com.eatthepath.json.JsonSerializer Maven / Gradle / Ivy
package com.eatthepath.json;
import java.io.IOException;
import java.util.Collection;
import java.util.Map;
import java.util.Optional;
/**
* A JSON serializer is responsible for producing complete and legal JSON texts (objects or arrays). It can serialize
* a {@link Map} as a JSON object or any {@link Collection} or array as a JSON list. The keys of a {@code Map} are
* always serialized as strings. Values within a {@code Map}, {@code Collection}, or array are converted to JSON values
* as follows:
*
*
* Mapping of Java types to JSON types
*
*
* Object type
* JSON representation
*
*
*
*
* {@code null}
* {@code null}
*
*
*
* {@link Map}
* {@code object}
*
*
*
* {@link Collection}
* {@code list}
*
*
*
* {@code byte[]}
* {@code list}
*
*
*
* {@code short[]}
* {@code list}
*
*
*
* {@code int[]}
* {@code list}
*
*
*
* {@code long[]}
* {@code list}
*
*
*
* {@code float[]}
* {@code list}
*
*
*
* {@code double[]}
* {@code list}
*
*
*
* {@code boolean[]}
* {@code list}
*
*
*
* {@code char[]}
* {@code list}
*
*
*
* {@link Object}{@code []}
* {@code list}
*
*
*
* {@link Number}
* {@code number} (or {@code null})
*
*
*
* {@link Boolean}
* {@code true} or {@code false} (or {@code null})
*
*
*
* all others
* the result of {@code obj.toString()}
*
*
*
*
* @author Jon Chambers
*
* @see ECMA-404 The JSON Data
* Interchange Standard
*/
public class JsonSerializer {
/**
* Don't allow direct instantiation.
*
* @throws InstantiationException in all cases
*/
JsonSerializer() throws InstantiationException {
throw new InstantiationException("JsonSerializer must not be instantiated directly.");
}
/**
* Writes the given {@link Map} as a JSON object to the given {@link Appendable}. Note that the keys of the given
* map will be represented as {@code Strings} (via their {@link Object#toString() toString} method) regardless of
* their actual type.
*
* @param map the map to write as a JSON text
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final Map map, final Appendable out) throws IOException {
if (map == null) {
out.append("null");
} else if (map.isEmpty()) {
out.append("{}");
} else {
out.append('{');
boolean valuesWritten = false;
for (final Map.Entry entry : map.entrySet()) {
if (entry.getKey() == null) {
throw new NullPointerException("JSON object keys must not be null.");
}
if (valuesWritten) {
out.append(',');
}
writeJsonValue(entry.getKey().toString(), out);
out.append(':');
writeJsonValue(entry.getValue(), out);
valuesWritten = true;
}
out.append('}');
}
}
/**
* Returns the given {@link Map} as a JSON string. Note that the keys of the given map will be represented as
* {@code Strings} (via their {@link Object#toString() toString} method) regardless of their actual type.
*
* @param map the map to return as a JSON text
*
* @return a JSON string representing the given map
*/
public static String writeJsonTextAsString(final Map map) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(map, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given {@link Collection} as a JSON list to the given {@link Appendable}.
*
* @param collection the collection to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final Collection collection, final Appendable out) throws IOException {
if (collection == null) {
out.append("null");
} else if (collection.isEmpty()) {
out.append("[]");
} else {
out.append('[');
boolean valuesWritten = false;
for (final Object o : collection) {
if (valuesWritten) {
out.append(',');
}
writeJsonValue(o, out);
valuesWritten = true;
}
out.append(']');
}
}
/**
* Returns the given {@link Collection} as a JSON string.
*
* @param collection the collection to return as a JSON text
*
* @return a JSON string representing the given collection
*/
public static String writeJsonTextAsString(final Collection collection) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(collection, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code bytes} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final byte[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code bytes} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final byte[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code shorts} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final short[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code shorts} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final short[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code ints} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final int[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code ints} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final int[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code longs} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final long[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code longs} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final long[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code floats} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final float[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code floats} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final float[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code doubles} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final double[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code doubles} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final double[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@code booleans} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final boolean[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
out.append(String.valueOf(array[0]));
for (int i = 1; i < array.length; i++) {
out.append(',');
out.append(String.valueOf(array[i]));
}
out.append(']');
}
}
/**
* Returns the given array of {@code booleans} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final boolean[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of characters as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final char[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
writeJsonValue(array[0], out);
for (int i = 1; i < array.length; i++) {
out.append(',');
writeJsonValue(array[i], out);
}
out.append(']');
}
}
/**
* Returns the given array of {@code chars} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final char[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given array of {@link Object Objects} as a JSON list to the given {@link Appendable}.
*
* @param array the array to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON text
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
public static void writeJsonText(final Object[] array, final Appendable out) throws IOException {
if (array == null) {
out.append("null");
} else if (array.length == 0) {
out.append("[]");
} else {
out.append('[');
writeJsonValue(array[0], out);
for (int i = 1; i < array.length; i++) {
out.append(',');
writeJsonValue(array[i], out);
}
out.append(']');
}
}
/**
* Returns the given array of {@code Objects} as a JSON string.
*
* @param array the array to return as a JSON text
*
* @return a JSON string representing the given array
*/
public static String writeJsonTextAsString(final Object[] array) {
final StringBuilder stringBuilder = new StringBuilder();
try {
writeJsonText(array, stringBuilder);
return stringBuilder.toString();
} catch (final IOException e) {
// This should never happen for a StringBuilder
throw new RuntimeException(e);
}
}
/**
* Writes the given object as a JSON value.
*
* @param o the object to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final Object o, final Appendable out) throws IOException {
if (o == null) {
out.append("null");
} else if (o instanceof Optional) {
final Optional optional = (Optional) o;
if (optional.isPresent()) {
writeJsonValue(optional.get(), out);
} else {
writeJsonValue((Object) null, out);
}
} else if (o instanceof Map) {
writeJsonText((Map) o, out);
} else if (o instanceof Collection) {
writeJsonText((Collection) o, out);
} else if (o instanceof byte[]) {
writeJsonText((byte[]) o, out);
} else if (o instanceof short[]) {
writeJsonText((short[]) o, out);
} else if (o instanceof int[]) {
writeJsonText((int[]) o, out);
} else if (o instanceof long[]) {
writeJsonText((long[]) o, out);
} else if (o instanceof float[]) {
writeJsonText((float[]) o, out);
} else if (o instanceof double[]) {
writeJsonText((double[]) o, out);
} else if (o instanceof boolean[]) {
writeJsonText((boolean[]) o, out);
} else if (o instanceof char[]) {
writeJsonText((char[]) o, out);
} else if (o instanceof Object[]) {
writeJsonText((Object[]) o, out);
} else if (o instanceof Number) {
writeJsonValue((Number) o, out);
} else if (o instanceof Boolean) {
writeJsonValue((Boolean) o, out);
} else {
writeJsonValue(o.toString(), out);
}
}
/**
* Writes the given {@link String} as a JSON string.
*
* @param string the string to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final String string, final Appendable out) throws IOException {
if (string == null) {
out.append("null");
} else if ("".equals(string)) {
out.append("\"\"");
} else {
out.append('\"');
int start = 0;
// The strategy here is to make as few writes as possible by looking for substrings of characters that don't
// need to be escaped. Whenever we hit a character that needs to be escaped, we write all of the
// previously-unwritten characters up to that point, then add the escaped version of that character.
for (int i = 0; i < string.length(); i++) {
final char c = string.charAt(i);
if (c == '"' || c == '\\' || c == '/' || c == '\b' || c == '\f' || c == '\n' || c == '\r' || c == '\t' ||
Character.isISOControl(c)) {
out.append(string, start, i);
appendEscapedCharacter(c, out);
start = i + 1;
}
}
if (start == 0) {
// We hit the end of the string without appending anything
out.append(string);
} else if (start < string.length()) {
out.append(string, start, string.length());
}
out.append('\"');
}
}
/**
* Writes the given {@code char} as a JSON string.
*
* @param c the character to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final char c, final Appendable out) throws IOException {
out.append('"');
appendEscapedCharacter(c, out);
out.append('"');
}
/**
* Appends the given {@code char} to the given {@link Appendable}, escaping it if necessary.
*
* @param c the character to append
* @param out the {@code Appendable} to which to write the given character
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
private static void appendEscapedCharacter(final char c, final Appendable out) throws IOException {
switch (c) {
case '"':
out.append("\\\"");
break;
case '\\':
out.append("\\\\");
break;
case '/':
out.append("\\/");
break;
case '\b':
out.append("\\b");
break;
case '\f':
out.append("\\f");
break;
case '\n':
out.append("\\n");
break;
case '\r':
out.append("\\r");
break;
case '\t':
out.append("\\t");
break;
default:
if (Character.isISOControl(c)) {
out.append("\\u");
out.append(Integer.toHexString(0x10000 | c), 1, 5);
} else {
out.append(c);
}
break;
}
}
/**
* Writes the given {@link Number} as a JSON number.
*
* @param number the number to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final Number number, final Appendable out) throws IOException {
if (number == null) {
out.append("null");
} else if (number instanceof Float) {
// Floats can have NaN or infinite values; pass them off to a dedicated handler
writeJsonValue(number.floatValue(), out);
} else if (number instanceof Double) {
// Doubles can have NaN or infinite values; pass them off to a dedicated handler
writeJsonValue(number.doubleValue(), out);
} else {
out.append(number.toString());
}
}
/**
* Writes the given {@code byte} as a JSON number.
*
* @param b the byte to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final byte b, final Appendable out) throws IOException {
out.append(Byte.toString(b));
}
/**
* Writes the given {@code short} as a JSON number.
*
* @param s the short to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final short s, final Appendable out) throws IOException {
out.append(Short.toString(s));
}
/**
* Writes the given {@code int} as a JSON number.
*
* @param i the integer to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final int i, final Appendable out) throws IOException {
out.append(Integer.toString(i));
}
/**
* Writes the given {@code long} as a JSON number.
*
* @param l the long to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final long l, final Appendable out) throws IOException {
out.append(Long.toString(l));
}
/**
* Writes the given {@code float} as a JSON number. Note that {@code NaN} values and non-finite numbers cannot be
* written as JSON values.
*
* @param f the float to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
* @throws IllegalArgumentException if the given float was not a number or was not finite
*/
static void writeJsonValue(final float f, final Appendable out) throws IOException {
if (Float.isInfinite(f)) {
throw new IllegalArgumentException("Cannot write non-finite numbers as JSON values.");
}
if (Float.isNaN(f)) {
throw new IllegalArgumentException("Cannot write NaN as a JSON value.");
}
out.append(Float.toString(f));
}
/**
* Writes the given {@code double} as a JSON number. Note that {@code NaN} values and non-finite numbers cannot be
* written as JSON values.
*
* @param d the double to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
* @throws IllegalArgumentException if the given double was not a number or was not finite
*/
static void writeJsonValue(final double d, final Appendable out) throws IOException {
if (Double.isInfinite(d)) {
throw new IllegalArgumentException("Cannot write non-finite numbers as JSON values.");
}
if (Double.isNaN(d)) {
throw new IllegalArgumentException("Cannot write NaN as a JSON value.");
}
out.append(Double.toString(d));
}
/**
* Writes the given {@link Boolean} as a JSON value.
*
* @param b the boolean to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final Boolean b, final Appendable out) throws IOException {
if (b == null) {
out.append("null");
} else {
writeJsonValue(b.booleanValue(), out);
}
}
/**
* Writes the given {@code boolean} as a JSON value.
*
* @param b the boolean to write as a JSON value
* @param out the {@code Appendable} to which to write the JSON value
*
* @throws IOException in the event of an I/O error when writing to the given {@code Appendable}
*/
static void writeJsonValue(final boolean b, final Appendable out) throws IOException {
out.append(b ? "true" : "false");
}
}
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