java注解（一）概念及JABX使用例子
一、概念____________________________________________________________
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注解，作用类似有xml配置文件，避免同一份信息保存在两个地方。
@Override,@Deprecated (key,value)都省略了
@SupressWarnings({"uncheck", "unused"})大括号表示数组类型，key只有一个，省略
@XmlElement(name = "id")配置参数，键值对
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注解用@interface用来声明定义，元注解，在java.lang.annotation包里面，有4个
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@Documented@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.ANNOTATION_TYPE)public @interface Documented {//are to be documented by javadoc and similar tools by default}??
@Documented@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.ANNOTATION_TYPE)public @interface Inherited {//}?
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//@Retention保留策略: CLASS、RUNTIME和SOURCE,分别表示注解保存在类文件、JVM运行时刻和源代码中。 //只有RUNTIME，才能在运行时刻通过反射API来获取到注解的信息，类似SSH的xml配置文件的注入作用 @Documented@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.ANNOTATION_TYPE)public @interface Retention { RetentionPolicy value();}?
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//@Target用来声明注解的作用范围，如类型、方法和域等@Documented@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.ANNOTATION_TYPE)public @interface Target { ElementType[] value();}?
二、JAXB例子____________________________________________________________
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JAXB（Java Architecture for XML Binding)?
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/** * @author timeriver.wang * @date 2013-01-09 8:07:01 PM */@XmlRootElement@XmlAccessorType(XmlAccessType.PROPERTY)public class Student {private String id;private String name;public String getId() {return id;}@XmlElement(name = "id")public void setId(String id) {this.id = id;}@XmlElement(name = "name")public String getName() {return name;}public void setName(String name) {this.name = name;}}?
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/** * @author timeriver.wang * @date 2013-01-09 8:07:09 PM */@XmlRootElementpublic class Teacher { private String id; private String name; private List<Student>students; @XmlAttribute (name = "tid") public String getId() { return id; } public void setId( String id ) { this.id = id; } @XmlElement(name = "tname") public String getName() { return name; } public void setName( String name ) { this.name = name; } @XmlElement(name = "students") public List<Student> getStudents() { return students; } public void setStudents( List<Student> students ) { this.students = students; }}?
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/** * @author timeriver.wang * @date 2013-01-09 8:08:15 PM */public class Test { public static void main( String[] args )throws Exception {// toXml();// toStu(); toXmls(); } public static void toXml()throws Exception { Student stu = new Student(); stu.setId( "007" ); stu.setName( "zhouxingxing" ); File file = new File( "D:/stu.xml" ); JAXBContext jaxbContext = JAXBContext.newInstance( Student.class ); Marshaller jaxbMarshaller = jaxbContext.createMarshaller(); jaxbMarshaller.setProperty( Marshaller.JAXB_FORMATTED_OUTPUT, true ); jaxbMarshaller.marshal( stu, file ); jaxbMarshaller.marshal( stu, System.out ); } public static void toStu()throws Exception { File file = new File( "D:/stu.xml" ); JAXBContext jaxbContext = JAXBContext.newInstance( Student.class ); Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller(); Student stu = (Student) jaxbUnmarshaller.unmarshal( file ); System.out.println( stu ); } public static void toXmls()throws Exception { Student stu = new Student(); stu.setId( "007" ); stu.setName( "zhouxingxing" ); Student stu2 = new Student(); stu2.setId( "008" ); stu2.setName( "dawenxi" ); List<Student>students = new ArrayList<Student>(); students.add( stu ); students.add( stu2 ); Teacher teacher = new Teacher(); teacher.setId( "101" ); teacher.setName( "DASHI" ); teacher.setStudents( students ); File file = new File( "D:/teacher.xml" ); JAXBContext jaxbContext = JAXBContext.newInstance( Teacher.class ); Marshaller jaxbMarshaller = jaxbContext.createMarshaller(); jaxbMarshaller.setProperty( Marshaller.JAXB_FORMATTED_OUTPUT, true ); jaxbMarshaller.marshal( teacher, file ); jaxbMarshaller.marshal( teacher, System.out ); }}??