【发布时间】：2019-06-20 11:46:25
【问题描述】：
我正在尝试使用 Spring Batch 将 XML 解析为 Java 对象，并且我正在使用 HierarchicalStreamReader 作为转换器来解析对象值并将其从 XML 标记转换为我的 POJO 字段。但是，在转换时，我必须使用 moveup() 和 moveDown() 方法来解析数据，我认为这不是一个好的做法，因为如果 XML 标记中的字段位置发生更改，则会导致代码重写。我已经尝试过 getAttribute(String name) 方法来实现对我试图通过使用其标签名称获取的参数的更多控制，但它给了我无法修复的错误。
此外，没有为界面提供足够的文档。请帮助我解决这个问题或建议我一些控制转换器的方法。提前谢谢...
Student.xml
<students>
<student>
<name>Tony Tester</name>
<rollNo>1</rollNo>
<enrollmentDate>2016-10-31</enrollmentDate>
<sampleTimeStamp>2016-11-07T05:50:45</sampleTimeStamp>
<salary>16.57</salary>
</student>
<student>
<name>Nick Newbie</name>
<rollNo>2</rollNo>
<enrollmentDate>2017-10-31</enrollmentDate>
<sampleTimeStamp>2016-11-07T05:50:45</sampleTimeStamp>
<salary>29.68</salary>
</student>
<student>
<name>Ian Intermediate</name>
<rollNo>3</rollNo>
<enrollmentDate>2018-10-31</enrollmentDate>
<sampleTimeStamp>2016-11-07T05:50:45</sampleTimeStamp>
<salary>789.62</salary>
</student>
</students>
StudentDTO.java
@XmlRootElement(name="student")
public class StudentDTO
{
private String name;
private Integer rollNo;
private Date enrollmentDate;
private Date sampleTimeStamp;
private BigDecimal salary;
... getter, setter and constructor
}
StudentConverter.java
public class StudentConverter implements Converter
{
@Override
public boolean canConvert(@SuppressWarnings("rawtypes") Class type)
{
return type.equals(StudentDTO.class);
}
@Override
public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context)
{
// Nothing to marshal
}
@Override
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context)
{
//reader.getAttribute(0) -- line causing error
//reader.getAttribute("name") -- return null
//reader.getAttributeCount() -- always return 0
reader.moveDown();
StudentDTO student = new StudentDTO();
student.setName(reader.getValue());
reader.moveUp();
reader.moveDown();
student.setRollNo(Integer.parseInt(reader.getValue()));
reader.moveUp();
reader.moveDown();
try
{
student.setEnrollmentDate(new SimpleDateFormat("yyyy-MM-dd").parse(reader.getValue()));
}
catch (ParseException e)
{
e.printStackTrace();
}
reader.moveUp();
reader.moveDown();
try
{
student.setSampleTimeStamp(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss").parse(reader.getValue()));
}
catch (ParseException e)
{
e.printStackTrace();
}
reader.moveUp();
reader.moveDown();
student.setSalary(new BigDecimal(reader.getValue()));
return student;
}
}
reader.getAttribute(0) 的 StackTrace
java.lang.IllegalArgumentException
at org.springframework.util.xml.XMLEventStreamReader.getAttribute(XMLEventStreamReader.java:211)
at org.springframework.util.xml.XMLEventStreamReader.getAttributeValue(XMLEventStreamReader.java:192)
at com.thoughtworks.xstream.io.xml.StaxReader.getAttribute(StaxReader.java:92)
at com.thoughtworks.xstream.io.ReaderWrapper.getAttribute(ReaderWrapper.java:56)
at com.example.demo.utility.StudentConverter.unmarshal(StudentConverter.java:33)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:70)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1230)
at org.springframework.oxm.xstream.XStreamMarshaller.doUnmarshal(XStreamMarshaller.java:826)
at org.springframework.oxm.xstream.XStreamMarshaller.unmarshalXmlStreamReader(XStreamMarshaller.java:786)
at org.springframework.oxm.xstream.XStreamMarshaller.unmarshalXmlEventReader(XStreamMarshaller.java:777)
at org.springframework.oxm.support.AbstractMarshaller.unmarshalStaxSource(AbstractMarshaller.java:411)
at org.springframework.oxm.support.AbstractMarshaller.unmarshal(AbstractMarshaller.java:354)
at org.springframework.batch.item.xml.StaxEventItemReader.doRead(StaxEventItemReader.java:255)
at org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader.read(AbstractItemCountingItemStreamItemReader.java:92)
at org.springframework.batch.item.support.SynchronizedItemStreamReader.read(SynchronizedItemStreamReader.java:55)
at org.springframework.batch.item.support.SynchronizedItemStreamReader$$FastClassBySpringCGLIB$$987ea09.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:749)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688)
at org.springframework.batch.item.support.SynchronizedItemStreamReader$$EnhancerBySpringCGLIB$$66d53b5e.read(<generated>)
at org.springframework.batch.core.step.item.SimpleChunkProvider.doRead(SimpleChunkProvider.java:94)
at org.springframework.batch.core.step.item.SimpleChunkProvider.read(SimpleChunkProvider.java:161)
at org.springframework.batch.core.step.item.SimpleChunkProvider$1.doInIteration(SimpleChunkProvider.java:119)
at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:375)
at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215)
at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:145)
at org.springframework.batch.core.step.item.SimpleChunkProvider.provide(SimpleChunkProvider.java:113)
at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:69)
at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:407)
at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:331)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)
at org.springframework.batch.core.step.tasklet.TaskletStep$2.doInChunkContext(TaskletStep.java:273)
at org.springframework.batch.core.scope.context.StepContextRepeatCallback.doInIteration(StepContextRepeatCallback.java:82)
at org.springframework.batch.repeat.support.TaskExecutorRepeatTemplate$ExecutingRunnable.run(TaskExecutorRepeatTemplate.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
[注意]：我尝试使用以下属性进行调试：
reader.getAttribute(0) -- 抛出错误
reader.getAttribute("name") -- 返回 null
reader.getAttributeCount() -- 总是返回 0
我不确定为什么 reader.getAttributeCount() 返回零，因为每个学生条目有 5 个字段。
我想要的只是对 StudentConverter.unmarshal 部分进行更多控制，我想通过它们的名称或某些标识符来获取属性值，而不是通过它们在 xml 中的位置，因为位置是动态的，以后可能会改变。
【问题讨论】：
标签： java spring-boot spring-batch xstream