Package dev.morphia.aggregation.expressions

Class ArrayExpressions

java.lang.Object

dev.morphia.aggregation.expressions.ArrayExpressions

public final class ArrayExpressions
extends Object

Defines helper methods for the array expressions

Since:

2.0

Method Summary

Modifier and Type	Method	Description
static ArrayExpression	array(Expression... expressions)	Creates an array of the given expressions.
static ArrayExpression	array(Object... objects)	Creates an array of the given objects.
static Expression	arrayToObject(Expression array)	Converts an array of key value pairs to a document.
static Expression	concatArrays(Expression array, Expression additional)	Concatenates arrays to return the concatenated array.
static Expression	elementAt(Expression array, Expression index)	Returns the element at the specified array index.
static ArrayFilterExpression	filter(Expression array, Expression conditional)	Selects a subset of the array to return an array with only the elements that match the filter condition.
static Expression	in(Expression search, Expression array)	Returns a boolean indicating whether a specified value is in an array.
static Expression	indexOfArray(Expression array, Expression search)	Searches an array for an occurrence of a specified value and returns the array index of the first occurernce.
static Expression	isArray(Expression array)	Determines if the operand is an array.
static MapExpression	map(Expression input, Expression in)	Applies a subexpression to each element of an array and returns the array of resulting values in order.
static Expression	objectToArray(Expression array)	Converts a document to an array of documents representing key-value pairs.
static RangeExpression	range(int start, int end)	Outputs an array containing a sequence of integers according to user-defined inputs.
static Expression	reduce(Expression input, Expression initial, Expression in)	Applies an expression to each element in an array and combines them into a single value.
static Expression	reverseArray(Expression array)	Returns an array with the elements in reverse order.
static Expression	size(Expression array)	Counts and returns the total number of items in an array.
static Expression	slice(Expression array, int size)	Returns a subset of an array.
static Expression	sortArray(Expression input, Sort... sort)	Sorts an array based on its elements.
static ZipExpression	zip(Expression... arrays)	Merge two arrays together.

Methods inherited from class java.lang.Object

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

Method Detail

array

public static ArrayExpression array(Expression... expressions)

Creates an array of the given expressions. This "expression" isn't so much a mongodb expression as it is a convenience method for building pipeline definitions.

Parameters:

expressions - the expressions

Returns:

the new expression

array

@MorphiaExperimental
public static ArrayExpression array(Object... objects)

Creates an array of the given objects. This method is an experiment in accepting a wider breadth of types and finding the expressions at encoding time and dealing with them appropriately. There might be bugs in this approach. This method might go away. But it's useful in some Morphia tests, at least.

Parameters:

objects - the objects

Returns:

the new expression

Since:

2.3

Developer note.

This is an experimental item. Its function and presence are subject to change. Feedback on features and usability extremely welcome.

arrayToObject

public static Expression arrayToObject(Expression array)

Converts an array of key value pairs to a document.

Parameters:

array - the array to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $arrayToObject

concatArrays

public static Expression concatArrays(Expression array,
                                      Expression additional)

Concatenates arrays to return the concatenated array.

Parameters:

array - the array to use

additional - any additional arrays to concatenate

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $concatArrays

elementAt

public static Expression elementAt(Expression array,
                                   Expression index)

Returns the element at the specified array index.

Parameters:

array - the array to use

index - the index to return

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $arrayElemAt

filter

public static ArrayFilterExpression filter(Expression array,
                                           Expression conditional)

Selects a subset of the array to return an array with only the elements that match the filter condition.

Parameters:

array - the array to use

conditional - the conditional to use for filtering

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $filter

in

public static Expression in(Expression search,
                            Expression array)

Returns a boolean indicating whether a specified value is in an array.

Parameters:

search - the expression to search for

array - the array to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $in

indexOfArray

public static Expression indexOfArray(Expression array,
                                      Expression search)

Searches an array for an occurrence of a specified value and returns the array index of the first occurernce. If the substring is not found, returns -1.

Parameters:

array - the array to use

search - the expression to search for

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $indexOfArray

isArray

public static Expression isArray(Expression array)

Determines if the operand is an array. Returns a boolean.

Parameters:

array - the array to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $isArray

map

public static MapExpression map(Expression input,
                                Expression in)

Applies a subexpression to each element of an array and returns the array of resulting values in order. Accepts named parameters.

Parameters:

input - the array to use

in - An expression that is applied to each element of the input array.

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $map

objectToArray

public static Expression objectToArray(Expression array)

Converts a document to an array of documents representing key-value pairs.

Parameters:

array - the array to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $objectToArray

range

public static RangeExpression range(int start,
                                    int end)

Outputs an array containing a sequence of integers according to user-defined inputs.

Parameters:

start - the starting value

end - the ending value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $range

reduce

public static Expression reduce(Expression input,
                                Expression initial,
                                Expression in)

Applies an expression to each element in an array and combines them into a single value.

Parameters:

input - the array to use

initial - The initial cumulative value set before in is applied to the first element of the input array.

in - A valid expression that $reduce applies to each element in the input array in left-to-right order.

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $reduce

reverseArray

public static Expression reverseArray(Expression array)

Returns an array with the elements in reverse order.

Parameters:

array - the array to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $reverseArray

size

public static Expression size(Expression array)

Counts and returns the total number of items in an array.

Parameters:

array - the array to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $size

slice

public static Expression slice(Expression array,
                               int size)

Returns a subset of an array.

Parameters:

array - the array to use

size - the number of elements to return

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $slice

sortArray

public static Expression sortArray(Expression input,
                                   Sort... sort)

Sorts an array based on its elements. To sort by value, use Sort.naturalAscending() or Sort.naturalDescending(). See here for details.

Parameters:

input - the array to be sorted.

sort - the sort order

Returns:

the new expression

Since:

2.3

Since server release

5.2

MongoDB documentation

Aggregration Expression: $sortArray

zip

public static ZipExpression zip(Expression... arrays)

Merge two arrays together.

Parameters:

arrays - the arrays to use

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $zip