spring-boot/org.springframework.boot.json/JsonWriter

JsonWriter

@FunctionalInterface

interface JsonWriter<T>

Interface that can be used to write JSON output. Typically used to generate JSON when a dependency on a fully marshalling library (such as Jackson or Gson) cannot be assumed.

For standard Java types, the standard factory method may be used to obtain an instance of this interface. It supports String, Number and Boolean as well as Collection, Array, Map and WritableJson types. Typical usage would be:

JsonWriter<Map<String,Object>> writer = JsonWriter.standard();
writer.write(Map.of("Hello", "World!"), out);

More complex mappings can be created using the of method with a callback to configure the JSON members that should be written. Typical usage would be:

JsonWriter<Person> writer = JsonWriter.of((members) -> {
    members.add("first", Person::firstName);
    members.add("last", Person::lastName);
    members.add("dob", Person::dateOfBirth)
        .whenNotNull()
        .as(DateTimeFormatter.ISO_DATE::format);
});
writer.write(person, out);

The writeToString method can be used if you want to write the JSON directly to a String. To write to other types of output, the write method may be used to obtain a WritableJson instance.

Author

Phillip Webb

Moritz Halbritter

Since

3.4.0

Parameters

<T>

the type being written

Types

class Member<T>

A member that contributes JSON.

class MemberPath : Record

A path used to identify a specific JSON member.

class Members<T>

Callback used to configure JSON members.

@FunctionalInterface

interface NameProcessor

Callback interface that can be applied to Members to change names or filter members.

interface PairExtractor<E>

Interface that can be used to extract name/value pairs from an element.

@FunctionalInterface

interface ValueProcessor<T>

Callback interface that can be applied to Members to process values before they are written.

Functions

open fun <T> of(members: Consumer<JsonWriter.Members<T>>): JsonWriter<T>

Factory method to return a JsonWriter with specific member mapping.

open fun <T> standard(): JsonWriter<T>

Factory method to return a JsonWriter for standard Java types.

withNewLineAtEnd

open fun withNewLineAtEnd(): JsonWriter<T>

Return a new JsonWriter instance that appends a new line after the JSON has been written.

open fun withSuffix(suffix: String): JsonWriter<T>

Return a new JsonWriter instance that appends the given suffix after the JSON has been written.

open fun write(instance: T): WritableJson

Provide a WritableJson implementation that may be used to write the given instance to various outputs.

abstract fun write(instance: T, out: Appendable)

Write the given instance to the provided Appendable.

open fun writeToString(instance: T): String

Write the given instance to a JSON string.