JAX-RS客户端对Java8日期/时间的杰克逊（德）序列化

Question

我正在为REST端点制作serivce客户端，使用JAX-RS客户端进行HTTP请求，并使用杰克逊对（序列化）JSON实体。为了处理JSR-310（Java8）日期/时间对象，我将com.fasterxml.jackson.datatype:jackson-datatype-jsr310模块作为依赖项添加到服务客户端，但我没有得到它的工作。

如何配置JAX-RS和/或Jackson使用jsr310模块？

我用下面的依赖关系：

<dependency> 
    <groupId>javax.ws.rs</groupId> 
    <artifactId>javax.ws.rs-api</artifactId> 
    <version>${jax-rs.version}</version> 
</dependency> 
<dependency> 
    <groupId>com.fasterxml.jackson.core</groupId> 
    <artifactId>jackson-annotations</artifactId> 
    <version>${jackson.version}</version> 
</dependency> 
<dependency> 
    <groupId>com.fasterxml.jackson.datatype</groupId> 
    <artifactId>jackson-datatype-jsr310</artifactId> 
    <version>${jackson.version}</version> 
</dependency> 

我不想让服务客户端（被释放库）依赖于任何特定的实现 - 新泽西州一样，所以我只能依靠JAX-RS API。运行我的集成测试我说：

<dependency> 
    <groupId>org.glassfish.jersey.core</groupId> 
    <artifactId>jersey-client</artifactId> 
    <version>${jersey.version}</version> 
    <scope>test</scope> 
</dependency> 
<dependency> 
    <groupId>org.glassfish.jersey.inject</groupId> 
    <artifactId>jersey-hk2</artifactId> 
    <version>${jersey.version}</version> 
    <scope>test</scope> 
</dependency> 
<dependency> 
    <groupId>org.glassfish.jersey.media</groupId> 
    <artifactId>jersey-media-json-jackson</artifactId> 
    <version>${jersey.version}</version> 
    <scope>test</scope> 
</dependency> 

的JAX-RS客户端的实例化是在工厂对象来完成，如下所示：

import javax.ws.rs.Produces; 
import javax.ws.rs.client.Client; 
import javax.ws.rs.client.ClientBuilder; 

@Produces 
public Client produceClient() { 
    return ClientBuilder.newClient(); 
} 

一个典型的DTO是这样的：

import com.fasterxml.jackson.annotation.JsonCreator; 
import com.fasterxml.jackson.annotation.JsonProperty; 
import com.fasterxml.jackson.annotation.JsonPropertyOrder; 

import java.time.Instant; 

import static java.util.Objects.requireNonNull; 

@JsonPropertyOrder({"n", "t"}) 
public final class Message { 

    private final String name; 
    private final Instant timestamp; 

    @JsonCreator 
    public Message(@JsonProperty("n" final String name, 
        @JsonProperty("t" final Instant timestamp) { 
     this.name = requireNonNull(name); 
     this.timestamp = requireNonNull(timestamp); 
    } 

    @JsonProperty("n") 
    public String getName() { 
     return this.name; 
    } 

    @JsonProperty("t") 
    public Instant getTimestamp() { 
     return this.timestamp; 
    } 

    // equals(Object), hashCode() and toString() 
} 

的请求做过这样的：

import javax.ws.rs.client.Entity; 
import javax.ws.rs.client.WebTarget; 
import javax.ws.rs.core.MediaType; 

public final class Gateway { 

    private final WebTarget endpoint; 

    public Message postSomething(final Something something) { 
     return this.endpoint 
       .request(MediaType.APPLICATION_JSON_TYPE) 
       .post(Entity.json(something), Message.class); 
    } 

    // where Message is the class defined above and Something is a similar DTO 
} 

JSON序列化和反序列化工作正常的字符串，整型，BigIntegers，列表等。然而，当我做这样的事情在我的测试System.out.println(gateway.postSomthing(new Something("x", "y"));我得到以下异常：

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `java.time.Instant` (no Creators, like default construct, exist): no String-argument constructor/factory method to deserialize from String value ('Fri, 22 Sep 2017 10:26:52 GMT') 
at [Source: (org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream); line: 1, column: 562] (through reference chain: Message["t"]) 
     at org.example.com.ServiceClientTest.test(ServiceClientTest.java:52) 
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: 
Cannot construct instance of `java.time.Instant` (no Creators, like default construct, exist): no String-argument constructor/factory method to deserialize from String value ('Fri, 22 Sep 2017 10:26:52 GMT') 
at [Source: (org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream); line: 1, column: 562] (through reference chain: Message["t"]) 
     at org.example.com.ServiceClientTest.test(ServiceClientTest.java:52) 

从中我得出结论，杰克逊没有按不知道如何将字符串反序列化为Instants。我发现了关于这个主题的博客和SO问题，但是我没有找到关于如何使其工作的明确解释。

请注意，我希望服务客户端处理日期字符串，如"Fri, 22 Sep 2017 10:26:52 GMT"以及"2017-09-22T10:26:52.123Z"，但我希望它始终序列化为ISO 8601日期字符串。

谁可以解释如何使反序列化成Instant工作？

Answer 1

在示例代码中，您当前取决于jersey-media-json-jackson。根据杰克逊的JAX-RS JSON，您可能会更好一些，因为您可以使用标准JAX-RS API（以及Jackson API的cource）配置杰克逊映射器。

<dependency> 
     <groupId>com.fasterxml.jackson.jaxrs</groupId> 
     <artifactId>jackson-jaxrs-json-provider</artifactId> 
     <version>${jackson.version}</version> 
    </dependency> 

卸下球衣，媒体JSON - 杰克逊并添加杰克逊JAXRS JSON的提供商的依赖后，你可以配置JacksonJaxbJsonProvider和产生客户端类注册它：

import com.fasterxml.jackson.databind.ObjectMapper; 
import com.fasterxml.jackson.databind.SerializationFeature; 
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule; 
import com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider; 
import com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider; 

import javax.ws.rs.Produces; 
import javax.ws.rs.client.Client; 
import javax.ws.rs.client.ClientBuilder; 

import static com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider.DEFAULT_ANNOTATIONS; 

public class ClientProducer { 

    private JacksonJsonProvider jsonProvider; 

    public ClientProducer() { 
     // Create an ObjectMapper to be used for (de)serializing to/from JSON. 
     ObjectMapper objectMapper = new ObjectMapper(); 
     // Register the JavaTimeModule for JSR-310 DateTime (de)serialization 
     objectMapper.registerModule(new JavaTimeModule()); 
     // Configure the object mapper te serialize to timestamp strings. 
     objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false); 
     // Create a Jackson Provider 
     this.jsonProvider = new JacksonJaxbJsonProvider(objectMapper, DEFAULT_ANNOTATIONS); 
    } 

    @Produces 
    public Client produceClient() { 

     return ClientBuilder.newClient() 
       // Register the jsonProvider 
       .register(this.jsonProvider); 
    } 
} 

希望这有助于。