com.squareup.moshi.JsonValueReader Maven / Gradle / Ivy
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/*
* Copyright (C) 2017 Square, 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.squareup.moshi;
import com.jn.easyjson.core.JSONBuilderProvider;
import com.jn.langx.annotation.Nullable;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import static com.squareup.moshi.JsonScope.CLOSED;
/**
* This class reads a JSON document by traversing a Java object comprising maps, lists, and JSON
* primitives. It does depth-first traversal keeping a stack starting with the root object. During
* traversal a stack tracks the current position in the document:
*
*
* - The next element to act upon is on the top of the stack.
*
- When the top of the stack is a {@link List}, calling {@link #beginArray()} replaces the
* list with a {@link JsonIterator}. The first element of the iterator is pushed on top of the
* iterator.
*
- Similarly, when the top of the stack is a {@link Map}, calling {@link #beginObject()}
* replaces the map with an {@link JsonIterator} of its entries. The first element of the
* iterator is pushed on top of the iterator.
*
- When the top of the stack is a {@link Map.Entry}, calling {@link #nextName()} returns the
* entry's key and replaces the entry with its value on the stack.
*
- When an element is consumed it is popped. If the new top of the stack has a non-exhausted
* iterator, the next element of that iterator is pushed.
*
- If the top of the stack is an exhausted iterator, calling {@link #endArray} or {@link
* #endObject} will pop it.
*
*/
final class JsonValueReader extends JsonReader {
/**
* Sentinel object pushed on {@link #stack} when the reader is closed.
*/
private static final Object JSON_READER_CLOSED = new Object();
private Object[] stack;
private String sourceJsonString;
JsonValueReader(Object root) {
scopes[stackSize] = JsonScope.NONEMPTY_DOCUMENT;
stack = new Object[32];
stack[stackSize++] = root;
sourceJsonString = JSONBuilderProvider.simplest().toJson(root);
}
/**
* Copy-constructor makes a deep copy for peeking.
*/
JsonValueReader(JsonValueReader copyFrom) {
super(copyFrom);
stack = copyFrom.stack.clone();
for (int i = 0; i < stackSize; i++) {
if (stack[i] instanceof JsonIterator) {
stack[i] = ((JsonIterator) stack[i]).clone();
}
}
sourceJsonString = copyFrom.sourceJsonString;
}
@Override
public void beginArray() throws IOException {
List peeked = require(List.class, Token.BEGIN_ARRAY);
JsonIterator iterator = new JsonIterator(
Token.END_ARRAY, peeked.toArray(new Object[peeked.size()]), 0);
stack[stackSize - 1] = iterator;
scopes[stackSize - 1] = JsonScope.EMPTY_ARRAY;
pathIndices[stackSize - 1] = 0;
// If the iterator isn't empty push its first value onto the stack.
if (iterator.hasNext()) {
push(iterator.next());
}
}
@Override
public void endArray() throws IOException {
JsonIterator peeked = require(JsonIterator.class, Token.END_ARRAY);
if (peeked.endToken != Token.END_ARRAY || peeked.hasNext()) {
throw typeMismatch(peeked, Token.END_ARRAY);
}
remove();
}
@Override
public void beginObject() throws IOException {
Map peeked = require(Map.class, Token.BEGIN_OBJECT);
JsonIterator iterator = new JsonIterator(
Token.END_OBJECT, peeked.entrySet().toArray(new Object[peeked.size()]), 0);
stack[stackSize - 1] = iterator;
scopes[stackSize - 1] = JsonScope.EMPTY_OBJECT;
// If the iterator isn't empty push its first value onto the stack.
if (iterator.hasNext()) {
push(iterator.next());
}
}
@Override
public void endObject() throws IOException {
JsonIterator peeked = require(JsonIterator.class, Token.END_OBJECT);
if (peeked.endToken != Token.END_OBJECT || peeked.hasNext()) {
throw typeMismatch(peeked, Token.END_OBJECT);
}
pathNames[stackSize - 1] = null;
remove();
}
@Override
public boolean hasNext() throws IOException {
if (stackSize == 0) {
return false;
}
Object peeked = stack[stackSize - 1];
return !(peeked instanceof Iterator) || ((Iterator) peeked).hasNext();
}
@Override
public Token peek() throws IOException {
if (stackSize == 0) {
return Token.END_DOCUMENT;
}
// If the top of the stack is an iterator, take its first element and push it on the stack.
Object peeked = stack[stackSize - 1];
if (peeked instanceof JsonIterator) {
return ((JsonIterator) peeked).endToken;
}
if (peeked instanceof List) {
return Token.BEGIN_ARRAY;
}
if (peeked instanceof Map) {
return Token.BEGIN_OBJECT;
}
if (peeked instanceof Map.Entry) {
return Token.NAME;
}
if (peeked instanceof String) {
return Token.STRING;
}
if (peeked instanceof Boolean) {
return Token.BOOLEAN;
}
if (peeked instanceof Number) {
return Token.NUMBER;
}
if (peeked == null) {
return Token.NULL;
}
if (peeked == JSON_READER_CLOSED) {
throw new IllegalStateException("JsonReader is closed");
}
throw typeMismatch(peeked, "a JSON value");
}
@Override
public String nextName() throws IOException {
Map.Entry peeked = require(Map.Entry.class, Token.NAME);
// Swap the Map.Entry for its value on the stack and return its key.
String result = stringKey(peeked);
stack[stackSize - 1] = peeked.getValue();
pathNames[stackSize - 2] = result;
return result;
}
@Override
public int selectName(Options options) throws IOException {
Map.Entry peeked = require(Map.Entry.class, Token.NAME);
String name = stringKey(peeked);
for (int i = 0, length = options.strings.length; i < length; i++) {
// Swap the Map.Entry for its value on the stack and return its key.
if (options.strings[i].equals(name)) {
stack[stackSize - 1] = peeked.getValue();
pathNames[stackSize - 2] = name;
return i;
}
}
return -1;
}
@Override
public void skipName() throws IOException {
if (failOnUnknown) {
// Capture the peeked value before nextName() since it will reset its value.
Token peeked = peek();
nextName(); // Move the path forward onto the offending name.
throw new JsonDataException("Cannot skip unexpected " + peeked + " at " + getPath());
}
Map.Entry peeked = require(Map.Entry.class, Token.NAME);
// Swap the Map.Entry for its value on the stack.
stack[stackSize - 1] = peeked.getValue();
pathNames[stackSize - 2] = "null";
}
@Override
public String nextString() throws IOException {
Object peeked = (stackSize != 0 ? stack[stackSize - 1] : null);
if (peeked instanceof String) {
remove();
return (String) peeked;
}
if (peeked instanceof Number) {
remove();
return peeked.toString();
}
if (peeked == JSON_READER_CLOSED) {
throw new IllegalStateException("JsonReader is closed");
}
throw typeMismatch(peeked, Token.STRING);
}
@Override
public int selectString(Options options) throws IOException {
Object peeked = (stackSize != 0 ? stack[stackSize - 1] : null);
if (!(peeked instanceof String)) {
if (peeked == JSON_READER_CLOSED) {
throw new IllegalStateException("JsonReader is closed");
}
return -1;
}
String peekedString = (String) peeked;
for (int i = 0, length = options.strings.length; i < length; i++) {
if (options.strings[i].equals(peekedString)) {
remove();
return i;
}
}
return -1;
}
@Override
public boolean nextBoolean() throws IOException {
Boolean peeked = require(Boolean.class, Token.BOOLEAN);
remove();
return peeked;
}
@Override
public @Nullable
T nextNull() throws IOException {
require(Void.class, Token.NULL);
remove();
return null;
}
@Override
public double nextDouble() throws IOException {
Object peeked = require(Object.class, Token.NUMBER);
double result;
if (peeked instanceof Number) {
result = ((Number) peeked).doubleValue();
} else if (peeked instanceof String) {
try {
result = Double.parseDouble((String) peeked);
} catch (NumberFormatException e) {
throw typeMismatch(peeked, Token.NUMBER);
}
} else {
throw typeMismatch(peeked, Token.NUMBER);
}
if (!lenient && (Double.isNaN(result) || Double.isInfinite(result))) {
throw new JsonEncodingException("JSON forbids NaN and infinities: " + result
+ " at path " + getPath());
}
remove();
return result;
}
@Override
public long nextLong() throws IOException {
Object peeked = require(Object.class, Token.NUMBER);
long result;
if (peeked instanceof Number) {
result = ((Number) peeked).longValue();
} else if (peeked instanceof String) {
try {
result = Long.parseLong((String) peeked);
} catch (NumberFormatException e) {
try {
BigDecimal asDecimal = new BigDecimal((String) peeked);
result = asDecimal.longValueExact();
} catch (NumberFormatException e2) {
throw typeMismatch(peeked, Token.NUMBER);
}
}
} else {
throw typeMismatch(peeked, Token.NUMBER);
}
remove();
return result;
}
@Override
public int nextInt() throws IOException {
Object peeked = require(Object.class, Token.NUMBER);
int result;
if (peeked instanceof Number) {
result = ((Number) peeked).intValue();
} else if (peeked instanceof String) {
try {
result = Integer.parseInt((String) peeked);
} catch (NumberFormatException e) {
try {
BigDecimal asDecimal = new BigDecimal((String) peeked);
result = asDecimal.intValueExact();
} catch (NumberFormatException e2) {
throw typeMismatch(peeked, Token.NUMBER);
}
}
} else {
throw typeMismatch(peeked, Token.NUMBER);
}
remove();
return result;
}
@Override
public void skipValue() throws IOException {
if (failOnUnknown) {
throw new JsonDataException("Cannot skip unexpected " + peek() + " at " + getPath());
}
// If this element is in an object clear out the key.
if (stackSize > 1) {
pathNames[stackSize - 2] = "null";
}
Object skipped = stackSize != 0 ? stack[stackSize - 1] : null;
if (skipped instanceof JsonIterator) {
throw new JsonDataException("Expected a value but was " + peek() + " at path " + getPath());
}
if (skipped instanceof Map.Entry) {
// We're skipping a name. Promote the map entry's value.
Map.Entry entry = (Map.Entry) stack[stackSize - 1];
stack[stackSize - 1] = entry.getValue();
} else if (stackSize > 0) {
// We're skipping a value.
remove();
} else {
throw new JsonDataException("Expected a value but was " + peek() + " at path " + getPath());
}
}
@Override
public JsonReader peekJson() {
return new JsonValueReader(this);
}
@Override
void promoteNameToValue() throws IOException {
if (hasNext()) {
String name = nextName();
push(name);
}
}
@Override
public void close() throws IOException {
Arrays.fill(stack, 0, stackSize, null);
stack[0] = JSON_READER_CLOSED;
scopes[0] = CLOSED;
stackSize = 1;
}
private void push(Object newTop) {
if (stackSize == stack.length) {
if (stackSize == 256) {
throw new JsonDataException("Nesting too deep at " + getPath());
}
scopes = Arrays.copyOf(scopes, scopes.length * 2);
pathNames = Arrays.copyOf(pathNames, pathNames.length * 2);
pathIndices = Arrays.copyOf(pathIndices, pathIndices.length * 2);
stack = Arrays.copyOf(stack, stack.length * 2);
}
stack[stackSize++] = newTop;
}
/**
* Returns the top of the stack which is required to be a {@code type}. Throws if this reader is
* closed, or if the type isn't what was expected.
*/
private @Nullable
T require(Class type, Token expected) throws IOException {
Object peeked = (stackSize != 0 ? stack[stackSize - 1] : null);
if (type.isInstance(peeked)) {
return type.cast(peeked);
}
if (peeked == null && expected == Token.NULL) {
return null;
}
if (peeked == JSON_READER_CLOSED) {
throw new IllegalStateException("JsonReader is closed");
}
throw typeMismatch(peeked, expected);
}
private String stringKey(Map.Entry entry) {
Object name = entry.getKey();
if (name instanceof String) {
return (String) name;
}
throw typeMismatch(name, Token.NAME);
}
/**
* Removes a value and prepares for the next. If we're iterating a map or list this advances the
* iterator.
*/
private void remove() {
stackSize--;
stack[stackSize] = null;
scopes[stackSize] = 0;
// If we're iterating an array or an object push its next element on to the stack.
if (stackSize > 0) {
pathIndices[stackSize - 1]++;
Object parent = stack[stackSize - 1];
if (parent instanceof Iterator && ((Iterator) parent).hasNext()) {
push(((Iterator) parent).next());
}
}
}
static final class JsonIterator implements Iterator