反射与XML解析

   public class Demo1 {
        public static void main(String[] args) throws Exception {
              getClazz();
              getConstructor();
              getMethod();
              getField();      
        }

（1）获取类的类对象
public static void getClazz() throws Exception{
== 方式1：使用class属性获取==
Class clazz1=Person.class;
System.out.println(clazz1.hashCode());
== 方法2 使用getClass方法==
Person shaobo=new Person();
Class clazz2 = shaobo.getClass();
System.out.println(clazz2.hashCode());
== 方式3 使用Class.forName方法：耦合性低，不依赖于具体的类，可以编译通过==
Class clazz3=Class.forName(“com.qf.Person”);
System.out.println(clazz3.hashCode());
//扩展
== 获取父类==
Class superclass = clazz3.getSuperclass();
System.out.println(superclass.getName());
Type genericSuperclass = clazz3.getGenericSuperclass();
System.out.println(genericSuperclass.getTypeName());
== 获取接口==
Class[] interfaces = clazz3.getInterfaces();
System.out.println(interfaces.length);
for (Class anInterface : interfaces) {
System.out.println(anInterface.toString());
}
== 获取包名==
Package aPackage = clazz3.getPackage();
System.out.println(aPackage.getName());
}
public static void getConstructor() throws Exception{
Class clazz=Class.forName(“com.qf.Person”);
构造方法
Constructor[] constructors = clazz.getConstructors();
for (Constructor constructor : constructors) {
System.out.println(constructor);
}
System.out.println("--------------------------");
== //2.1获取无参构造方法==
Constructor constructor = clazz.getConstructor();
//2.2获取带参
Constructor constructor1 = clazz.getConstructor(String.class, int.class, String.class);
System.out.println(constructor);
System.out.println(constructor1);
== //3利用构造方法创建对象==
System.out.println("---------利用构造方法创建对象------------");
Person zhangsan=new Person();
Object lisi = constructor.newInstance();
System.out.println(zhangsan);
System.out.println(lisi);

Object wangwu = constructor1.newInstance("王五", 20, "男");
    System.out.println(wangwu);

//简单创建对象的方法
Object o = clazz.newInstance();
System.out.println(o.toString());
}

public static void getMethod() throws Exception{
//1获取无参的方法
Class clazz=Class.forName(“com.qf.Person”);
//Method[] methods = clazz.getMethods();//获取公类自己公开的方法，继承的公开方法
Method[] methods = clazz.getDeclaredMethods();//获取公类自己所有的方法，包括非公开的方法
System.out.println("-----------getMethods();----------");
for (Method method : methods) {
System.out.println(method);
}
Person p=new Person();
p.show();
Object zhangsan = clazz.newInstance();
Method show = clazz.getMethod(“show”);
show.invoke(zhangsan);// zhangsan.show();
2获取有参
Method show2=clazz.getMethod(“show”,String.class);
show2.invoke(zhangsan, “北京”);
== 3获取带返回值的方法==
Method getInfo = clazz.getMethod(“getInfo”);
Object value=getInfo.invoke(zhangsan);
System.out.println(value);
4获取静态方法
Method print = clazz.getMethod(“print”);
print.invoke(null);// Person.print();
5私有方法
Method show3 = clazz.getDeclaredMethod(“show”, String.class, String.class);
//设置访问权限无效
show3.setAccessible(true);
show3.invoke(zhangsan, “上海”,“[email protected]”);
}
public static void getField() throws Exception{
== 1获取类对象==
Class clazz = Class.forName(“com.qf.Person”);
== 2获取==
Field[] declaredFields = clazz.getDeclaredFields();
for (Field declaredField : declaredFields) {
System.out.println(declaredField);
}

获取单个
System.out.println("--------------------------");
Field name = clazz.getDeclaredField(“name”);
Person wangwu=new Person();
wangwu.name=“王五”;
Object wangwu = clazz.newInstance();
== 赋值==
name.setAccessible(true);
name.set(wangwu, “王五”);// wangwu.name=“王五”;
== 获取==
Object object=name.get(wangwu);// wangwu.name
System.out.println(object);
}

注解

三个基本的 Annotation:

​ @Override:限定重写父类方法, 该注解只能用于方法

​ @Deprecated:用于表示某个程序元素(类, 方法等)已过时

​ @SuppressWarnings: 抑制编译器警告.
注解属性的作用：原来写在配置文件中的信息，可以通过注解的属性进行描述。
Annotation的属性声明方式：String name();
属性默认值声明方式：Stringname() default “xxx”;
特殊属性value：如果注解中有一个名称value的属性，那么使用注解时可以省略value=部分，如@MyAnnotation(“xxx")
特殊属性value[];

创建和使用

public @interface MyAnnocation {
	String name();
	int num() default 10;
	MyAnnocation2 anno();
}
public @interface MyAnnocation2 {
	String value();
}

public class Demo1 {
	@MyAnnocation(name="哈哈",num=50,anno=@MyAnnocation2(value = "xxx"))
	public void show() {
		System.out.println("xxxxxxx");
	}
}

XML解析

public class Demo1 {
    public static void main(String[] args) throws Exception{
        //readXML();
//        writeXML();
//        updateAndDelete();
        readXMLXPath();
    }

    //(1)读取xml文件
    public static void readXML() throws Exception{
        //1创建SaxReader读取器(类似 流)
        SAXReader reader=new SAXReader();
        //2读取,返回Document对象(代表DOM树)
        Document document=reader.read(new FileReader("aaa.xml"));
        //3获取跟节点
        Element root = document.getRootElement();
        System.out.println(root);//books
        //4获取子节点
        List bookList = root.elements("book");
        //5遍历
        for (Element element : bookList) {
//            System.out.println(element);
            //获取id属性
            String id = element.attributeValue("id");
            //获取name
            String name = element.elementText("name");
            //获取author
            String author = element.elementText("author");
            //获取price
            String price = element.elementText("price");
            System.out.println(id+" "+name+" "+author+" "+price);
        }


    }
    //(2)写入xml文件
    public static void writeXML() throws Exception{
        //1创建SaxReader
        SAXReader reader=new SAXReader();
        //2读取,获取Document对象
        Document document=reader.read(new FileReader("aaa.xml"));
        //3获取根节点
        Element root = document.getRootElement();
        //4添加元素
        Element book = root.addElement("book");
        //5添加属性
        book.addAttribute("id", "1003");
        //6添加子元素
        book.addElement("name").setText("java基础入门");
        book.addElement("author").setText("xxx");
        book.addElement("price").setText("100");
        //数据都在内存中


        //写入books.xml文件中
        //1创建输出格式
        OutputFormat outputFormat=OutputFormat.createCompactFormat();
        outputFormat.setEncoding("utf-8");
        //2创建XMLWriter
        XMLWriter writer=new XMLWriter(new FileWriter("aaa.xml"), outputFormat);
        //3写入
        writer.write(document);
        //4关闭
        writer.close();


    }
    //(3)修改和删除
    public static void updateAndDelete() throws Exception{
        //1创建SaxReader
        SAXReader reader=new SAXReader();
        //2读取,获取Document对象
        Document document=reader.read(new FileReader("aaa.xml"));
        //3获取根节点
        Element root = document.getRootElement();
        List bookList = root.elements("book");
        //4更新价格
        Element firstbook = bookList.get(0);
        firstbook.element("price").setText("99");
        Element secondbook = bookList.get(1);
        secondbook.element("price").setText("8");

        //5删除最后一个

        Element lastbook = bookList.get(bookList.size() - 1);
        root.remove(lastbook);

        //6写入文件
        OutputFormat outputFormat=OutputFormat.createPrettyPrint();
        outputFormat.setEncoding("utf-8");
        //7创建XMLWriter
        XMLWriter writer=new XMLWriter(new FileWriter("books.xml"), outputFormat);
        //8写入
        writer.write(document);
        //9关闭
        writer.close();

    }



}