bind.JsonTreeWriter.java Source code

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Here is the source code for bind.JsonTreeWriter.java

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/*
 * Copyright (C) 2011 Google Inc.
 *
 * 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 bind;

import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonNull;
import com.google.gson.JsonObject;
import com.google.gson.JsonPrimitive;
import com.google.gson.stream.JsonWriter;

/**
 * This writer creates a JsonElement.
 */
public final class JsonTreeWriter extends JsonWriter {
    private static final Writer UNWRITABLE_WRITER = new Writer() {
        @Override
        public void write(char[] buffer, int offset, int counter) {
            throw new AssertionError();
        }

        @Override
        public void flush() throws IOException {
            throw new AssertionError();
        }

        @Override
        public void close() throws IOException {
            throw new AssertionError();
        }
    };
    /** Added to the top of the stack when this writer is closed to cause following ops to fail. */
    private static final JsonPrimitive SENTINEL_CLOSED = new JsonPrimitive("closed");

    /** The JsonElements and JsonArrays under modification, outermost to innermost. */
    private final List<JsonElement> stack = new ArrayList<JsonElement>();

    /** The name for the next JSON object value. If non-null, the top of the stack is a JsonObject. */
    private String pendingName;

    /** the JSON element constructed by this writer. */
    private JsonElement product = JsonNull.INSTANCE; // TODO: is this really what we want?;

    public JsonTreeWriter() {
        super(UNWRITABLE_WRITER);
    }

    /**
     * Returns the top level object produced by this writer.
     */
    public JsonElement get() {
        if (!stack.isEmpty()) {
            throw new IllegalStateException("Expected one JSON element but was " + stack);
        }
        return product;
    }

    private JsonElement peek() {
        return stack.get(stack.size() - 1);
    }

    private void put(JsonElement value) {
        if (pendingName != null) {
            if (!value.isJsonNull() || getSerializeNulls()) {
                JsonObject object = (JsonObject) peek();
                object.add(pendingName, value);
            }
            pendingName = null;
        } else if (stack.isEmpty()) {
            product = value;
        } else {
            JsonElement element = peek();
            if (element.isJsonArray()) {
                element.getAsJsonArray().add(value);
            } else {
                throw new IllegalStateException();
            }
        }
    }

    @Override
    public JsonWriter beginArray() throws IOException {
        JsonArray array = new JsonArray();
        put(array);
        stack.add(array);
        return this;
    }

    @Override
    public JsonWriter endArray() throws IOException {
        if (stack.isEmpty() || pendingName != null) {
            throw new IllegalStateException();
        }
        JsonElement element = peek();
        if (element.isJsonArray()) {
            stack.remove(stack.size() - 1);
            return this;
        }
        throw new IllegalStateException();
    }

    @Override
    public JsonWriter beginObject() throws IOException {
        JsonObject object = new JsonObject();
        put(object);
        stack.add(object);
        return this;
    }

    @Override
    public JsonWriter endObject() throws IOException {
        if (stack.isEmpty() || pendingName != null) {
            throw new IllegalStateException();
        }
        JsonElement element = peek();
        if (element.isJsonObject()) {
            stack.remove(stack.size() - 1);
            return this;
        }
        throw new IllegalStateException();
    }

    @Override
    public JsonWriter name(String name) throws IOException {
        if (stack.isEmpty() || pendingName != null) {
            throw new IllegalStateException();
        }
        JsonElement element = peek();
        if (element.isJsonObject()) {
            pendingName = name;
            return this;
        }
        throw new IllegalStateException();
    }

    @Override
    public JsonWriter value(String value) throws IOException {
        if (value == null) {
            return nullValue();
        }
        put(new JsonPrimitive(value));
        return this;
    }

    @Override
    public JsonWriter nullValue() throws IOException {
        put(JsonNull.INSTANCE);
        return this;
    }

    @Override
    public JsonWriter value(boolean value) throws IOException {
        put(new JsonPrimitive(value));
        return this;
    }

    @Override
    public JsonWriter value(double value) throws IOException {
        if (!isLenient() && (Double.isNaN(value) || Double.isInfinite(value))) {
            throw new IllegalArgumentException("JSON forbids NaN and infinities: " + value);
        }
        put(new JsonPrimitive(value));
        return this;
    }

    @Override
    public JsonWriter value(long value) throws IOException {
        put(new JsonPrimitive(value));
        return this;
    }

    @Override
    public JsonWriter value(Number value) throws IOException {
        if (value == null) {
            return nullValue();
        }

        if (!isLenient()) {
            double d = value.doubleValue();
            if (Double.isNaN(d) || Double.isInfinite(d)) {
                throw new IllegalArgumentException("JSON forbids NaN and infinities: " + value);
            }
        }

        put(new JsonPrimitive(value));
        return this;
    }

    @Override
    public void flush() throws IOException {
    }

    @Override
    public void close() throws IOException {
        if (!stack.isEmpty()) {
            throw new IOException("Incomplete document");
        }
        stack.add(SENTINEL_CLOSED);
    }
}