com.google.gson.internal.bind.JsonTreeReader Maven / Gradle / Ivy
/*
* 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 com.google.gson.internal.bind;
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.JsonReader;
import com.google.gson.stream.JsonToken;
import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;
import java.util.Map;
import java.util.Arrays;
/**
* This reader walks the elements of a JsonElement as if it was coming from a
* character stream.
*
* @author Jesse Wilson
*/
public final class JsonTreeReader extends JsonReader {
private static final Reader UNREADABLE_READER = new Reader() {
@Override public int read(char[] buffer, int offset, int count) throws IOException {
throw new AssertionError();
}
@Override public void close() throws IOException {
throw new AssertionError();
}
};
private static final Object SENTINEL_CLOSED = new Object();
/*
* The nesting stack. Using a manual array rather than an ArrayList saves 20%.
*/
private Object[] stack = new Object[32];
private int stackSize = 0;
/*
* The path members. It corresponds directly to stack: At indices where the
* stack contains an object (EMPTY_OBJECT, DANGLING_NAME or NONEMPTY_OBJECT),
* pathNames contains the name at this scope. Where it contains an array
* (EMPTY_ARRAY, NONEMPTY_ARRAY) pathIndices contains the current index in
* that array. Otherwise the value is undefined, and we take advantage of that
* by incrementing pathIndices when doing so isn't useful.
*/
private String[] pathNames = new String[32];
private int[] pathIndices = new int[32];
public JsonTreeReader(JsonElement element) {
super(UNREADABLE_READER);
push(element);
}
@Override public void beginArray() throws IOException {
expect(JsonToken.BEGIN_ARRAY);
JsonArray array = (JsonArray) peekStack();
push(array.iterator());
pathIndices[stackSize - 1] = 0;
}
@Override public void endArray() throws IOException {
expect(JsonToken.END_ARRAY);
popStack(); // empty iterator
popStack(); // array
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
}
@Override public void beginObject() throws IOException {
expect(JsonToken.BEGIN_OBJECT);
JsonObject object = (JsonObject) peekStack();
push(object.entrySet().iterator());
}
@Override public void endObject() throws IOException {
expect(JsonToken.END_OBJECT);
popStack(); // empty iterator
popStack(); // object
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
}
@Override public boolean hasNext() throws IOException {
JsonToken token = peek();
return token != JsonToken.END_OBJECT && token != JsonToken.END_ARRAY && token != JsonToken.END_DOCUMENT;
}
@Override public JsonToken peek() throws IOException {
if (stackSize == 0) {
return JsonToken.END_DOCUMENT;
}
Object o = peekStack();
if (o instanceof Iterator) {
boolean isObject = stack[stackSize - 2] instanceof JsonObject;
Iterator iterator = (Iterator) o;
if (iterator.hasNext()) {
if (isObject) {
return JsonToken.NAME;
} else {
push(iterator.next());
return peek();
}
} else {
return isObject ? JsonToken.END_OBJECT : JsonToken.END_ARRAY;
}
} else if (o instanceof JsonObject) {
return JsonToken.BEGIN_OBJECT;
} else if (o instanceof JsonArray) {
return JsonToken.BEGIN_ARRAY;
} else if (o instanceof JsonPrimitive) {
JsonPrimitive primitive = (JsonPrimitive) o;
if (primitive.isString()) {
return JsonToken.STRING;
} else if (primitive.isBoolean()) {
return JsonToken.BOOLEAN;
} else if (primitive.isNumber()) {
return JsonToken.NUMBER;
} else {
throw new AssertionError();
}
} else if (o instanceof JsonNull) {
return JsonToken.NULL;
} else if (o == SENTINEL_CLOSED) {
throw new IllegalStateException("JsonReader is closed");
} else {
throw new AssertionError();
}
}
private Object peekStack() {
return stack[stackSize - 1];
}
private Object popStack() {
Object result = stack[--stackSize];
stack[stackSize] = null;
return result;
}
private void expect(JsonToken expected) throws IOException {
if (peek() != expected) {
throw new IllegalStateException(
"Expected " + expected + " but was " + peek() + locationString());
}
}
@Override public String nextName() throws IOException {
expect(JsonToken.NAME);
Iterator i = (Iterator) peekStack();
Map.Entry entry = (Map.Entry) i.next();
String result = (String) entry.getKey();
pathNames[stackSize - 1] = result;
push(entry.getValue());
return result;
}
@Override public String nextString() throws IOException {
JsonToken token = peek();
if (token != JsonToken.STRING && token != JsonToken.NUMBER) {
throw new IllegalStateException(
"Expected " + JsonToken.STRING + " but was " + token + locationString());
}
String result = ((JsonPrimitive) popStack()).getAsString();
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
return result;
}
@Override public boolean nextBoolean() throws IOException {
expect(JsonToken.BOOLEAN);
boolean result = ((JsonPrimitive) popStack()).getAsBoolean();
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
return result;
}
@Override public void nextNull() throws IOException {
expect(JsonToken.NULL);
popStack();
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
}
@Override public double nextDouble() throws IOException {
JsonToken token = peek();
if (token != JsonToken.NUMBER && token != JsonToken.STRING) {
throw new IllegalStateException(
"Expected " + JsonToken.NUMBER + " but was " + token + locationString());
}
double result = ((JsonPrimitive) peekStack()).getAsDouble();
if (!isLenient() && (Double.isNaN(result) || Double.isInfinite(result))) {
throw new NumberFormatException("JSON forbids NaN and infinities: " + result);
}
popStack();
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
return result;
}
@Override public long nextLong() throws IOException {
JsonToken token = peek();
if (token != JsonToken.NUMBER && token != JsonToken.STRING) {
throw new IllegalStateException(
"Expected " + JsonToken.NUMBER + " but was " + token + locationString());
}
long result = ((JsonPrimitive) peekStack()).getAsLong();
popStack();
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
return result;
}
@Override public int nextInt() throws IOException {
JsonToken token = peek();
if (token != JsonToken.NUMBER && token != JsonToken.STRING) {
throw new IllegalStateException(
"Expected " + JsonToken.NUMBER + " but was " + token + locationString());
}
int result = ((JsonPrimitive) peekStack()).getAsInt();
popStack();
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
return result;
}
JsonElement nextJsonElement() throws IOException {
final JsonToken peeked = peek();
if (peeked == JsonToken.NAME
|| peeked == JsonToken.END_ARRAY
|| peeked == JsonToken.END_OBJECT
|| peeked == JsonToken.END_DOCUMENT) {
throw new IllegalStateException("Unexpected " + peeked + " when reading a JsonElement.");
}
final JsonElement element = (JsonElement) peekStack();
skipValue();
return element;
}
@Override public void close() throws IOException {
stack = new Object[] { SENTINEL_CLOSED };
stackSize = 1;
}
@Override public void skipValue() throws IOException {
if (peek() == JsonToken.NAME) {
nextName();
pathNames[stackSize - 2] = "null";
} else {
popStack();
if (stackSize > 0) {
pathNames[stackSize - 1] = "null";
}
}
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
}
}
@Override public String toString() {
return getClass().getSimpleName() + locationString();
}
public void promoteNameToValue() throws IOException {
expect(JsonToken.NAME);
Iterator i = (Iterator) peekStack();
Map.Entry entry = (Map.Entry) i.next();
push(entry.getValue());
push(new JsonPrimitive((String) entry.getKey()));
}
private void push(Object newTop) {
if (stackSize == stack.length) {
int newLength = stackSize * 2;
stack = Arrays.copyOf(stack, newLength);
pathIndices = Arrays.copyOf(pathIndices, newLength);
pathNames = Arrays.copyOf(pathNames, newLength);
}
stack[stackSize++] = newTop;
}
private String getPath(boolean usePreviousPath) {
StringBuilder result = new StringBuilder().append('$');
for (int i = 0; i < stackSize; i++) {
if (stack[i] instanceof JsonArray) {
if (++i < stackSize && stack[i] instanceof Iterator) {
int pathIndex = pathIndices[i];
// If index is last path element it points to next array element; have to decrement
// `- 1` covers case where iterator for next element is on stack
// `- 2` covers case where peek() already pushed next element onto stack
if (usePreviousPath && pathIndex > 0 && (i == stackSize - 1 || i == stackSize - 2)) {
pathIndex--;
}
result.append('[').append(pathIndex).append(']');
}
} else if (stack[i] instanceof JsonObject) {
if (++i < stackSize && stack[i] instanceof Iterator) {
result.append('.');
if (pathNames[i] != null) {
result.append(pathNames[i]);
}
}
}
}
return result.toString();
}
@Override public String getPreviousPath() {
return getPath(true);
}
@Override public String getPath() {
return getPath(false);
}
private String locationString() {
return " at path " + getPath();
}
}