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Elasticsearch subproject :libs:elasticsearch-x-content
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.xcontent;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
/**
* Like {@link ConstructingObjectParser} but works with objects which have a constructor that matches declared fields.
*
* Declaring a {@linkplain InstantiatingObjectParser} is intentionally quite similar to declaring an {@linkplain ConstructingObjectParser}
* with two important differences.
*
* The main differences being that it is using Builder to construct the parser and takes a class of the target object instead of the object
* builder. The target object must have exactly one constructor with the number and order of arguments matching the number of order of
* declared fields. If there are more than 2 constructors with the same number of arguments, one of them needs to be marked with
* {@linkplain ParserConstructor} annotation.
*
* It is also possible for the constructor to accept Context as the first parameter, in this case as in the case with multiple constructors
* it is required for the constructor to be marked with {@linkplain ParserConstructor} annotation.
*
*
{@code
* public static class Thing{
* public Thing(String animal, String vegetable, int mineral) {
* ....
* }
*
* public void setFruit(int fruit) { ... }
*
* public void setBug(int bug) { ... }
*
* }
*
* private static final InstantiatingObjectParser PARSER;
* static {
* InstantiatingObjectParser.Builder parser =
* InstantiatingObjectParser,builder<>("thing", true, Thing.class);
* parser.declareString(constructorArg(), new ParseField("animal"));
* parser.declareString(constructorArg(), new ParseField("vegetable"));
* parser.declareInt(optionalConstructorArg(), new ParseField("mineral"));
* parser.declareInt(Thing::setFruit, new ParseField("fruit"));
* parser.declareInt(Thing::setBug, new ParseField("bug"));
* PARSER = parser.build()
* }
* }
* {@code
*
* public static class AnotherThing {
* @ParserConstructor
* public AnotherThing(SomeContext continent, String animal, String vegetable, int mineral) {
* ....
* }
* }
*
* private static final InstantiatingObjectParser PARSER;
* static {
* InstantiatingObjectParser.Builder parser =
* InstantiatingObjectParser,builder<>("thing", true, AnotherThing.class);
* parser.declareString(constructorArg(), new ParseField("animal"));
* parser.declareString(constructorArg(), new ParseField("vegetable"));
* parser.declareInt(optionalConstructorArg(), new ParseField("mineral"));
* PARSER = parser.build()
* }
* }
*/
public class InstantiatingObjectParser
implements
BiFunction,
ContextParser {
public static Builder builder(String name, boolean ignoreUnknownFields, Class valueClass) {
return new Builder<>(name, ignoreUnknownFields, valueClass);
}
public static Builder builder(String name, Class valueClass) {
return new Builder<>(name, valueClass);
}
public static class Builder extends AbstractObjectParser {
private final ConstructingObjectParser constructingObjectParser;
private final Class valueClass;
private Constructor constructor;
public Builder(String name, Class valueClass) {
this(name, false, valueClass);
}
public Builder(String name, boolean ignoreUnknownFields, Class valueClass) {
this.constructingObjectParser = new ConstructingObjectParser<>(name, ignoreUnknownFields, this::buildInstance);
this.valueClass = valueClass;
}
@SuppressWarnings({ "unchecked", "checkstyle:HiddenField" })
public InstantiatingObjectParser build() {
Constructor constructor = null;
int neededArguments = constructingObjectParser.getNumberOfFields();
// Try to find an annotated constructor
for (Constructor c : valueClass.getConstructors()) {
if (c.getAnnotation(ParserConstructor.class) != null) {
if (constructor != null) {
throw new IllegalArgumentException(
"More then one public constructor with @ParserConstructor annotation exist in "
+ "the class "
+ valueClass.getName()
);
}
if (c.getParameterCount() < neededArguments || c.getParameterCount() > neededArguments + 1) {
throw new IllegalArgumentException(
"Annotated constructor doesn't have "
+ neededArguments
+ " or "
+ (neededArguments + 1)
+ " arguments in the class "
+ valueClass.getName()
);
}
constructor = c;
}
}
if (constructor == null) {
// fallback to a constructor with required number of arguments
for (Constructor c : valueClass.getConstructors()) {
if (c.getParameterCount() == neededArguments) {
if (constructor != null) {
throw new IllegalArgumentException(
"More then one public constructor with "
+ neededArguments
+ " arguments found. The use of @ParserConstructor annotation is required for class "
+ valueClass.getName()
);
}
constructor = c;
}
}
}
if (constructor == null) {
throw new IllegalArgumentException(
"No public constructors with " + neededArguments + " parameters exist in the class " + valueClass.getName()
);
}
this.constructor = (Constructor) constructor;
return new InstantiatingObjectParser<>(constructingObjectParser);
}
@Override
public void declareField(
BiConsumer consumer,
ContextParser parser,
ParseField parseField,
ObjectParser.ValueType type
) {
constructingObjectParser.declareField(consumer, parser, parseField, type);
}
@Override
public void declareNamedObject(
BiConsumer consumer,
ObjectParser.NamedObjectParser namedObjectParser,
ParseField parseField
) {
constructingObjectParser.declareNamedObject(consumer, namedObjectParser, parseField);
}
@Override
public void declareNamedObjects(
BiConsumer> consumer,
ObjectParser.NamedObjectParser namedObjectParser,
ParseField parseField
) {
constructingObjectParser.declareNamedObjects(consumer, namedObjectParser, parseField);
}
@Override
public void declareNamedObjects(
BiConsumer> consumer,
ObjectParser.NamedObjectParser namedObjectParser,
Consumer orderedModeCallback,
ParseField parseField
) {
constructingObjectParser.declareNamedObjects(consumer, namedObjectParser, orderedModeCallback, parseField);
}
@Override
public String getName() {
return constructingObjectParser.getName();
}
@Override
public void declareRequiredFieldSet(String... requiredSet) {
constructingObjectParser.declareRequiredFieldSet(requiredSet);
}
@Override
public void declareExclusiveFieldSet(String... exclusiveSet) {
constructingObjectParser.declareExclusiveFieldSet(exclusiveSet);
}
private Value buildInstance(Object[] args, Context context) {
if (constructor == null) {
throw new IllegalArgumentException(
"InstantiatingObjectParser for type " + valueClass.getName() + " has to be finalized " + "before the first use"
);
}
try {
if (constructor.getParameterCount() != args.length) {
Object[] newArgs = new Object[args.length + 1];
System.arraycopy(args, 0, newArgs, 1, args.length);
newArgs[0] = context;
return constructor.newInstance(newArgs);
} else {
return constructor.newInstance(args);
}
} catch (Exception ex) {
throw new IllegalArgumentException("Cannot instantiate an object of " + valueClass.getName(), ex);
}
}
}
private final ConstructingObjectParser constructingObjectParser;
private InstantiatingObjectParser(ConstructingObjectParser constructingObjectParser) {
this.constructingObjectParser = constructingObjectParser;
}
@Override
public Value parse(XContentParser parser, Context context) throws IOException {
return constructingObjectParser.parse(parser, context);
}
@Override
public Value apply(XContentParser xContentParser, Context context) {
return constructingObjectParser.apply(xContentParser, context);
}
}