我是一名学习Java的.NET开发人员。请参阅以下代码：
班级HelloWorld
import javax.ws.rs.core.Context;
import javax.ws.rs.core.UriInfo;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PUT;
import javax.ws.rs.core.MediaType;
@Path("generic")
public class HelloWorld {
@Context
private UriInfo context;
public HelloWorld() {
}
@GET
@Produces("application/xml")
public String getHtml() {
return "<?xml version='1.0'?><PARTS><TITLE>Computer Parts</TITLE><PART><ITEM>Motherboard</ITEM></PART></PARTS>";
}
}
班级JavaApplication3
package javaapplication3;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.stream.Collectors;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import sun.misc.IOUtils;
/**
*
* @author 3212627
*/
public class JavaApplication3 {
private static String charset;
/**
* @param args the command line arguments
*/
public static void main(String[] args) throws MalformedURLException, IOException, JAXBException {
//Get the URI by selecting the RESTful web services folder under the web app project. Then right click on the underlying node
//and select: TestResourceURI
String content;
String uri ="http://localhost:8080/HelloRestService/webresources/generic";
URL url = new URL(uri);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
//connection.setRequestProperty("Accept", "application/xml");
connection.setRequestProperty("Accept", "application/xml");
JAXBContext jc = JAXBContext.newInstance(String.class); //I changed Customer.class to String.class
InputStream xml = connection.getInputStream();
String str = (String) jc.createUnmarshaller().unmarshal(xml); //line causing exception
connection.disconnect();
}
}
返回的异常是：
Exception in thread "main" javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"PARTS"). Expected elements are (none)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:726)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:247)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:242)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:109)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1131)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:556)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:538)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:153)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:509)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:380)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:619)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3129)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:880)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:118)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:504)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:243)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:214)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:204)
at javaapplication3.JavaApplication3.main(JavaApplication3.java:46)
Java Result: 1
BUILD SUCCESSFUL (total time: 5 seconds)
我已标记导致异常的行。有什么问题？
答案 0 :(得分：2)
JAXB的主要目的是在XML和Java Bean之间进行映射，但为了能够做到这一点，它依赖于来自javax.xml.bind.annotation的注释。需要在目标Java Bean的字段或getter上声明。
例如，在这里，您的映射可以定义为下一个：
班级Parts
public class Parts {
@XmlElement(name = "TITLE")
private String title;
@XmlElement(name = "PART")
private List<Part> parts;
public String getTitle() {
return this.title;
}
public void setTitle(final String title) {
this.title = title;
}
public List<Part> getParts() {
return this.parts;
}
public void setParts(final List<Part> parts) {
this.parts = parts;
}
}
班级Part
@XmlAccessorType(XmlAccessType.FIELD)
public class Part {
@XmlElement(name = "ITEM")
private String item;
public String getItem() {
return this.item;
}
public void setItem(final String item) {
this.item = item;
}
}
定义映射后，您需要将其提供给JAXBContext，以便能够unmarshal您的XML内容获取班级Parts的实例：
JAXBContext jc = JAXBContext.newInstance(Parts.class);
InputStream xml = connection.getInputStream();
Parts parts = (Parts) jc.createUnmarshaller().unmarshal(xml);
以下是a good tutorial，您应该阅读JAXB。您还应该阅读the one from oracle。