如何在Restlet中注册Jackson Jdk8模块

Question

是否可以在Restlet org.restlet.ext.jackson扩展包中注册jackson-datatype-jdk8模块？我需要利用新的 Optional 功能。我的猜测是它应该可以通过转换器服务访问 (getConverterService())，但是我在文档中找不到任何内容可以准确地说明如何设置模块。

Answer 1

我最终从各种来源拼凑出一个适用于 Restlet 2.3 的答案。我的猜测是，这将针对 Restlet 3 进行重构，并且不适用于 < 2.3 的版本，因此请注意，此解决方案的保质期很可能有限。

第一步是创建一个自定义 Jackson 转换器来实现您的任何自定义要求：

public class CustomJacksonConverter extends JacksonConverter { 
    @Override 
    protected <T> JacksonRepresentation<T> create(MediaType mediaType, T source) { 
        ObjectMapper mapper = createMapper(); 
        JacksonRepresentation<T> jr = new JacksonRepresentation<T>(mediaType, source); 
        jr.setObjectMapper(mapper); 
        return jr; 
    } 

    @Override 
    protected <T> JacksonRepresentation<T> create(Representation source, Class<T> objectClass) { 
        ObjectMapper mapper = createMapper(); 
        JacksonRepresentation<T> jr = new JacksonRepresentation<T>(source, objectClass); 
        jr.setObjectMapper(mapper); 
        return jr; 
    } 


    private ObjectMapper createMapper() { 
        JsonFactory jsonFactory = new JsonFactory(); 
        jsonFactory.configure(JsonGenerator.Feature.AUTO_CLOSE_TARGET, false); 
        ObjectMapper mapper = new ObjectMapper(jsonFactory); 
        mapper.registerModule(new Jdk8Module()); 
        return mapper; 
    } 

}

然后您需要创建一种方法，用您的新转换器替换默认的 Jackson 转换器：

static void replaceConverter(
            Class<? extends ConverterHelper> converterClass,
            ConverterHelper newConverter) {

        ConverterHelper oldConverter = null;

        List<ConverterHelper> converters = Engine.getInstance().getRegisteredConverters();
        for (ConverterHelper converter : converters) {
            if (converter.getClass().equals(converterClass)) {
                converters.remove(converter);
                oldConverter = converter;
                break;
            }
        }

        converters.add(newConverter);
    }

您现在可以替换入站根中的转换器：

replaceConverter(JacksonConverter.class, new CustomJacksonConverter());

Answer 2

@tarka 开场不错，但给我流式传输错误；我提出一些 [影响较小] 的改进：

public class CustomJacksonConverter extends JacksonConverter {

    @Override
    protected <T> JacksonRepresentation<T> create(MediaType mediaType, T source) {
        return new CustomJacksonRepresentation<>(mediaType, source);
    }

    @Override
    protected <T> JacksonRepresentation<T> create(Representation source, Class<T> objectClass) {
        return new CustomJacksonRepresentation<>(source, objectClass);
    }

}

然后...

public class CustomJacksonRepresentation<T> extends JacksonRepresentation<T> {

    public CustomJacksonRepresentation(MediaType mediaType, T object) {
        super(mediaType, object);
    }

    public CustomJacksonRepresentation(Representation representation, Class<T> objectClass) {
        super(representation, objectClass);
    }

    public CustomJacksonRepresentation(T object) {
        super(object);
    }

    @Override
    protected ObjectMapper createObjectMapper() {
        ObjectMapper mapper = super.createObjectMapper();
        mapper.registerModule(new Jdk8Module());
        return mapper;
    }

}

并以与@tarka 相同的方式更换转换器

如何在Restlet中注册Jackson Jdk8模块

How to register Jackson Jdk8 module in Restlet

json

jackson

java-8

restlet-2.0