java内省

　　内省：操作javabean的属性，属性指的是字段拥有get或set方法叫做属性

    /*   内省 Introspector    */
    public void test() throws Exception{
        BeanInfo info = Introspector.getBeanInfo(Person.class);
        PropertyDescriptor[] pds = info.getPropertyDescriptors();
        for(PropertyDescriptor pd : pds){
            System.out.println(pd.getName());
        }
    }
    @Test
    public void test1() throws Exception{
        Person p =  new Person();
        PropertyDescriptor pdS = new PropertyDescriptor("name", Person.class);
        Method methodS = pdS.getWriteMethod();
        methodS.invoke(p, "大梦");
        PropertyDescriptor pd = new PropertyDescriptor("name", Person.class);
        Method method = pd.getReadMethod();
        System.out.println(method.invoke(p, null));
        System.out.println(pdS.getPropertyType());
    }

　　这个有一个第三方jar，叫做BeanUtils（apche）,运行这个第三方jar需要一个日志文件commons-loggin.jar

　　这个BeanUtils可以支持8种的基本数据类型的相互转化，除此之外的类型转换都需要我们自己写注册转化器

    public void test() throws Exception, Exception, Exception {
        Person p = new Person();
        ConvertUtils.register(new Converter() {
            @Override
            public Object convert(Class type, Object value) {
                if(value == null){
                    return null;
                }
                if(!(value instanceof String)){
                    throw new ConversionException("数据不是String类型");
                }
                String str = (String) value;
                if(str.trim() == null){
                    return null;
                }
                SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
                try {
                    return df.parse(str);
                } catch (ParseException e) {
                    throw new ConversionException(e);
                }
            }
        },Date.class);
        String brithday = "1920-09-06";    
        BeanUtils.setProperty(p, "name", "duweneli");
        BeanUtils.setProperty(p, "pwd", "123456");
        BeanUtils.setProperty(p, "age", "23");
        BeanUtils.setProperty(p, "brithday", brithday);
        System.out.println(BeanUtils.getProperty(p, "name"));
        System.out.println(BeanUtils.getProperty(p, "pwd"));
        System.out.println(BeanUtils.getProperty(p, "age"));
        System.out.println(BeanUtils.getProperty(p, "brithday"));
    }
    
    public void test1(){
        Map<Integer,String> map = new LinkedHashMap<Integer, String>();
        map.put(1, "aa"); 
        map.put(2, "bb"); 
        map.put(3, "cc");
        for(Map.Entry<Integer, String> entry : map.entrySet()){
            Integer key = entry.getKey();
            String value = entry.getValue();
            System.out.println(key+"="+value);
            
        }