import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;

import java.io.IOException;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class LocalDateSerializer extends StdSerializer<LocalDate> {

    private static final long serialVersionUID = 1L;

    public LocalDateSerializer() {
        super(LocalDate.class);
    }

    @Override
    public void serialize(LocalDate value, JsonGenerator gen, SerializerProvider sp) throws IOException {
        gen.writeString(value.format(DateTimeFormatter.ISO_LOCAL_DATE));
    }
}

This is an example of a custom serializer for the Java 8 LocalDate class, using the com.fasterxml.jackson.databind.ser.std.StdSerializer class from the Jackson library. The serializer overrides the serialize method to write the LocalDate object as an ISO-formatted string.

The com.fasterxml.jackson.databind.annotation.JacksonStdImpl annotation is used in Jackson to indicate that a class is the standard implementation of a certain type of serializer or deserializer.

For example, the following class is a standard deserializer for the java.time.LocalDate class:

@JacksonStdImpl
public class LocalDateDeserializer extends StdDeserializer<LocalDate> {
    ...
}

By annotating this class with @JacksonStdImpl, Jackson will know that this is the standard deserializer for the LocalDate class and it will be used by default unless another deserializer is registered for this class.

It is important to note that this annotation is only used as a marker, it doesn't add any functionality itself.