org.bstats.json.JsonObjectBuilder Maven / Gradle / Ivy
package org.bstats.json;
import java.util.Arrays;
import java.util.stream.Collectors;
/**
* An extremely simple JSON builder.
*
* While this class is neither feature-rich nor the most performant one,
* it's sufficient enough for its use-case.
*/
public class JsonObjectBuilder {
private StringBuilder builder = new StringBuilder();
private boolean hasAtLeastOneField = false;
public JsonObjectBuilder() {
builder.append("{");
}
/**
* Appends a null field to the JSON.
*
* @param key The key of the field.
* @return A reference to this object.
*/
public JsonObjectBuilder appendNull(String key) {
appendFieldUnescaped(key, "null");
return this;
}
/**
* Appends a string field to the JSON.
*
* @param key The key of the field.
* @param value The value of the field.
* @return A reference to this object.
*/
public JsonObjectBuilder appendField(String key, String value) {
if (value == null) {
throw new IllegalArgumentException("JSON value must not be null");
}
appendFieldUnescaped(key, "\"" + escape(value) + "\"");
return this;
}
/**
* Appends an integer field to the JSON.
*
* @param key The key of the field.
* @param value The value of the field.
* @return A reference to this object.
*/
public JsonObjectBuilder appendField(String key, int value) {
appendFieldUnescaped(key, String.valueOf(value));
return this;
}
/**
* Appends an object to the JSON.
*
* @param key The key of the field.
* @param object The object.
* @return A reference to this object.
*/
public JsonObjectBuilder appendField(String key, JsonObject object) {
if (object == null) {
throw new IllegalArgumentException("JSON object must not be null");
}
appendFieldUnescaped(key, object.toString());
return this;
}
/**
* Appends a string array to the JSON.
*
* @param key The key of the field.
* @param values The string array.
* @return A reference to this object.
*/
public JsonObjectBuilder appendField(String key, String[] values) {
if (values == null) {
throw new IllegalArgumentException("JSON values must not be null");
}
String escapedValues = Arrays.stream(values)
.map(value -> "\"" + escape(value) + "\"")
.collect(Collectors.joining(","));
appendFieldUnescaped(key, "[" + escapedValues + "]");
return this;
}
/**
* Appends an integer array to the JSON.
*
* @param key The key of the field.
* @param values The integer array.
* @return A reference to this object.
*/
public JsonObjectBuilder appendField(String key, int[] values) {
if (values == null) {
throw new IllegalArgumentException("JSON values must not be null");
}
String escapedValues = Arrays.stream(values)
.mapToObj(String::valueOf)
.collect(Collectors.joining(","));
appendFieldUnescaped(key, "[" + escapedValues + "]");
return this;
}
/**
* Appends an object array to the JSON.
*
* @param key The key of the field.
* @param values The integer array.
* @return A reference to this object.
*/
public JsonObjectBuilder appendField(String key, JsonObject[] values) {
if (values == null) {
throw new IllegalArgumentException("JSON values must not be null");
}
String escapedValues = Arrays.stream(values)
.map(JsonObject::toString)
.collect(Collectors.joining(","));
appendFieldUnescaped(key, "[" + escapedValues + "]");
return this;
}
/**
* Appends a field to the object.
*
* @param key The key of the field.
* @param escapedValue The escaped value of the field.
*/
private void appendFieldUnescaped(String key, String escapedValue) {
if (builder == null) {
throw new IllegalStateException("JSON has already been built");
}
if (key == null) {
throw new IllegalArgumentException("JSON key must not be null");
}
if (hasAtLeastOneField) {
builder.append(",");
}
builder.append("\"").append(escape(key)).append("\":").append(escapedValue);
hasAtLeastOneField = true;
}
/**
* Builds the JSON string and invalidates this builder.
*
* @return The built JSON string.
*/
public JsonObject build() {
if (builder == null) {
throw new IllegalStateException("JSON has already been built");
}
JsonObject object = new JsonObject(builder.append("}").toString());
builder = null;
return object;
}
/**
* Escapes the given string like stated in https://www.ietf.org/rfc/rfc4627.txt.
*
*
This method escapes only the necessary characters '"', '\'. and '\u0000' - '\u001F'.
* Compact escapes are not used (e.g., '\n' is escaped as "\u000a" and not as "\n").
*
* @param value The value to escape.
* @return The escaped value.
*/
private static String escape(String value) {
final StringBuilder builder = new StringBuilder();
for (int i = 0; i < value.length(); i++) {
char c = value.charAt(i);
if (c == '"') {
builder.append("\\\"");
} else if (c == '\\') {
builder.append("\\\\");
} else if (c <= '\u000F') {
builder.append("\\u000").append(Integer.toHexString(c));
} else if (c <= '\u001F') {
builder.append("\\u00").append(Integer.toHexString(c));
} else {
builder.append(c);
}
}
return builder.toString();
}
/**
* A super simple representation of a JSON object.
*
*
This class only exists to make methods of the {@link JsonObjectBuilder} type-safe and
* not allow a raw string inputs for methods like {@link JsonObjectBuilder#appendField(String, JsonObject)}.
*/
public static class JsonObject {
private final String value;
private JsonObject(String value) {
this.value = value;
}
@Override
public String toString() {
return value;
}
}
}