JAXB解析與生成XML
阿新 • • 發佈:2019-01-23
使用JAXB可以快速完成Java類到XML的對映,方便XML檔案的解析與生成。
常用註解
@XmlRootElement(name = "Country")將Java類或列舉型別對映成XML中根元素,設定name屬性的值可指定義根元素名稱,不設定則預設為型別首字母小寫的名稱。
@XmlType(propOrder = {"name", "capital", "population", "foundationTime"})
將Java類後列舉型別對映到XML模式型別,設定propOrder可以指定生成XML中各元素的先後順序。
@XmlElement(name = "CFoundationTime")
將JavaBean中的欄位值對映到XML元素,設定name屬性的值可指定XML元素的名稱。
@XmlAttribute
將JavaBean中的欄位對映到XML中元素的屬性,設定name屬性的值可指定xml中元素屬性的名稱;
至於required屬性,官方文件是說指定 XML 模式屬性是可選的還是必需的,不是特別理解。
@XmlElementWrapper(name = "CountryWrapper")
為集合生成xml包裝器元素,簡單來講就是使XML元素更有層次感,更美觀,該註解只能用在集合上。
例子
1、類結構如下
Country與Countries為對映物件;
JAXBUtils提供讀寫XML的方法;
JAXBXMLTest提供讀寫測試方法;
2、各個類如下
Country類:
package com.jaxb; import javax.xml.bind.annotation.*; @XmlType(propOrder = {"name", "capital", "population", "foundationTime"}) @XmlRootElement(name = "Country") public class Country { private int population; private String name; private String capital; private int rank; private String foundationTime; public String getFoundationTime() { return foundationTime; } @XmlElement(name = "CFoundationTime") public void setFoundationTime(String foundationTime) { this.foundationTime = foundationTime; } public int getPopulation() { return population; } @XmlElement(name = "CPopulation") public void setPopulation(int population) { this.population = population; } public String getName() { return name; } @XmlElement(name = "CName") public void setName(String name) { this.name = name; } public String getCapital() { return capital; } @XmlElement(name = "CCapital") public void setCapital(String capital) { this.capital = capital; } public int getRank() { return rank; } @XmlAttribute(name = "CRank", required = true) public void setRank(int rank) { this.rank = rank; } @Override public String toString() { return "Country=[Name=" + this.getName() + ", Capital=" + this.getCapital() + ", Population=" + this.getPopulation() + ", FoundationTime=" + this.getFoundationTime() + "]"; } }
Countries類:
package com.jaxb;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import java.util.List;
@XmlRootElement(name = "Countries")
public class Countries {
private List<Country> countries;
public List<Country> getCountries() {
return countries;
}
@XmlElementWrapper(name = "CountryWrapper")
@XmlElement(name = "Country")
public void setCountries(List<Country> countries) {
this.countries = countries;
}
@Override
public String toString() {
return "Countries=[" + this.getCountries() + "]";
}
}
JAXBUtils類:
package com.jaxb;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import java.io.File;
public class JAXBUtils {
public static void writeXML(Object obj, File path, Class... clazz) throws JAXBException {
JAXBContext jctx = JAXBContext.newInstance(clazz);
Marshaller marshaller = jctx.createMarshaller();
// 格式化輸出,設定換行和縮排,不設定則會顯示在一行
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(obj, path);
// 設定控制檯輸出
marshaller.marshal(obj, System.out);
}
public static Object readXML(File path, Class... clazz) throws JAXBException {
JAXBContext jctx = JAXBContext.newInstance(clazz);
Unmarshaller unMarshaller = jctx.createUnmarshaller();
Object obj = unMarshaller.unmarshal(path);
return obj;
}
}
JAXBXMLTest類:
package com.jaxb;
import javax.xml.bind.JAXBException;
import java.io.File;
import java.time.LocalDate;
import java.util.ArrayList;
public class JAXBXMLTest {
private static final String XML_PATH_COUNTRY = "./Country.xml";
private static final String XML_PATH_COUNTRIES = "./Countries.xml";
public static void main(String[] args) throws JAXBException {
Country china = new Country();
china.setName("中國");
china.setCapital("北京");
china.setPopulation(1400000000);
china.setRank(25);
String fTimeChina = LocalDate.of(1949, 10, 1).toString();
china.setFoundationTime(fTimeChina);
Country america = new Country();
america.setName("United States of America");
america.setCapital("New York");
america.setPopulation(300000000);
america.setRank(11);
String fTimeAmerica = LocalDate.of(1776, 7, 4).toString();
america.setFoundationTime(fTimeAmerica);
File xmlFile = new File(XML_PATH_COUNTRY);
File xmlFile1 = new File(XML_PATH_COUNTRIES);
System.out.println("\n【寫入到" + XML_PATH_COUNTRY + "】");
JAXBUtils.writeXML(china, xmlFile, Country.class);
System.out.println("\n【寫入list到" + XML_PATH_COUNTRIES + "】");
Countries countries = new Countries();
ArrayList<Country> list = new ArrayList<>();
list.add(china);
list.add(america);
countries.setCountries(list);
JAXBUtils.writeXML(countries, xmlFile1, Countries.class);
System.out.println("\n【從" + XML_PATH_COUNTRIES + "中讀取】");
Countries countriesRead = (Countries) JAXBUtils.readXML(xmlFile1, Countries.class, Country.class);
System.out.println(countriesRead);
System.out.println("\n【從" + XML_PATH_COUNTRY + "中讀取】");
Country countryRead = (Country) JAXBUtils.readXML(xmlFile, Country.class);
System.out.println(countryRead);
}
}
執行測試類,結果如下: