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

Author:

Phillip Webb, Moritz Halbritter

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static final class	JsonWriter.Member<T>	A member that contributes JSON.
static final record	JsonWriter.MemberPath	A path used to identify a specific JSON member.
static final class	JsonWriter.Members<T>	Callback used to configure JSON members.
static interface	JsonWriter.NameProcessor	Callback interface that can be applied to JsonWriter.Members to change names or filter members.
static interface	JsonWriter.PairExtractor<E>	Interface that can be used to extract name/value pairs from an element.
static interface	JsonWriter.ValueProcessor<T>	Callback interface that can be applied to JsonWriter.Members to process values before they are written.

Method Summary

Modifier and Type	Method	Description
static <T> JsonWriter<T>	of(Consumer<JsonWriter.Members<T>> members)	Factory method to return a JsonWriter with specific member mapping.
static <T> JsonWriter<T>	standard()	Factory method to return a JsonWriter for standard Java types.
default JsonWriter<T>	withNewLineAtEnd()	Return a new JsonWriter instance that appends a new line after the JSON has been written.
default JsonWriter<T>	withSuffix(String suffix)	Return a new JsonWriter instance that appends the given suffix after the JSON has been written.
default WritableJson	write(T instance)	Provide a WritableJson implementation that may be used to write the given instance to various outputs.
void	write(T instance, Appendable out)	Write the given instance to the provided Appendable.
default String	writeToString(T instance)	Write the given instance to a JSON string.

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:

• JsonWriter.Members