Package graphql.schema

Interface DataFetchingFieldSelectionSet

All Known Implementing Classes:
DataFetchingFieldSelectionSetImpl
@PublicApi public interface DataFetchingFieldSelectionSet
This class allows you to retrieve the selection set of fields that have been asked for when the DataFetcher was invoked.

For example imagine we are fetching the field 'user' in the following query 

 

  {
      user {
          name
          age
          weight
          friends {
              name
          }
      }
  }

The selection set in the case above consists of the fields "name, age, weight, friends and friends/name".

You can use this selection set perhaps to "peek" ahead and decide that field values you might need from the underlying data system. Imagine a SQL system where this might represent the SQL 'projection' of columns say.

However composite types such as Interfaces and Unions add some complexity. You cant know ahead of time the exact field and object types involved. There in fact be multiple possible `conditional` fields.

This class represents this by returning a list of fields and having two addressing mechanisms, a simple `x/y` one and the more specific `Foo.x/Bar.y` mechanism.

For example imagine a `Pet` interface type that has `Cat` and `Dog` object type implementations. The query might be: 

 
  {
      pet {
          name
      }
  }

In the example above you have a `Cat.name`and `Dog.name` as possible sub selections of the `pet` field. They are can be addressed by either `name` or `Dog.name` or `Cat.name` 

 
  selectionSet.contains("name") == true
  selectionSet.contains("Dog.name", "Cat.name") == true

  List<SelectedField> petNames = selectionSet.getFields("name")
  petNames.size() == 2

  List<SelectedField> dogNames = selectionSet.getFields("Dog.name")
  dogNames.size() == 1

The simple naming is easier to work with but the type prefixed naming is more precise.

Another complication is any field aliasing that a client can specify. 

 
  {
      pet {
          name(arg : "foo")
          ... on Dog {
             aliasedName : name(arg : "bar")
          }
     }
  }

In the example above the `selectionSet.getFields("name")` actually returns three SelectedFields, one for `Dog.name`, one for `Cat.name` and one for `Dog.name` with an alias of `aliasedName`. The arguments can differ on SelectedFields that have different SelectedField.getResultKey()s, hence the multiple selected fields returned.

To help you there is the getFieldsGroupedByResultKey() that returns a Map<String,List<SelectedField>> keyed by result key, that is by the field alias or by the field name.

  • Method Details

    • contains

      boolean contains(String fieldGlobPattern)
      This will return true if the field selection set matches a specified "glob" pattern matching ie the glob pattern matching supported by FileSystem.getPathMatcher(java.lang.String).

      This will allow you to use '*', '**' and '?' as special matching characters such that "invoice/customer*" would match an invoice field with child fields that start with 'customer'.

      Parameters:
      fieldGlobPattern - the glob pattern to match fields against
      Returns:
      true if the selection set contains these fields
      See Also:

    • containsAnyOf

      boolean containsAnyOf(String fieldGlobPattern, String... fieldGlobPatterns)
      This will return true if the field selection set matches any of the specified "glob" pattern matches ie the glob pattern matching supported by FileSystem.getPathMatcher(java.lang.String).

      This will allow you to use '*', '**' and '?' as special matching characters such that "invoice/customer*" would match an invoice field with child fields that start with 'customer'.

      Parameters:
      fieldGlobPattern - the glob pattern to match fields against
      fieldGlobPatterns - optionally more glob pattern to match fields against
      Returns:
      true if the selection set contains any of these these fields
      See Also:

    • containsAllOf

      boolean containsAllOf(String fieldGlobPattern, String... fieldGlobPatterns)
      This will return true if the field selection set matches all of the specified "glob" pattern matches ie the glob pattern matching supported by FileSystem.getPathMatcher(java.lang.String).

      This will allow you to use '*', '**' and '?' as special matching characters such that "invoice/customer*" would match an invoice field with child fields that start with 'customer'.

      Parameters:
      fieldGlobPattern - the glob pattern to match fields against
      fieldGlobPatterns - optionally more glob pattern to match fields against
      Returns:
      true if the selection set contains all of these these fields
      See Also:

    • getFields

      List<SelectedField> getFields()
      This will return all selected fields.

      The fields are guaranteed to be in pre-order as they appear in the query.

      A selected field may have an alias - and hence is a unique field in the returned list. It may have the same field names as others in the list but when you also consider the alias then it is indeed unique because it would be another entry in the graphql result.

      Returns:
      a list of all selected fields or empty list if none match

    • getImmediateFields

      List<SelectedField> getImmediateFields()
      This will return all selected fields that are immediate child fields of the field being fetched.

      The fields are guaranteed to be in pre-order as they appear in the query.

      A selected field may have an alias - and hence is a unique field in the returned list. It may have the same field names as others in the list but when you also consider the alias then it is indeed unique because it would be another entry in the graphql result.

      Returns:
      a list of all selected immediate child fields or empty list if none match

    • getFields

      List<SelectedField> getFields(String fieldGlobPattern, String... fieldGlobPatterns)
      This will return a list of selected fields that match a specified "glob" pattern matching ie the glob pattern matching supported by FileSystem.getPathMatcher(java.lang.String).

      This will allow you to use '*', '**' and '?' as special matching characters such that "invoice/customer*" would match an invoice field with child fields that start with 'customer'.

      The fields are guaranteed to be in pre-order as they appear in the query.

      A selected field may have an alias - and hence is a unique field in the returned list. It may have the same field names as others in the list but when you also consider the alias then it is indeed unique because it would be another entry in the graphql result.

      Parameters:
      fieldGlobPattern - the glob pattern to match fields against
      fieldGlobPatterns - optionally more glob pattern to match fields against
      Returns:
      a list of selected fields or empty list if none match

    • getFieldsGroupedByResultKey

      Map<String,List<SelectedField>> getFieldsGroupedByResultKey()
      The result key of a selected field represents what the graphql return value will be. The same GraphQLFieldDefinition may lead to a field being asked for multiple times (with differing arguments) if field aliases are used. This method helps you get all possible field invocations grouped by their result key. The arguments are guaranteed to be the same if the result key is the same, otherwise the query would not have validated correctly.
      Returns:
      a map of selected fields grouped by result key or an empty map if none match

    • getFieldsGroupedByResultKey

      Map<String,List<SelectedField>> getFieldsGroupedByResultKey(String fieldGlobPattern, String... fieldGlobPatterns)
      The result key of a selected field represents what the graphql return value will be. The same GraphQLFieldDefinition may lead to a field being asked for multiple times (with differing arguments) if field aliases are used. This method helps you get all possible field invocations grouped by their result key. The arguments are guaranteed to be the same if the result key is the same, otherwise the query would not have validated correctly.
      Parameters:
      fieldGlobPattern - the glob pattern to match fields against
      fieldGlobPatterns - optionally more glob pattern to match fields against
      Returns:
      a map of selected fields grouped by result key or an empty map if none match