ClientRequest，如何正确地将 POJO 序列化为 json 数据？找不到内容类型应用程序/json 类型的编写器：答案

【问题标题】：ClientRequest, how to serialize POJO's to json data correctly? could not find writer for content-type application/json type:ClientRequest，如何正确地将 POJO 序列化为 json 数据？找不到内容类型应用程序/json 类型的编写器：
【发布时间】：2013-08-07 15:07:27
【问题描述】：

对于 REST 服务 (RESTeasy)，我创建了 JUnit 测试用例，例如：

@Test
public void a100_insertAddressTest() throws Exception {
     Address addr = new Address(1, "testStreet", "1", (short) 1234,
     "testCity");

    ClientRequest request = new ClientRequest(BASE_URL + "customerID/{id}",
            sslExecutor_schusb);
    request.body(MediaType.APPLICATION_XML, addr).pathParameter(
            "id", 1);
    ClientResponse<String> response = request.post(String.class);

    Assert.assertEquals(201, response.getStatus());

    response.releaseConnection();
    request.clear();
}

如果我将请求正文的媒体类型更改为“application/json”，则测试用例失败并出现错误：

java.lang.RuntimeException: could not find writer for content-type application/json type: at.fhj.ase.dao.data.Address
    at org.jboss.resteasy.client.ClientRequest.writeRequestBody(ClientRequest.java:469)
    at org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.loadHttpMethod(ApacheHttpClient4Executor.java:221)
    at org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.execute(ApacheHttpClient4Executor.java:107)
    at org.jboss.resteasy.core.interception.ClientExecutionContextImpl.proceed(ClientExecutionContextImpl.java:39)
    at org.jboss.resteasy.plugins.interceptors.encoding.AcceptEncodingGZIPInterceptor.execute(AcceptEncodingGZIPInterceptor.java:40)
    at org.jboss.resteasy.core.interception.ClientExecutionContextImpl.proceed(ClientExecutionContextImpl.java:45)
    at org.jboss.resteasy.client.ClientRequest.execute(ClientRequest.java:443)
    at org.jboss.resteasy.client.ClientRequest.httpMethod(ClientRequest.java:674)
    at org.jboss.resteasy.client.ClientRequest.post(ClientRequest.java:565)
    at org.jboss.resteasy.client.ClientRequest.post(ClientRequest.java:570)
    at at.fhj.ase.business.ServiceAddressImplTest.a100_insertAddressTest(ServiceAddressImplTest.java:59)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:168)
    at org.junit.rules.RunRules.evaluate(RunRules.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    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.run(ParentRunner.java:309)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

因此，我创建了一个 MessageBodyWriter，如果我使用 firefox 插件 RESTClient 发出 POST 请求，它可以正常工作：

@Provider
@Produces(MediaType.APPLICATION_JSON)
public class JsonMsbWriter implements MessageBodyWriter<Address> {

    @Override
    public boolean isWriteable(Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType) {
        if(type == Address.class){
            return true;
        }
        return false;
    }

    @Override
    public long getSize(Address t, Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType) {
        return -1;
    }

    @Override
    public void writeTo(Address t, Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType,
            MultivaluedMap<String, Object> httpHeaders,
            OutputStream entityStream) throws IOException,
            WebApplicationException {

        ObjectMapper m = new ObjectMapper();
        m.writeValue(entityStream, t);

    }
}

并将 JUnit 测试用例更新为：

@Test
public void a100_insertAddressTest() throws Exception {
    Address addr = new Address(1, "testStreet", "1", (short) 1234,
            "testCity");

    ResteasyProviderFactory fact = ResteasyProviderFactory.getInstance();
    fact.addMessageBodyWriter(JsonMsbWriter.class);

    ClientRequest request = new ClientRequest(BASE_URL + "customerID/{id}",
            sslExecutor_schusb);
    request.body(MediaType.APPLICATION_JSON, addr).pathParameter("id", 1);
    ClientResponse<String> response = request.post(String.class);

    Assert.assertEquals(201, response.getStatus());

    response.releaseConnection();
    request.clear();
}

但现在我得到了错误：

java.lang.VerifyError: (class: org/codehaus/jackson/map/ObjectMapper, method: writeValueAsBytes signature: (Ljava/lang/Object;)[B) Incompatible argument to function
    at at.fhj.ase.xmlvalidation.msbreader.JsonMsbWriter.writeTo(JsonMsbWriter.java:46)
    at at.fhj.ase.xmlvalidation.msbreader.JsonMsbWriter.writeTo(JsonMsbWriter.java:1)
    at org.jboss.resteasy.core.interception.MessageBodyWriterContextImpl.proceed(MessageBodyWriterContextImpl.java:117)
    at org.jboss.resteasy.plugins.interceptors.encoding.GZIPEncodingInterceptor.write(GZIPEncodingInterceptor.java:100)
    at org.jboss.resteasy.core.interception.MessageBodyWriterContextImpl.proceed(MessageBodyWriterContextImpl.java:123)
    at org.jboss.resteasy.client.ClientRequest.writeRequestBody(ClientRequest.java:472)
    at org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.loadHttpMethod(ApacheHttpClient4Executor.java:221)
    at org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.execute(ApacheHttpClient4Executor.java:107)
    at org.jboss.resteasy.core.interception.ClientExecutionContextImpl.proceed(ClientExecutionContextImpl.java:39)
    at org.jboss.resteasy.plugins.interceptors.encoding.AcceptEncodingGZIPInterceptor.execute(AcceptEncodingGZIPInterceptor.java:40)
    at org.jboss.resteasy.core.interception.ClientExecutionContextImpl.proceed(ClientExecutionContextImpl.java:45)
    at org.jboss.resteasy.client.ClientRequest.execute(ClientRequest.java:443)
    at org.jboss.resteasy.client.ClientRequest.httpMethod(ClientRequest.java:674)
    at org.jboss.resteasy.client.ClientRequest.post(ClientRequest.java:565)
    at org.jboss.resteasy.client.ClientRequest.post(ClientRequest.java:570)
    at at.fhj.ase.business.ServiceAddressImplTest.a100_insertAddressTest(ServiceAddressImplTest.java:65)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:168)
    at org.junit.rules.RunRules.evaluate(RunRules.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    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.run(ParentRunner.java:309)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

如何为 json 附加这样的编写器？
为什么它适用于内容类型application/xml 盒子？

对于 GET 请求和 application/json 存在同样的问题，但是是读取器而不是写入器。

【问题讨论】：

标签： java json serialization resteasy

【解决方案1】：

问题已解决，不幸的是，我没有将所有必要的 3rd 方库包含到项目构建路径中。最后我添加了以下罐子：

jackson-core-asl-1.6.3.jar
jackson-jaxrs-1.6.3.jar
jackson-mapper-asl-1.6.3.jar
jackson-xc-1.6.3.jar
resteasy-jackson-provider-2.2.1.GA.jar

这个例子把 Maven 的力量带到了前面。使用 Maven，只需一个条目即可满足这些依赖关系。

<dependency>
    <groupId>org.jboss.resteasy</groupId>
    <artifactId>resteasy-jackson-provider</artifactId>
    <version>2.2.1.GA</version>
</dependency>

【讨论】：