AstTransformer.java
package graphql.language;
import graphql.PublicApi;
import graphql.util.TraversalControl;
import graphql.util.TraverserContext;
import graphql.util.TraverserVisitor;
import graphql.util.TraverserVisitorStub;
import graphql.util.TreeParallelTransformer;
import graphql.util.TreeTransformer;
import java.util.Map;
import java.util.concurrent.ForkJoinPool;
import static graphql.Assert.assertNotNull;
import static graphql.language.AstNodeAdapter.AST_NODE_ADAPTER;
/**
* Allows for an easy way to "manipulate" the immutable Ast by changing specific nodes and getting back a new Ast
* containing the changed nodes while everything else is the same.
*/
@PublicApi
public class AstTransformer {
/**
* Transforms the input tree using the Visitor Pattern.
* @param root the root node of the input tree.
* @param nodeVisitor the visitor which will transform the input tree.
* @return the transformed tree.
*/
public Node transform(Node root, NodeVisitor nodeVisitor) {
assertNotNull(root);
assertNotNull(nodeVisitor);
TraverserVisitor<Node> traverserVisitor = getNodeTraverserVisitor(nodeVisitor);
TreeTransformer<Node> treeTransformer = new TreeTransformer<>(AST_NODE_ADAPTER);
return treeTransformer.transform(root, traverserVisitor);
}
/**
* Transforms the input tree using the Visitor Pattern.
* @param root the root node of the input tree.
* @param nodeVisitor the visitor which will transform the input tree.
* @param rootVars a context argument to pass information into the nodeVisitor. Pass a contextual
* object to your visitor by adding it to this map such that such that the key
* is the class of the object, and the value is the object itself. The object
* can be retrieved within the visitor by calling context.getVarFromParents().
* @return the transformed tree.
*/
public Node transform(Node root, NodeVisitor nodeVisitor, Map<Class<?>, Object> rootVars) {
assertNotNull(root);
assertNotNull(nodeVisitor);
TraverserVisitor<Node> traverserVisitor = getNodeTraverserVisitor(nodeVisitor);
TreeTransformer<Node> treeTransformer = new TreeTransformer<>(AST_NODE_ADAPTER);
return treeTransformer.transform(root, traverserVisitor, rootVars);
}
public Node transformParallel(Node root, NodeVisitor nodeVisitor) {
return transformParallel(root, nodeVisitor, ForkJoinPool.commonPool());
}
public Node transformParallel(Node root, NodeVisitor nodeVisitor, ForkJoinPool forkJoinPool) {
assertNotNull(root);
assertNotNull(nodeVisitor);
TraverserVisitor<Node> traverserVisitor = new TraverserVisitorStub<Node>() {
@Override
public TraversalControl enter(TraverserContext<Node> context) {
return context.thisNode().accept(context, nodeVisitor);
}
};
TreeParallelTransformer<Node> treeParallelTransformer = TreeParallelTransformer.parallelTransformer(AST_NODE_ADAPTER, forkJoinPool);
return treeParallelTransformer.transform(root, traverserVisitor);
}
private TraverserVisitor<Node> getNodeTraverserVisitor(NodeVisitor nodeVisitor) {
return new TraverserVisitor<Node>() {
@Override
public TraversalControl enter(TraverserContext<Node> context) {
return context.thisNode().accept(context, nodeVisitor);
}
@Override
public TraversalControl leave(TraverserContext<Node> context) {
return TraversalControl.CONTINUE;
}
};
}
}