21 KiB
Exceptions
Overview
Base type
All exceptions inherit from class json::exception (which in turn inherits from std::exception). It is used as the base class for all exceptions thrown by the basic_json class. This class can hence be used as "wildcard" to catch exceptions.
Switch off exceptions
Exceptions are used widely within the library. They can, however, be switched off with either using the compiler flag -fno-exceptions or by defining the symbol JSON_NOEXCEPTION. In this case, exceptions are replaced by abort() calls. You can further control this behavior by defining JSON_THROW_USER (overriding #!cpp throw), JSON_TRY_USER (overriding #!cpp try), and JSON_CATCH_USER (overriding #!cpp catch).
Note that JSON_THROW_USER should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.
Parse errors
This exception is thrown by the library when a parse error occurs. Parse errors can occur during the deserialization of JSON text, CBOR, MessagePack, as well as when using JSON Patch.
Exceptions have ids 1xx.
!!! info "Byte index"
Member `byte` holds the byte index of the last read character in the input
file.
For an input with n bytes, 1 is the index of the first character and n+1
is the index of the terminating null byte or the end of file. This also
holds true when reading a byte vector (CBOR or MessagePack).
json.exception.parse_error.101
This error indicates a syntax error while deserializing a JSON text. The error message describes that an unexpected token (character) was encountered, and the member byte indicates the error position.
!!! example
Input ended prematurely:
```
[json.exception.parse_error.101] parse error at 2: unexpected end of input; expected string literal
```
No input:
```
[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal
```
Control character was not escaped:
```
[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: control character U+0009 (HT) must be escaped to \u0009 or \\; last read: '"<U+0009>'"
```
String was not closed:
```
[json.exception.parse_error.101] parse error at line 1, column 2: syntax error while parsing value - invalid string: missing closing quote; last read: '"'
```
Invalid number format:
```
[json.exception.parse_error.101] parse error at line 1, column 3: syntax error while parsing value - invalid number; expected '+', '-', or digit after exponent; last read: '1E'
```
`\u` was not be followed by four hex digits:
```
[json.exception.parse_error.101] parse error at line 1, column 6: syntax error while parsing value - invalid string: '\u' must be followed by 4 hex digits; last read: '"\u01"'
```
Invalid UTF-8 surrogate pair:
```
[json.exception.parse_error.101] parse error at line 1, column 13: syntax error while parsing value - invalid string: surrogate U+DC00..U+DFFF must follow U+D800..U+DBFF; last read: '"\uD7FF\uDC00'"
```
Invalid UTF-8 byte:
```
[json.exception.parse_error.101] parse error at line 3, column 24: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '"vous \352t'
```
!!! tip
- Make sure the input is correctly read. Try to write the input to standard output to check if, for instance, the input file was successfully openened.
- Paste the input to a JSON validator like <http://jsonlint.com> or a tool like [jq](https://stedolan.github.io/jq/).
json.exception.parse_error.102
JSON uses the \uxxxx format to describe Unicode characters. Code points above above 0xFFFF are split into two \uxxxx entries ("surrogate pairs"). This error indicates that the surrogate pair is incomplete or contains an invalid code point.
!!! example
```
parse error at 14: missing or wrong low surrogate
```
json.exception.parse_error.103
Unicode supports code points up to 0x10FFFF. Code points above 0x10FFFF are invalid.
!!! example
```
parse error: code points above 0x10FFFF are invalid
```
json.exception.parse_error.104
RFC 6902 requires a JSON Patch document to be a JSON document that represents an array of objects.
!!! example
```
[json.exception.parse_error.104] parse error: JSON patch must be an array of objects
```
json.exception.parse_error.105
An operation of a JSON Patch document must contain exactly one "op" member, whose value indicates the operation to perform. Its value must be one of "add", "remove", "replace", "move", "copy", or "test"; other values are errors.
!!! example
```
[json.exception.parse_error.105] parse error: operation 'add' must have member 'value'
```
```
[json.exception.parse_error.105] parse error: operation 'copy' must have string member 'from'
```
```
[json.exception.parse_error.105] parse error: operation value 'foo' is invalid
```
json.exception.parse_error.106
An array index in a JSON Pointer (RFC 6901) may be 0 or any number without a leading 0.
!!! example
```
[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'
```
json.exception.parse_error.107
A JSON Pointer must be a Unicode string containing a sequence of zero or more reference tokens, each prefixed by a / character.
!!! example
```
[json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'foo'
```
json.exception.parse_error.108
In a JSON Pointer, only ~0 and ~1 are valid escape sequences.
!!! example
```
[json.exception.parse_error.108] parse error: escape character '~' must be followed with '0' or '1'
```
json.exception.parse_error.109
A JSON Pointer array index must be a number.
!!! example
```
[json.exception.parse_error.109] parse error: array index 'one' is not a number
```
```
[json.exception.parse_error.109] parse error: array index '+1' is not a number
```
json.exception.parse_error.110
When parsing CBOR or MessagePack, the byte vector ends before the complete value has been read.
!!! example
```
[json.exception.parse_error.110] parse error at byte 5: syntax error while parsing CBOR string: unexpected end of input
```
```
[json.exception.parse_error.110] parse error at byte 2: syntax error while parsing UBJSON value: expected end of input; last byte: 0x5A
```
json.exception.parse_error.112
Not all types of CBOR or MessagePack are supported. This exception occurs if an unsupported byte was read.
!!! example
```
[json.exception.parse_error.112] parse error at byte 1: syntax error while parsing CBOR value: invalid byte: 0x1C
```
json.exception.parse_error.113
While parsing a map key, a value that is not a string has been read.
!!! example
```
[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF
```
```
[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing MessagePack string: expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0xFF
```
```
[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing UBJSON char: byte after 'C' must be in range 0x00..0x7F; last byte: 0x82
```
json.exception.parse_error.114
The parsing of the corresponding BSON record type is not implemented (yet).
!!! example
```
[json.exception.parse_error.114] parse error at byte 5: Unsupported BSON record type 0xFF
```
Iterator errors
This exception is thrown if iterators passed to a library function do not match the expected semantics.
Exceptions have ids 2xx.
json.exception.invalid_iterator.201
The iterators passed to constructor basic_json(InputIT first, InputIT last) are not compatible, meaning they do not belong to the same container. Therefore, the range (first, last) is invalid.
!!! example
```
[json.exception.invalid_iterator.201] iterators are not compatible
```
json.exception.invalid_iterator.202
In an erase or insert function, the passed iterator @a pos does not belong to the JSON value for which the function was called. It hence does not define a valid position for the deletion/insertion.
!!! example
```
[json.exception.invalid_iterator.202] iterator does not fit current value
```
```
[json.exception.invalid_iterator.202] iterators first and last must point to objects
```
json.exception.invalid_iterator.203
Either iterator passed to function erase(IteratorType first, IteratorType last) does not belong to the JSON value from which values shall be erased. It hence does not define a valid range to delete values from.
!!! example
```
[json.exception.invalid_iterator.203] iterators do not fit current value
```
json.exception.invalid_iterator.204
When an iterator range for a primitive type (number, boolean, or string) is passed to a constructor or an erase function, this range has to be exactly (begin(), end()), because this is the only way the single stored value is expressed. All other ranges are invalid.
!!! example
```
[json.exception.invalid_iterator.204] iterators out of range
```
json.exception.invalid_iterator.205
When an iterator for a primitive type (number, boolean, or string) is passed to an erase function, the iterator has to be the begin() iterator, because it is the only way to address the stored value. All other iterators are invalid.
!!! example
```
[json.exception.invalid_iterator.205] iterator out of range
```
json.exception.invalid_iterator.206
The iterators passed to constructor basic_json(InputIT first, InputIT last) belong to a JSON null value and hence to not define a valid range.
!!! example
```
[json.exception.invalid_iterator.206] cannot construct with iterators from null
```
json.exception.invalid_iterator.207
The key() member function can only be used on iterators belonging to a JSON object, because other types do not have a concept of a key.
!!! example
```
[json.exception.invalid_iterator.207] cannot use key() for non-object iterators
```
json.exception.invalid_iterator.208
The operator[] to specify a concrete offset cannot be used on iterators belonging to a JSON object, because JSON objects are unordered.
!!! example
```
[json.exception.invalid_iterator.208] cannot use operator[] for object iterators
```
json.exception.invalid_iterator.209
The offset operators (+, -, +=, -=) cannot be used on iterators belonging to a JSON object, because JSON objects are unordered.
!!! example
```
[json.exception.invalid_iterator.209] cannot use offsets with object iterators
```
json.exception.invalid_iterator.210
The iterator range passed to the insert function are not compatible, meaning they do not belong to the same container. Therefore, the range (first, last) is invalid.
!!! example
```
[json.exception.invalid_iterator.210] iterators do not fit
```
json.exception.invalid_iterator.211
The iterator range passed to the insert function must not be a subrange of the container to insert to.
!!! example
```
[json.exception.invalid_iterator.211] passed iterators may not belong to container
```
json.exception.invalid_iterator.212
When two iterators are compared, they must belong to the same container.
!!! example
```
[json.exception.invalid_iterator.212] cannot compare iterators of different containers
```
json.exception.invalid_iterator.213
The order of object iterators cannot be compared, because JSON objects are unordered.
!!! example
```
[json.exception.invalid_iterator.213] cannot compare order of object iterators
```
json.exception.invalid_iterator.214
Cannot get value for iterator: Either the iterator belongs to a null value or it is an iterator to a primitive type (number, boolean, or string), but the iterator is different to begin().
!!! example
```
[json.exception.invalid_iterator.214] cannot get value
```
Type errors
This exception is thrown in case of a type error; that is, a library function is executed on a JSON value whose type does not match the expected semantics.
Exceptions have ids 3xx.
json.exception.type_error.301
To create an object from an initializer list, the initializer list must consist only of a list of pairs whose first element is a string. When this constraint is violated, an array is created instead.
!!! example
```
[json.exception.type_error.301] cannot create object from initializer list
```
json.exception.type_error.302
During implicit or explicit value conversion, the JSON type must be compatible to the target type. For instance, a JSON string can only be converted into string types, but not into numbers or boolean types.
!!! example
```
[json.exception.type_error.302] type must be object, but is null
```
```
[json.exception.type_error.302] type must be string, but is object
```
json.exception.type_error.303
To retrieve a reference to a value stored in a basic_json object with get_ref, the type of the reference must match the value type. For instance, for a JSON array, the ReferenceType must be array_t &.
!!! example
```
[json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is object
```
```
[json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is number"
```
json.exception.type_error.304
The at() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.304] cannot use at() with string
```
```
[json.exception.type_error.304] cannot use at() with number
```
json.exception.type_error.305
The operator[] member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.305] cannot use operator[] with a string argument with array
```
```
[json.exception.type_error.305] cannot use operator[] with a numeric argument with object
```
json.exception.type_error.306
The value() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.306] cannot use value() with number
```
json.exception.type_error.307
The erase() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.307] cannot use erase() with string
```
json.exception.type_error.308
The push_back() and operator+= member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.308] cannot use push_back() with string
```
json.exception.type_error.309
The insert() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.309] cannot use insert() with array
```
```
[json.exception.type_error.309] cannot use insert() with number
```
json.exception.type_error.310
The swap() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.310] cannot use swap() with number
```
json.exception.type_error.311
The emplace() and emplace_back() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.311] cannot use emplace() with number
```
```
[json.exception.type_error.311] cannot use emplace_back() with number
```
json.exception.type_error.312
The update() member functions can only be executed for certain JSON types.
!!! example
```
[json.exception.type_error.312] cannot use update() with array
```
json.exception.type_error.313
The unflatten function converts an object whose keys are JSON Pointers back into an arbitrary nested JSON value. The JSON Pointers must not overlap, because then the resulting value would not be well defined.
!!! example
```
[json.exception.type_error.313] invalid value to unflatten
```
json.exception.type_error.314
The unflatten function only works for an object whose keys are JSON Pointers.
!!! example
Calling `unflatten()` on an array `#!json [1,2,3]`:
```
[json.exception.type_error.314] only objects can be unflattened
```
json.exception.type_error.315
The unflatten() function only works for an object whose keys are JSON Pointers and whose values are primitive.
!!! example
Calling `unflatten()` on an object `#!json {"/1", [1,2,3]}`:
```
[json.exception.type_error.315] values in object must be primitive
```
json.exception.type_error.316
The dump() function only works with UTF-8 encoded strings; that is, if you assign a std::string to a JSON value, make sure it is UTF-8 encoded.
!!! example
Calling `dump()` on a JSON value containing an ISO 8859-1 encoded string:
```
[json.exception.type_error.316] invalid UTF-8 byte at index 15: 0x6F
```
!!! tip
- Store the source file with UTF-8 encoding.
- Pass an error handler as last parameter to the `dump()` function to avoid this exception:
- `json::error_handler_t::replace` will replace invalid bytes sequences with `U+FFFD`
- `json::error_handler_t::ignore` will silently ignore invalid byte sequences
json.exception.type_error.317
The dynamic type of the object cannot be represented in the requested serialization format (e.g. a raw true or null JSON object cannot be serialized to BSON)
!!! example
Serializing `#!json null` to BSON:
```
[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is null
```
Serializing `#!json [1,2,3]` to BSON:
```
[json.exception.type_error.317] to serialize to BSON, top-level type must be object, but is array
```
!!! tip
Encapsulate the JSON value in an object. That is, instead of serializing `#!json true`, serialize `#!json {"value": true}`
Out of range
This exception is thrown in case a library function is called on an input parameter that exceeds the expected range, for instance in case of array indices or nonexisting object keys.
Exceptions have ids 4xx.
json.exception.out_of_range.401
The provided array index i is larger than size-1.
!!! example
```
array index 3 is out of range
```
json.exception.out_of_range.402
The special array index - in a JSON Pointer never describes a valid element of the array, but the index past the end. That is, it can only be used to add elements at this position, but not to read it.
!!! example
```
array index '-' (3) is out of range
```
json.exception.out_of_range.403
The provided key was not found in the JSON object.
!!! example
```
key 'foo' not found
```
json.exception.out_of_range.404
A reference token in a JSON Pointer could not be resolved.
!!! example
```
unresolved reference token 'foo'
```
json.exception.out_of_range.405
The JSON Patch operations 'remove' and 'add' can not be applied to the root element of the JSON value.
!!! example
```
JSON pointer has no parent
```
json.exception.out_of_range.406
A parsed number could not be stored as without changing it to NaN or INF.
!!! example
```
number overflow parsing '10E1000'
```
json.exception.out_of_range.407
UBJSON and BSON only support integer numbers up to 9223372036854775807.
!!! example
```
number overflow serializing '9223372036854775808'
```
json.exception.out_of_range.408
The size (following #) of an UBJSON array or object exceeds the maximal capacity.
!!! example
```
excessive array size: 8658170730974374167
```
json.exception.out_of_range.409
Key identifiers to be serialized to BSON cannot contain code point U+0000, since the key is stored as zero-terminated c-string.
!!! example
```
BSON key cannot contain code point U+0000 (at byte 2)
```
Further exceptions
This exception is thrown in case of errors that cannot be classified with the other exception types.
Exceptions have ids 5xx.
json.exception.other_error.501
A JSON Patch operation 'test' failed. The unsuccessful operation is also printed.
!!! example
Executing `#!json {"op":"test", "path":"/baz", "value":"bar"}` on `#!json {"baz": "qux"}`:
```
[json.exception.other_error.501] unsuccessful: {"op":"test","path":"/baz","value":"bar"}
```