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使用Jettison从Java中的JSON转到DOM

[英]Using Jettison to go from JSON to DOM in Java

 原文  2009-05-12 19:09:53  8   3    java/ xml/ json/ dom/ jettison

问题描述

到目前为止，这是一个失败的故事，欢迎任何建议。 我尝试了以下方法：

使用JAXP和Saxon的XMLStreamReader到Document

编码： 

JSONObject obj = new JSONObject("{\"alice\":{\"bob\": \"a\"}}");
AbstractXMLStreamReader reader = new MappedXMLStreamReader(obj);

StAXSource source = new StAXSource(reader);
Document document = XMLUtils.createDocument();
DOMResult result = new DOMResult(document);
Transformer identity = TransformerUtils.getIdentityTransformer();
identity.transform(source, result);
result.getNode();

这失败是因为我们使用的Saxon变换器不支持StAXSource。 例外是： 

org.orbeon.saxon.trans.DynamicError: A source of type javax.xml.transform.stax.StAXSource is not supported in this environment
    org.orbeon.saxon.event.Sender.send(Sender.java:185)
    org.orbeon.saxon.IdentityTransformer.transform(IdentityTransformer.java:29)
    org.orbeon.oxf.xml.TransformerWrapper.transform(TransformerUtils.java:597)
    org.apache.jsp.gaga_jsp._jspService(gaga_jsp.java:93)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

使用JAXP和Xalan的XMLStreamReader到Document

编码： 

JSONObject obj = new JSONObject("{\"alice\":{\"bob\": \"a\"}}");
AbstractXMLStreamReader reader = new MappedXMLStreamReader(obj);

StAXSource source = new StAXSource(reader);
Document document = XMLUtils.createDocument();
DOMResult result = new DOMResult(document);
Transformer identity = orbeon.apache.xalan.processor.TransformerFactoryImpl.newInstance().newTransformer();
identity.transform(source, result);
result.getNode();

这与Xalan 2.5.1（我们使用的版本）失败了。 最新版本是2.7.1，也许他们在该版本中添加了对StAXSource的支持。 

javax.xml.transform.TransformerException: Can't transform a Source of type javax.xml.transform.stax.StAXSource
    orbeon.apache.xalan.transformer.TransformerIdentityImpl.transform(TransformerIdentityImpl.java:372)
    org.apache.jsp.gaga_jsp._jspService(gaga_jsp.java:82)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

使用XMLEventWriter和DOMResult的XMLStreamReader到Document

编码： 

JSONObject obj = new JSONObject("{\"alice\":{\"bob\": \"a\"}}");
AbstractXMLStreamReader streamReader = new MappedXMLStreamReader(obj);
XMLInputFactory readerFactory = XMLInputFactory.newInstance();
XMLEventReader eventReader = readerFactory.createXMLEventReader(streamReader);

Document document = XMLUtils.createDocument();
DOMResult result = new DOMResult(document);
XMLOutputFactory outputFactory = XMLOutputFactory.newInstance();
XMLEventWriter eventWriter = outputFactory.createXMLEventWriter(result);
eventWriter.add(eventReader);
eventWriter.close();

result.getNode();

这个导致了Xerces中的NPE： 

java.lang.NullPointerException
    orbeon.apache.xerces.dom.CoreDocumentImpl.setXmlVersion(CoreDocumentImpl.java:850)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    com.sun.xml.internal.stream.writers.XMLDOMWriterImpl.writeStartDocument(XMLDOMWriterImpl.java:583)
    com.sun.xml.internal.stream.writers.XMLEventWriterImpl.add(XMLEventWriterImpl.java:96)
    com.sun.xml.internal.stream.writers.XMLEventWriterImpl.add(XMLEventWriterImpl.java:72)
    org.apache.jsp.gaga_jsp._jspService(gaga_jsp.java:95)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

使用XMLEventWriter和Writer的XMLStreamReader到Document

编码： 

JSONObject obj = new JSONObject("{\"alice\": {\"bob\": \"a\"}}");
AbstractXMLStreamReader streamReader = new MappedXMLStreamReader(obj);
XMLInputFactory readerFactory = XMLInputFactory.newInstance();
XMLEventReader eventReader = readerFactory.createXMLEventReader(streamReader);

StringWriter stringWriter = new StringWriter();
XMLOutputFactory outputFactory = XMLOutputFactory.newInstance();
XMLEventWriter eventWriter = outputFactory.createXMLEventWriter(stringWriter);
eventWriter.add(eventReader);
eventWriter.close();

out.print(stringWriter.toString());

使用Java 5，它会查找无处可寻的com.bea.xml.stream.MXParserFactory ： 

javax.xml.stream.FactoryConfigurationError: Provider com.bea.xml.stream.MXParserFactory not found
    javax.xml.stream.FactoryFinder.newInstance(FactoryFinder.java:72)
    javax.xml.stream.FactoryFinder.find(FactoryFinder.java:178)
    javax.xml.stream.FactoryFinder.find(FactoryFinder.java:92)
    javax.xml.stream.XMLInputFactory.newInstance(XMLInputFactory.java:136)
    org.apache.jsp.gaga_jsp._jspService(gaga_jsp.java:79)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

使用Java 6，它会在Sun的XMLEventAllocatorImpl导致NPE： 

java.lang.NullPointerException
    com.sun.xml.internal.stream.events.XMLEventAllocatorImpl.getXMLEvent(XMLEventAllocatorImpl.java:82)
    com.sun.xml.internal.stream.events.XMLEventAllocatorImpl.allocate(XMLEventAllocatorImpl.java:55)
    com.sun.xml.internal.stream.XMLEventReaderImpl.nextEvent(XMLEventReaderImpl.java:86)
    com.sun.xml.internal.stream.writers.XMLEventWriterImpl.add(XMLEventWriterImpl.java:72)
    org.apache.jsp.gaga_jsp._jspService(gaga_jsp.java:85)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

使用BadgerFishDOMDocumentParser

码： 

ByteArrayInputStream bais = new ByteArrayInputStream("{\"alice\": {\"bob\": \"a\"}}".getBytes());
Document resDOM = new BadgerFishDOMDocumentParser().parse(bais);

这个在Sun的XMLEventAllocatorImpl为我们提供了一个NPE： 

java.lang.NullPointerException
    com.sun.xml.internal.stream.events.XMLEventAllocatorImpl.getXMLEvent(XMLEventAllocatorImpl.java:82)
    com.sun.xml.internal.stream.events.XMLEventAllocatorImpl.allocate(XMLEventAllocatorImpl.java:55)
    com.sun.xml.internal.stream.XMLEventReaderImpl.nextEvent(XMLEventReaderImpl.java:86)
    com.sun.xml.internal.stream.writers.XMLEventWriterImpl.add(XMLEventWriterImpl.java:72)
    org.codehaus.jettison.AbstractDOMDocumentParser.parse(AbstractDOMDocumentParser.java:66)
    org.apache.jsp.gaga_jsp._jspService(gaga_jsp.java:79)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

3 个解决方案

解决方案1
 1  

不，我不认为Xalan支持Stax，出于某种原因。 撒克逊人 ，所以也许你可以试试呢？

但如果没有，也许您应该使用链接文本从Stax构建DOM树，就像本文解释的那样？ Xalan确实接受DOM源作为输入。

解决方案2
 0  

我也有这个问题，并经历了与OP相同的挫折。 有人提到这种行为是某个woodstox邮件列表上的一个错误。 然而，我能够开发出一种解决方案。 我编写了一个非常基本的XMLEventReader，它包装了一个XMLStreamReader，它就可以了。 两个重要说明：1）此代码按原样提供; 特别是我没有在我自己有限的使用范围之外对它进行彻底的测试，2）事实上这个问题在互联网上的其他地方几乎不存在，以及这似乎是Jettison应该执行的相对基本的操作，强烈告诉我，我们正在做一些根本错误的事情，并且这个解决方案不应该是必要的。 用你自己的判断。

首先，这是一个有效的XMLEventReader： 

import java.util.LinkedList;
import java.util.Queue;

import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.events.XMLEvent;

import com.sun.xml.internal.stream.events.AttributeImpl;
import com.sun.xml.internal.stream.events.CharacterEvent;
import com.sun.xml.internal.stream.events.CommentEvent;
import com.sun.xml.internal.stream.events.DTDEvent;
import com.sun.xml.internal.stream.events.EndDocumentEvent;
import com.sun.xml.internal.stream.events.EndElementEvent;
import com.sun.xml.internal.stream.events.NamespaceImpl;
import com.sun.xml.internal.stream.events.ProcessingInstructionEvent;
import com.sun.xml.internal.stream.events.StartDocumentEvent;
import com.sun.xml.internal.stream.events.StartElementEvent;

public class WorkingXMLEventReader implements XMLEventReader {

    private final XMLStreamReader streamReader;
    private final Queue<XMLEvent> eventQueue = new LinkedList<XMLEvent>();

    public WorkingXMLEventReader (XMLStreamReader streamReader) {
        this.streamReader = streamReader;
    }

    @Override public Object next () {
        try {
            return nextEvent();
        } catch (XMLStreamException x) {
            return null;
        }
    }

    @Override public void remove () {
        throw new UnsupportedOperationException("WorkingXMLEventReader iterator interface does not support remove()");
    }

    @Override public void close () throws XMLStreamException {
        streamReader.close();
        eventQueue.clear();
    }

    @Override public String getElementText () throws XMLStreamException {
        return streamReader.getElementText();
    }

    @Override public Object getProperty (String key) throws IllegalArgumentException {
        return streamReader.getProperty(key);
    }

    @Override public boolean hasNext () {
        try {
            return !eventQueue.isEmpty() || streamReader.hasNext();
        } catch (XMLStreamException x) {
            return false;
        }
    }

    @Override public XMLEvent nextEvent () throws XMLStreamException {
        if (eventQueue.isEmpty())
            parseEvents(eventQueue, streamReader, streamReader.next());
        return eventQueue.remove();
    }

    @Override public XMLEvent nextTag () throws XMLStreamException {
        if (eventQueue.isEmpty())
            parseEvents(eventQueue, streamReader, streamReader.nextTag());
        return eventQueue.remove();        
    }

    @Override public XMLEvent peek () throws XMLStreamException {
        return eventQueue.peek();
    }

    protected static void parseEvents (Queue<XMLEvent> events, XMLStreamReader reader, int type) {
        switch (type) {
        case XMLEvent.START_ELEMENT: 
            events.add(new StartElementEvent(reader.getName()));
            break;
        case XMLEvent.END_ELEMENT: 
            events.add(new EndElementEvent(reader.getName()));
            break;
        case XMLEvent.CDATA:
            events.add(new CharacterEvent(reader.getText(), true, false));
            break;
        case XMLEvent.SPACE:
            events.add(new CharacterEvent(reader.getText(), false, true));
            break;
        case XMLEvent.CHARACTERS: 
            events.add(new CharacterEvent(reader.getText(), false, false));
            break;
        case XMLEvent.ATTRIBUTE:
            for (int n = 0; n < reader.getAttributeCount(); ++ n) {
                AttributeImpl attr = new AttributeImpl(reader.getAttributePrefix(n), 
                        reader.getAttributeNamespace(n), reader.getAttributeLocalName(n), 
                        reader.getAttributeValue(n), reader.getAttributeType(n));
                events.add(attr);
            }
            break;
        case XMLEvent.NAMESPACE:
            for (int n = 0; n < reader.getNamespaceCount(); ++ n) {
                NamespaceImpl ns = new NamespaceImpl(reader.getNamespacePrefix(n), 
                        reader.getNamespaceURI(n));
                events.add(ns);
            }
            break;
        case XMLEvent.PROCESSING_INSTRUCTION:
            events.add(new ProcessingInstructionEvent(reader.getPITarget(), reader.getPIData()));
            break;
        case XMLEvent.COMMENT:
            events.add(new CommentEvent(reader.getText()));
            break;
        case XMLEvent.START_DOCUMENT:
            events.add(new StartDocumentEvent(reader.getEncoding(), reader.getVersion()));
            break;
        case XMLEvent.END_DOCUMENT:
            events.add(new EndDocumentEvent());
            break;
        case XMLEvent.DTD:
            events.add(new DTDEvent(reader.getText()));
            break;
        }   
    }

}

接下来，这是如何将它用于OP的示例： 

XMLStreamReader streamReader = new MappedXMLStreamReader(new JSONObject("{\"alice\":{\"bob\": \"a\"}}"));
XMLEventReader eventReader = new WorkingXMLEventReader(streamReader);

Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
XMLEventWriter eventWriter = XMLOutputFactory.newInstance().createXMLEventWriter(new DOMResult(document));
eventWriter.add(eventReader);
eventWriter.close();

// test
Source testSource = new DOMSource(document);
Result testResult = new StreamResult(System.out);
TransformerFactory.newInstance().newTransformer().transform(testSource, testResult);

输出应该是这样的： 

<?xml version="1.0" encoding="UTF-8" standalone="no"?><alice><bob>a</bob></alice>

希望这有助于某人。

解决方案3
 0  

JSON不是XML - 看起来您正在尝试使用XML解析器解析JSON对象？ 但是，我可能会误解你所得到的东西。

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