JAXB：在JAXB中創建Unmarshaller時引發NullPointerException

Question

我已經爲我的XML創建了一個結構以與JAXB解組一起工作 問題是，Unmarshaller沒有被創建。

JAXBContext jc = JAXBContext.newInstance("A Fully qualified class name"); 
Unmarshaller um = jc.createUnmarshaller(); 

java.lang.NullPointerException is being thrown at 
Unmarshaller um = jc.createUnmarshaller(); 

除了java.lang.NullPointerException外，沒有什麼關於statcktrace的，所以無法調試它。 任何人都可以請告訴我如何解決這個在創建一個Unmarshaller？對於JAXB 2.0

對於refernece這是我的分析器類

public class BADFMMessageParser { 
private static JAXBContext jc = null; 
    static { 
     try { 
     jc = JAXBContext.newInstance("My Fully Qualified class name"); 
     } catch (Exception x) { 
     } 
    } 
    public static MyClass parse(String str) throws Exception { 
     Unmarshaller um = jc.createUnmarshaller(); 
     BADFM badfmMessage = (BADFM) um.unmarshal(new StringReader(requestStr)); 
     JAXBElement<? extends MyClass> value = badfmMessage.getMessage(); 
     return value.getValue(); 
    } 
} 

Answer 1

我不知道爲什麼你看到一個NPE，但你似乎是正確創建JAXBContext。你可以做以下假設你有一個jaxb.index文件或ObjectFactory類指定包：

JAXBContext jc = JAXBContext.newInstance("your.domain.model.package"); 

否則，你可以在一個或多個類直接創建一個JAXBContext：

JAXBContext jc = JAXBContext.newInstance(Foo.class,Bar.class); 

jaxb.index文件示例

• http://blog.bdoughan.com/2010/08/using-xmlanyelement-to-build-generic.html

引導JAXBContext上生成的模型實施例

• http://blog.bdoughan.com/2010/09/processing-atom-feeds-with-jaxb.html

Bootstap JAXBContext從類實施例

• http://blog.bdoughan.com/2010/09/jaxb-collection-properties.html