java反射

　　反射：就是加载类，然后在解剖类的各个组成部分（反射都是用于做框架的）

/**
     * 反射--->提取构造方法-->public 
     * @throws Exception
     */
    public void test() throws Exception{
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Constructor c = clazz.getConstructor(null);
        Person p = (Person) c.newInstance(null);
        System.out.println(p.context);
        System.out.println("*************************************");
        Constructor constructor = clazz.getConstructor(String.class,String.class,int.class);
        Person person = (Person) constructor.newInstance("aaa","123",12);
        System.out.println(person.getAge());
        System.out.println(person.getName());
        
    }
    /**
     * 反射--->提取构造方法-->private
     * @throws Exception
     */
    public void test1() throws Exception{
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Constructor c = clazz.getDeclaredConstructor(String.class);
        c.setAccessible(true);//暴力反射
        Person p = (Person) c.newInstance("du");
    }
    
    /**
     * 反射--->直接new方法
     * @throws Exception
     */
    public void test2() throws Exception{
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Person p = (Person) clazz.newInstance();
        System.out.println(p.context);
    }
    /**
     * 正常方法反射调用
     * @throws Exception
     */
    public void test3() throws Exception{
        Person p = new Person();
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Method methof = clazz.getMethod("aa", null);
        methof.invoke(p, null);
    }
    /**
     * 私有方法反射调用
     * @throws Exception
     */
    public void test4() throws Exception{
        Person p = new Person();
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Method methof = clazz.getDeclaredMethod("find", null);
        methof.setAccessible(true);
        methof.invoke(p, null);
    }
    /**
     * 有参方法--反射调用
     * @throws Exception
     */
    public void test5() throws Exception{
        Person p = new Person();
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Method method = clazz.getMethod("aa", String.class,int.class);
        method.invoke(p, "老大",12);
        
    }
    /**
     * 静态方法调用,带返回值
     * @throws Exception
     */
    public void test6() throws Exception{
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Method method = clazz.getMethod("bb", String[].class);
        String[] str = (String[]) method.invoke(null, new Object[]{new String[]{"1","2","3","4"}});
        System.out.println(str);
    }
    /**
     * 调用mian方法
     * @throws Exception
     */
    public void test7() throws Exception{
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Method method = clazz.getMethod("main", String[].class);
        method.invoke(null, (Object)new String[]{"aa","bb"});
        
    }
    /**
     * 反射出字段 public
     * @throws Exception
     */
    public void test8() throws Exception{
        Person p = new Person();
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Field filed = clazz.getField("context");
        filed.set(p, "456");
        System.out.println(filed.get(p));
        
        
    }
    
    /**
     * 反射出字段 private
     * @throws Exception
     */
    @Test
    public void test9() throws Exception{
        Person p = new Person();
        Class clazz = Class.forName("com.tkbs.du.refle.Person");
        Field filed = clazz.getDeclaredField("context1");
        filed.setAccessible(true);
        System.out.println(filed.get(p));
    }
    
    /**************************反射****************************************/

　　在反射mian方法时有错，jdk1.4升级到jdk5.0出现了，mian方法的参数如果是这样写method.invoke(null,new String[]{"aa","bb"});它会抛一个异常，jvm会把aa和bb解析成两个参数，所以控制台会抛出一个参数错误的异常。

　　解决办法：method.invoke(null,new Object[]{new String[]{"aa","bb"}});  或者 invoke(null,(Object)new String[]{"aa","bb"};