未检测到XmlJavaTypeAdapter
希望对JAXB专家来说很简单：
我试图编组一个不定义默认无参数构造函数的不可变类。 我已经定义了一个XmlAdapter实现，但它似乎没有被选中。 我已经整理了一个简单的自包含示例，但仍然无法正常工作。 任何人都可以建议我做错了什么？
不可改变的阶级
@XmlJavaTypeAdapter(FooAdapter.class) @XmlRootElement public class Foo { private final String name; private final int age; public Foo(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public int getAge() { return age; } }
适配器和值类型
public class FooAdapter extends XmlAdapter { public Foo unmarshal(AdaptedFoo af) throws Exception { return new Foo(af.getName(), af.getAge()); } public AdaptedFoo marshal(Foo foo) throws Exception { return new AdaptedFoo(foo); } } class AdaptedFoo { private String name; private int age; public AdaptedFoo() {} public AdaptedFoo(Foo foo) { this.name = foo.getName(); this.age = foo.getAge(); } @XmlAttribute public String getName() { return name; } public void setName(String name) { this.name = name; } @XmlAttribute public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
编组
public class Marshal { public static void main(String[] args) { Foo foo = new Foo("Adam", 34); try { JAXBContext jaxbContext = JAXBContext.newInstance(Foo.class); Marshaller jaxbMarshaller = jaxbContext.createMarshaller(); // output pretty printed jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); jaxbMarshaller.marshal(foo, System.out); } catch (JAXBException e) { e.printStackTrace(); } } }
堆栈跟踪
com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions Foo does not have a no-arg default constructor. this problem is related to the following location: at Foo at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91) at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:451) at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.(JAXBContextImpl.java:283) at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.(JAXBContextImpl.java:126) at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1142) at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:130) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:248) at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:235) at javax.xml.bind.ContextFinder.find(ContextFinder.java:445) at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:637) at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584) at Marshal2.main(Marshal2.java:11)
请注意，我使用的是JDK 1.7.0_05。
以下应该有所帮助：
作为根本对象的FOO
当在类型级别指定@XmlJavaTypeAdapter时，它仅适用于引用该类的字段/属性，而不适用于该类的实例是XML树中的根对象。 这意味着您必须自己将Foo转换为AdaptedFoo ，并在AdaptedFoo而不是Foo上创建JAXBContext 。
元帅
package forum11966714; import javax.xml.bind.*; public class Marshal { public static void main(String[] args) { Foo foo = new Foo("Adam", 34); try { JAXBContext jaxbContext = JAXBContext.newInstance(AdaptedFoo.class); Marshaller jaxbMarshaller = jaxbContext.createMarshaller(); // output pretty printed jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); jaxbMarshaller.marshal(new AdaptedFoo(foo), System.out); } catch (JAXBException e) { e.printStackTrace(); } } }
AdaptedFoo
您需要将一个@XmlRootElement注释添加到AdaptedFoo类。 您可以从Foo类中删除相同的注释。
package forum11966714; import javax.xml.bind.annotation.*; @XmlRootElement class AdaptedFoo { private String name; private int age; public AdaptedFoo() { } public AdaptedFoo(Foo foo) { this.name = foo.getName(); this.age = foo.getAge(); } @XmlAttribute public String getName() { return name; } public void setName(String name) { this.name = name; } @XmlAttribute public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
FOO as NESTED OBJECT
当Foo不是根对象时，一切都按照映射的方式工作。 我已经扩展了你的模型来演示它是如何工作的。
酒吧
package forum11966714; import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement public class Bar { private Foo foo; public Foo getFoo() { return foo; } public void setFoo(Foo foo) { this.foo = foo; } }
演示
请注意，JAXB引用实现不允许您在引导JAXBContext时指定Foo类。
package forum11966714; import java.io.File; import javax.xml.bind.JAXBContext; import javax.xml.bind.JAXBException; import javax.xml.bind.Marshaller; import javax.xml.bind.Unmarshaller; public class Demo { public static void main(String[] args) { try { JAXBContext jaxbContext = JAXBContext.newInstance(Bar.class); Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller(); File xml = new File("src/forum11966714/input.xml"); Bar bar = (Bar) jaxbUnmarshaller.unmarshal(xml); Marshaller jaxbMarshaller = jaxbContext.createMarshaller(); jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); jaxbMarshaller.marshal(bar, System.out); } catch (JAXBException e) { e.printStackTrace(); } } }
input.xml中/输出