Does it make sense to use reflection when implementing toString()?

Question

@Override  public String toString() {      return new Gson().toJson(this); } 

Am I breaking some good practice, "Joshua"-pattern thing, general design pattern or other convention by simply doing this as default behavior for my model objects?

toString() will anyhow only be used in debugging in the paradigm (Android) that we are currently using. That's also the reason why I like seeing the object in JSON since much ORM/json persistence will be happening through http->php/python->mysql and to the local SQLite.

Answer 1

Yes. It's OK to use GSON/Jackson/Reflections library to implement toString() method.

There are few ways to implement toString method.

1. Reflections (Apache library)

   @Override public String toString(){     return org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(this); } 

2. JSON based implementation (GSON, Jackson libraries)

   // GSON library for JSON @Override public String toString(){     return new com.google.gson.Gson().toJson(this); }  // Jackson libabry for JSON/YAML @Override public String toString() {     try {         return new com.fasterxml.jackson.databind.ObjectMapper().writerWithDefaultPrettyPrinter().writeValueAsString(this);     } catch (com.fasterxml.jackson.core.JsonProcessingException e) {         e.printStackTrace();     }     return null; } 

3. ToStringBuilder (available with apache-commons library)

   @Override public String toString() {     return new org.apache.commons.lang3.builder.ToStringBuilder(this).         append("field1", field1).         append("field2", field2).         toString(); } 

4. Hard-core toString() implementation

   @Override public String toString() {     return new StringBuilder()         .append("field1:"+field1)         .append("field2:"+field2)         .toString(); } 

5. Lombok annotations : Generates toString() at compile time

   import lombok.ToString;  @ToString public class ToStringExample {} 

Answer 2

There's no harm in doing it this way. I would suggest you to create a static variable for your Gson instance and enable pretty printing:

static Gson gson = new GsonBuilder().setPrettyPrinting().create(); 

This way the output from toString method will be formatted.