在Java中使用正则表达式从日志中提取表达式时需要帮助

Question

I have a log as a string, and I am trying to capture the error message from it. the regex I tried did not work.

String = "Retrying for error: [[\\"billing\\",\\{u'non_field_errors': [u'Invalid payment email provided']}\\"]]"

I need to extract the error message which is

Invalid payment email provided

How I can extract this, using regex?

I tried the pattern Retrying for error: (\\\\.+) , but it doesn't work:

String pattern = "Retrying for error: (\\.+)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(unescapedStr);
if (m.find()) {
  error = m.group(1);
}

How can I get the expected result?

Invalid payment email provided, Actual: null

Answer 1

you dont have to use regex. how about this

        String x = "Retrying for error: [[\"billing\",\\{u'non_field_errors': [u'Invalid payment email provided']}\"]]";

        String c = x.replace("Retrying for error: ","");

        String g = c.substring(c.lastIndexOf('[')+1);

        String v = g.substring(0, g.indexOf(']'));

        System.out.println(v);

this prints

u'Invalid payment email provided'

now do your logs have multiple instances of Retrying for error: ? also, does this

"Retrying for error: [[\\"billing\\",\\\\{u'non_field_errors': [u'Invalid payment email provided']}\\"]]";

represent a single line in your logs?

The main idea is this: If each line in your log file has just one instance of Retrying for error: , then you can easily parse the log one line at a time and iteratively strip away stuff that you dont need.

Answer 2

You may use the following regex:

Retrying for error:.*\[u'([^']+)

See the regex demo .

Details

• Retrying for error: - a literal substring
• .* - any 0+ chars other than line break chars, as many as possible
• \\[u' - a [u' substring
• ([^']+) - Capturing group #1 ( matcher.group(1) value): 1+ chars other than ' .

See the Java demo :

String unescapedStr = "Retrying for error: [[\"billing\",\\{u'non_field_errors': [u'Invalid payment email provided']}\"]]";
String pattern = "Retrying for error:.*\\[u'([^']+)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(unescapedStr);
if (m.find()) {
  System.out.println(m.group(1));
}
// => Invalid payment email provided