上下文
我需要解析一个XML。这个XML很大,所以我使用StAx来处理我感兴趣的每个元素。我使用JDK附带的默认实现。
问题
当一个XML元素位于同一类型的另一个元素(例如<person>
)之前,并且它们之间没有任何字符时,它会跳过第二个。所以,如果我有10个人一个接一个,我只能拆散5个人。例如:
<people><person>..</person><person>..</person></people>
我针对封装在方法countUnmarshalledPersonEntities()
中的一段代码构建了一个测试来显示这种行为。
问题是,当元素之间有空格时,比如:
<people><person><id>1</id></person> <person><id>2</id></person></people>
它分解了两个实体,这没关系
但当节点之间没有空格时,如:
<people><person><id>1</id></person><person><id>2</id></person></people>
第一次解组跳过下一个打开的标签<person>
,然后忽略第二个人。我只解析1个实体。
测试
package org.opensource.lab.stream;
import static org.junit.Assert.assertEquals;
import java.io.InputStream;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamReader;
import org.apache.commons.io.IOUtils;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class StreamParserProblemTest {
private XMLInputFactory xmlif;
private XMLStreamReader xmlStreamReader;
private Unmarshaller personUnmarshaller;
private final InputStream xmlStreamPersonsNoSeparated = IOUtils.toInputStream(
"<people><person><id>1</id></person><person><id>2</id></person></people>"
);
private final InputStream xmlStreamWithPersonsWhitespaceSeparated = IOUtils.toInputStream(
"<people><person><id>1</id></person> <person><id>2</id></person></people>"
);
@Before
public void setUp() throws Exception {
JAXBContext jaxbContext = JAXBContext.newInstance(Person.class);
personUnmarshaller = jaxbContext.createUnmarshaller();
xmlif = XMLInputFactory.newInstance();
}
@After
public void cleanUp() throws Exception {
if(xmlStreamReader != null) {
xmlStreamReader.close();
}
}
@XmlRootElement(name = "person")
static class Person {
String id;
}
@Test
public void whenNoSpacesBetweenNodes_shouldFind2Persons_FAIL() throws Exception {
xmlStreamReader = xmlif.createXMLStreamReader(xmlStreamPersonsNoSeparated, "UTF-8");
int personTagsFound = countUnmarshalledPersonEntities();
assertEquals(personTagsFound, 2);
}
/**
* I don't know why, but if there's at least one whitespace character between node of the same type it won't skip.
*
* @throws Exception in a test
*/
@Test
public void whenWithSpacesBetweenNodes_shouldFind2Persons_SUCCESS() throws Exception {
xmlStreamReader = xmlif.createXMLStreamReader(xmlStreamWithPersonsWhitespaceSeparated, "UTF-8");
int personTagsFound = countUnmarshalledPersonEntities();
assertEquals(personTagsFound, 2);
}
/**
* CODE to test.
*
* @return number of unmarshalled persons (people).
* @throws Exception
*/
private int countUnmarshalledPersonEntities() throws Exception {
int personTagsFound = 0;
while (xmlStreamReader.hasNext()) {
int type = xmlStreamReader.next();
if (type == XMLStreamConstants.START_ELEMENT && xmlStreamReader.getName().toString().equalsIgnoreCase("person")) {
personUnmarshaller.unmarshal(xmlStreamReader, Person.class);
personTagsFound++;
}
}
return personTagsFound;
}
}
你知道代码出了什么问题吗?
谢谢。
感谢您附加的单元测试,这真的让理解变得更容易了!
当您在xmlStreamReader
上执行unmarshal
时,只要有属于您的实体的标记,XMLStreamReader就会自己隐式调用next
。因此,在关闭person
标记后,它将调用next
并指向下一个实体的第一个person
标记。在下一次迭代中调用xmlStreamReader.next()
时,您可以跳过它。如果实体之间存在空白,则不会发生这种情况,因为解析后,读者会指向空白。
这个修改后的代码对我有效,你的两个单元测试都成功了:
while (xmlStreamReader.hasNext()) {
if (xmlStreamReader.isStartElement() && xmlStreamReader.getName().toString().equalsIgnoreCase("person")) {
personUnmarshaller.unmarshal(xmlStreamReader, Person.class);
personTagsFound++;
} else {
xmlStreamReader.next();
}
}