Java 杰克逊';s JSON(2.5.0)验证未按预期工作
简单测试用例:Java 杰克逊';s JSON(2.5.0)验证未按预期工作,java,json,jackson,Java,Json,Jackson,简单测试用例: import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; public static void main(String[] args) throws Exception { String json = "1,2"; ObjectMapper parser = new ObjectMapper(); JsonNode
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public static void main(String[] args) throws Exception {
String json = "1,2";
ObjectMapper parser = new ObjectMapper();
JsonNode rootNode = parser.readTree(json);
}
引发异常:
Exception in thread "main" com.fasterxml.jackson.core.JsonParseException:
Unexpected character (',' (code 44)): Expected space separating root-level values
at [Source: 1,2; line: 1, column: 3]
一切都很好,但如果我将String json
更改为以下任何一项:
String json = "null,false";
String json = "[1,2,3,null,\"hello\"],false";
String json = "true,3";
String json = "true,{\"test\":3}";
没有抛出异常
为什么会出现这种差异?默认情况下,Jackson使用的是
ReaderBasedJsonParser
,在读取/初始化要解析的JSON时,会进行显式检查
switch (i) {
case '"':
_tokenIncomplete = true;
t = JsonToken.VALUE_STRING;
break;
case '[':
if (!inObject) {
_parsingContext = _parsingContext.createChildArrayContext(_tokenInputRow, _tokenInputCol);
}
t = JsonToken.START_ARRAY;
break;
case '{':
if (!inObject) {
_parsingContext = _parsingContext.createChildObjectContext(_tokenInputRow, _tokenInputCol);
}
t = JsonToken.START_OBJECT;
break;
case ']':
case '}':
// Error: neither is valid at this point; valid closers have
// been handled earlier
_reportUnexpectedChar(i, "expected a value");
case 't':
_matchTrue();
t = JsonToken.VALUE_TRUE;
break;
case 'f':
_matchFalse();
t = JsonToken.VALUE_FALSE;
break;
case 'n':
_matchNull();
t = JsonToken.VALUE_NULL;
break;
case '-':
/* Should we have separate handling for plus? Although
* it is not allowed per se, it may be erroneously used,
* and could be indicate by a more specific error message.
*/
t = _parseNegNumber();
break;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
t = _parsePosNumber(i);
break;
从上面的代码中,您可以看到它检查您提到的字符-null、true、{、[、false等,如果有匹配,它将返回有效的json令牌
String json = "true,3";
到
它将再次抛出众所周知的异常
请注意,对于以字母“n”开头的给定字符串,也会进行检查,以验证它是否与null匹配(对于以“t”、“f”开头的字符串,也会进行相同的检查)
然后有趣的是\u parsePosNumber(i)
方法,它基本上调用\u reportmissingtrootws
来检查根-它显然失败了
因此,基本上,如果json是有效的,它永远不会达到“failer”的情况,或者如果给定的字符串以“true”、“false”、“null”、“[”、“{”、“]”、“}”开头,它也将被视为有效的json
我假设此功能位于Jackson列表中,因此上述格式被视为有效的JSON
String json = "3,true";