我正在为 REST 端点制作服务客户端,使用 JAX-RS 客户端处理 HTTP 请求,并使用 Jackson 来(反)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,但我没有让它工作。
如何配置 JAX-RS 和/或 Jackson 以使用 jsr310 模块?
我使用以下依赖项:
<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>${jackson.version}</version>
</dependency>
我不想让服务客户端(作为库发布)依赖于任何特定的实现——比如 Jersey,所以我只依赖 JAX-RS API。为了运行我的集成测试,我添加了:
<dependency>
<groupId>org.glassfish.jersey.core</groupId>
<artifactId>jersey-client</artifactId>
<version>${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>
JAX-RS 客户端的实例化在工厂对象中完成,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();
}
典型的 DTO 如下所示:
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()
}
请求是这样完成的:
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 序列化和反序列化适用于字符串、整数、BigIntegers、列表等。但是,当我System.out.println(gateway.postSomthing(new Something("x", "y"));
在测试中执行类似操作时,会出现以下异常:
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,杰克逊不知道如何将字符串反序列化为即时。我找到了关于这个主题的博客和 SO 问题,但我没有找到关于如何使其工作的明确解释。
请注意,我希望服务客户端能够处理"Fri, 22 Sep 2017 10:26:52 GMT"
以及之类的日期字符串"2017-09-22T10:26:52.123Z"
,但我希望它始终序列化为 ISO 8601 日期字符串。
谁能解释一下如何将反序列化变成Instant
作品?