How to fluently build JSON in Java?
I am using the org.json library and found it to be nice and friendly.
Example:
String jsonString = new JSONObject()
.put("JSON1", "Hello World!")
.put("JSON2", "Hello my World!")
.put("JSON3", new JSONObject().put("key1", "value1"))
.toString();
System.out.println(jsonString);
OUTPUT:
{"JSON2":"Hello my World!","JSON3":{"key1":"value1"},"JSON1":"Hello World!"}
I recently created a library for creating Gson objects fluently:
http://jglue.org/fluent-json/
It works like this:
JsonObject jsonObject = JsonBuilderFactory.buildObject() //Create a new builder for an object
.addNull("nullKey") //1. Add a null to the object
.add("stringKey", "Hello") //2. Add a string to the object
.add("stringNullKey", (String) null) //3. Add a null string to the object
.add("numberKey", 2) //4. Add a number to the object
.add("numberNullKey", (Float) null) //5. Add a null number to the object
.add("booleanKey", true) //6. Add a boolean to the object
.add("booleanNullKey", (Boolean) null) //7. Add a null boolean to the object
.add("characterKey", 'c') //8. Add a character to the object
.add("characterNullKey", (Character) null) //9. Add a null character to the object
.addObject("objKey") //10. Add a nested object
.add("nestedPropertyKey", 4) //11. Add a nested property to the nested object
.end() //12. End nested object and return to the parent builder
.addArray("arrayKey") //13. Add an array to the object
.addObject() //14. Add a nested object to the array
.end() //15. End the nested object
.add("arrayElement") //16. Add a string to the array
.end() //17. End the array
.getJson(); //Get the JsonObject
String json = jsonObject.toString();
And through the magic of generics it generates compile errors if you try to add an element to an array with a property key or an element to an object without a property name:
JsonObject jsonArray = JsonBuilderFactory.buildArray().addObject().end().add("foo", "bar").getJson(); //Error: tried to add a string with property key to array.
JsonObject jsonObject = JsonBuilderFactory.buildObject().addArray().end().add("foo").getJson(); //Error: tried to add a string without property key to an object.
JsonArray jsonArray = JsonBuilderFactory.buildObject().addArray("foo").getJson(); //Error: tried to assign an object to an array.
JsonObject jsonObject = JsonBuilderFactory.buildArray().addObject().getJson(); //Error: tried to assign an object to an array.
Lastly there is mapping support in the API which allows you to map your domain objects to JSON. The goal being when Java8 is released you'll be able to do something like this:
Collection<User> users = ...;
JsonArray jsonArray = JsonBuilderFactory.buildArray(users, { u-> buildObject()
.add("userName", u.getName())
.add("ageInYears", u.getAge()) })
.getJson();
If you are using Jackson do a lot of JsonNode building in code, you may be interesting in the following set of utilities. The benefit of using them is that they support a more natural chaining style that better shows the structure of the JSON under construction.
Here is an example usage:
import static JsonNodeBuilders.array;
import static JsonNodeBuilders.object;
...
val request = object("x", "1").with("y", array(object("z", "2"))).end();
Which is equivalent to the following JSON:
{"x":"1", "y": [{"z": "2"}]}
Here are the classes:
import static lombok.AccessLevel.PRIVATE;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.ObjectNode;
import lombok.NoArgsConstructor;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
import lombok.val;
/**
* Convenience {@link JsonNode} builder.
*/
@NoArgsConstructor(access = PRIVATE)
public final class JsonNodeBuilders {
/**
* Factory methods for an {@link ObjectNode} builder.
*/
public static ObjectNodeBuilder object() {
return object(JsonNodeFactory.instance);
}
public static ObjectNodeBuilder object(@NonNull String k1, boolean v1) {
return object().with(k1, v1);
}
public static ObjectNodeBuilder object(@NonNull String k1, int v1) {
return object().with(k1, v1);
}
public static ObjectNodeBuilder object(@NonNull String k1, float v1) {
return object().with(k1, v1);
}
public static ObjectNodeBuilder object(@NonNull String k1, String v1) {
return object().with(k1, v1);
}
public static ObjectNodeBuilder object(@NonNull String k1, String v1, @NonNull String k2, String v2) {
return object(k1, v1).with(k2, v2);
}
public static ObjectNodeBuilder object(@NonNull String k1, String v1, @NonNull String k2, String v2,
@NonNull String k3, String v3) {
return object(k1, v1, k2, v2).with(k3, v3);
}
public static ObjectNodeBuilder object(@NonNull String k1, JsonNodeBuilder<?> builder) {
return object().with(k1, builder);
}
public static ObjectNodeBuilder object(JsonNodeFactory factory) {
return new ObjectNodeBuilder(factory);
}
/**
* Factory methods for an {@link ArrayNode} builder.
*/
public static ArrayNodeBuilder array() {
return array(JsonNodeFactory.instance);
}
public static ArrayNodeBuilder array(@NonNull boolean... values) {
return array().with(values);
}
public static ArrayNodeBuilder array(@NonNull int... values) {
return array().with(values);
}
public static ArrayNodeBuilder array(@NonNull String... values) {
return array().with(values);
}
public static ArrayNodeBuilder array(@NonNull JsonNodeBuilder<?>... builders) {
return array().with(builders);
}
public static ArrayNodeBuilder array(JsonNodeFactory factory) {
return new ArrayNodeBuilder(factory);
}
public interface JsonNodeBuilder<T extends JsonNode> {
/**
* Construct and return the {@link JsonNode} instance.
*/
T end();
}
@RequiredArgsConstructor
private static abstract class AbstractNodeBuilder<T extends JsonNode> implements JsonNodeBuilder<T> {
/**
* The source of values.
*/
@NonNull
protected final JsonNodeFactory factory;
/**
* The value under construction.
*/
@NonNull
protected final T node;
/**
* Returns a valid JSON string, so long as {@code POJONode}s not used.
*/
@Override
public String toString() {
return node.toString();
}
}
public final static class ObjectNodeBuilder extends AbstractNodeBuilder<ObjectNode> {
private ObjectNodeBuilder(JsonNodeFactory factory) {
super(factory, factory.objectNode());
}
public ObjectNodeBuilder withNull(@NonNull String field) {
return with(field, factory.nullNode());
}
public ObjectNodeBuilder with(@NonNull String field, int value) {
return with(field, factory.numberNode(value));
}
public ObjectNodeBuilder with(@NonNull String field, float value) {
return with(field, factory.numberNode(value));
}
public ObjectNodeBuilder with(@NonNull String field, boolean value) {
return with(field, factory.booleanNode(value));
}
public ObjectNodeBuilder with(@NonNull String field, String value) {
return with(field, factory.textNode(value));
}
public ObjectNodeBuilder with(@NonNull String field, JsonNode value) {
node.set(field, value);
return this;
}
public ObjectNodeBuilder with(@NonNull String field, @NonNull JsonNodeBuilder<?> builder) {
return with(field, builder.end());
}
public ObjectNodeBuilder withPOJO(@NonNull String field, @NonNull Object pojo) {
return with(field, factory.pojoNode(pojo));
}
@Override
public ObjectNode end() {
return node;
}
}
public final static class ArrayNodeBuilder extends AbstractNodeBuilder<ArrayNode> {
private ArrayNodeBuilder(JsonNodeFactory factory) {
super(factory, factory.arrayNode());
}
public ArrayNodeBuilder with(boolean value) {
node.add(value);
return this;
}
public ArrayNodeBuilder with(@NonNull boolean... values) {
for (val value : values)
with(value);
return this;
}
public ArrayNodeBuilder with(int value) {
node.add(value);
return this;
}
public ArrayNodeBuilder with(@NonNull int... values) {
for (val value : values)
with(value);
return this;
}
public ArrayNodeBuilder with(float value) {
node.add(value);
return this;
}
public ArrayNodeBuilder with(String value) {
node.add(value);
return this;
}
public ArrayNodeBuilder with(@NonNull String... values) {
for (val value : values)
with(value);
return this;
}
public ArrayNodeBuilder with(@NonNull Iterable<String> values) {
for (val value : values)
with(value);
return this;
}
public ArrayNodeBuilder with(JsonNode value) {
node.add(value);
return this;
}
public ArrayNodeBuilder with(@NonNull JsonNode... values) {
for (val value : values)
with(value);
return this;
}
public ArrayNodeBuilder with(JsonNodeBuilder<?> value) {
return with(value.end());
}
public ArrayNodeBuilder with(@NonNull JsonNodeBuilder<?>... builders) {
for (val builder : builders)
with(builder);
return this;
}
@Override
public ArrayNode end() {
return node;
}
}
}
Note that the implementation uses Lombok, but you can easily desugar it to fill in the Java boilerplate.
See the Java EE 7 Json specification. This is the right way:
String json = Json.createObjectBuilder()
.add("key1", "value1")
.add("key2", "value2")
.build()
.toString();