java - 如何使用 Apache Daffodil 的 DataProcessor.unparse() 方法来重建原始解析消息？

Question

我是 Apache Daffodil 的初学者。

我使用 Daffodil Java API 成功将输入文本消息解析为 XML 字符串，即

        Compiler dfdlCompiler = Daffodil.compiler();
        dfdlCompiler.setValidateDFDLSchemas(true);
        File schemaFile = this.getFileFromResources("EDIFACT-SupplyChain-D03B/EDIFACT-SupplyChain-Messages-D.03B.xsd");
        ProcessorFactory processorFactory = dfdlCompiler.compileFile(schemaFile);
        DataProcessor dataProcessor = processorFactory.onPath("/");
        java.io.File file = getFileFromResources("TestData/ORDERS_D.03B_Interchange.txt");
        java.io.FileInputStream fis = new java.io.FileInputStream(file);
        InputSourceDataInputStream dis = new InputSourceDataInputStream(fis);
        JDOMInfosetOutputter outputter = new JDOMInfosetOutputter();
        ParseResult parseResult = dataProcessor.parse(dis, outputter);
        Document doc = outputter.getResult().getDocument();
        XMLOutputter xo = new XMLOutputter(org.jdom2.output.Format.getPrettyFormat());
        String xmlString = xo.outputString(doc);

        System.out.println("parsed text... resulting xmlString=" + xmlString);

但是，现在，我不清楚如何使用 unparse() 方法来重构原始文本消息(似乎缺乏使用 Daffodil 的 Java API 进行解解析以重构原始消息的示例)。

试试这个:

        SAXBuilder builder = new SAXBuilder();
        Document d2 = builder.build(new StringReader(xmlString));
        JDOMInfosetInputter inputter = new JDOMInfosetInputter(d2);
        WritableByteChannel output = Channels.newChannel(new DataOutputStream(new ByteArrayOutputStream()));
        UnparseResult result = dataProcessor.unparse(inputter, output);

如何提取原始消息？或者说，这种做法不正确吗？

Apache Daffodil 版本:2.3

Java版本:jdk8+

<小时/>

使用这个精简的 Java 应用程序进行测试...

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.StringReader;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.WritableByteChannel;
import org.jdom2.Document;
import org.jdom2.output.XMLOutputter;

import org.apache.daffodil.japi.Compiler;
import org.apache.daffodil.japi.Daffodil;
import org.apache.daffodil.japi.DataProcessor;
import org.apache.daffodil.japi.ParseResult;
import org.apache.daffodil.japi.ProcessorFactory;
import org.apache.daffodil.japi.UnparseResult;
import org.apache.daffodil.japi.infoset.JDOMInfosetInputter;
import org.apache.daffodil.japi.infoset.JDOMInfosetOutputter;
import org.apache.daffodil.japi.io.InputSourceDataInputStream;
import org.jdom2.input.SAXBuilder;

public class Blah2 {

    public static void main(String[] args) throws IOException, Exception {
        Blah2 b = new Blah2();
        b.process();
    }

    private void process() throws IOException, Exception {

        Compiler dfdlCompiler = Daffodil.compiler();
        dfdlCompiler.setValidateDFDLSchemas(true);
        File schemaFile = this.getFileFromResources("EDIFACT-SupplyChain-D03B/EDIFACT-SupplyChain-Messages-D.03B.xsd");
        ProcessorFactory processorFactory = dfdlCompiler.compileFile(schemaFile);
        DataProcessor dataProcessor = processorFactory.onPath("/");
        java.io.File file = getFileFromResources("TestData/ORDERS_D.03B_Interchange.txt");
        java.io.FileInputStream fis = new java.io.FileInputStream(file);
        InputSourceDataInputStream dis = new InputSourceDataInputStream(fis);
        JDOMInfosetOutputter outputter = new JDOMInfosetOutputter();
        ParseResult parseResult = dataProcessor.parse(dis, outputter);
        Document doc = outputter.getResult().getDocument();
        XMLOutputter xo = new XMLOutputter(org.jdom2.output.Format.getPrettyFormat());
        String xmlString = xo.outputString(doc);

        System.out.println("parsed text... resulting xmlString=" + xmlString);

        SAXBuilder builder = new SAXBuilder();
        Document d2 = builder.build(new StringReader(xmlString));
        JDOMInfosetInputter inputter = new JDOMInfosetInputter(d2);
        WritableByteChannel output = Channels.newChannel(new DataOutputStream(new ByteArrayOutputStream()));
        UnparseResult result = dataProcessor.unparse(inputter, output);

        System.out.println("unparsed xml document.. result.toString()=" + String.valueOf(result));        

        //how can I obtain the original input text???
    }

    private File getFileFromResources(String fileName) throws IOException {
        URL resource = this.getClass().getClassLoader().getResource(fileName);
        return new File(resource.getFile());
    }
}   

解析操作的输出如下。

(我仍然不明白如何完成相反的操作 - 即“解析”)

parsed text... resulting xmlString=<?xml version="1.0" encoding="UTF-8"?>
<D03B:Interchange xmlns:D03B="http://www.ibm.com/dfdl/edi/un/edifact/SupplyChain/D03B">
  <UNB>
    <S001>
      <E0001>UNOA</E0001>
      <E0002>4</E0002>
    </S001>
    <S002>
      <E0004>APPLICATION</E0004>
      <E0007>1</E0007>
    </S002>
    <S003>
      <E0010>COMPANY</E0010>
      <E0007>1</E0007>
    </S003>
    <S004>
      <E0017>20051107</E0017>
      <E0019>1159</E0019>
    </S004>
    <E0020>6002</E0020>
  </UNB>
  <D03B:Message>
    <UNH>
      <E0062>SSDD1</E0062>
      <S009>
        <E0065>ORDERS</E0065>
        <E0052>D</E0052>
        <E0054>03B</E0054>
        <E0051>UN</E0051>
        <E0057>EAN008</E0057>
      </S009>
    </UNH>
    <D03B:BadMessage>
      <Segment>
        <Name>BGM</Name>
        <Data>2B3232302B424B4F4439392B39</Data>
      </Segment>
      <Segment>
        <Name>DTM</Name>
        <Data>2B3133373A32303035313130373A313032</Data>
      </Segment>
      <Segment>
        <Name>NAD</Name>
        <Data>2B42592B353431323334353030303137363A3A39</Data>
      </Segment>
      <Segment>
        <Name>NAD</Name>
        <Data>2B53552B343031323334353030303039343A3A39</Data>
      </Segment>
      <Segment>
        <Name>CTA</Name>
        <Data>2B4141</Data>
      </Segment>
      <Segment>
        <Name>COM</Name>
        <Data>2B7331313A41412A7332313A41412A7333313A4141</Data>
      </Segment>
      <Segment>
        <Name>LIN</Name>
        <Data>2B312B312B303736343536393130343A4942</Data>
      </Segment>
      <Segment>
        <Name>QTY</Name>
        <Data>2B313A3235</Data>
      </Segment>
      <Segment>
        <Name>FTX</Name>
        <Data>2B41464D2B312B2B4C6F7264206F66207468652052696E6773</Data>
      </Segment>
      <Segment>
        <Name>LIN</Name>
        <Data>2B322B312B303736343536393039303A4942</Data>
      </Segment>
      <Segment>
        <Name>QTY</Name>
        <Data>2B313A3235</Data>
      </Segment>
      <Segment>
        <Name>FTX</Name>
        <Data>2B41464D2B312B2B54686520486F62626974</Data>
      </Segment>
      <Segment>
        <Name>LIN</Name>
        <Data>2B332B312B313836313030343635363A4942</Data>
      </Segment>
      <Segment>
        <Name>QTY</Name>
        <Data>2B313A3136</Data>
      </Segment>
      <Segment>
        <Name>FTX</Name>
        <Data>2B41464D2B312B2B5468652053696C6D6172696C6C696F6E</Data>
      </Segment>
      <Segment>
        <Name>LIN</Name>
        <Data>2B342B312B303539363030363735363A4942</Data>
      </Segment>
      <Segment>
        <Name>QTY</Name>
        <Data>2B313A3130</Data>
      </Segment>
      <Segment>
        <Name>FTX</Name>
        <Data>2B41464D2B312B2B546865204368696C6472656E206F6620487572696E</Data>
      </Segment>
      <Segment>
        <Name>UNS</Name>
        <Data>2B53</Data>
      </Segment>
      <Segment>
        <Name>CNT</Name>
        <Data>2B323A34</Data>
      </Segment>
    </D03B:BadMessage>
    <UNT>
      <E0074>22</E0074>
      <E0062>SSDD1</E0062>
    </UNT>
  </D03B:Message>
  <UNZ>
    <E0036>1</E0036>
    <E0020>6002</E0020>
  </UNZ>
</D03B:Interchange>

unparsed xml document.. result.toString()=org.apache.daffodil.japi.UnparseResult@2e734540

Answer 1

UnparseResult实际不包含解解析的结果(是的，也许我们可以更好地命名它；)。 UnparseResult实际上只包含解解析是否成功(通过 isError 方法)以及失败时的任何诊断。解解析数据写入WritableByteChannel您传递给 unparse()作为参数。

问题是，在您的情况下，您可以使用以下内容来定义该 channel :

WritableByteChannel output = Channels.newChannel(new DataOutputStream(new ByteArrayOutputStream()));

因此，您定义的 channel 将写入底层 ByteArrayOutputStream ，但您无权访问这些字节，因为它没有分配给变量。所以你真正想做的是分配一个 ByteArrayOutputStream到一个变量并将其传递给您的新 channel ，然后在解解析后访问字节数组 - 如下所示:

ByteArrayOutputStream boas = new ByteArrayOutputStream();
WritableByteChannel output = Channels.newChannel(new DataOutputStream(boas));
UnparseResult result = dataProcessor.unparse(inputter, output);
System.out.println(boas.toString());

此外，我们的 Java API 测试还提供了一些有关 Daffodil Java API 使用的好资源:

https://github.com/apache/incubator-daffodil/blob/master/daffodil-japi/src/test/java/org/apache/daffodil/example/TestJavaAPI.java

其中包含使用 ByteArrayOutputStream 和 WritableByteChannel 来解析字节并转换为字符串的示例。