XmlAdapter 到 JAXB 绑定 Joda 的时间间隔？

我已经被 Web 服务的 JAXB 绑定问题困扰了几个小时：

为了准备一个必须返回 Joda Time 类实例（即时、持续时间、间隔等）的更大的 Web 服务，我从一个只有一个返回 Interval 的方法的 Web 服务开始：

package jodaws;

import javax.jws.WebService;
import javax.xml.ws.Endpoint;

import org.joda.time.Interval;

@WebService(name = "JodaWS")
public class JodaWebService {

    public Interval readInterval() {
        return new Interval(30, 40);
    }

    public static void main(String[] args) {
        Endpoint.publish("http://localhost:10100/JodaWS", new JodaWebService());
    }
}

发布此 Web 服务时，我收到一个异常，指出“org.joda.time.Interval 没有无参数默认构造函数”：

29.05.2011 17:24:07 com.sun.xml.internal.ws.model.RuntimeModeler getRequestWrapperClass
INFO: Dynamically creating request wrapper Class jodaws.jaxws.ReadInterval
29.05.2011 17:24:07 com.sun.xml.internal.ws.model.RuntimeModeler getResponseWrapperClass
INFO: Dynamically creating response wrapper bean Class jodaws.jaxws.ReadIntervalResponse
Exception in thread "main" javax.xml.ws.WebServiceException: Unable to create JAXBContext
    at com.sun.xml.internal.ws.model.AbstractSEIModelImpl.createJAXBContext(AbstractSEIModelImpl.java:153)
    at com.sun.xml.internal.ws.model.AbstractSEIModelImpl.postProcess(AbstractSEIModelImpl.java:83)
    at com.sun.xml.internal.ws.model.RuntimeModeler.buildRuntimeModel(RuntimeModeler.java:244)
    at com.sun.xml.internal.ws.server.EndpointFactory.createSEIModel(EndpointFactory.java:312)
    at com.sun.xml.internal.ws.server.EndpointFactory.createEndpoint(EndpointFactory.java:178)
    at com.sun.xml.internal.ws.api.server.WSEndpoint.create(WSEndpoint.java:456)
    at com.sun.xml.internal.ws.api.server.WSEndpoint.create(WSEndpoint.java:475)
    at com.sun.xml.internal.ws.transport.http.server.EndpointImpl.createEndpoint(EndpointImpl.java:213)
    at com.sun.xml.internal.ws.transport.http.server.EndpointImpl.publish(EndpointImpl.java:143)
    at com.sun.xml.internal.ws.spi.ProviderImpl.createAndPublishEndpoint(ProviderImpl.java:102)
    at javax.xml.ws.Endpoint.publish(Endpoint.java:170)
    at jodaws.JodaWebService.main(JodaWebService.java:17)
Caused by: java.security.PrivilegedActionException: com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 2 counts of IllegalAnnotationExceptions
org.joda.time.Interval does not have a no-arg default constructor.
    this problem is related to the following location:
        at org.joda.time.Interval
        at public org.joda.time.Interval jodaws.jaxws.ReadIntervalResponse._return
        at jodaws.jaxws.ReadIntervalResponse
org.joda.time.base.BaseInterval does not have a no-arg default constructor.
    this problem is related to the following location:
        at org.joda.time.base.BaseInterval
        at org.joda.time.Interval
        at public org.joda.time.Interval jodaws.jaxws.ReadIntervalResponse._return
        at jodaws.jaxws.ReadIntervalResponse

    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.xml.internal.ws.model.AbstractSEIModelImpl.createJAXBContext(AbstractSEIModelImpl.java:140)
    ... 11 more
Caused by: com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 2 counts of IllegalAnnotationExceptions
org.joda.time.Interval does not have a no-arg default constructor.
    this problem is related to the following location:
        at org.joda.time.Interval
        at public org.joda.time.Interval jodaws.jaxws.ReadIntervalResponse._return
        at jodaws.jaxws.ReadIntervalResponse
org.joda.time.base.BaseInterval does not have a no-arg default constructor.
    this problem is related to the following location:
        at org.joda.time.base.BaseInterval
        at org.joda.time.Interval
        at public org.joda.time.Interval jodaws.jaxws.ReadIntervalResponse._return
        at jodaws.jaxws.ReadIntervalResponse

    at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:436)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:277)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1100)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:143)
    at com.sun.xml.internal.bind.api.JAXBRIContext.newInstance(JAXBRIContext.java:95)
    at com.sun.xml.internal.ws.developer.JAXBContextFactory$1.createJAXBContext(JAXBContextFactory.java:97)
    at com.sun.xml.internal.ws.model.AbstractSEIModelImpl$1.run(AbstractSEIModelImpl.java:148)
    at com.sun.xml.internal.ws.model.AbstractSEIModelImpl$1.run(AbstractSEIModelImpl.java:140)
    ... 13 more

因此，我阅读了几个教程等，最终为 Interval 类编写了我自己的 XmlAdapter - 第一个实现返回有效但恒定的值：

package jodaws;

import javax.xml.bind.annotation.adapters.XmlAdapter;

import org.joda.time.Interval;

public class IntervalAdapter extends XmlAdapter<String, Interval> {
    @Override
    public Interval unmarshal(String v) throws Exception {
        return new Interval(10, 20);
    }

    @Override
    public String marshal(Interval v) throws Exception {
        return "10-20";
    }
}

另外，我还注释了我的网络方法来使用适配器：

package jodaws;

import javax.jws.WebService;
// import added
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import javax.xml.ws.Endpoint;

import org.joda.time.Interval;

@WebService(name = "JodaWS")
public class JodaWebService {

    // annotation added
    @XmlJavaTypeAdapter(IntervalAdapter.class)
    public Interval readInterval() {
        return new Interval(30, 40);
    }

    public static void main(String[] args) {
        Endpoint.publish("http://localhost:10100/JodaWS", new JodaWebService());
    }
}

现在应该可以了。但是当我再次启动 Web 服务时，我仍然收到异常，尽管是不同的异常：

29.05.2011 17:27:33 com.sun.xml.internal.ws.model.RuntimeModeler getRequestWrapperClass
INFO: Dynamically creating request wrapper Class jodaws.jaxws.ReadInterval
29.05.2011 17:27:34 com.sun.xml.internal.ws.model.RuntimeModeler getResponseWrapperClass
INFO: Dynamically creating response wrapper bean Class jodaws.jaxws.ReadIntervalResponse
Exception in thread "main" javax.xml.ws.WebServiceException: java.lang.IllegalArgumentException: value class jodaws.IntervalAdapter
    at com.sun.xml.internal.ws.model.WrapperBeanGenerator.createResponseWrapperBean(WrapperBeanGenerator.java:269)
    at com.sun.xml.internal.ws.model.RuntimeModeler.getResponseWrapperClass(RuntimeModeler.java:293)
    at com.sun.xml.internal.ws.model.RuntimeModeler.processDocWrappedMethod(RuntimeModeler.java:688)
    at com.sun.xml.internal.ws.model.RuntimeModeler.processMethod(RuntimeModeler.java:612)
    at com.sun.xml.internal.ws.model.RuntimeModeler.processClass(RuntimeModeler.java:401)
    at com.sun.xml.internal.ws.model.RuntimeModeler.buildRuntimeModel(RuntimeModeler.java:240)
    at com.sun.xml.internal.ws.server.EndpointFactory.createSEIModel(EndpointFactory.java:312)
    at com.sun.xml.internal.ws.server.EndpointFactory.createEndpoint(EndpointFactory.java:178)
    at com.sun.xml.internal.ws.api.server.WSEndpoint.create(WSEndpoint.java:456)
    at com.sun.xml.internal.ws.api.server.WSEndpoint.create(WSEndpoint.java:475)
    at com.sun.xml.internal.ws.transport.http.server.EndpointImpl.createEndpoint(EndpointImpl.java:213)
    at com.sun.xml.internal.ws.transport.http.server.EndpointImpl.publish(EndpointImpl.java:143)
    at com.sun.xml.internal.ws.spi.ProviderImpl.createAndPublishEndpoint(ProviderImpl.java:102)
    at javax.xml.ws.Endpoint.publish(Endpoint.java:170)
    at jodaws.JodaWebService.main(JodaWebService.java:18)
Caused by: java.lang.IllegalArgumentException: value class jodaws.IntervalAdapter
    at com.sun.xml.internal.ws.org.objectweb.asm.ClassWriter.newConstItem(ClassWriter.java:893)
    at com.sun.xml.internal.ws.org.objectweb.asm.AnnotationWriter.visit(AnnotationWriter.java:185)
    at com.sun.xml.internal.ws.model.WrapperBeanGenerator.createBeanImage(WrapperBeanGenerator.java:111)
    at com.sun.xml.internal.ws.model.WrapperBeanGenerator.createResponseWrapperBean(WrapperBeanGenerator.java:265)
    ... 14 more

这就是我被困住的地方。我究竟做错了什么？

你是对的，你需要使用XmlAdapter http://download.oracle.com/javase/6/docs/api/javax/xml/bind/annotation/adapters/XmlAdapter.html对于这个用例。下面是如何完成此操作的示例：

间隔字符串适配器

下面的适配器将以 start-end 格式将 Interval 实例与字符串进行转换。

package blog.joda;

import javax.xml.bind.annotation.adapters.XmlAdapter;

import org.joda.time.Interval;

public class IntervalStringAdapter extends XmlAdapter<String, Interval>{

    @Override
    public Interval unmarshal(String v) throws Exception {
        int dashIndex = v.indexOf('-');
        long start = Long.valueOf(v.substring(0, dashIndex));
        long end = Long.valueOf(v.substring(dashIndex + 1));
        return new Interval(start, end);
    }

    @Override
    public String marshal(Interval v) throws Exception {
        return v.getStartMillis() + "-" + v.getEndMillis();
    }

}

Root

以下是如何配置属性以使用适配器的示例：

package blog.joda;

import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

import org.joda.time.Interval;

@XmlRootElement
public class Root {

    private Interval interval;

    @XmlJavaTypeAdapter(IntervalStringAdapter.class)
    public Interval getInterval() {
        return interval;
    }

    public void setInterval(Interval interval) {
        this.interval = interval;
    }

}

Demo

package blog.joda;

import java.io.File;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        Root root = (Root) unmarshaller.unmarshal(new File("src/blog/joda/input.xml"));

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }

}

输入.xml

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <interval>10-20</interval>
</root>

了解更多信息

• http://bdoughan.blogspot.com/2011/05/jaxb-and-joda-time-dates-and-times.html http://bdoughan.blogspot.com/2011/05/jaxb-and-joda-time-dates-and-times.html