Package org.springframework.boot.json

Interface JsonWriter<T>

Type Parameters:
T - the type being written
Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface public 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(Consumer) 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(Object) method can be used if you want to write the JSON directly to a String. To write to other types of output, the write(Object) method may be used to obtain a WritableJson instance.

Since:
3.4.0

  • Method Details

    • write

      void write(T instance, Appendable out) throws IOException
      Write the given instance to the provided Appendable.
      Parameters:
      instance - the instance to write (may be null
      out - the output that should receive the JSON
      Throws:
      IOException - on IO error

    • writeToString

      default String writeToString(T instance)
      Write the given instance to a JSON string.
      Parameters:
      instance - the instance to write (may be null)
      Returns:
      the JSON string

    • write

      default WritableJson write(T instance)
      Provide a WritableJson implementation that may be used to write the given instance to various outputs.
      Parameters:
      instance - the instance to write (may be null)
      Returns:
      a WritableJson instance that may be used to write the JSON

    • withNewLineAtEnd

      default JsonWriter<T> withNewLineAtEnd()
      Return a new JsonWriter instance that appends a new line after the JSON has been written.
      Returns:
      a new JsonWriter instance that appends a new line after the JSON

    • withSuffix

      default JsonWriter<T> withSuffix(String suffix)
      Return a new JsonWriter instance that appends the given suffix after the JSON has been written.
      Parameters:
      suffix - the suffix to write, if any
      Returns:
      a new JsonWriter instance that appends a suffixafter the JSON

    • standard

      static <T> JsonWriter<T> standard()
      Factory method to return a JsonWriter for standard Java types. See class-level javadoc for details.
      Type Parameters:
      T - the type to write
      Returns:
      a JsonWriter instance

    • of

      static <T> JsonWriter<T> of(Consumer<JsonWriter.Members<T>> members)
      Factory method to return a JsonWriter with specific member mapping. See class-level javadoc and JsonWriter.Members for details.
      Type Parameters:
      T - the type to write
      Parameters:
      members - a consumer, which should configure the members
      Returns:
      a JsonWriter instance
      See Also: