Convert Java pojo to json String

Question

I have the following java class

public  class TabularDescriptor extends ReportDescriptor {

    private String generatorClass;
    private String targetClass;
    private String name;
    private String sublabel;
    private String reportName;
    private List<MappingMetadata> mappings = null;
    private List<TabularColumnGroup> columnGroups = null;
    private List<TabularStates> states = null;
:
:
     and its getters and settere

I have entity classes for each of those List like MappingMetadata,TabularColumnGroup,TabularStates. I want to get a json data for this pojo classes. What can I do for it.

And what is the use of

    public JSONObject toJSON() {
        JSONObject ret = new JSONObject();
        ret.put("generatorClass", this.generatorClass);
        ret.put("targetClass", this.targetClass);
        ret.put("name", this.name);
        :
        :
        return ret;
    }

And is there anyway I can display my json content on browser if yes how can I? Thanks.

Have a look at github.com/google/gson. It seems to be exactly what you're looking for. You can easily serialize and deserialize Java Objects using it. — Ian Rehwinkel
– Ian Rehwinkel, Commented Jan 9, 2020 at 20:23

improbable · Accepted Answer · 2023-09-11 16:11:34Z

There are 2 libraries that deal with JSON serialization/deserialization using Java:

Jackson

The go-to library for Java serialization/deserialization(docs). A default choice for the JSON interaction within Java for the majority of developers. Comes completely embedded with all dependencies in spring-boot-starter-web and spring-boot-starter-webflux, dependency starters of Spring Boot - popular Java IOC/DI framework.

Dependencies _{(databind is the main dependency, for annotations and additional features you will need more Jackson dependencies)}:

Maven:
```
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>${jackson.version}</version>   
</dependency>
```
Gradle:
```
dependencies {
   implementation "com.fasterxml.jackson.core:jackson-databind:${yourVersion}"
}
```
Serialization Snippet:
```
TabularDescriptor tabularDescriptor = new TabularDescriptor();
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(tabularDescriptor);
```

Gson

Google's library for a Java serialization/deserialization(docs).

Dependencies:

Gradle:

dependencies { 
    implementation "com.google.code.gson:gson:${yourVersion}"
}

Maven:

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>${gson.version}</version>
</dependency>

Serialization Snippet:

TabularDescriptor tabularDescriptor = new TabularDescriptor();
Gson gson = new Gson();
String json = gson.toJson(obj);

Details worth noting: You have to have all getters/setters public for both complete serialization and complete deserialization of an object(in its simplest form). An empty constructor is a must in any case.

Reference Information:

Vladucu Voican · Accepted Answer · 2020-01-09 20:25:54Z

6

I would recommend you to add Jackson to your project, it's rather easy to use.

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.8</version>
</dependency>

And in Java Code can be used as so:

ObjectMapper objectMapper = new ObjectMapper();
String json = objectMapper.writeValueAsString(tabularDescriptor);
TabularDescriptor newTabularDescriptor = objectMapper.readValue(json, TabularDescriptor.class);

answered Jan 9, 2020 at 20:25

Vladucu Voican

2851 silver badge11 bronze badges

3 Comments

Lilac Over a year ago

Thank you. What is value in tabularDescriptor. Is it the value I set using its setter? If yes how can I set value to pojo classes like MappingMetadata.

Vladucu Voican Over a year ago

@Lilac 1) tabularDescriptor is your object e.g. TabularDescriptor tabularDescriptor = new TabularDescriptor(...); 2) Not sure that I get what you mean here. Are you refering to how to create objects? Easiest way is to use a Builder Pattern, especially in your case since you have a lot of inner objects in the tabular descriptor.

Lilac Over a year ago

Thank you. I wasn't sure how to give values for the inner objects.

Community · Accepted Answer · 2020-06-20 09:12:55Z

4

You can use ObjectMapper or Gson for Class to JSON conversion and vice-versa.

(I would recommend ObjectMapper)

Object Mapper

Intro to the Jackson ObjectMapper

GSON

How to convert Java object to / from JSON

Comparison

Jackson(ObjectMapper) vs Gson

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Jan 9, 2020 at 20:29

Mehrdad Yami

1,6911 gold badge14 silver badges26 bronze badges

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Convert Java pojo to json String

3 Answers 3

Jackson

Dependencies _{(databind is the main dependency, for annotations and additional features you will need more Jackson dependencies)}:

Serialization Snippet:

Gson

Dependencies:

Serialization Snippet:

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Dependencies (databind is the main dependency, for annotations and additional features you will need more Jackson dependencies):

Serialization Snippet:

Dependencies:

Serialization Snippet:

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Dependencies _{(databind is the main dependency, for annotations and additional features you will need more Jackson dependencies)}: