在侧花括号中获取字符串，在其中的花括号中也有更多值

Question

So here's my (java) string

String s = "Some string preceding this {\"Key1\": \"Val1\", \"Key2\": {\"embedKey1\": \"embedVal1\", \"embedKey2\": \"embedVal2\"}, \"Key3\" : \"Val3\", \"Key3\": \"Val4\"}, some value proceeding it"

I want to get everything that is within the outer curly braces. How do I do that? So far I've tried the following

    Pattern p = Pattern.compile("\\{([^}]*)\\}");
    Matcher m = p.matcher(s);
    while(m.find()){
       System.out.println(m.group(1));
    }

This however, only prints

"Key1": "Val1", "Key2": {"embedKey1": "embedVal1", "embedKey2": "embedVal2"

Can someone please help me with this?

Answer 1

To get everything in between outer braces, or between the first { and the last } , use greedy matching with a . matching all symbols (with DOTALL mode):

String s = "Some string preceding this {\"Key1\": \"Val1\", \"Key2\": {\"embedKey1\": \"embedVal1\", \"embedKey2\": \"embedVal2\"}, \"Key3\" : \"Val3\", \"Key3\": \"Val4\"}, some value proceeding it";
Pattern p = Pattern.compile("(?s)\\{(.*)}");
Matcher m = p.matcher(s);
while(m.find()){
    System.out.println(m.group(1));
}

See IDEONE demo

The (?s) is an inline version of the Pattern.DOTALL modifier.

Answer 2

For your particular example you can use a regex like this:

\{(.*?)\{.*?}(.*?)}

Working demo

Match information

MATCH 1
1.  [40-64] `"Key1": "Val1", "Key2": `
2.  [116-149]   `, "Key3" : "Val3", "Key3": "Val4"`

On the other hand, if you want to even capture the inner curly braces you can use something easier like this:

\{(.*)}

Working demo

Match information

MATCH 1
1.  [40-149]    `"Key1": "Val1", "Key2": {"embedKey1": "embedVal1", "embedKey2": "embedVal2"}, "Key3" : "Val3", "Key3": "Val4"`
QUICK REFERENCE

Remember to escape backslashes in java:

Pattern p = Pattern.compile("\\{(.*)}");
Matcher m = p.matcher(s);
while(m.find()){
   System.out.println(m.group(1));
}

Answer 3

If It's just about outermost "{" and "}" as you mentioned in your problem, this may be one of the non-regex approach.

    int first=s.indexOf('{');
    int last=s.lastIndexOf('}');

    String result=s.substring(first, last+1);