jakarta-ee - JAXB 编码器 : StringWriter output has a truncated tag value

Question

我想将 java 对象编码为 xml 字符串。因此，我获得了一个模式，我可以从中生成 JAXB 类。有一个 set 方法(对应于模式中 hexbinary 类型的元素)，我必须在其中设置一个字符串。字符串大小约为 2566。通过 setter 方法将数据设置到对象后，我调用 marshaller 传递 stringWriter 参数。

但是在打印 stringWriter 时，我看到它被截断了。我没有看到完整的 2566 个字符。

怎么了？有什么想法吗？

谢谢!

更新:

我想我找到了问题所在。我必须找到一个合适的标题，因为我对问题的推理是错误的!!问题如下:我的架构中有一个“hexbinary”元素。生成的类有对应的set/get方法。要设置值，我使用了 apache commons 包的 HexEncodeString 方法，并意识到编码器在十六进制标记中显示 36383639 字符串“hi”，其实际十六进制编码为 6869 :( 因此，问题是编码后的 xml 有一个标记# of chars 的值大于原始值，并且没有像我之前想的那样被截断!

感谢 Blaise Doughan 的代码。我已经修改并重现了这个问题。

首先是一个示例架构:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:complexType name="Root">
    <xs:sequence>
      <xs:element name="string" type="xs:string" minOccurs="0"/>
            <xs:element name="a" type="xs:hexBinary" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

由此我生成了 ObjectFactory 类和 Root 类。我必须修改 ObjectFactory 类以包含 JAXBElement，以便我可以将它传递给 Marshaller。有了这些，我将 Blaise Doughan 的 Demo 类修改为:

public class Demo {

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

    // The object factory
    ObjectFactory objFactory = new ObjectFactory();
    Root root = new Root();
    String str = new String("hi");
    String val = Hex.encodeHexString(str.getBytes());
    root.setString(str);
    root.setArr(val.getBytes());

        System.out.println("val="+val);
        System.out.println("getString ="+root.getString());
        System.out.println("getArr="+new String(root.getArr()));

        // Marshal the object to a StringWriter
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
        marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "http://www.example.com/schema.xsd");
        StringWriter stringWriter = new StringWriter();
        marshaller.marshal(objFactory.createRoot(root),stringWriter);
//      marshaller.marshal(root, stringWriter);

        // Convert StringWriter to String
        String xml = stringWriter.toString();
        System.out.println(xml);

        // Unmarshal the XML and check length of long String
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        Root unmarshalledRoot = (Root) unmarshaller.unmarshal(new StringReader(xml));
        System.out.println(root.getString().length());
        System.out.println(root.getString());
        System.out.println(new String(root.getArr()).length());
        System.out.println(new String(root.getArr()));
    }

}

我得到的输出是:

val=6869
getString =hi
getArr=6869
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns3:Root xsi:schemaLocation="http://www.example.com/schema.xsd" xmlns:ns3="http://example.com/root" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <string>hi</string>
    <arr>36383639</arr>
</ns3:Root>

Exception in thread "main" javax.xml.bind.UnmarshalException: unexpected element (uri:"http://example.com/root", local:"Root"). Expected elements are (none)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:631)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:236)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:231)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:105)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1038)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:467)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:448)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:137)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:400)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:626)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3103)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:922)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:200)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:173)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:137)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:194)
    at example.Demo.main(Demo.java:43)

为什么 arr 标签是 36383639 而不是 6869？

Answer 1

新答案

在您的示例代码中，val 是 str.getBytes() 的 hexBinary 表示。但是您在 arr 属性上设置的值是来自十六进制编码字符串的字节。

String str = new String("hi");
String val = Hex.encodeHexString(str.getBytes());
root.setString(str);
root.setArr(val.getBytes());

我相信你的意思是:

String str = new String("hi");
String val = Hex.encodeHexString(str.getBytes());
root.setString(str);
root.setArr(str.getBytes());

这将产生以下输出

val=6869
getString =hi
getArr=hi
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root xsi:schemaLocation="http://www.example.com/schema.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <string>hi</string>
    <a>6869</a>
</root>

换个说法

    String str = new String("hi");
    System.out.print("String:  " + str);
    System.out.println(" hexBinary:  " + Hex.encodeHexString(str.getBytes()));
    String val = Hex.encodeHexString(str.getBytes());
    System.out.print("String:  " + val);
    System.out.println(" hexBinary:  " + Hex.encodeHexString(val.getBytes()));

将输出:

String:  hi hexBinary:  6869
String:  6869 hexBinary:  36383639

---

原始答案

我无法重现您遇到的问题。我使用的 String 大小为 500000。以下是我尝试过的方法(此示例对您有用吗？)。截断是否可能是由于您正在向其中写入长字符串的控制台造成的？

演示

package forum12146217;

import java.io.*;
import javax.xml.bind.*;

public class Demo {

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

        // Build a long String
        StringBuilder stringBuilder = new StringBuilder();
        for(int x=0; x<500000; x++) {
            stringBuilder.append("a");
        }
        Root root = new Root();
        root.setString(stringBuilder.toString());
        System.out.println(root.getString().length());

        // Marshal the object to a StringWriter
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
        marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "http://www.example.com/schema.xsd");
        StringWriter stringWriter = new StringWriter();
        marshaller.marshal(root, stringWriter);

        // Convert StringWriter to String
        String xml = stringWriter.toString();
        //System.out.println(xml);

        // Unmarshal the XML and check length of long String
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        Root unmarshalledRoot = (Root) unmarshaller.unmarshal(new StringReader(xml));
        System.out.println(unmarshalledRoot.getString().length());
    }

}

根

package forum12146217;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Root {

    private String string;

    public String getString() {
        return string;
    }

    public void setString(String string) {
        this.string = string;
    }

}

输出

500000
500000