<dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
        <version>3.4</version>
    </dependency>

public Class X {

  private String a;
  private String b;
  private Y y;
}

public Class Y {
  private String c;
  private String d;
}

ToStringStyle style = ToStringStyle.JSON_STYLE;
LOGGER.debug(ReflectionToStringBuilder.toString(new X(), style, false, false));

{"a":"<a>","b":"<b>","y": com.<packages>.y@<hash>}

RecursiveToStringStyle style = new RecursiveToStringStyle();
LOGGER.debug(ReflectionToStringBuilder.toString(new X(), style, false, false));

[com.<packages>.x@<hash>[a=<a>,b=<b>,y=com.<packages>.y@<hash>[c=<c>,d=<d>]]

`Merge of Approach 1 and Approach 2` but how to achieve this?

{"a":"<a>","b":"<b>","y":{"c":"<c>","d":"<d>"}}

public Class X {

  private String a;
  private String b;
  private Y y;

  @Override
  public String toString() {
    return ToStringBuilder.reflectionToString(this, ToStringStyle.JSON_STYLE);
  }
}

public Class Y {
  private String c;
  private String d;

  @Override
  public String toString() {
    return ToStringBuilder.reflectionToString(this, ToStringStyle.JSON_STYLE);
  }
}

class CustomStyle extends RecursiveToStringStyle {

    public CustomStyle() {
        super();
        super.setUseClassName(false);
        super..setUseIdentityHashCode(false);
        super.setContentStart("{");
        super.setContentEnd("}");
        super.setArrayStart("[");
        super.setArrayEnd("]");
        super.setFieldSeparator(",");
        super.setFieldNameValueSeparator(":");
        super.setNullText("null");
        super.setSummaryObjectStartText(""<");
        super.setSummaryObjectEndText(">"");
        super.setSizeStartText(""<size=");
        super.setSizeEndText(">"");
    }
}

public class Z {
    public String objectToString(Object obj) {
        ToStringStyle style = new CustomStyle();
        return new ReflectionToStringBuilder(obj, style).toString();
    }
}