在Jax-RS应用程序中注册JodaModule [英] Register JodaModule in Jax-RS Application

问题描述

我正在使用Jersey编写Jax-RS应用程序，并使用Jackson2来促进JSON i / o。服务本身工作正常，但我想通过让Jackson映射器自动将日期和日期时间序列化/反序列化为JodaTime对象来改进它。

I'm writing a Jax-RS application using Jersey, and Jackson2 under the hood to facilitate JSON i/o. The service itself works fine, but I'd like to improve it by having the Jackson mapper automagically serialize/deserialize date and date-times to JodaTime objects.

我是按照文档这里并添加了相关的罐子，但我在这个指令上丢失了：

I'm following the documentation here and have added the relevant jars, but I'm lost on this instruction:

Registering module

To use Joda datatypes with Jackson, you will first need to register the module first (same as with all Jackson datatype modules):

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JodaModule());

我试图在扩展jax.ws.rs.core的自定义类中执行此操作。应用程序，但我对该解决方案完全没有信心。我目前收到此错误：

I've tried to do this in the custom class that extends jax.ws.rs.core.Application, but I'm not at all confident in that solution. I'm currently getting this error:

Can not instantiate value of type [simple type, class org.joda.time.DateTime] from String value ('2014-10-22'); no single-String constructor/factory method
 at [Source: org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream@3471b6d5; line: 7, column: 25]

除了这个模块注册需要在应用程序（servlet？）启动，我不知道如何处理这些信息。我是否需要使用特定的东西来注释自定义类以使其被拾取？我应该延长课程吗？

Other than the general impression that this module registration needs to happen at application (servlet?) startup, I have no idea what to do with this information. Do I need to annotate a custom class with something in particular to have it picked up ? Should I be extending some class ?

我在StackOverflow上找到的示例通常会将其粘贴在 main（）中并直接调用映射器，但是我我依赖杰克逊数据绑定，因此这些例子无关紧要。任何方向都很受欢迎。

The examples I find on StackOverflow usually stick it in main() and call the mapper directly, but I'm relying on Jackson Databinding so the examples aren't relevant. Any direction is appreciated.

推荐答案

你基本上想要创建/配置/返回 ObjectMapper 在 ContextResolver 中。类似

You'll basically want to create/configure/return the ObjectMapper in a ContextResolver. Something like

@Provider
public class ObjectMapperContextResolver implements ContextResolver<ObjectMapper> {

    final ObjectMapper mapper = new ObjectMapper();

    public ObjectMapperContextResolver() {
        mapper.registerModule(new JodaModule());
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return mapper;
    }  
}

如果您使用包扫描来发现资源，那么 @Provider 注释应该允许发现和注册这个类。

If you are using package scanning to discover your resources, then the @Provider annotation should allow this class to be discovered and registered also.

基本上会发生什么，是 MessageBodyReader 和 MessageBodyWriter ，分别用于解组和编组，将调用 ContextResolver 中的 getContext 方法，以确定 ObjectMapper 使用。读者/作者将在类中传入（在读者中它将是方法参数中预期的类型，在编写器中它将是返回为-a / in-a响应的类型），这意味着我们可以使用不同的方式为不同的类配置 ObjectMapper ，如此处。在上面的解决方案中，它用于所有类。

Basically what happens, is the the MessageBodyReader and MessageBodyWriter provided by Jackson, used for unmarshalling and marshalling, respectively, will call the getContext method in the ContextResolver, to determine the ObjectMapper to use. The reader/writer will pass in the class (in a reader it will be the type expected in a method param, in a writer it will be the type returned as-a/in-a response), meaning we are allowed to use differently configured ObjectMapper for different classes, as seen here. In the above solution, it is used for all classes.

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