In this example, we will see how to write a JSON to a file with JSON-P library.
The code example is available at my Github repository.
- Check out complete JSON-P tutorial at Java JSON Processing Tutorial.
- Check out the Jackson JSON tutorial at https://www.javaguides.net/p/java-jackson-json-tutorial-with-examples.html.
- Check out google GSON tutorial at Google GSON Tutorial.
JSON-P
JSON Processing (JSON-P) is a Java API to process (for e.g. parse, generate, transform and query) JSON messages. It produces and consumes JSON text in a streaming fashion (similar to StAX API for XML) and allows to build a Java object model for JSON text using API classes (similar to DOM API for XML).
Read more about JSON-P at official documentation - https://javaee.github.io/jsonp.
Add Dependencies
JSON-P is the reference implementation for Java JSON Processing API. We can use this in maven project by adding the following dependencies:
<dependency>
<groupId>javax.json</groupId>
<artifactId>javax.json-api</artifactId>
<version>1.1</version>
</dependency>
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.json</artifactId>
<version>1.1</version>
</dependency>
Let's create a JSON file named "posts.json":
{
"id": 100,
"title": "JSONP Tutorial",
"description": "Post about JSONP",
"content": "HTML content here",
"tags": [
"Java",
"JSON"
]
}
We have Java bean classes that represent above JSON format as:
package net.javaguides.jsonp.tutorial;
import java.util.Arrays;
public class Post {
private int id;
private String title;
private String description;
private String content;
private String[] tags;
public Post() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public String[] getTags() {
return tags;
}
public void setTags(String[] tags) {
this.tags = tags;
}
@Override
public String toString() {
return "Post [id=" + id + ", title=" + title + ", description=" + description + ", content=" + content +
", tags=" + Arrays.toString(tags) + "]";
}
}
Java JSON Write Example
In this example, we write Post Java bean object into JSON file "posts.json". In the below example we use JsonGenerator.PRETTY_PRINTING configuration setting so we can set the writer for pretty printing.
package net.javaguides.jsonp.tutorial;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;
import javax.json.Json;
import javax.json.JsonArrayBuilder;
import javax.json.JsonObject;
import javax.json.JsonObjectBuilder;
import javax.json.JsonWriter;
import javax.json.JsonWriterFactory;
import javax.json.stream.JsonGenerator;
/**
* Class to write json to a posts.json file.
* @author Ramesh fadatare
*
*/
public class WriteJSON {
public static void main(String[] args) throws FileNotFoundException {
Post post = createPost();
JsonObjectBuilder postBuilder = Json.createObjectBuilder();
JsonArrayBuilder tagsBuilder = Json.createArrayBuilder();
for (String tag: post.getTags()) {
tagsBuilder.add(tag);
}
postBuilder.add("id", post.getId())
.add("title", post.getTitle())
.add("description", post.getDescription())
.add("content", post.getContent())
.add("tags", tagsBuilder);
JsonObject postJsonObject = postBuilder.build();
System.out.println("Post JSON String -> " + postJsonObject);
//write to file
OutputStream os = new FileOutputStream("posts.json");
JsonWriter jsonWriter = Json.createWriter(os);
Map < String, Boolean > config = new HashMap < String, Boolean > ();
config.put(JsonGenerator.PRETTY_PRINTING, true);
JsonWriterFactory factory = Json.createWriterFactory(config);
jsonWriter = factory.createWriter(os);
jsonWriter.writeObject(postJsonObject);
jsonWriter.close();
}
private static Post createPost() {
// create a post
Post post = new Post();
post.setTitle("JSONP Tutorial");
post.setId(100);
post.setDescription("Post about JSONP");
post.setContent("HTML content here");
String[] tags = {
"Java",
"JSON"
};
// create some predefined tags
post.setTags(tags);
// set tags to post
return post;
}
}
Let's understand above Java JSON write an example.
The main JSON-P entry point is the Json class. It provides all the necessary methods to parse and build JSON strings from Java. Json is a singleton containing static factory methods for all relevant elements of the JSON-P API.
JsonObjectBuilder postBuilder = Json.createObjectBuilder();
JsonArrayBuilder tagsBuilder = Json.createArrayBuilder();
We created a Json object as:
postBuilder.add("id", post.getId())
.add("title", post.getTitle())
.add("description", post.getDescription())
.add("content", post.getContent())
.add("tags", tagsBuilder);
JsonObject postJsonObject = postBuilder.build();
Writing above created to "posts.json" file and print pretty with JsonGenerator.PRETTY_PRINTING setting:
//write to file
OutputStream os = new FileOutputStream("posts.json");
JsonWriter jsonWriter = Json.createWriter(os);
Map<String, Boolean> config = new HashMap<String, Boolean>();
config.put(JsonGenerator.PRETTY_PRINTING, true);
JsonWriterFactory factory = Json.createWriterFactory(config);
jsonWriter = factory.createWriter(os);
jsonWriter.writeObject(postJsonObject);
jsonWriter.close();
The code example is available at my Github repository.
- Check out complete JSON-P tutorial at Java JSON Processing Tutorial.
- Check out the Jackson JSON tutorial at https://www.javaguides.net/p/java-jackson-json-tutorial-with-examples.html.
- Check out google GSON tutorial at Google GSON Tutorial.
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