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JSON to Java Converters - Quick and Dirty JBang style

By David Norris on
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Table of Contents

  1. JSON to Java Converters: Quick and Dirty Jbang Scripts
  2. TL;DR
  3. Download the Precompiled Binary
  4. Comparison
  5. JSON to Lombok DTO Generator
  6. JSON to Java Record Generator

TL;DR

Mostly for myself I wrote two JSON to POJO converters to quickly generate pojos from json:

These are JBang scripts. Definitely check that project out if you haven’t already.

Download the Precompiled Binary

You can download the precompiled x86_64 Linux binaries here:

You can also compile your own native binary if you follow the details below.

Comparison

FeatureLombok DTO GeneratorJava Record Generator
OutputNested Java DTOsJava Records
AnnotationsLombokNone

JSON to Lombok DTO Generator

Features

How to Use

  1. Install JBang
  2. Run the following commands:
wget https://gist.githubusercontent.com/Hillrunner2008/507c323bcc2538f1b406528c80c9a7f1/raw/64213ad53ef56593f61f01d034f7a7da57ef1c38/Json2Dto.java
wget https://gist.githubusercontent.com/Hillrunner2008/fad85a7ac05ef9411e4217143005bff8/raw/aa450b9fa2250d3aa5bb8073404c9c86b9acc860/example.json
jbang Json2Dto.java example.json --package com.example.model --name Squad

How to Use the Precompiled Binary

If you prefer to use the precompiled binary instead of JBang, you can download and run it directly. Follow these steps:

  1. Download the precompiled binary from the link above.
  2. Make the binary executable:
chmod +x json2dto_x86_64
  1. Run the binary with the appropriate arguments:
./json2dto_x86_64 example.json --package com.example.model --name Squad

Example Output

package com.example.model;
 
import lombok.Data;
import lombok.Builder;
import lombok.NoArgsConstructor;
import lombok.AllArgsConstructor;
import lombok.AccessLevel;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import java.util.List;
 
@Data
@Builder
@NoArgsConstructor(force = true, access = AccessLevel.PRIVATE)
@AllArgsConstructor
@JsonIgnoreProperties(ignoreUnknown = true)
public class Squad {
 
    private String squadName;
 
    private String homeTown;
 
    private int formed;
 
    @JsonProperty("secret-base")
    private String secretBase;
 
    private boolean active;
 
    private List<Member> members;
 
    @Data
    @Builder
    @NoArgsConstructor(force = true, access = AccessLevel.PRIVATE)
    @AllArgsConstructor
    public static class Member {
 
        private String name;
 
        private int age;
 
        private String secretIdentity;
 
        private List<String> powers;
 
    }
 
}

Compiling to a Native Binary with JBang

If you’d like to compile this script to a native binary, JBang makes it simple using GraalVM native-image under the hood. This allows you to create a fast, standalone executable from your script.

For the Json2Records.java script, I used the following command:

jbang --native --native-option="-H:ReflectionConfigurationFiles=reflect-config.json" Json2Dto.java

Here is the content of the reflect-config.json file, which specifies the reflection requirements needed for the native image:

[
  {
    "name": "Json2Dto",
    "allDeclaredConstructors": true,
    "allPublicConstructors": true,
    "allDeclaredMethods": true,
    "allPublicMethods": true,
    "fields": [
      { "name": "jsonFile" },
      { "name": "rootName" },
      { "name": "packageName" }
    ]
  },
  {
    "name": "picocli.CommandLine$AutoHelpMixin",
    "allDeclaredConstructors": true,
    "allPublicConstructors": true,
    "allDeclaredMethods": true,
    "allPublicMethods": true,
    "fields": [
      { "name": "helpRequested" },
      { "name": "versionRequested" }
    ]
  }
]

JSON to Java Record Generator

Features

How to Use

  1. Install JBang
  2. Run the following commands: 
    wget https://gist.githubusercontent.com/Hillrunner2008/721a4e504b638b17540e604b7713d5cb/raw/0fbf32dd518113f28b7e8a2b5242f8cf54ec760e/Json2Records.java
wget https://gist.githubusercontent.com/Hillrunner2008/fad85a7ac05ef9411e4217143005bff8/raw/aa450b9fa2250d3aa5bb8073404c9c86b9acc860/example.json
jbang Json2Records.java example.json --nest --package com.example.model --name Squad

How to Use the Precompiled Binary

If you prefer to use the precompiled binary instead of JBang, you can download and run it directly. Follow these steps:

  1. Download the precompiled binary from the link above.
  2. Make the binary executable:
chmod +x json2records_x86_64
  1. Run the binary with the appropriate arguments:
./json2records_x86_64 example.json --package com.example.model --name Squad

output

package com.example.model;
 
import java.util.*;
 
public record Squad (
    String squadName,
    String homeTown,
    int formed,
    @JsonProperty("secret-base")
    String secretBase,
    boolean active,
    List<Member> members
) {
 
    public static record Member (
            String name,
            int age,
            String secretIdentity,
            List<String> powers
    ) {}
}

Compiling to a Native Binary with JBang

If you’d like to compile this script to a native binary, JBang makes it simple using GraalVM native-image under the hood. This allows you to create a fast, standalone executable from your script.

For the Json2Records.java script, I used the following command:

jbang --native --native-option="-H:ReflectionConfigurationFiles=reflect-config.json" Json2Records.java

Here is the content of the reflect-config.json file, which specifies the reflection requirements needed for the native image:

[
  {
    "name": "Json2Records",
    "allDeclaredConstructors": true,
    "allPublicConstructors": true,
    "allDeclaredMethods": true,
    "allPublicMethods": true,
    "fields": [
      { "name": "jsonFile" },
      { "name": "rootName" },
      { "name": "packageName" },
      { "name": "nest" },
      { "name": "classFieldTypes" }
    ]
  },
  {
    "name": "picocli.CommandLine$AutoHelpMixin",
    "allDeclaredConstructors": true,
    "allPublicConstructors": true,
    "allDeclaredMethods": true,
    "allPublicMethods": true,
    "fields": [
      { "name": "helpRequested" },
      { "name": "versionRequested" }
    ]
  }
]

The reflection configuration is in theory something that can be sourced from info.picocli:picocli-codegen, but i found that isn’t working for me with jbang.

demo

You can view an example of the output in this asciinema recording:

© Copyright 2023 by David Norris.