java反射

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反射就是把java类中各种成分映射成相应的java类

Constructor:

Method:

Field:

Constructor con=Pet.class.getConstructor(Integer.class,String.class);Pet p=(Pet)con.newInstance(new Integer(456),new String("hello word!"));System.out.println(p.getName()+p.getId());Field field=p.getClass().getDeclaredField("id");//获得定义了的字段  ||  getField("id")公有field.setAccessible(true);//当获得私有字段时需设置System.out.println(field.get(p));


1、java的反射用法:

①找到类:Class cl = Class.forName("java.util.Date");
②创建对象(要求这个类中含有空参数的构造方法):Object obj = cl.newInstence();
③根据名称和参数找方法:Method method1 = cl.getMethod("getTime");//如果没有参数不用写第二个参数如果有参数的如:Method method2 = cl.getMethod("setTime",long.class);   

④在某个对象上面执行方法,Object result = method1.invoke(obj);//如果有参数的Object result = method2.invoke(obj,21317362721);

执行的方如果有返回值,将返回值返回,否则返回null 

⑤如果invoke方法的第一个参数为NULL,说明该Method对象对应的是一个静态的方法


public static void test(Object o,String str) throws Exception{o=Class.forName("org.han.entity.Pet").newInstance();Method method = o.getClass().getMethod(str, new Class[] {String.class});method.invoke(o, new Object[]{"hello word!"}); //JDK1.4   ||   JDK1.5 
invoke(o,Object...args)

}

2、封装javaBeen

public static void beenObject(Object object, String[] fields,Object[] params) throws Exception {Class<?> cl = object.getClass();for (int i = 0; i < fields.length; i++) {StringBuffer buffer = new StringBuffer();Field field = cl.getDeclaredField(fields[i]);Class<?> paramType = field.getType();buffer.append("set");buffer.append(fields[i].substring(0, 1).toUpperCase());buffer.append(fields[i].substring(1));Method method = cl.getDeclaredMethod(buffer.toString(), paramType);method.invoke(object, params[i]);}}

public Object mysetter1(String s,Map<String,Object> k_v) throws Exception{Class o = Class.forName(s);Object obj = o.newInstance();Iterator<String> it = k_v.keySet().iterator();Pattern pattern = Pattern.compile("^\\w");while(it.hasNext()){String pro = it.next();Matcher matcher = pattern.matcher(pro);String m_name = "set";if(matcher.find()){m_name += matcher.replaceFirst(matcher.group(0).toUpperCase());}o.getMethod(m_name, k_v.get(pro).getClass()).invoke(obj, k_v.get(pro));}return obj;}