Scala create multi-line JSON String - json

Question

I'm trying to create a multi-line String in Scala as below.
val errorReport: String =
"""
|{
|"errorName":"blah",
|"moreError":"blah2",
|"errorMessage":{
| "status": "bad",
| "message": "Unrecognized token 'noformatting': was expecting 'null', 'true', 'false' or NaN
at [Source: (ByteArrayInputStream); line: 1, column: 25]"
| }
|}
"""
.stripMargin
It's a nested JSON and it's not displaying properly when I print it. The message field inside errorMessage (which is the output of calling getMessage on an instance of a Throwable) is causing the issue because it looks like there is a newline right before
at [Source: ....
If I get rid of that line the JSON displays properly. Any ideas on how to properly format this are appreciated.
EDIT: The issue is with the newline character. So I think the question is more concisely - how to handle the newline within the triple quotes so that it's still recognized as a JSON?
EDIT 2: message is being set by a variable like so:
"message": "${ex.getMessage}"
where ex is a Throwable. An example of the contents of that getMessage call is provided above.

Answer 1

I assume that your question has nothing to do with JSON, and that you're simply asking how to create very wide strings without violating the horizontal 80-character limit in your Scala code. Fortunately, Scala's string literals have at least the following properties:
You can go from ordinary code to string-literal mode using quotes "..." and triple quotes """...""".
You can go from string-literal mode to ordinary code mode using ${...}
Free monoid over characters is reified as methods, that is, there is the + operation that concatenates string literals.
The whole construction can be made robust to whitespace and indentation using | and stripMargin.
All together, it allows you to write down arbitrary string literals without ever violating horizontal character limits, in a way that is robust w.r.t. indentation.
In this particular case, you want to make a line break in the ambient scala code without introducing a line break in your text. For this, you simply
exit the string-literal mode by closing """
insert concatenation operator + in code mode
make a line-break
indent however you want
re-enter the string-literal mode again by opening """
That is,
"""blah-""" +
"""blah"""
will create the string "blah-blah", without line break in the produced string.
Applied to your concrete problem:
val errorReport: String = (
"""{
| "errorName": "blah",
| "moreError": "blah2",
| "errorMessage": {
| "status": "bad",
| "message": "Unrecognized token 'noformatting'""" +
""": was expecting 'null', 'true', 'false' or NaN at """ +
"""[Source: (ByteArrayInputStream); line: 1, column: 25]"
| }
|}
"""
).stripMargin
Maybe a more readable option would be to construct the lengthy message separately from the neatly indented JSON, and then use string interpolation to combine the two components:
val errorReport: String = {
val msg =
"""Unrecognized token 'noformatting': """ +
"""was expecting 'null', 'true', 'false' or NaN at """ +
"""[Source: (ByteArrayInputStream); line: 1, column: 25]"""
s"""{
| "errorName": "blah",
| "moreError": "blah2",
| "errorMessage": {
| "status": "bad",
| "message": "${msg}"
| }
|}
"""
}.stripMargin
If the message itself contains line breaks
Since JSON does not allow multiline string literals, you have to do something else:
To remove line breaks, use .replaceAll("\\n", "") or rather .replaceAll("\\n", " ")
To encode line breaks with the escape sequence \n, use .replaceAll("\\n", "\\\\n") (yes... backslashes...)