Named placeholders in string formatting

Question

In Python, when formatting string, I can fill placeholders by name rather than by position, like that:

print \"There\'s an incorrect value \'%(value)s\' in c         


        

Answer 1

Another example of Apache Common StringSubstitutor for simple named placeholder.

String template = "Welcome to {theWorld}. My name is {myName}.";

Map<String, String> values = new HashMap<>();
values.put("theWorld", "Stackoverflow");
values.put("myName", "Thanos");

String message = StringSubstitutor.replace(template, values, "{", "}");

System.out.println(message);

// Welcome to Stackoverflow. My name is Thanos.

Answer 2

You can use StringTemplate library, it offers what you want and much more.

import org.antlr.stringtemplate.*;

final StringTemplate hello = new StringTemplate("Hello, $name$");
hello.setAttribute("name", "World");
System.out.println(hello.toString());

Answer 3

For very simple cases you can simply use a hardcoded String replace, no need for a library there:

    String url = "There's an incorrect value '%(value)' in column # %(column)";
    url = url.replace("%(value)", x); // 1
    url = url.replace("%(column)", y); // 2

WARNING: I just wanted to show the simplest code possible. Of course DO NOT use this for serious production code where security matters, as stated in the comments: escaping, error handling and security are an issue here. But in the worst case you now know why using a 'good' lib is required :-)

Answer 4

Apache Commons Lang's replaceEach method may come in handy dependeding on your specific needs. You can easily use it to replace placeholders by name with this single method call:

StringUtils.replaceEach("There's an incorrect value '%(value)' in column # %(column)",
            new String[] { "%(value)", "%(column)" }, new String[] { x, y });

Given some input text, this will replace all occurrences of the placeholders in the first string array with the corresponding values in the second one.

Answer 5

Try Freemarker, templating library.

Answer 6

I tried in just a quick way

public static void main(String[] args) 
{
    String rowString = "replace the value ${var1} with ${var2}";
    
    Map<String,String> mappedValues = new HashMap<>();
    
    mappedValues.put("var1", "Value 1");
    mappedValues.put("var2", "Value 2");
    
    System.out.println(replaceOccurence(rowString, mappedValues));
}

private static  String replaceOccurence(String baseStr ,Map<String,String> mappedValues)
{
    for(String key :mappedValues.keySet())
    {
        baseStr = baseStr.replace("${"+key+"}", mappedValues.get(key));
    }
    
    return baseStr;
}