将具体的实现连接到blueprint.xml中的接口

Question

Background

Looking to wire a concrete class to a parameter for a REST server's @POST method within blueprint.xml .

Problem

Jackson data binding cannot find the concrete implementation for the method's send parameter.

Code

Java

The REST server has a single send method, defined as:

public interface NotificationServer {
    @POST
    Response send(NotificationRequest notificationRequest);
}

The NotificationRequest is also an interface:

public interface NotificationRequest {

A concrete implementation of NotificationServer , called EmailNotificationServerImpl , implements the interface:

public class EmailNotificationServerImpl implements NotificationServer {
    @Override
    public Response send(final NotificationRequest request) {

Blueprint

The relevant parts of blueprint.xml include:

<bean class="EmailNotificationServerImpl" id="emailNotificationServerImpl">...</bean>
<bean class="NotificationRequestImpl" id="notificationRequestImpl" />
<service interface="NotificationRequest" ref="notificationRequestImpl" />

Exception

The Jackson error message:

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of NotificationRequest: abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information

Deserialize

It is possible to deserialize the class using:

@JsonDeserialize(as = NotificationRequestImpl.class)
public interface NotificationRequest {

While this works, it doesn't fully decouple the implementation from the interface.

Question

How can the concrete implementation be wired in blueprint.xml so that the @JsonDeseralize annotation is not necessary?

Environment

• Java 1.8
• Apache Camel 2.x
• JAX-RS 2.1
• Jackson JAX-RS JSON Provider 2.9.x
• OSGi 1.2.1
• Not using Spring

Answer 1

Use a custom provider that extends JacksonJsonProvider in JAX-RS server definition within the <jaxrs:providers> tag.

Or use a custom deserializer that extends StdSerializer :

@JsonDeserialize(using = YourDeserializer.java)

Or use polymorphism and @JsonTypeInfo + @JsonSubtypes annotations.