graphql.analysis.QueryTransformer Maven / Gradle / Ivy
package graphql.analysis;
import graphql.PublicApi;
import graphql.language.FragmentDefinition;
import graphql.language.Node;
import graphql.schema.GraphQLCompositeType;
import graphql.schema.GraphQLSchema;
import graphql.util.TraversalControl;
import graphql.util.TraverserContext;
import graphql.util.TraverserVisitor;
import graphql.util.TreeTransformer;
import java.util.LinkedHashMap;
import java.util.Map;
import static graphql.Assert.assertNotNull;
import static graphql.language.AstNodeAdapter.AST_NODE_ADAPTER;
/**
* Helps to transform 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 {@link 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 {@code { user{firstName} user{firstName}} } will result in four
* visitField calls.
*/
@PublicApi
public class QueryTransformer {
private final Node root;
private final GraphQLSchema schema;
private final Map fragmentsByName;
private final Map variables;
private final GraphQLCompositeType rootParentType;
private QueryTransformer(GraphQLSchema schema,
Node root,
GraphQLCompositeType rootParentType,
Map fragmentsByName,
Map variables) {
this.schema = assertNotNull(schema, () -> "schema can't be null");
this.variables = assertNotNull(variables, () -> "variables can't be null");
this.root = assertNotNull(root, () -> "root can't be null");
this.rootParentType = assertNotNull(rootParentType);
this.fragmentsByName = assertNotNull(fragmentsByName, () -> "fragmentsByName can't be null");
}
/**
* Visits the Document in pre-order and allows to transform it using {@link graphql.util.TreeTransformerUtil}
* methods. Please note that fragment spreads are not followed and need to be
* processed explicitly by supplying them as root.
*
* @param queryVisitor the query visitor that will be called back.
*
* @return changed root
*
* @throws IllegalArgumentException if there are multiple root nodes.
*/
public Node transform(QueryVisitor queryVisitor) {
QueryVisitor noOp = new QueryVisitorStub();
NodeVisitorWithTypeTracking nodeVisitor = new NodeVisitorWithTypeTracking(queryVisitor, noOp, variables, schema, fragmentsByName);
Map, Object> rootVars = new LinkedHashMap<>();
rootVars.put(QueryTraversalContext.class, new QueryTraversalContext(rootParentType, null, null));
TraverserVisitor nodeTraverserVisitor = new TraverserVisitor() {
@Override
public TraversalControl enter(TraverserContext context) {
return context.thisNode().accept(context, nodeVisitor);
}
@Override
public TraversalControl leave(TraverserContext context) {
//Transformations are applied preOrder only
return TraversalControl.CONTINUE;
}
};
return new TreeTransformer<>(AST_NODE_ADAPTER).transform(root, nodeTraverserVisitor, rootVars);
}
public static Builder newQueryTransformer() {
return new Builder();
}
@PublicApi
public static class Builder {
private GraphQLSchema schema;
private Map variables;
private Node root;
private GraphQLCompositeType rootParentType;
private Map fragmentsByName;
/**
* The schema used to identify the types of the query.
*
* @param schema the schema to use
*
* @return this builder
*/
public Builder schema(GraphQLSchema schema) {
this.schema = schema;
return this;
}
/**
* Variables used in the query.
*
* @param variables the variables to use
*
* @return this builder
*/
public Builder variables(Map variables) {
this.variables = variables;
return this;
}
/**
* Specify the root node for the transformation.
*
* @param root the root node to use
*
* @return this builder
*/
public Builder root(Node root) {
this.root = root;
return this;
}
/**
* The type of the parent of the root node. (See {@link Builder#root(Node)}
*
* @param rootParentType the root parent type
*
* @return this builder
*/
public Builder rootParentType(GraphQLCompositeType rootParentType) {
this.rootParentType = rootParentType;
return this;
}
/**
* Fragment by name map. Needs to be provided together with a {@link Builder#root(Node)} and {@link Builder#rootParentType(GraphQLCompositeType)}
*
* @param fragmentsByName the map of fragments
*
* @return this builder
*/
public Builder fragmentsByName(Map fragmentsByName) {
this.fragmentsByName = fragmentsByName;
return this;
}
public QueryTransformer build() {
return new QueryTransformer(schema, root, rootParentType, fragmentsByName, variables);
}
}
}