StringQuotingChecker.java
package com.fasterxml.jackson.dataformat.yaml.util;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
/**
* Helper class that defines API used by
* {@link com.fasterxml.jackson.dataformat.yaml.YAMLGenerator}
* to check whether property names and String values need to be quoted or not.
* Also contains default logic implementation; may be sub-classed to provide
* alternate implementation.
*
* @since 2.12
*/
public abstract class StringQuotingChecker
implements java.io.Serializable
{
private static final long serialVersionUID = 1L;
/**
* As per YAML <a href="https://yaml.org/type/null.html">null</a>
* and <a href="https://yaml.org/type/bool.html">boolean</a> type specs,
* better retain quoting for some keys (property names) and values.
*/
private final static Set<String> RESERVED_KEYWORDS = new HashSet<>(Arrays.asList(
// 02-Apr-2019, tatu: Some names will look funny if escaped: let's leave out
// single letter case (esp so 'y' won't get escaped)
// 17-Sep-2020, tatu: [dataformats-text#226] No, let's be consistent w/ values
"false", "False", "FALSE",
"n", "N",
"no", "No", "NO",
"null", "Null", "NULL",
"on", "On", "ON",
"off", "Off", "OFF",
"true", "True", "TRUE",
"y", "Y",
"yes", "Yes", "YES"
));
/**
* Method called by
* {@link com.fasterxml.jackson.dataformat.yaml.YAMLGenerator}
* to check whether given property name should be quoted: usually
* to prevent it from being read as non-String key (boolean or number)
*/
public abstract boolean needToQuoteName(String name);
/**
* Method called by
* {@link com.fasterxml.jackson.dataformat.yaml.YAMLGenerator}
* to check whether given String value should be quoted: usually
* to prevent it from being value of different type (boolean or number).
*/
public abstract boolean needToQuoteValue(String value);
/**
* Helper method that sub-classes may use to see if given String value is
* one of:
*<ul>
* <li>YAML 1.1 keyword representing
* <a href="https://yaml.org/type/bool.html">boolean</a>
* </li>
* <li>YAML 1.1 keyword representing
* <a href="https://yaml.org/type/null.html">null</a> value
* </li>
* <li>empty String (length 0)
* </li>
*</li>
* and returns {@code true} if so.
*
* @param value String to check
*
* @return {@code true} if given value is a Boolean or Null representation
* (as per YAML 1.1 specification) or empty String
*/
protected boolean isReservedKeyword(String value) {
if (value.length() == 0) {
return true;
}
return _isReservedKeyword(value.charAt(0), value);
}
protected boolean _isReservedKeyword(int firstChar, String name) {
switch (firstChar) {
// First, reserved name starting chars:
case 'f': // false
case 'n': // no/n/null
case 'o': // on/off
case 't': // true
case 'y': // yes/y
case 'F': // False
case 'N': // No/N/Null
case 'O': // On/Off
case 'T': // True
case 'Y': // Yes/Y
return RESERVED_KEYWORDS.contains(name);
case '~': // null alias (see [dataformats-text#274])
return true;
}
return false;
}
/**
* Helper method that sub-classes may use to see if given String value
* looks like a YAML 1.1 numeric value and would likely be considered
* a number when parsing unless quoting is used.
*/
protected boolean looksLikeYAMLNumber(String name) {
if (name.length() > 0) {
return _looksLikeYAMLNumber(name.charAt(0), name);
}
return false;
}
protected boolean _looksLikeYAMLNumber(int firstChar, String name) {
switch (firstChar) {
// And then numbers
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case '-' : case '+': case '.':
return true;
}
return false;
}
/**
* As per YAML <a href="https://yaml.org/spec/1.2/spec.html#id2788859">Plain Style</a>unquoted
* strings are restricted to a reduced charset and must be quoted in case they contain
* one of the following characters or character combinations.
*/
protected boolean valueHasQuotableChar(String inputStr)
{
final int end = inputStr.length();
for (int i = 0; i < end; ++i) {
switch (inputStr.charAt(i)) {
case '[':
case ']':
case '{':
case '}':
case ',':
return true;
case '#':
// [dataformats-text#201]: limit quoting with MINIMIZE_QUOTES
// (but not recognized as comment unless starts line or preceded by whitespace)
if (precededOnlyByBlank(inputStr, i)) {
return true;
}
break;
case ':':
// [dataformats-text#201]: limit quoting with MINIMIZE_QUOTES
// (but recognized as separator only if end-of-line or followed by whitespace)
if (followedOnlyByBlank(inputStr, i)) {
return true;
}
break;
default:
}
}
return false;
}
// @since 2.17
protected boolean precededOnlyByBlank(String inputStr, int offset) {
if (offset == 0) {
return true;
}
return isBlank(inputStr.charAt(offset - 1));
}
// @since 2.17
protected boolean followedOnlyByBlank(String inputStr, int offset) {
if (offset == inputStr.length() - 1) {
return true;
}
return isBlank(inputStr.charAt(offset + 1));
}
// @since 2.17
protected boolean isBlank(char value) {
return (' ' == value || '\t' == value);
}
/**
* Looks like we may get names with "funny characters" so.
*
* @since 2.13.2
*/
protected boolean nameHasQuotableChar(String inputStr)
{
// 31-Jan-2022, tatu: As per [dataformats-text#306] linefeed is
// problematic. I'm sure there are likely other cases, but let's
// start with the obvious ones, control characters
final int end = inputStr.length();
for (int i = 0; i < end; ++i) {
int ch = inputStr.charAt(i);
if (ch < 0x0020) {
return true;
}
}
return false;
}
/**
* Default {@link StringQuotingChecker} implementation used unless
* custom implementation registered.
*/
public static class Default
extends StringQuotingChecker
implements java.io.Serializable
{
private static final long serialVersionUID = 1L;
private final static Default INSTANCE = new Default();
public Default() { }
public static Default instance() { return INSTANCE; }
/**
* Default implementation will call
* {@link #isReservedKeyword(String)} and
* {@link #looksLikeYAMLNumber(String)} to determine
* if quoting should be applied.
*/
@Override
public boolean needToQuoteName(String name)
{
return isReservedKeyword(name) || looksLikeYAMLNumber(name)
// 31-Jan-2022, tatu: as per [dataformats-text#306] may also
// have other characters requiring quoting...
|| nameHasQuotableChar(name);
}
/**
* Default implementation will call
* {@link #isReservedKeyword(String)}
* and {@link #valueHasQuotableChar(String)} to determine
* if quoting should be applied.
*/
@Override
public boolean needToQuoteValue(String value)
{
// Only consider reserved keywords but not numbers?
return isReservedKeyword(value) || valueHasQuotableChar(value);
}
}
}