CXF:没有为类找到消息正文编写器 - 自动映射非简单资源

Question

我正在使用CXF rest客户端,它适用于简单的数据类型(例如:字符串,整数).但是,当我尝试使用自定义对象时,我得到了这个:

Exception in thread "main" org.apache.cxf.interceptor.Fault: .No message body writer found for class : class com.company.datatype.normal.MyObject.
    at org.apache.cxf.jaxrs.client.ClientProxyImpl$BodyWriter.handleMessage(ClientProxyImpl.java:523)
    at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:263)
    at org.apache.cxf.jaxrs.client.ClientProxyImpl.doChainedInvocation(ClientProxyImpl.java:438)
    at org.apache.cxf.jaxrs.client.ClientProxyImpl.invoke(ClientProxyImpl.java:177)
    at $Proxy13.execute(Unknown Source)
    at com.company.JaxTestClient.main(JaxTestClient.java:26)
Caused by: org.apache.cxf.jaxrs.client.ClientWebApplicationException: .No message body writer found for class : class com.company.datatype.normal.MyObject.
    at org.apache.cxf.jaxrs.client.AbstractClient.reportMessageHandlerProblem(AbstractClient.java:491)
    at org.apache.cxf.jaxrs.client.AbstractClient.writeBody(AbstractClient.java:401)
    at org.apache.cxf.jaxrs.client.ClientProxyImpl$BodyWriter.handleMessage(ClientProxyImpl.java:515)
    ... 5 more

我这样称呼它:

JaxExample jaxExample = JAXRSClientFactory.create( "http://localhost:8111/", JaxExample.class );
MyObject before = ...
MyObject after = jaxExample.execute( before );

这是界面中的方法:

@POST
@Path( "execute" )
@Produces( "application/json" )
MyObject execute( MyObject myObject );

restlet库通过将XStream依赖项添加到您的"正常工作"的路径,非常简单.CXF有类似之处吗？

编辑#1:

我已将此作为功能改进发布到此处的CXF问题管理系统.我只能希望这会得到照顾.

Answer 1

它不是开箱即用,但CXF确实支持JSON绑定到休息服务.请参阅cxf jax-rs json docs.您仍然需要进行一些最小配置才能使提供程序可用,如果您想要更好地控制JSON的形成方式,则需要熟悉jettison.

编辑:每个评论请求,这里是一些代码.我对此没有太多经验,但以下代码在快速测试系统中作为示例.

//TestApi parts
@GET
@Path ( "test" )
@Produces ( "application/json" )
public Demo getDemo () {
    Demo d = new Demo ();
    d.id = 1;
    d.name = "test";
    return d;
}

//client config for a TestApi interface
List providers = new ArrayList ();
JSONProvider jsonProvider = new JSONProvider ();
Map<String, String> map = new HashMap<String, String> ();
map.put ( "http://www.myserviceapi.com", "myapi" );
jsonProvider.setNamespaceMap ( map );
providers.add ( jsonProvider );
TestApi proxy = JAXRSClientFactory.create ( url, TestApi.class, 
    providers, true );

Demo d = proxy.getDemo ();
if ( d != null ) {
    System.out.println ( d.id + ":" + d.name );
}

//the Demo class
@XmlRootElement ( name = "demo", namespace = "http://www.myserviceapi.com" )
@XmlType ( name = "demo", namespace = "http://www.myserviceapi.com", 
    propOrder = { "name", "id" } )
@XmlAccessorType ( XmlAccessType.FIELD )
public class Demo {

    public String name;
    public int id;
}

笔记:

1. 提供程序列表是您在客户端上配置JSON提供程序的代码.特别是,您可以看到命名空间映射.这需要与服务器端配置相匹配.我对Jettison的选项知之甚少,所以我对操纵控制编组过程的各种旋钮没什么帮助.
2. CXF中的Jettison通过将来自JAXB提供程序的XML编组为JSON来工作.因此,您必须确保将有效负载对象全部标记(或以其他方式配置)以编组为application/xml,然后才能将它们作为JSON进行编组.如果你知道解决这个问题的方法(除了写自己的信息主体作者),我很乐意听到它.
3. 我在服务器上使用spring,所以我的配置有所有xml的东西.实质上,您需要通过相同的过程将JSONProvider添加到具有相同命名空间配置的服务.没有那个方便的代码,但我想它会很好地反映客户端.

作为一个例子,这有点脏,但希望能让你前进.

Edit2:基于xstream的消息体编写器的示例,以避免使用jaxb.

@Produces ( "application/json" )
@Consumes ( "application/json" )
@Provider
public class XstreamJsonProvider implements MessageBodyReader<Object>,
    MessageBodyWriter<Object> {

@Override
public boolean isWriteable ( Class<?> type, Type genericType, 
    Annotation[] annotations, MediaType mediaType ) {
    return MediaType.APPLICATION_JSON_TYPE.equals ( mediaType ) 
        && type.equals ( Demo.class );
}

@Override
public long getSize ( Object t, Class<?> type, Type genericType, 
    Annotation[] annotations, MediaType mediaType ) {
    // I'm being lazy - should compute the actual size
    return -1;
}

@Override
public void writeTo ( Object t, Class<?> type, Type genericType, 
    Annotation[] annotations, MediaType mediaType, 
    MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream ) 
    throws IOException, WebApplicationException {
    // deal with thread safe use of xstream, etc.
    XStream xstream = new XStream ( new JettisonMappedXmlDriver () );
    xstream.setMode ( XStream.NO_REFERENCES );
    // add safer encoding, error handling, etc.
    xstream.toXML ( t, entityStream );
}

@Override
public boolean isReadable ( Class<?> type, Type genericType, 
    Annotation[] annotations, MediaType mediaType ) {
    return MediaType.APPLICATION_JSON_TYPE.equals ( mediaType ) 
        && type.equals ( Demo.class );
}

@Override
public Object readFrom ( Class<Object> type, Type genericType, 
    Annotation[] annotations, MediaType mediaType, 
    MultivaluedMap<String, String> httpHeaders, InputStream entityStream ) 
    throws IOException, WebApplicationException {
    // add error handling, etc.
    XStream xstream = new XStream ( new JettisonMappedXmlDriver () );
    return xstream.fromXML ( entityStream );
}
}

//now your client just needs this
List providers = new ArrayList ();
XstreamJsonProvider jsonProvider = new XstreamJsonProvider ();
providers.add ( jsonProvider );
TestApi proxy = JAXRSClientFactory.create ( url, TestApi.class, 
    providers, true );

Demo d = proxy.getDemo ();
if ( d != null ) {
    System.out.println ( d.id + ":" + d.name );
}

示例代码缺少强大的媒体类型支持,错误处理,线程安全等部分.但是,它应该用最少的代码解决jaxb问题.

编辑3 - 示例服务器端配置 正如我之前所说,我的服务器端是弹簧配置.以下是一个用于在提供程序中连接的示例配置:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:jaxrs="http://cxf.apache.org/jaxrs"
xmlns:cxf="http://cxf.apache.org/core"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd
    http://cxf.apache.org/core http://cxf.apache.org/schemas/core.xsd">

<import resource="classpath:META-INF/cxf/cxf.xml" />

<jaxrs:server id="TestApi">
    <jaxrs:serviceBeans>
        <ref bean="testApi" />
    </jaxrs:serviceBeans>
    <jaxrs:providers>
        <bean id="xstreamJsonProvider" class="webtests.rest.XstreamJsonProvider" />
    </jaxrs:providers>
</jaxrs:server>

<bean id="testApi" class="webtests.rest.TestApi">
</bean>

</beans>

我还注意到,在我使用的最新版本的cxf中,媒体类型存在差异,因此上面关于xstream消息体读取器/写入器的示例需要快速修改,其中isWritable/isReadable更改为:

return MediaType.APPLICATION_JSON_TYPE.getType ().equals ( mediaType.getType () )
    && MediaType.APPLICATION_JSON_TYPE.getSubtype ().equals ( mediaType.getSubtype () )
    && type.equals ( Demo.class );

编辑4 - 非弹簧配置 使用您选择的servlet容器,进行配置

org.apache.cxf.jaxrs.servlet.CXFNonSpringJaxrsServlet

至少有2个init参数:

jaxrs.serviceClasses
jaxrs.providers

其中serviceClasses是您想要绑定的服务实现的空格分隔列表,例如上面提到的TestApi,provider是一个空格分隔的消息体提供者列表,例如上面提到的XstreamJsonProvider.在tomcat中,您可以将以下内容添加到web.xml:

<servlet>
    <servlet-name>cxfservlet</servlet-name>
    <servlet-class>org.apache.cxf.jaxrs.servlet.CXFNonSpringJaxrsServlet</servlet-class>
    <init-param>
        <param-name>jaxrs.serviceClasses</param-name>
        <param-value>webtests.rest.TestApi</param-value>
    </init-param>
    <init-param>
        <param-name>jaxrs.providers</param-name>
        <param-value>webtests.rest.XstreamJsonProvider</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

这是在没有弹簧的情况下运行它的最快捷方式.如果您不使用servlet容器,则需要使用XstreamJsonProvider实例配置JAXRSServerFactoryBean.setProviders,并通过JAXRSServerFactoryBean.setResourceProvider方法设置服务实现.检查CXFNonSpringJaxrsServlet.init方法以查看在servlet容器中进行设置时如何执行此操作.

无论你的情况如何,这应该让你去.

Answer 2

从CXF 2.7.0升级到3.0.2时遇到此问题.以下是我要解决的问题:

在我的pom.xml中包含以下内容

    <dependency>
        <groupId>org.apache.cxf</groupId>
        <artifactId>cxf-rt-rs-extension-providers</artifactId>
        <version>3.0.2</version>
    </dependency>

    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-jaxrs</artifactId>
        <version>1.9.0</version>
    </dependency>

并添加了以下提供商

    <jaxrs:providers>
        <bean class="org.codehaus.jackson.jaxrs.JacksonJaxbJsonProvider" />
    </jaxrs:providers>