在this answer的基础上，我建立了一个简单的项目来测试使用Jersey来发送JSON序列化的POJO作为对HTTP请求的响应。但是，我无法从另一端的响应中提取POJO。
这是我与Jackson兼容的POJO，用于发送：
public class BoringObject {
private int val;
//empty constructor for Jackson
public BoringObject() {}
public BoringObject(int val) {
this.val = val;
}
public int getVal() {
return val;
}
public void setVal(int val) {
this.val = val;
}
}
以下是使用Jersey的测试框架来尝试发送和接收POJO的测试类：
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.client.Entity;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.test.DeploymentContext;
import org.glassfish.jersey.test.JerseyTest;
import org.glassfish.jersey.test.grizzly.GrizzlyTestContainerFactory;
import org.glassfish.jersey.test.spi.TestContainerFactory;
import static org.junit.Assert.assertEquals;
import org.junit.Test;
public class TestSendBoringObject extends JerseyTest {
@Override
protected TestContainerFactory getTestContainerFactory() {
return new GrizzlyTestContainerFactory();
}
@Override
protected DeploymentContext configureDeployment() {
return DeploymentContext.builder(new ResourceConfig(TestResource.class))
.contextPath("context1/context2")
.build();
}
@Path("test")
public static class TestResource {
@GET
@Produces(MediaType.APPLICATION_JSON)
public Response getJson() {
Response response = Response.status(Response.Status.OK)
.entity(Entity.json(new BoringObject(5)))
.type(MediaType.APPLICATION_JSON).build();
return response;
}
}
@Test
public void testGet() {
final WebTarget target = target("test");
Response response = target.request().get();
Entity<BoringObject> entity = response.readEntity(Entity.class);
BoringObject boringObj = entity.getEntity();
assertEquals(5, boringObj.getVal());
}
}
但是，当我运行此测试时，response.readEntity(Entity.class)调用会引发以下异常：
javax.ws.rs.ProcessingException: Error reading entity from input stream.
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:889)
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:808)
at org.glassfish.jersey.client.ClientResponse.readEntity(ClientResponse.java:321)
at org.glassfish.jersey.client.InboundJaxrsResponse$1.call(InboundJaxrsResponse.java:115)
at org.glassfish.jersey.internal.Errors.process(Errors.java:316)
at org.glassfish.jersey.internal.Errors.process(Errors.java:298)
at org.glassfish.jersey.internal.Errors.process(Errors.java:229)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:389)
at org.glassfish.jersey.client.InboundJaxrsResponse.runInScopeIfPossible(InboundJaxrsResponse.java:264)
at org.glassfish.jersey.client.InboundJaxrsResponse.readEntity(InboundJaxrsResponse.java:112)
at TestSendBoringObject.testGet(TestSendBoringObject.java:48)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.apache.maven.surefire.junit4.JUnit4TestSet.execute(JUnit4TestSet.java:53)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:123)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:104)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:164)
at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:110)
at org.apache.maven.surefire.booter.SurefireStarter.invokeProvider(SurefireStarter.java:175)
at org.apache.maven.surefire.booter.SurefireStarter.runSuitesInProcessWhenForked(SurefireStarter.java:107)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:68)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of javax.ws.rs.client.Entity: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
at [Source: org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream@c4ed84; line: 1, column: 2]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1456)
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1012)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1206)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148)
at com.fasterxml.jackson.databind.ObjectReader._bind(ObjectReader.java:1583)
at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:964)
at org.glassfish.jersey.jackson.internal.jackson.jaxrs.base.ProviderBase.readFrom(ProviderBase.java:838)
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$TerminalReaderInterceptor.invokeReadFrom(ReaderInterceptorExecutor.java:257)
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$TerminalReaderInterceptor.aroundReadFrom(ReaderInterceptorExecutor.java:236)
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor.proceed(ReaderInterceptorExecutor.java:156)
at org.glassfish.jersey.message.internal.MessageBodyFactory.readFrom(MessageBodyFactory.java:1091)
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:874)
... 41 more
这是我的POM：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.mine</groupId>
<artifactId>test</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.glassfish.jersey.test-framework</groupId>
<artifactId>jersey-test-framework-core</artifactId>
<version>2.27</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.test-framework.providers</groupId>
<artifactId>jersey-test-framework-provider-grizzly2</artifactId>
<version>2.27</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-jackson</artifactId>
<version>2.27</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.inject</groupId>
<artifactId>jersey-hk2</artifactId>
<version>2.27</version>
</dependency>
</dependencies>
</project>
为什么会出现此异常？我是否无法以某种方式正确配置Jackson？我特别困惑，因为它可以很好地序列化并发送Entity，但是当我尝试反序列化时却死了。我仍然对Jersey还是陌生的，所以我可能搞砸了一些基本的知识。非常感谢您的帮助！
已编辑，更多信息：
如果我改用readEntity(BoringObject.class)，则会得到一个异常，归结为“这不是序列化的BoringObject”：
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "entity" (class BoringObject), not marked as ignorable (one known property: "val"])
at [Source: org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream@40844aab; line: 1, column: 12] (through reference chain: BoringObject["entity"])
我认为这是因为我将BoringObject封装在Entity.json()调用中，同时将其放入响应中。 （我这样做是因为这就是我要通过此实验调试的真实代码所做的事情。）
如果我做readEntity(String.class)，则会得到以下内容，我认为这是一个序列化的Entity对象，因此尝试了readEntity(Entity.class)：
{
"entity": {
"val": 5
},
"variant": {
"language": null,
"mediaType": {
"type": "application",
"subtype": "json",
"parameters": {
},
"wildcardSubtype": false,
"wildcardType": false
},
"encoding": null,
"languageString": null
},
"annotations": [],
"language": null,
"encoding": null,
"mediaType": {
"type": "application",
"subtype": "json",
"parameters": {
},
"wildcardSubtype": false,
"wildcardType": false
}
}