java使用jaxb操作xml示例
本文导语: 首先定义两个示例类ClassA,ClassB,用于后续的示例演示 代码如下:package cn.lzrabbit; public class ClassA { private int classAId; private String classAName; private ClassB classB; public int getClassAId() { return classAId; } ...
首先定义两个示例类ClassA,ClassB,用于后续的示例演示
package cn.lzrabbit;
public class ClassA {
private int classAId;
private String classAName;
private ClassB classB;
public int getClassAId() {
return classAId;
}
public void setClassAId(int classAId) {
this.classAId = classAId;
}
public String getClassAName() {
return classAName;
}
public void setClassAName(String classAName) {
this.classAName = classAName;
}
public ClassB getClassB() {
return classB;
}
public void setClassB(ClassB classB) {
this.classB = classB;
}
}
ClassA
package cn.lzrabbit;
public class ClassB {
private int classBId;
private String classBName;
public int getClassBId() {
return classBId;
}
public void setClassBId(int classBId) {
this.classBId = classBId;
}
public String getClassBName() {
return classBName;
}
public void setClassBName(String classBName) {
this.classBName = classBName;
}
}
ClassB
用于序列化的XmlUtil
package cn.lzrabbit;
import java.io.StringReader;
import java.io.StringWriter;
import javax.xml.bind.*;
public class XmlUtil {
public static String toXML(Object obj) {
try {
JAXBContext context = JAXBContext.newInstance(obj.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");// //编码格式
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);// 是否格式化生成的xml串
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, false);// 是否省略xm头声明信息
StringWriter writer = new StringWriter();
marshaller.marshal(obj, writer);
return writer.toString();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
@SuppressWarnings("unchecked")
public static T fromXML(String xml, Class valueType) {
try {
JAXBContext context = JAXBContext.newInstance(valueType);
Unmarshaller unmarshaller = context.createUnmarshaller();
return (T) unmarshaller.unmarshal(new StringReader(xml));
} catch (Exception e) {
throw new RuntimeException(e.getMessage());
}
}
}
XmlUtil
调用如下:
package cn.lzrabbit;
public class MainRun {
/**
* @param args
*/
public static void main(String[] args) {
ClassB classB = new ClassB();
classB.setClassBId(22);
classB.setClassBName("B2");
ClassA classA = new ClassA();
classA.setClassAId(11);
classA.setClassAName("A1");
classA.setClassB(classB);
System.out.println(XmlUtil.toXML(classA));
}
}
MainRun
输出结果如下:
11
A1
22
B2
这里要注意以下几点
1要序列化的类加上 @XmlRootElement注解,否则会报错(错误提示很清晰,这里就不贴出来了)
2JAXB序列化XML时 默认序列化getter和setter,且getter和setter必须成对出现才会被序列化
3属性名称,默认序列化出来的类和属性名称默认是首字母转换为小写,若需要控制属性名称需要在getter或setter上使用 @XmlElement(name="ClassAId") 指定名称,这里要注意的是@XmlElement放置在getter或setter上都行,但只能放一个,也就是说不能同时在getter和setter上使用@XmlElement注解
4如何控制根节点名称?
使用@XmlRootElement指定name属性即可,如@XmlRootElement(name="ClassA")
5怎么添加命名空间
使用@XmlRootElement(namespace="cn.lzrabbit") 指定namespace属性
6怎么精确控制每个属性名称
JAXB自动转化为首字母小写会导致不可预料的属性名称出现, 不嫌麻烦的话为每个属性设置@XmlElement(name=""),想省事的话使用Field
7怎么样实现序列化时使用Field字段而不是使用setter和getter
在要使用的类上面加上@XmlAccessorType(XmlAccessType.FIELD)注解,并指定为XmlAccessType.FIELD,这里强烈推荐使用@XmlAccessorType(XmlAccessType.FIELD)注解,因为这样你可以精确的控制每个元素的名称,而不需要为每个属性去设置@XmlElement(name="")注解,当然也可以在Field上使用@XmlElement注解
下面给出使用了使用如上注解后的代码示例
@XmlRootElement(namespace="cn.lzrabbit")
@XmlAccessorType(XmlAccessType.FIELD)
public class ClassA {
private int classAId;
@XmlElement(name="ClassAName")
private String classAName;
private ClassB classB;
public int getClassAId() {
return classAId;
}
public void setClassAId(int classAId) {
this.classAId = classAId;
}
public String getClassAName() {
return classAName;
}
public void setClassAName(String classAName) {
this.classAName = classAName;
}
public ClassB getClassB() {
return classB;
}
public void setClassB(ClassB classB) {
this.classB = classB;
}
}
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class ClassB {
private int ClassBId;
private String ClassBName;
public int getClassBId() {
return ClassBId;
}
public void setClassBId(int classBId) {
this.ClassBId = classBId;
}
public String getClassBName() {
return ClassBName;
}
public void setClassBName(String classBName) {
this.ClassBName = classBName;
}
}
输出xml为
11
A1
22
B2