Method	Description
static <TExpression> Bson	computed(String fieldName, TExpression expression)	Creates a projection of a field whose value is computed from the given expression.
static Bson	elemMatch(String fieldName)	Creates a projection that includes for the given field only the first element of an array that matches the query filter.
static Bson	elemMatch(String fieldName, Bson filter)	Creates a projection that includes for the given field only the first element of the array value of that field that matches the given query filter.
static Bson	exclude(String... fieldNames)	Creates a projection that excludes all of the given fields.
static Bson	exclude(List<String> fieldNames)	Creates a projection that excludes all of the given fields.
static Bson	excludeId()	Creates a projection that excludes the _id field.
static Bson	fields(List<? extends Bson> projections)	Creates a projection that combines the list of projections into a single one.
static Bson	fields(Bson... projections)	Creates a projection that combines the list of projections into a single one.
static Bson	include(String... fieldNames)	Creates a projection that includes all of the given fields.
static Bson	include(List<String> fieldNames)	Creates a projection that includes all of the given fields.
static Bson	metaTextScore(String fieldName)	Creates a projection to the given field name of the textScore, for use with text queries.
static Bson	slice(String fieldName, int limit)	Creates a projection to the given field name of a slice of the array value of that field.
static Bson	slice(String fieldName, int skip, int limit)	Creates a projection to the given field name of a slice of the array value of that field.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

computed

public static <TExpression> Bson computed(String fieldName,
                                          TExpression expression)

Creates a projection of a field whose value is computed from the given expression. Projection with an expression is only supported using the $project aggregation pipeline stage.

Type Parameters:

TExpression - the expression type

Parameters:

fieldName - the field name

expression - the expression

Returns:

the projection

See Also:

Aggregates.project(Bson)

include

public static Bson include(String... fieldNames)

Creates a projection that includes all of the given fields.

Parameters:

fieldNames - the field names

Returns:

the projection

include

public static Bson include(List<String> fieldNames)

Creates a projection that includes all of the given fields.

Parameters:

fieldNames - the field names

Returns:

the projection

exclude

public static Bson exclude(String... fieldNames)

Creates a projection that excludes all of the given fields.

Parameters:

fieldNames - the field names

Returns:

the projection

exclude

public static Bson exclude(List<String> fieldNames)

Creates a projection that excludes all of the given fields.

Parameters:

fieldNames - the field names

Returns:

the projection

excludeId

public static Bson excludeId()

Creates a projection that excludes the _id field. This suppresses the automatic inclusion of _id that is the default, even when other fields are explicitly included.

Returns:

the projection

elemMatch

public static Bson elemMatch(String fieldName)

Creates a projection that includes for the given field only the first element of an array that matches the query filter. This is referred to as the positional $ operator.

Parameters:

fieldName - the field name whose value is the array

Returns:

the projection

MongoDB documentation

Project the first matching element ($ operator)

elemMatch

public static Bson elemMatch(String fieldName,
                             Bson filter)

Creates a projection that includes for the given field only the first element of the array value of that field that matches the given query filter.

Parameters:

fieldName - the field name

filter - the filter to apply

Returns:

the projection

MongoDB documentation

elemMatch

metaTextScore

public static Bson metaTextScore(String fieldName)

Creates a projection to the given field name of the textScore, for use with text queries.

Parameters:

fieldName - the field name

Returns:

the projection

MongoDB documentation

textScore

slice

public static Bson slice(String fieldName,
                         int limit)

Creates a projection to the given field name of a slice of the array value of that field.

Parameters:

fieldName - the field name

limit - the number of elements to project.

Returns:

the projection

MongoDB documentation

Slice

slice

public static Bson slice(String fieldName,
                         int skip,
                         int limit)

Creates a projection to the given field name of a slice of the array value of that field.

Parameters:

fieldName - the field name

skip - the number of elements to skip before applying the limit

limit - the number of elements to project

Returns:

the projection

MongoDB documentation

Slice

fields

public static Bson fields(Bson... projections)

Creates a projection that combines the list of projections into a single one. If there are duplicate keys, the last one takes precedence.

Parameters:

projections - the list of projections to combine

Returns:

the combined projection

fields

public static Bson fields(List<? extends Bson> projections)

Creates a projection that combines the list of projections into a single one. If there are duplicate keys, the last one takes precedence.

Parameters:

projections - the list of projections to combine

Returns:

the combined projection