JAVA-反射学习（3）

import java.lang.reflect.*;

class Stu{
    private String name;
    private int age;
    public boolean flag =true;
    public Stu(){}
    public Stu(String name,int age){
        this.setName(name);
        this.setAge(age);
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }

    public void study(){
        System.out.println("i can study");
    }
    private void speak(String languge,int x){
        System.out.println("I can speak :"+languge+" "+x);
    }
    public String toString(){
        return this.name+" ： "+this.age;
    }

}

public class ReflectThree {

    public static void classForInstance() throws Exception{
        //第一步：我们通过上面的三种方式可以得到类的信息；
        @SuppressWarnings("unchecked")
        Class<Stu> stuClass =       (Class<Stu>)Class.forName("GeneIterAdaptReflect.com.Stu");

        //第二步：如果该类Stu有无参的构造器，那么就可以用类信息调用newInstance();来创建一个实例
        //好处：降低了于类(子类)之间的耦合，比如Stu是一个接口或者超类，我们就可以利用多态直接与接口打交道，来调用子类的方法
        Stu stu1 = stuClass.newInstance();
        stu1.setName("丽丽");
        System.out.println(stu1.getName());

        //第三步：通过有参数的构造器实例对象；
        @SuppressWarnings("unchecked")
        Constructor<Stu>[] constructor = (Constructor<Stu>[]) 
        stuClass.getConstructors();
        Stu stu2 = constructor[1].newInstance("qian",36);
        System.out.println(stu2.toString());
    }
    public static void methodInfo() throws Exception{
        @SuppressWarnings("unchecked")
        Class<Stu> stuClass = (Class<Stu>) 
        Class.forName("GeneIterAdaptReflect.com.Stu");
        //第四步：获取类的全部方法 public void study();
        Method[] methods  = stuClass.getDeclaredMethods();  
        for(Method m:methods){
            StringBuilder s = new StringBuilder();

            //返回修饰符：
            int x = m.getModifiers();
            String modifyString = Modifier.toString(x);

            //返回值类型；
            Class<?> returnType = m.getReturnType();
            //Type returnType = m.getGenericReturnType();

            //参数个数及类型：
            Class<?>[] paraClass = m.getParameterTypes();
            if(paraClass.length==0){
                s.append("");
            }
            else{
                for(int i=0;i<paraClass.length;i++){
                    s.append(paraClass[i].getSimpleName()+" ");
                }
            }       
            System.out.println(modifyString+" 
            "+returnType.getSimpleName()+" "+m.getName()
            +"("+s+")");
        }   
    }

    public static void fieldInfo() throws Exception{
        Class<Stu> stuClass = (Class<Stu>) 
        Class.forName("GeneIterAdaptReflect.com.Stu");
        Field[] fields = stuClass.getDeclaredFields();
        for(int i=0;i<fields.length;i++){
            System.out.println(Modifier.toString(fields[i].
            getModifiers())+" "+fields[i].getName());
        }
    }

    public static void callSpeakMethod()throws Exception{
        //第一步拿到对象
        Class<Stu> stuClass = (Class<Stu>)  Class.forName
        ("GeneIterAdaptReflect.com.Stu");
        Constructor<Stu>[] constructor=
        (Constructor<Stu>[]) stuClass.getConstructors();
        Stu stu3 = constructor[1].newInstance("qian",26);
        //第二步拿到方法
        Class<?>[] paraClass =new Class[]
        {String.class,int.class};
        Method privateMethod = 
        stuClass.getDeclaredMethod("speak",paraClass);

        //设置私有方法的可访问权
        privateMethod.setAccessible(true);
        //调用方法
        privateMethod.invoke(stu3, "English  French",2);

    }
    /**
     * @param obj: 对象
     * @param fieldName ：属性名称(字段名)
     * @param paraType  : 参数类型
     * @param value  ：想赋予的值
     * @throws Exception 
     */
    public static void setter(Object obj,String fieldName,Class<?> paraType,Object value) throws Exception{
        //set的方法的标准写法：setName,而传进来的fieldName是字段
        名 比如 name;要转换成标准形式；
        String firstChar =
        fieldName.substring(0, 1).toUpperCase();
        String methodName = firstChar+fieldName.substring(1);

        obj.getClass().getDeclaredMethod
        ("set"+methodName, paraType).invoke(obj, value);
    }
    /**
     * @param obj :对象名
     * @param fieldName  ：要get的字段名
     * @return Object :返回任意类型值
     * @throws Exception
     */
    public static Object getter(Object obj,String fieldName) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException, SecurityException{
        String firstChar =
        fieldName.substring(0, 1).toUpperCase();
        String methodName = firstChar+fieldName.substring(1);
        //return obj.getClass().getDeclaredMethod("get"+methodName,null).invoke(obj,null);
        return obj.getClass().getDeclaredMethod("get"+methodName).invoke(obj);
    }
    public static void main(String[] args) throws Exception {

        Class<Stu> stuClass = (Class<Stu>) Class.forName("GeneIterAdaptReflect.com.Stu");
        Stu stuObj = stuClass.newInstance();
        setter(stuObj,"name",String.class,"zhangsan");
        String getString =(String)getter(stuObj,"name");
        System.out.println(getString);

    }

}