graphql.analysis

Class QueryTraverser

java.lang.Object

graphql.analysis.QueryTraverser

@PublicApi
public class QueryTraverser
extends java.lang.Object

Helps to traverse (or reduce) a Document (or parts of it) and tracks at the same time the corresponding Schema types.

This is an important distinction to just traversing the Document without any type information: Each field has a clearly defined type. See QueryVisitorFieldEnvironment.

Furthermore are the built in Directives skip/include automatically evaluated: if parts of the Document should be ignored they will not be visited. But this is not a full evaluation of a Query: every fragment will be visited/followed regardless of the type condition.

It also doesn't consider field merging, which means for example { user{firstName} user{firstName}} will result in four visitField calls.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	QueryTraverser.Builder

Method Summary

Modifier and Type	Method and Description
static QueryTraverser.Builder	newQueryTraverser()
<T> T	reducePostOrder(QueryReducer<T> queryReducer, T initialValue) Reduces the fields of a Document (or parts of it) to a single value.
<T> T	reducePreOrder(QueryReducer<T> queryReducer, T initialValue) Reduces the fields of a Document (or parts of it) to a single value.
java.lang.Object	visitDepthFirst(QueryVisitor queryVisitor)
void	visitPostOrder(QueryVisitor visitor) Visits the Document (or parts of it) in post-order.
void	visitPreOrder(QueryVisitor visitor) Visits the Document (or parts of it) in pre-order.

Methods inherited from class java.lang.Object

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

Method Detail

visitDepthFirst

public java.lang.Object visitDepthFirst(QueryVisitor queryVisitor)

visitPostOrder

public void visitPostOrder(QueryVisitor visitor)

Visits the Document (or parts of it) in post-order.

Parameters:

visitor - the query visitor that will be called back

visitPreOrder

public void visitPreOrder(QueryVisitor visitor)

Visits the Document (or parts of it) in pre-order.

Parameters:

visitor - the query visitor that will be called back

reducePostOrder

public <T> T reducePostOrder(QueryReducer<T> queryReducer,
                             T initialValue)

Reduces the fields of a Document (or parts of it) to a single value. The fields are visited in post-order.

Type Parameters:

T - the type of reduced value

Parameters:

queryReducer - the query reducer

initialValue - the initial value to pass to the reducer

Returns:

the calculated overall value

reducePreOrder

public <T> T reducePreOrder(QueryReducer<T> queryReducer,
                            T initialValue)

Reduces the fields of a Document (or parts of it) to a single value. The fields are visited in pre-order.

Type Parameters:

T - the type of reduced value

Parameters:

queryReducer - the query reducer

initialValue - the initial value to pass to the reducer

Returns:

the calucalated overall value

newQueryTraverser

public static QueryTraverser.Builder newQueryTraverser()