How to format Java code snippets programmatically

Question

I'm looking for a java library to format/beautify Java code snippets. So for I have been using Google Java Format however it seems to work just for fully-fledged Java classes and not for code snippets. For example, the following code snippet has been formatted online without an issue:

@Bean public ConfigurableServletWebServerFactory webServerFactory() {
  JettyServletWebServerFactory factory = new JettyServletWebServerFactory();
  factory.setPort(9000);
  factory.setContextPath("/myapp");
  factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html"));
  return factory;
}

But using Google Formatter, the following error is returned:

 error: class, interface, or enum expected

I've used the following code to attempt parsing it:

String formattedSource = new Formatter().formatSource(code);

Any idea how to fix it?

Take a look at org.eclipse.jdt.core.formatter.CodeFormatter. This plugin uses it github.com/revelc/formatter-maven-plugin/blob/main/src/main/… — Ghokun
– Ghokun, Commented Jun 13, 2021 at 10:23
Looks like the Google formatter only formats entire Java compilation units, not single methods. If you know it's a method, you could put a class declaration around the method before formatting. If the declaration that you put around it is properly formatted, the formatSource method shouldn't change it, so you can lift out the formatted method again after formatting. — Erwin Bolwidt
– Erwin Bolwidt, Commented Jun 14, 2021 at 0:07

MoneyPenny · Accepted Answer · 2022-07-24 06:28:25Z

1

Create custom template code as a full compilation unit and remove the template back to snippet after formatting.

see below

    public String formatSnippet(String snippet) throws FormatterException {
    final String CUNIT = "class code { public method() { /*;*/";
    String fCode = new Formatter().formatSource(CUNIT + snippet + "/*;*/}}");
    int startIndex = fCode.indexOf("/*;*/") + 5;
    int endIndex = fCode.indexOf("/*;*/", startIndex) - 1;
    return startIndex > 0 && endIndex > 0 && endIndex > startIndex ? fCode.substring(startIndex, endIndex) : snippet;
}

edited Jul 24, 2022 at 6:28

answered Jul 24, 2022 at 6:09

MoneyPenny

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2 Comments

JumperBot_ Over a year ago

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JumperBot_ Over a year ago

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