JsonUtil.java
/*
* Copyright 2015 Red Hat, Inc. and/or its affiliates.
*
* 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.dashbuilder.json;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
/**
* Direct port of json2.js at http://www.json.org/json2.js to GWT.
*/
public class JsonUtil {
private static class StringifyJsonVisitor extends JsonVisitor {
private String indentLevel;
private Set<JsonValue> visited;
private final String indent;
private final StringBuilder sb;
private final boolean pretty;
public StringifyJsonVisitor(String indent, StringBuilder sb,
boolean pretty) {
this.indent = indent;
this.sb = sb;
this.pretty = pretty;
indentLevel = "";
visited = new HashSet<JsonValue>();
}
@Override
public void endVisit(JsonArray array, JsonContext ctx) {
if (pretty) {
indentLevel = indentLevel
.substring(0, indentLevel.length() - indent.length());
sb.append('\n');
sb.append(indentLevel);
}
sb.append("]");
visited.remove(array);
}
@Override
public void endVisit(JsonObject object, JsonContext ctx) {
if (pretty) {
indentLevel = indentLevel
.substring(0, indentLevel.length() - indent.length());
sb.append('\n');
sb.append(indentLevel);
}
sb.append("}");
visited.remove(object);
assert !visited.contains(object);
}
@Override
public void visit(double number, JsonContext ctx) {
sb.append(Double.isInfinite(number) ? "null" : format(number));
}
@Override
public void visit(String string, JsonContext ctx) {
sb.append(quote(string));
}
@Override
public void visit(boolean bool, JsonContext ctx) {
sb.append(bool);
}
@Override
public boolean visit(JsonArray array, JsonContext ctx) {
checkCycle(array);
sb.append("[");
if (pretty) {
sb.append('\n');
indentLevel += indent;
sb.append(indentLevel);
}
return true;
}
@Override
public boolean visit(JsonObject object, JsonContext ctx) {
checkCycle(object);
sb.append("{");
if (pretty) {
sb.append('\n');
indentLevel += indent;
sb.append(indentLevel);
}
return true;
}
@Override
public boolean visitIndex(int index, JsonContext ctx) {
commaIfNotFirst(ctx);
return true;
}
@Override
public boolean visitKey(String key, JsonContext ctx) {
if ("".equals(key)) {
return true;
}
commaIfNotFirst(ctx);
sb.append(quote(key) + ":");
if (pretty) {
sb.append(' ');
}
return true;
}
@Override
public void visitNull(JsonContext ctx) {
sb.append("null");
}
private void checkCycle(JsonValue value) {
if (visited.contains(value)) {
throw new JsonException("Cycled detected during stringify");
} else {
visited.add(value);
}
}
private void commaIfNotFirst(JsonContext ctx) {
if (!ctx.isFirst()) {
sb.append(",");
if (pretty) {
sb.append('\n');
sb.append(indentLevel);
}
}
}
private String format(double number) {
String n = String.valueOf(number);
if (n.endsWith(".0")) {
n = n.substring(0, n.length() - 2);
}
return n;
}
}
/**
* Convert special control characters into unicode escape format.
*/
public static String escapeControlChars(String text) {
StringBuilder toReturn = new StringBuilder();
for (int i = 0; i < text.length(); i++) {
char c = text.charAt(i);
if (isControlChar(c)) {
toReturn.append(escapeStringAsUnicode(String.valueOf(c)));
} else {
toReturn.append(c);
}
}
return toReturn.toString();
}
public static <T extends JsonValue> T parse(String json) throws JsonException {
return Json.instance().parse(json);
}
/**
* Safely escape an arbitrary string as a JSON string literal.
*/
public static String quote(String value) {
StringBuilder toReturn = new StringBuilder("\"");
for (int i = 0; i < value.length(); i++) {
char c = value.charAt(i);
String toAppend = String.valueOf(c);
switch (c) {
case '\b':
toAppend = "\\b";
break;
case '\t':
toAppend = "\\t";
break;
case '\n':
toAppend = "\\n";
break;
case '\f':
toAppend = "\\f";
break;
case '\r':
toAppend = "\\r";
break;
case '"':
toAppend = "\\\"";
break;
case '\\':
toAppend = "\\\\";
break;
default:
if (isControlChar(c)) {
toAppend = escapeStringAsUnicode(String.valueOf(c));
}
}
toReturn.append(toAppend);
}
toReturn.append("\"");
return toReturn.toString();
}
/**
* Converts a Json Object to Json format.
*
* @param jsonValue json object to stringify
* @return json formatted string
*/
public static String stringify(JsonValue jsonValue) {
return stringify(jsonValue, 0);
}
/**
* Converts a JSO to Json format.
*
* @param jsonValue json object to stringify
* @param spaces number of spaces to indent in pretty print mode
* @return json formatted string
*/
public static String stringify(JsonValue jsonValue, int spaces) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < spaces; i++) {
sb.append(' ');
}
return stringify(jsonValue, sb.toString());
}
/**
* Converts a Json object to Json formatted String.
*
* @param jsonValue json object to stringify
* @param indent optional indention prefix for pretty printing
* @return json formatted string
*/
public static String stringify(JsonValue jsonValue, final String indent) {
final StringBuilder sb = new StringBuilder();
final boolean isPretty = indent != null && !"".equals(indent);
new StringifyJsonVisitor(indent, sb, isPretty).accept(jsonValue);
return sb.toString();
}
/**
* Turn a single unicode character into a 32-bit unicode hex literal.
*/
private static String escapeStringAsUnicode(String match) {
String hexValue = Integer.toString(match.charAt(0), 16);
hexValue = hexValue.length() > 4 ? hexValue.substring(hexValue.length() - 4)
: hexValue;
return "\\u0000" + hexValue;
}
private static boolean isControlChar(char c) {
return (c >= 0x00 && c <= 0x1f)
|| (c >= 0x7f && c <= 0x9f)
|| c == '\u00ad' || c == '\u070f' || c == '\u17b4' || c == '\u17b5'
|| c == '\ufeff'
|| (c >= '\u0600' && c <= '\u0604')
|| (c >= '\u200c' && c <= '\u200f')
|| (c >= '\u2028' && c <= '\u202f')
|| (c >= '\u2060' && c <= '\u206f')
|| (c >= '\ufff0' && c <= '\uffff');
}
}