com.google.gerrit.index.query.QueryBuilder Maven / Gradle / Ivy
// Copyright (C) 2009 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.index.query;
import static com.google.gerrit.index.query.Predicate.and;
import static com.google.gerrit.index.query.Predicate.not;
import static com.google.gerrit.index.query.Predicate.or;
import static com.google.gerrit.index.query.QueryParser.AND;
import static com.google.gerrit.index.query.QueryParser.DEFAULT_FIELD;
import static com.google.gerrit.index.query.QueryParser.EXACT_PHRASE;
import static com.google.gerrit.index.query.QueryParser.FIELD_NAME;
import static com.google.gerrit.index.query.QueryParser.NOT;
import static com.google.gerrit.index.query.QueryParser.OR;
import static com.google.gerrit.index.query.QueryParser.SINGLE_WORD;
import com.google.common.base.Strings;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.antlr.runtime.tree.Tree;
/**
* Base class to support writing parsers for query languages.
*
* Subclasses may document their supported query operators by declaring public methods that
* perform the query conversion into a {@link Predicate}. For example, to support "is:starred",
* "is:unread", and nothing else, a subclass may write:
*
*
* @Operator
* public Predicate is(String value) {
* if ("starred".equals(value)) {
* return new StarredPredicate();
* }
* if ("unread".equals(value)) {
* return new UnreadPredicate();
* }
* throw new IllegalArgumentException();
* }
*
*
* The available operator methods are discovered at runtime via reflection. Method names (after
* being converted to lowercase), correspond to operators in the query language, method string
* values correspond to the operator argument. Methods must be declared {@code public}, returning
* {@link Predicate}, accepting one {@link String}, and annotated with the {@link Operator}
* annotation.
*
*
Subclasses may also declare a handler for values which appear without operator by overriding
* {@link #defaultField(String)}.
*
* @param type of object the predicates can evaluate in memory.
*/
public abstract class QueryBuilder {
/** Converts a value string passed to an operator into a {@link Predicate}. */
public interface OperatorFactory> {
Predicate create(Q builder, String value) throws QueryParseException;
}
/**
* Defines the operators known by a QueryBuilder.
*
* This class is thread-safe and may be reused or cached.
*
* @param type of object the predicates can evaluate in memory.
* @param type of the query builder subclass.
*/
public static class Definition> {
private final Map> opFactories = new HashMap<>();
public Definition(Class clazz) {
// Guess at the supported operators by scanning methods.
//
Class c = clazz;
while (c != QueryBuilder.class) {
for (Method method : c.getDeclaredMethods()) {
if (method.getAnnotation(Operator.class) != null
&& Predicate.class.isAssignableFrom(method.getReturnType())
&& method.getParameterTypes().length == 1
&& method.getParameterTypes()[0] == String.class
&& (method.getModifiers() & Modifier.ABSTRACT) == 0
&& (method.getModifiers() & Modifier.PUBLIC) == Modifier.PUBLIC) {
final String name = method.getName().toLowerCase();
if (!opFactories.containsKey(name)) {
opFactories.put(name, new ReflectionFactory(name, method));
}
}
}
c = c.getSuperclass();
}
}
}
/**
* Locate a predicate in the predicate tree.
*
* @param p the predicate to find.
* @param clazz type of the predicate instance.
* @return the predicate, null if not found.
*/
@SuppressWarnings("unchecked")
public static > P find(Predicate p, Class clazz) {
if (clazz.isAssignableFrom(p.getClass())) {
return (P) p;
}
for (Predicate c : p.getChildren()) {
P r = find(c, clazz);
if (r != null) {
return r;
}
}
return null;
}
/**
* Locate a predicate in the predicate tree.
*
* @param p the predicate to find.
* @param clazz type of the predicate instance.
* @param name name of the operator.
* @return the first instance of a predicate having the given type, as found by a depth-first
* search.
*/
@SuppressWarnings("unchecked")
public static > P find(
Predicate p, Class clazz, String name) {
if (p instanceof OperatorPredicate
&& ((OperatorPredicate) p).getOperator().equals(name)
&& clazz.isAssignableFrom(p.getClass())) {
return (P) p;
}
for (Predicate c : p.getChildren()) {
P r = find(c, clazz, name);
if (r != null) {
return r;
}
}
return null;
}
protected final Definition> builderDef;
protected final Map> opFactories;
@SuppressWarnings({"unchecked", "rawtypes"})
protected QueryBuilder(Definition> def) {
builderDef = def;
opFactories = (Map) def.opFactories;
}
/**
* Parse a user-supplied query string into a predicate.
*
* @param query the query string.
* @return predicate representing the user query.
* @throws QueryParseException the query string is invalid and cannot be parsed by this parser.
* This may be due to a syntax error, may be due to an operator not being supported, or due to
* an invalid value being passed to a recognized operator.
*/
public Predicate parse(String query) throws QueryParseException {
if (Strings.isNullOrEmpty(query)) {
throw new QueryParseException("query is empty");
}
return toPredicate(QueryParser.parse(query));
}
/**
* Parse multiple user-supplied query strings into a list of predicates.
*
* @param queries the query strings.
* @return predicates representing the user query, in the same order as the input.
* @throws QueryParseException one of the query strings is invalid and cannot be parsed by this
* parser. This may be due to a syntax error, may be due to an operator not being supported,
* or due to an invalid value being passed to a recognized operator.
*/
public List> parse(List queries) throws QueryParseException {
List> predicates = new ArrayList<>(queries.size());
for (String query : queries) {
predicates.add(parse(query));
}
return predicates;
}
private Predicate toPredicate(Tree r) throws QueryParseException, IllegalArgumentException {
switch (r.getType()) {
case AND:
return and(children(r));
case OR:
return or(children(r));
case NOT:
return not(toPredicate(onlyChildOf(r)));
case DEFAULT_FIELD:
return defaultField(onlyChildOf(r));
case FIELD_NAME:
return operator(r.getText(), onlyChildOf(r));
default:
throw error("Unsupported operator: " + r);
}
}
private Predicate operator(String name, Tree val) throws QueryParseException {
switch (val.getType()) {
// Expand multiple values, "foo:(a b c)", as though they were written
// out with the longer form, "foo:a foo:b foo:c".
//
case AND:
case OR:
{
List> p = new ArrayList<>(val.getChildCount());
for (int i = 0; i < val.getChildCount(); i++) {
final Tree c = val.getChild(i);
if (c.getType() != DEFAULT_FIELD) {
throw error("Nested operator not expected: " + c);
}
p.add(operator(name, onlyChildOf(c)));
}
return val.getType() == AND ? and(p) : or(p);
}
case SINGLE_WORD:
case EXACT_PHRASE:
if (val.getChildCount() != 0) {
throw error("Expected no children under: " + val);
}
return operator(name, val.getText());
default:
throw error("Unsupported node in operator " + name + ": " + val);
}
}
@SuppressWarnings("unchecked")
private Predicate operator(String name, String value) throws QueryParseException {
@SuppressWarnings("rawtypes")
OperatorFactory f = opFactories.get(name);
if (f == null) {
throw error("Unsupported operator " + name + ":" + value);
}
return f.create(this, value);
}
private Predicate defaultField(Tree r) throws QueryParseException {
switch (r.getType()) {
case SINGLE_WORD:
case EXACT_PHRASE:
if (r.getChildCount() != 0) {
throw error("Expected no children under: " + r);
}
return defaultField(r.getText());
default:
throw error("Unsupported node: " + r);
}
}
/**
* Handle a value present outside of an operator.
*
* This default implementation always throws an "Unsupported query: " message containing the
* input text. Subclasses may override this method to perform do-what-i-mean guesses based on the
* input string.
*
* @param value the value supplied by itself in the query.
* @return predicate representing this value.
* @throws QueryParseException the parser does not recognize this value.
*/
protected Predicate defaultField(String value) throws QueryParseException {
throw error("Unsupported query:" + value);
}
private List> children(Tree r) throws QueryParseException, IllegalArgumentException {
List> p = new ArrayList<>(r.getChildCount());
for (int i = 0; i < r.getChildCount(); i++) {
p.add(toPredicate(r.getChild(i)));
}
return p;
}
private Tree onlyChildOf(Tree r) throws QueryParseException {
if (r.getChildCount() != 1) {
throw error("Expected exactly one child: " + r);
}
return r.getChild(0);
}
protected static QueryParseException error(String msg) {
return new QueryParseException(msg);
}
protected static QueryParseException error(String msg, Throwable why) {
return new QueryParseException(msg, why);
}
/** Denotes a method which is a query operator. */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
protected @interface Operator {}
private static class ReflectionFactory>
implements OperatorFactory {
private final String name;
private final Method method;
ReflectionFactory(String name, Method method) {
this.name = name;
this.method = method;
}
@SuppressWarnings("unchecked")
@Override
public Predicate create(Q builder, String value) throws QueryParseException {
try {
return (Predicate) method.invoke(builder, value);
} catch (RuntimeException | IllegalAccessException e) {
throw error("Error in operator " + name + ":" + value, e);
} catch (InvocationTargetException e) {
if (e.getCause() instanceof QueryParseException) {
throw (QueryParseException) e.getCause();
}
throw error("Error in operator " + name + ":" + value, e.getCause());
}
}
}
}