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Simple parser and formatter for JSON
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/*
* @(#) Formatter.java
*
* json-simple Simple JSON Parser and Formatter
* Copyright (c) 2021, 2023 Peter Wall
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package net.pwall.json.format;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import net.pwall.json.JSONFunctions;
import net.pwall.util.IntOutput;
/**
* JSON Formatter - formats a data structure as JSON using the specified indentation and line termination settings.
* Objects are converted as follows:
*
* - {@code null}
* - The JSON null value "{@code null}"
* - A {@link Map}
* - A JSON object, with the keys as property names and the values converted by this class recursively
* (keys that are not strings are converted by {@link Object#toString() toString()})
* - A {@link Collection} (e.g. {@link java.util.List List}, {@link java.util.Set Set})
* - A JSON array, where each value is converted by this class recursively
* - An array (of any object type)
* - A JSON array, where each value is converted by this class recursively
* - A {@link String}
* - A JSON string, with full Unicode character escaping
* - A {@link Number} (e.g. {@link Integer}, {@link java.math.BigDecimal BigDecimal})
* - A JSON number, using the {@link Object#toString() toString()} of the object
* - Anything else
* - If the {@link Object#toString() toString()} of the object is "{@code true}" or "{@code false}", that
* string is used as a JSON boolean value; otherwise the string is output as a JSON string (this will catch the
* {@link Boolean} class, as well as other classes representing boolean values).
*
* This is a superset of the output of the {@link net.pwall.json.parser.Parser Parser} class, so this class may be
* used as a complement to that one - to output structures created by that class or to create JSON data to be read
* by it. It also works well with the {@code JSONValue} structures produced by the {@code JSON.parse()} functions of
* the jsonutil and
* kjson-core libraries. It may also work for other similar data
* structures, but the results in such cases are not guaranteed.
*
* @author Peter Wall
*/
public class Formatter {
public static final int defaultIndent = 2;
public static final String systemLineSeparator = System.getProperty("line.separator");
public static final String unixLineSeparator = "\n";
private static final Formatter defaultFormatter = new Formatter();
private final int indent;
private final String lineSeparator;
/**
* Construct a {@code Formatter} with the specified indentation size and line separator.
*
* @param indent the indentation size
* @param lineSeparator the line separator
* @throws IllegalArgumentException if the indentation size is less than 0, or if the line separator is
* {@code null}
*/
public Formatter(int indent, String lineSeparator) {
this.indent = checkIndent(indent);
this.lineSeparator = checkLineSeparator(lineSeparator);
}
/**
* Construct a {@code Formatter} with the specified indentation size and the default line separator.
*
* @param indent the indentation size
* @throws IllegalArgumentException if the indentation size is less than 0
*/
public Formatter(int indent) {
this.indent = checkIndent(indent);
this.lineSeparator = systemLineSeparator;
}
/**
* Construct a {@code Formatter} with the default indentation size and the specified line separator.
*
* @param lineSeparator the line separator
* @throws IllegalArgumentException if the line separator is {@code null}
*/
public Formatter(String lineSeparator) {
this.indent = defaultIndent;
this.lineSeparator = checkLineSeparator(lineSeparator);
}
/**
* Construct a {@code Formatter} with the default indentation size and line separator.
*/
public Formatter() {
this.indent = defaultIndent;
this.lineSeparator = systemLineSeparator;
}
/**
* Get the indentation size for this {@code Formatter}.
*
* @return the indentation size
*/
public int getIndent() {
return indent;
}
/**
* Get the line separator for this {@code Formatter}.
*
* @return the line separator
*/
public String getLineSeparator() {
return lineSeparator;
}
/**
* Append the specified number of spaces to an {@link Appendable}.
*
* @param a the {@link Appendable}
* @param count the number of spaces
* @throws IOException if thrown by the {@link Appendable}
*/
public void appendSpaces(Appendable a, int count) throws IOException {
for (int i = count; i > 0; i--)
a.append(' ');
}
/**
* Append a line separator to an {@link Appendable}.
*
* @param a the {@link Appendable}
* @throws IOException if thrown by the {@link Appendable}
*/
public void appendLineSeparator(Appendable a) throws IOException {
a.append(lineSeparator);
}
/**
* Format an arbitrary object as JSON, using the line separator and indentation value of the {@code Formatter}.
* JSON objects are output with each property on a separate line, and JSON arrays are output with each item on a
* line.
*
* @param value the value to be formatted
* @return the formatted value
*/
public String format(Object value) {
StringBuilder sb = new StringBuilder(64);
try {
formatTo(sb, value, 0);
}
catch (IOException ioe) {
throw new UncheckedIOException("Should not happen - StringBuilder doesn't throw IOException", ioe);
}
return sb.toString();
}
/**
* Format an arbitrary object as JSON by appending to an {@link Appendable}, using the line separator and
* indentation value of the {@code Formatter}. JSON objects are output with each property on a separate line, and
* JSON arrays are output with each item on a line.
*
* @param a the {@link Appendable}
* @param value the value to be formatted
* @throws IOException if thrown by the {@link Appendable}
*/
public void formatTo(Appendable a, Object value) throws IOException {
formatTo(a, value, 0);
}
/**
* Format an arbitrary object as JSON by appending to an {@link Appendable}, using the line separator and
* indentation value of the {@code Formatter}, and with the supplied initial indentation value. JSON objects are
* output with each property on a separate line, and JSON arrays are output with each item on a line.
*
* @param a the {@link Appendable}
* @param value the value to be formatted
* @param currentIndent the initial indentation value
* @throws IOException if thrown by the {@link Appendable}
*/
public void formatTo(Appendable a, Object value, int currentIndent) throws IOException {
if (value == null) {
a.append("null");
}
else if (value instanceof Map) {
Map map = (Map)value;
a.append('{');
if (!map.isEmpty()) {
// potential optimisation - if size == 1 and contents size <= 1, output on one line
Iterator> iterator = map.entrySet().iterator();
int indented = currentIndent + indent;
while (true) {
appendLineSeparator(a);
Map.Entry entry = iterator.next();
appendSpaces(a, indented);
JSONFunctions.appendString(a, entry.getKey().toString(), false);
a.append(':');
a.append(' ');
formatTo(a, entry.getValue(), indented);
if (!iterator.hasNext())
break;
a.append(',');
}
appendLineSeparator(a);
appendSpaces(a, currentIndent);
}
a.append('}');
}
else if (value instanceof Collection) {
Collection collection = (Collection)value;
a.append('[');
if (!collection.isEmpty()) {
// potential optimisation - if size == 1 and contents size <= 1, output on one line
Iterator iterator = collection.iterator();
int indented = currentIndent + indent;
while (true) {
appendLineSeparator(a);
appendSpaces(a, indented);
formatTo(a, iterator.next(), indented);
if (!iterator.hasNext())
break;
a.append(',');
}
appendLineSeparator(a);
appendSpaces(a, currentIndent);
}
a.append(']');
}
else if (value instanceof Object[]) {
Object[] array = (Object[])value;
a.append('[');
int n = array.length;
if (n > 0) {
// potential optimisation - if size == 1 and contents size <= 1, output on one line
int i = 0;
int indented = currentIndent + indent;
while (true) {
appendLineSeparator(a);
appendSpaces(a, indented);
formatTo(a, array[i++], indented);
if (i >= n)
break;
a.append(',');
}
appendLineSeparator(a);
appendSpaces(a, currentIndent);
}
a.append(']');
}
else {
appendPrimitive(a, value);
}
}
/**
* Output the given {@link Object} as JSON. JSON objects are output with each property on a separate line, and JSON
* arrays are output with each item on a line.
*
* @param value the {@link Object} (may be {@code null})
* @return the JSON output
*/
public static String output(Object value) {
StringBuilder sb = new StringBuilder(64);
try {
outputTo(sb, value);
}
catch (IOException ioe) {
throw new UncheckedIOException("Should not happen - StringBuilder doesn't throw IOException", ioe);
}
return sb.toString();
}
/**
* Output the given {@link Object} as JSON by appending to an {@link Appendable}.
*
* @param a the {@link Appendable}
* @param value the {@link Object} (may be {@code null})
* @throws IOException if thrown by the {@link Appendable}
*/
public static void outputTo(Appendable a, Object value) throws IOException {
if (value == null) {
a.append("null");
}
else if (value instanceof Map) {
Map map = (Map)value;
a.append('{');
if (!map.isEmpty()) {
Iterator> iterator = map.entrySet().iterator();
while (true) {
Map.Entry entry = iterator.next();
JSONFunctions.appendString(a, entry.getKey().toString(), false);
a.append(':');
outputTo(a, entry.getValue());
if (!iterator.hasNext())
break;
a.append(',');
}
}
a.append('}');
}
else if (value instanceof Collection) {
Collection collection = (Collection)value;
a.append('[');
if (!collection.isEmpty()) {
Iterator iterator = collection.iterator();
while (true) {
outputTo(a, iterator.next());
if (!iterator.hasNext())
break;
a.append(',');
}
}
a.append(']');
}
else if (value instanceof Object[]) {
Object[] array = (Object[])value;
a.append('[');
int n = array.length;
if (n > 0) {
int i = 0;
while (true) {
outputTo(a, array[i++]);
if (i >= n)
break;
a.append(',');
}
}
a.append(']');
}
else {
appendPrimitive(a, value);
}
}
/**
* Append a primitive value (string, number, boolean) to an {@link Appendable} in the form required by JSON.
*
* This is invoked for every object that is not an array or a {@link Collection} or {@link Map}. In the case of
* structures created by {@link net.pwall.json.parser.Parser Parser}
*
* @param a the {@link Appendable}
* @param value the primitive value
* @throws IOException if thrown by the {@link Appendable}
*/
public static void appendPrimitive(Appendable a, Object value) throws IOException {
if (value instanceof Integer)
IntOutput.appendInt(a, (int)value);
else if (value instanceof Long)
IntOutput.appendLong(a, (long)value);
else if (value instanceof Number)
a.append(value.toString());
else if (value instanceof CharSequence)
JSONFunctions.appendString(a, (CharSequence)value, false);
else {
String s = value.toString();
if (s.equals("true") || s.equals("false")) // Boolean, or Boolean-like
a.append(s);
else
JSONFunctions.appendString(a, s, false);
}
}
/**
* Get the default {@code Formatter} (a {@code Formatter} with an indentation setting of 2 and the line separator
* determined by the system.
*
* @return the default {@code Formatter}
*/
public static Formatter getDefaultFormatter() {
return defaultFormatter;
}
/**
* Validate the indent parameter.
*
* @param indent the indentation size
* @return the same value (following validation)
* @throws IllegalArgumentException if the value is negative
*/
private static int checkIndent(int indent) {
if (indent < 0)
throw new IllegalArgumentException("indent may not be negative");
return indent;
}
/**
* Validate the indent parameter.
*
* @param lineSeparator the line separator
* @return the same value (following validation)
* @throws IllegalArgumentException if the value is {@code null}
*/
private static String checkLineSeparator(String lineSeparator) {
if (lineSeparator == null)
throw new IllegalArgumentException("lineSeparator may not be null");
return lineSeparator;
}
}
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