Projections (mongo-java-driver 3.3.0-query-log-max-size API)

java.lang.Object
- com.mongodb.client.model.Projections

```
public final class Projections
extends java.lang.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()))
 
```
从以下版本开始:

3.0

MongoDB documentation

Projection

方法概要

所有方法静态方法具体方法
限定符和类型	方法和说明
`static <TExpression> Bson`	`computed(java.lang.String fieldName, TExpression expression)` Creates a projection of a field whose value is computed from the given expression.
`static Bson`	`elemMatch(java.lang.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(java.lang.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(java.util.List<java.lang.String> fieldNames)` Creates a projection that excludes all of the given fields.
`static Bson`	`exclude(java.lang.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(Bson... projections)` Creates a projection that combines the list of projections into a single one.
`static Bson`	`fields(java.util.List<Bson> projections)` Creates a projection that combines the list of projections into a single one.
`static Bson`	`include(java.util.List<java.lang.String> fieldNames)` Creates a projection that includes all of the given fields.
`static Bson`	`include(java.lang.String... fieldNames)` Creates a projection that includes all of the given fields.
`static Bson`	`metaTextScore(java.lang.String fieldName)` Creates a projection to the given field name of the textScore, for use with text queries.
`static Bson`	`slice(java.lang.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(java.lang.String fieldName, int skip, int limit)` Creates a projection to the given field name of a slice of the array value of that field.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 方法详细资料
  - computed
```
public static <TExpression> Bson computed(java.lang.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.
    
    类型参数:
    
    TExpression - the expression type
    
    参数:
    
    fieldName - the field name
    
    expression - the expression
    
    返回:
    
    the projection
    
    另请参阅:
    
    Aggregates.project(Bson)
  - include
```
public static Bson include(java.lang.String... fieldNames)
```
    Creates a projection that includes all of the given fields.
    
    参数:
    
    fieldNames - the field names
    
    返回:
    
    the projection
  - include
```
public static Bson include(java.util.List<java.lang.String> fieldNames)
```
    Creates a projection that includes all of the given fields.
    
    参数:
    
    fieldNames - the field names
    
    返回:
    
    the projection
  - exclude
```
public static Bson exclude(java.lang.String... fieldNames)
```
    Creates a projection that excludes all of the given fields.
    
    参数:
    
    fieldNames - the field names
    
    返回:
    
    the projection
  - exclude
```
public static Bson exclude(java.util.List<java.lang.String> fieldNames)
```
    Creates a projection that excludes all of the given fields.
    
    参数:
    
    fieldNames - the field names
    
    返回:
    
    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.
    
    返回:
    
    the projection
  - elemMatch
```
public static Bson elemMatch(java.lang.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.
    
    参数:
    
    fieldName - the field name whose value is the array
    
    返回:
    
    the projection
    
    MongoDB documentation
    
    Project the first matching element ($ operator)
  - elemMatch
```
public static Bson elemMatch(java.lang.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.
    
    参数:
    
    fieldName - the field name
    
    filter - the filter to apply
    
    返回:
    
    the projection
    
    MongoDB documentation
    
    elemMatch
  - metaTextScore
```
public static Bson metaTextScore(java.lang.String fieldName)
```
    Creates a projection to the given field name of the textScore, for use with text queries.
    
    参数:
    
    fieldName - the field name
    
    返回:
    
    the projection
    
    MongoDB documentation
    
    textScore
  - slice
```
public static Bson slice(java.lang.String fieldName,
                         int limit)
```
    Creates a projection to the given field name of a slice of the array value of that field.
    
    参数:
    
    fieldName - the field name
    
    limit - the number of elements to project.
    
    返回:
    
    the projection
    
    MongoDB documentation
    
    Slice
  - slice
```
public static Bson slice(java.lang.String fieldName,
                         int skip,
                         int limit)
```
    Creates a projection to the given field name of a slice of the array value of that field.
    
    参数:
    
    fieldName - the field name
    
    skip - the number of elements to skip before applying the limit
    
    limit - the number of elements to project
    
    返回:
    
    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.
    
    参数:
    
    projections - the list of projections to combine
    
    返回:
    
    the combined projection
  - fields
```
public static Bson fields(java.util.List<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.
    
    参数:
    
    projections - the list of projections to combine
    
    返回:
    
    the combined projection
    
    MongoDB documentation

类 Projections

方法概要

从类继承的方法 java.lang.Object

方法详细资料

computed

include

include

exclude

exclude

excludeId

elemMatch

elemMatch

metaTextScore

slice

slice

fields

fields