io.grpc.internal.JsonParser.java Source code

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Here is the source code for io.grpc.internal.JsonParser.java

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/*
 * Copyright 2018 The gRPC Authors
 *
 * 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 io.grpc.internal;

import static com.google.common.base.Preconditions.checkState;

import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Parses JSON with as few preconceived notions as possible.
 */
public final class JsonParser {

    private static final Logger logger = Logger.getLogger(JsonParser.class.getName());

    private JsonParser() {
    }

    /**
     * Parses a json string, returning either a {@code Map<String, ?>}, {@code List<?>},
     * {@code String}, {@code Double}, {@code Boolean}, or {@code null}.
     */
    public static Object parse(String raw) throws IOException {
        JsonReader jr = new JsonReader(new StringReader(raw));
        try {
            return parseRecursive(jr);
        } finally {
            try {
                jr.close();
            } catch (IOException e) {
                logger.log(Level.WARNING, "Failed to close", e);
            }
        }
    }

    private static Object parseRecursive(JsonReader jr) throws IOException {
        checkState(jr.hasNext(), "unexpected end of JSON");
        switch (jr.peek()) {
        case BEGIN_ARRAY:
            return parseJsonArray(jr);
        case BEGIN_OBJECT:
            return parseJsonObject(jr);
        case STRING:
            return jr.nextString();
        case NUMBER:
            return jr.nextDouble();
        case BOOLEAN:
            return jr.nextBoolean();
        case NULL:
            return parseJsonNull(jr);
        default:
            throw new IllegalStateException("Bad token: " + jr.getPath());
        }
    }

    private static Map<String, ?> parseJsonObject(JsonReader jr) throws IOException {
        jr.beginObject();
        Map<String, Object> obj = new LinkedHashMap<>();
        while (jr.hasNext()) {
            String name = jr.nextName();
            Object value = parseRecursive(jr);
            obj.put(name, value);
        }
        checkState(jr.peek() == JsonToken.END_OBJECT, "Bad token: " + jr.getPath());
        jr.endObject();
        return Collections.unmodifiableMap(obj);
    }

    private static List<?> parseJsonArray(JsonReader jr) throws IOException {
        jr.beginArray();
        List<Object> array = new ArrayList<>();
        while (jr.hasNext()) {
            Object value = parseRecursive(jr);
            array.add(value);
        }
        checkState(jr.peek() == JsonToken.END_ARRAY, "Bad token: " + jr.getPath());
        jr.endArray();
        return Collections.unmodifiableList(array);
    }

    private static Void parseJsonNull(JsonReader jr) throws IOException {
        jr.nextNull();
        return null;
    }
}