This is useful when testing web pages which consume Ajax-provided JSON.
I can define my JSON in a String and then use one of the below approaches to convert that into an object suitable to be processed as a JSON response to an Ajax request. In this way, I do not need to create custom POJOs or any nested maps/arrays.
Using Jackson
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<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.12.1</version>
</dependency>
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import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.JsonNode;
...
private JsonNode getJson() throws JsonProcessingException {
String jsonString = "your arbitrary JSON";
ObjectMapper objectMapper = new ObjectMapper();
return objectMapper.readTree(jsonString);
}
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Using Gson
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<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.6</version>
</dependency>
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Java
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import com.google.gson.Gson;
import java.util.ArrayList;
import java.util.LinkedHashMap;
...
// For a JSON object "{ ... }":
private LinkedHashMap getJsonObject() {
String jsonObject = "your arbitrary JSON object";
return new Gson().fromJson(jsonObject, LinkedHashMap.class);
}
// For a JSON array "[ ... ]":
private ArrayList getJsonArray() {
String jsonArray = "your arbitrary JSON array";
return new Gson().fromJson(jsonArray, ArrayList.class);
}
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Javalin
I often use Javalin![]()
as my web app - in which case I use its built-in support for Jackson.
A basic Javalin set-up:
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<dependency>
<groupId>io.javalin</groupId>
<artifactId>javalin-bundle</artifactId>
<version>3.13.6</version>
</dependency>
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import io.javalin.Javalin;
import io.javalin.http.Context;
...
public class App {
public static void main(String[] args) {
Javalin app = Javalin.create(config -> {
config.enableCorsForAllOrigins(); // for testing only!
}).start(7001);
app.get("/test", ctx -> ctx.json(getJson())); // uses Jackson
}
}
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