org.dominokit.jacksonapt.stream.impl.DefaultJsonWriter Maven / Gradle / Ivy
//@formatter:off
/*
* Copyright (C) 2010 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 org.dominokit.jacksonapt.stream.impl;
import org.dominokit.jacksonapt.JacksonContextProvider;
import org.dominokit.jacksonapt.exception.JsonSerializationException;
import org.dominokit.jacksonapt.stream.JsonWriter;
import org.dominokit.jacksonapt.stream.Stack;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* Writes a JSON (RFC 4627)
* encoded value to a stream, one token at a time. The stream includes both
* literal values (strings, numbers, booleans and nulls) as well as the begin
* and end delimiters of objects and arrays.
*
*
Encoding JSON
* To encode your data as JSON, create a new {@code JsonWriter}. Each JSON
* document must contain one top-level array or object. Call methods on the
* writer as you walk the structure's contents, nesting arrays and objects as
* necessary:
*
* - To write arrays, first call {@link #beginArray()}.
* Write each of the array's elements with the appropriate {@link #value}
* methods or by nesting other arrays and objects. Finally close the array
* using {@link #endArray()}.
*
- To write objects, first call {@link #beginObject()}.
* Write each of the object's properties by alternating calls to
* {@link #name} with the property's value. Write property values with the
* appropriate {@link #value} method or by nesting other objects or arrays.
* Finally close the object using {@link #endObject()}.
*
*
*
Example
* Suppose we'd like to encode a stream of messages such as the following: {@code
* [
* {
* "id": 912345678901,
* "text": "How do I stream JSON in Java?",
* "geo": null,
* "user": {
* "name": "json_newb",
* "followers_count": 41
* }
* },
* {
* "id": 912345678902,
* "text": "@json_newb just use JsonWriter!",
* "geo": [50.454722, -104.606667],
* "user": {
* "name": "jesse",
* "followers_count": 2
* }
* }
* ]}
* This code encodes the above structure: {@code
* public void writeJsonStream(OutputStream out, List messages) {
* JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));
* writer.setIndentSpaces(4);
* writeMessagesArray(writer, messages);
* writer.close();
* }
*
* public void writeMessagesArray(JsonWriter writer, List messages) {
* writer.beginArray();
* for (Message message : messages) {
* writeMessage(writer, message);
* }
* writer.endArray();
* }
*
* public void writeMessage(JsonWriter writer, Message message) {
* writer.beginObject();
* writer.name("id").value(message.getId());
* writer.name("text").value(message.getText());
* if (message.getGeo() != null) {
* writer.name("geo");
* writeDoublesArray(writer, message.getGeo());
* } else {
* writer.name("geo").nullValue();
* }
* writer.name("user");
* writeUser(writer, message.getUser());
* writer.endObject();
* }
*
* public void writeUser(JsonWriter writer, User user) {
* writer.beginObject();
* writer.name("name").value(user.getName());
* writer.name("followers_count").value(user.getFollowersCount());
* writer.endObject();
* }
*
* public void writeDoublesArray(JsonWriter writer, List doubles) {
* writer.beginArray();
* for (Double value : doubles) {
* writer.value(value);
* }
* writer.endArray();
* }}
*
*
Each {@code JsonWriter} may be used to write a single JSON stream.
* Instances of this class are not thread safe. Calls that would result in a
* malformed JSON string will fail with an {@link java.lang.IllegalStateException}.
*
* @author Jesse Wilson
* @version $Id: $
* @since 1.6
*/
public class DefaultJsonWriter implements JsonWriter {
private static final Logger logger = Logger.getLogger("JsonWriter");
/*
* From RFC 4627, "All Unicode characters may be placed within the
* quotation marks except for the characters that must be escaped:
* quotation mark, reverse solidus, and the control characters
* (U+0000 through U+001F)."
*
* We also escape '\u2028' and '\u2029', which JavaScript interprets as
* newline characters. This prevents eval() from failing with a syntax
* error. http://code.google.com/p/google-gson/issues/detail?id=341
*/
private static final String[] REPLACEMENT_CHARS;
static {
REPLACEMENT_CHARS = new String[128];
for (int i = 0; i <= 0x1f; i++) {
StringBuilder sb = new StringBuilder(6);
sb.append("\\u");
String hexa = Integer.toHexString(i);
for (int j = hexa.length(); j < 4; j++) {
sb.append('0');
}
sb.append(hexa);
REPLACEMENT_CHARS[i] = sb.toString();
}
REPLACEMENT_CHARS['"'] = "\\\"";
REPLACEMENT_CHARS['\\'] = "\\\\";
REPLACEMENT_CHARS['\t'] = "\\t";
REPLACEMENT_CHARS['\b'] = "\\b";
REPLACEMENT_CHARS['\n'] = "\\n";
REPLACEMENT_CHARS['\r'] = "\\r";
REPLACEMENT_CHARS['\f'] = "\\f";
}
/**
* The output data, containing at most one top-level array or object.
*/
private final StringBuilder out;
private Stack stack = JacksonContextProvider.get().integerStackFactory().make();
private int stackSize = 0;
{
push(JsonScope.EMPTY_DOCUMENT);
}
/**
* A string containing a full set of spaces for a single level of
* indentation, or null for no pretty printing.
*/
private String indent;
/**
* The name/value separator; either ":" or ": ".
*/
private String separator = ":";
private boolean lenient;
private String deferredUnescapeName;
private String deferredName;
private boolean serializeNulls = true;
/**
* Creates a new instance that writes a JSON-encoded stream to {@code out}.
*
* @param out a {@link java.lang.StringBuilder} object.
*/
public DefaultJsonWriter(StringBuilder out) {
if (out == null) {
throw new NullPointerException("out == null");
}
this.out = out;
}
/** {@inheritDoc} */
@Override
public final void setIndent(String indent) {
if (indent.length() == 0) {
this.indent = null;
this.separator = ":";
} else {
this.indent = indent;
this.separator = ": ";
}
}
/** {@inheritDoc} */
@Override
public final void setLenient(boolean lenient) {
this.lenient = lenient;
}
/**
* Returns true if this writer has relaxed syntax rules.
*
* @return a boolean.
*/
public boolean isLenient() {
return lenient;
}
/** {@inheritDoc} */
@Override
public final void setSerializeNulls(boolean serializeNulls) {
this.serializeNulls = serializeNulls;
}
/**
* {@inheritDoc}
*
* Returns true if object members are serialized when their value is null.
* This has no impact on array elements. The default is true.
*/
@Override
public final boolean getSerializeNulls() {
return serializeNulls;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter beginArray() {
writeDeferredName();
return open(JsonScope.EMPTY_ARRAY, "[");
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter endArray() {
return close(JsonScope.EMPTY_ARRAY, JsonScope.NONEMPTY_ARRAY, "]");
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter beginObject() {
writeDeferredName();
return open(JsonScope.EMPTY_OBJECT, "{");
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter endObject() {
return close(JsonScope.EMPTY_OBJECT, JsonScope.NONEMPTY_OBJECT, "}");
}
/**
* Enters a new scope by appending any necessary whitespace and the given
* bracket.
*/
private DefaultJsonWriter open(int empty, String openBracket) {
beforeValue(true);
push(empty);
out.append(openBracket);
return this;
}
/**
* Closes the current scope by appending any necessary whitespace and the
* given bracket.
*/
private DefaultJsonWriter close(int empty, int nonempty, String closeBracket) {
int context = peek();
if (context != nonempty && context != empty) {
throw new IllegalStateException("Nesting problem.");
}
if (deferredUnescapeName != null || deferredName != null) {
throw new IllegalStateException("Dangling name: " + (deferredUnescapeName == null ? deferredName : deferredUnescapeName));
}
stackSize--;
if (context == nonempty) {
newline();
}
out.append(closeBracket);
return this;
}
private void push(int newTop) {
stack.setAt(stackSize++, newTop);
}
/**
* Returns the value on the top of the stack.
*/
private int peek() {
if (stackSize == 0) {
throw new IllegalStateException("JsonWriter is closed.");
}
return stack.getAt(stackSize - 1);
}
/**
* Replace the value on the top of the stack with the given value.
*/
private void replaceTop(int topOfStack) {
stack.setAt(stackSize - 1, topOfStack);
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter name(String name) {
checkName(name);
deferredName = name;
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter unescapeName(String name) {
checkName(name);
deferredUnescapeName = name;
return this;
}
private void checkName(String name) {
if (name == null) {
throw new NullPointerException("name == null");
}
if (deferredUnescapeName != null || deferredName != null) {
throw new IllegalStateException();
}
if (stackSize == 0) {
throw new IllegalStateException("JsonWriter is closed.");
}
}
private void writeDeferredName() {
if (deferredUnescapeName != null) {
beforeName();
out.append('\"').append(deferredUnescapeName).append('\"');
deferredUnescapeName = null;
} else if (deferredName != null) {
beforeName();
string(deferredName);
deferredName = null;
}
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter value(String value) {
if (value == null) {
return nullValue();
}
writeDeferredName();
beforeValue(false);
string(value);
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter unescapeValue(String value) {
if (value == null) {
return nullValue();
}
writeDeferredName();
beforeValue(false);
out.append('\"').append(value).append('\"');
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter nullValue() {
if (deferredUnescapeName != null || deferredName != null) {
if (serializeNulls) {
writeDeferredName();
} else {
deferredUnescapeName = null;
deferredName = null;
return this; // skip the name and the value
}
}
beforeValue(false);
out.append("null");
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter cancelName() {
if (deferredUnescapeName != null) {
deferredUnescapeName = null;
} else if (deferredName != null) {
deferredName = null;
}
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter value(boolean value) {
writeDeferredName();
beforeValue(false);
out.append(value ? "true" : "false");
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter value(double value) {
if (Double.isNaN(value) || Double.isInfinite(value)) {
throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
}
writeDeferredName();
beforeValue(false);
out.append(Double.toString(value));
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter value(long value) {
writeDeferredName();
beforeValue(false);
out.append(Long.toString(value));
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter value(Number value) {
if (value == null) {
return nullValue();
}
writeDeferredName();
String string = value.toString();
if (!lenient
&& (string.equals("-Infinity") || string.equals("Infinity") || string.equals("NaN"))) {
throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
}
beforeValue(false);
out.append(string);
return this;
}
/** {@inheritDoc} */
@Override
public DefaultJsonWriter rawValue(Object value) {
if (value == null) {
return nullValue();
}
writeDeferredName();
beforeValue(false);
out.append(value.toString());
return this;
}
/** {@inheritDoc} */
@Override
public void flush() {
if (stackSize == 0) {
throw new IllegalStateException("JsonWriter is closed.");
}
}
/** {@inheritDoc} */
@Override
public void close() {
int size = stackSize;
if (size > 1 || size == 1 && stack.getAt(size - 1) != JsonScope.NONEMPTY_DOCUMENT) {
logger.log(Level.SEVERE, "Incomplete document");
throw new JsonSerializationException("Incomplete document");
}
stackSize = 0;
}
private void string(String value) {
out.append("\"");
encodeString(value, out);
out.append("\"");
}
/**
*
encodeString.
*
* @param value a {@link java.lang.String} object.
* @param out a {@link java.lang.StringBuilder} object.
*/
public static void encodeString(final String value, final StringBuilder out) {
String[] replacements = REPLACEMENT_CHARS;
int last = 0;
int length = value.length();
for (int i = 0; i < length; i++) {
char c = value.charAt(i);
String replacement;
if (c < 128) {
replacement = replacements[c];
if (replacement == null) {
continue;
}
} else if (c == '\u2028') {
replacement = "\\u2028";
} else if (c == '\u2029') {
replacement = "\\u2029";
} else {
continue;
}
if (last < i) {
out.append(value, last, i);
}
out.append(replacement);
last = i + 1;
}
if (last < length) {
out.append(value, last, length);
}
}
/**
* encodeString
*
* @param value a {@link java.lang.String} object.
* @return a {@link java.lang.String} object.
*/
public static String encodeString(final String value) {
StringBuilder out = new StringBuilder();
encodeString(value, out);
return out.toString();
}
private void newline() {
if (indent == null) {
return;
}
out.append("\n");
for (int i = 1, size = stackSize; i < size; i++) {
out.append(indent);
}
}
/**
* Inserts any necessary separators and whitespace before a name. Also
* adjusts the stack to expect the name's value.
*/
private void beforeName() {
int context = peek();
if (context == JsonScope.NONEMPTY_OBJECT) { // first in object
out.append(',');
} else if (context != JsonScope.EMPTY_OBJECT) { // not in an object!
throw new IllegalStateException("Nesting problem.");
}
newline();
replaceTop(JsonScope.DANGLING_NAME);
}
/**
* Inserts any necessary separators and whitespace before a literal value,
* inline array, or inline object. Also adjusts the stack to expect either a
* closing bracket or another element.
*
* @param root true if the value is a new array or object, the two values
* permitted as top-level elements.
*/
@SuppressWarnings("fallthrough")
private void beforeValue(boolean root) {
switch (peek()) {
case JsonScope.NONEMPTY_DOCUMENT:
if (!lenient) {
throw new IllegalStateException(
"JSON must have only one top-level value.");
}
// fall-through
case JsonScope.EMPTY_DOCUMENT: // first in document
if (!lenient && !root) {
throw new IllegalStateException(
"JSON must start with an array or an object.");
}
replaceTop(JsonScope.NONEMPTY_DOCUMENT);
break;
case JsonScope.EMPTY_ARRAY: // first in array
replaceTop(JsonScope.NONEMPTY_ARRAY);
newline();
break;
case JsonScope.NONEMPTY_ARRAY: // another in array
out.append(',');
newline();
break;
case JsonScope.DANGLING_NAME: // value for name
out.append(separator);
replaceTop(JsonScope.NONEMPTY_OBJECT);
break;
default:
throw new IllegalStateException("Nesting problem.");
}
}
/** {@inheritDoc} */
@Override
public String getOutput() {
return out.toString();
}
}
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