How do I format a string with properties from a bean

Question

I want to create a String using a format, replacing some tokens in the format with properties from a bean. Is there a library that supports this or am I going to have to create my own implementation?

Let me demonstate with an example. Say I have a bean Person;

public class Person {
  private String id;
  private String name;
  private String age;

  //getters and setters
}

I want to be able to specify format strings something like;

"{name} is {age} years old."
"Person id {id} is called {name}."

and automatically populate the format placeholders with values from the bean, something like;

String format = "{name} is {age} old."
Person p = new Person(1, "Fred", "32 years");
String formatted = doFormat(format, person); //returns "Fred is 32 years old."

I've had a look at MessageFormat but this only seems to allow me to pass numeric indexes, not bean properties.

Answer 1

Rolled my own, testing now. Comments welcome.

import java.lang.reflect.Field;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class BeanFormatter<E> {

  private Matcher matcher;
  private static final Pattern pattern = Pattern.compile("\\{(.+?)\\}");

  public BeanFormatter(String formatString) {
    this.matcher = pattern.matcher(formatString);
  }

  public String format(E bean) throws Exception {
    StringBuffer buffer = new StringBuffer();

    try {
      matcher.reset();
      while (matcher.find()) {
        String token = matcher.group(1);
        String value = getProperty(bean, token);
        matcher.appendReplacement(buffer, value);
      }
      matcher.appendTail(buffer);
    } catch (Exception ex) {
      throw new Exception("Error formatting bean " + bean.getClass() + " with format " + matcher.pattern().toString(), ex);
    }
    return buffer.toString();
  }

  private String getProperty(E bean, String token) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
    Field field = bean.getClass().getDeclaredField(token);
    field.setAccessible(true);
    return String.valueOf(field.get(bean));
  }

  public static void main(String[] args) throws Exception {
    String format = "{name} is {age} old.";
    Person p = new Person("Fred", "32 years", 1);

    BeanFormatter<Person> bf = new BeanFormatter<Person>(format);
    String s = bf.format(p);
    System.out.println(s);
  }

}

Answer 2

Yes, it's possible using the Pojomatic library. Implement and plug in your own implementation of PojoFormatter. Pojomator#doToString(T) may be also interesting.