Use a generic toString()Tag(s): Language


import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;

import java.util.ArrayList;
import java.util.List;

public class ClassUtils {

  private ClassUtils() {}

  public static String toString( Object o ) {
    ArrayList<String> list = new ArrayList<String>();
    ClassUtils.toString( o, o.getClass(), list );
    return o.getClass().getName().concat( list.toString() );
  }

  private static void toString( Object o, Class<?> clazz, List<String> list ) {
    Field f[] = clazz.getDeclaredFields();
    AccessibleObject.setAccessible( f, true );
    for ( int i = 0; i < f.length; i++ ) {
      try {
        list.add( f[i].getName() + "=" + f[i].get(o) );
      }
      catch ( IllegalAccessException e ) { e.printStackTrace(); }
      }
      if ( clazz.getSuperclass().getSuperclass() != null ) {
         toString( o, clazz.getSuperclass(), list );
      }
  }
}
To use it :
public class ClassUtilsTest {

  String hello = "world";
  int i = 42;

  public static void main(String ... args) {
    System.out.println(ClassUtils.toString(new ClassUtilsTest()));
    // output : ClassUtilsTest[hello=world, i=42]
  }
}

The generic toString() dumps the overrided values too :
public class ClassUtilsTest2 extends ClassUtilsTest {

  String hello="fubar";
  double d = Math.PI;

  public static void main(String ... args) {
    System.out.println(ClassUtils.toString(new ClassUtilsTest2()));
    // output : ClassUtilsTest2[hello=fubar, d=3.141592653589793, hello=world, i=42]
  }
}

Andres Santana wrote :

I saw this article (use a generic toString()) and I might have another solution 
for it using java.beans.Introspector.
/**
* Print all properties for a given bean. It's useful for overwriting
* toString method.
*
* @param bean
*            Object to get all properties from.
* @param showNulls
*            Determine if you wether you want to show null properties or
*            not.
* @return String representing bean state.
* @author andres santana
*/
public static String showBean(Object bean, boolean showNulls) {
  if (bean == null)  return null;
  StringBuilder sb =
     new StringBuilder(bean.getClass().getName()).append("[");
  try {
     BeanInfo bi = Introspector.getBeanInfo(bean.getClass());
     PropertyDescriptor[] pd = bi.getPropertyDescriptors();
     for (int i = 0; i < pd.length; i++) {
        if (!"class".equals(pd[i].getName())) {
          Object result = pd[i].getReadMethod().invoke(bean);
          if (showNulls || result != null) {
             sb.append(pd[i].getDisplayName()).append("=").append(result);
             if (i == pd.length - 1)  continue;
             sb.append(",");
          }
        }
     }
  }
  catch (Exception ex) {  }

  return sb.append("]").toString();
}

blog comments powered by Disqus