Add more options to custom DefaultPrettyPrinter (example with grafana json dashboards)

[gulecroc]

Jackson version: 2.15.3

Hi, I worked on Grafana dashboards json files and need to adapt the DefaultPrettyPrinter.

I would like tu suggest some improvment to custom DefaultPrettyPrinter without the need to override some methods :

1. Object key and value separator : remove space after object key

current  : "key" : "value"
expected : "key": "value"

I could not override this behavior, either with withSeparators or withoutSpacesInObjectEntries methods :

   // could not change spaces before or after separators
   public DefaultPrettyPrinter withSeparators(Separators separators) {
      this._separators = separators;
      this._objectFieldValueSeparatorWithSpaces = " " + separators.getObjectFieldValueSeparator() + " ";
      return this;
   }

   // disable spaces before and after
   public DefaultPrettyPrinter withoutSpacesInObjectEntries() {
      return this._withSpaces(false);
   }

   // need to override this method
   public void writeObjectFieldValueSeparator(JsonGenerator g) throws IOException {
      if (this._spacesInObjectEntries) {
         g.writeRaw(this._objectFieldValueSeparatorWithSpaces);
      } else {
         g.writeRaw(this._separators.getObjectFieldValueSeparator());
      }

   }

Need to override writeObjectFieldValueSeparator method :

    @Override
    public void writeObjectFieldValueSeparator(JsonGenerator g) throws IOException {
        g.writeRaw(": ");
    }

Maybe add new method withSeparators(String prefix, Separators separators, String suffix) ?

   public DefaultPrettyPrinter withSeparators(String prefix, Separators separators, String suffix) {
      this._separators = separators;
      this._objectFieldValueSeparatorWithSpaces = prefix + separators.getObjectFieldValueSeparator() + suffix;
      return this;
   }

2. Array indenter : ident each array object

current :
{
  "array" : [ {
     [...]
   }, {
     [...]
   } ]
}

expected :
{
  "array" : [
     {
       [...]
     }, 
     {
       [...]
     } 
   ]
}

This could be done with :

DefaultPrettyPrinter pp = new DefaultPrettyPrinter ();
pp.withArrayIndenter(DefaultIndenter.SYSTEM_LINEFEED_INSTANCE);

But it was not easy to find the good indenter, maybe add some documentation to indenters availables or add withArrayIndenterLineFeed method ?

3. Empty object/array : remove space

current :

{
  "links": [ ]
  "custom": { }
}

expected :

{
  "links": []
  "custom": {}
}

I need to override writeEndObject and writeEndArray method to comment the behavior when nrOfValues = 0 :

  @Override
   public void writeEndObject(JsonGenerator g, int nrOfEntries) throws IOException {
      if (!this._objectIndenter.isInline()) {
         --this._nesting;
      }

      if (nrOfEntries > 0) {
         this._objectIndenter.writeIndentation(g, this._nesting);
      } 
      // else {
      //   g.writeRaw(' ');
      // }

      g.writeRaw('}');
   }

  @Override
   public void writeEndArray(JsonGenerator g, int nrOfValues) throws IOException {
      if (!this._arrayIndenter.isInline()) {
         --this._nesting;
      }

      if (nrOfValues > 0) {
         this._arrayIndenter.writeIndentation(g, this._nesting);
      } 
      // else {
      //    g.writeRaw(' ');
      // }

      g.writeRaw(']');
   }

Maybe add new methods withEmptyArrayContent(String content) ?

Finally, here is my custom class for those who could need it :

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.util.DefaultIndenter;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;

public class GrafanaPrettyPrinter extends DefaultPrettyPrinter {

    @Override
    public DefaultPrettyPrinter createInstance() {
        GrafanaPrettyPrinter pp = new GrafanaPrettyPrinter();
        pp._arrayIndenter = DefaultIndenter.SYSTEM_LINEFEED_INSTANCE;
        return pp;
    }

    @Override
    public void writeObjectFieldValueSeparator(JsonGenerator g) throws IOException {
        g.writeRaw(": ");
    }

    @Override
    public void writeEndObject(JsonGenerator g, int nrOfEntries) throws IOException {
        if (!this._objectIndenter.isInline()) {
           --this._nesting;
        }
  
        if (nrOfEntries > 0) {
           this._objectIndenter.writeIndentation(g, this._nesting);
        }
  
        g.writeRaw('}');
     }

     @Override
     public void writeEndArray(JsonGenerator g, int nrOfValues) throws IOException {
        if (!this._arrayIndenter.isInline()) {
           --this._nesting;
        }
  
        if (nrOfValues > 0) {
           this._arrayIndenter.writeIndentation(g, this._nesting);
        }
  
        g.writeRaw(']');
     }
    
}

[cowtowncoder]

With respect to entry (1) did you notice #1042 that is going in 2.16? (2.16.0-rc1 being released today)?

As to others, PRs are always welcome; feature requests themselves sound reasonable to me.

[gulecroc]

Hi @cowtowncoder, thank's for the link #1042

I will open PRs for others features.

[gulecroc]

Update :

1. Object key and value separator : configurable since v2.16
2. Array indenter : N/A
3. Empty object/array : PR Allow configuring DefaultPrettyPrinter separators for empty Arrays and Objects #1178 (merged in 2.17)

[erik-meuwese-topicus]

The extra whitespace in 2.16 breaks previous behavior. This should not be a minor change. When it's a minor change there should be a method on the defaultPrettyPrinter to enable the whitespace before the separator

[cowtowncoder]

@erik-meuwese-topicus All of these are options for user to change behavior, not changing default behavior, so I am not sure what extra space you are referring to?

Intent at least is not to make such changes, to preserve backwards-compatibility.

[cowtowncoder]

@gulecroc Sounds like first and third entries have been implemented: should the second entry be moved to its own issue (create new one) and close this one?

[gulecroc]

@cowtowncoder for me it sounds good. I close the issue. Thank you