Java开发反射机制的实战经验总结

package com.example.demo;
import com.alibaba.fastJSON.annotation.jsONField;
public class User {
    private String name;
    @Value( value ="age_a")
    private String age;

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
     public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
}

Class clazz = User.class;
Field[] fields = clazz.getDeclaredFields();
for (Field field : fields) {
    System.out.println("属性名："+field.getName());
    System.out.println("属性的类型："+field.getGenericType().getTypeName());
}

Map<String,Object> fileds = new HashMap<>();
fileds.put("name","张三");
fileds.put("age","10");
Object o = User.class.newInstance();
 Field[] fields = o.getClass().getDeclaredFields();
 for (Field field : fields) {
     //设置后可用反射访问访问私有变量
     field.setAccessible(true);
     //通过反射给属性赋值
     field.set(o,fileds.get(field.getName()));
 }
 User user1 = (User) o;
 System.out.println(user1.toString());

Field[] fields = User.class.getDeclaredFields();
for (Field field : fields) {
    //设置后可用反射访问访问私有变量
    if ("age".equals(field.getName() )){
        field.setAccessible(true);
       //获取 annotation 这个代理实例所持有的 InvocationHandler
       InvocationHandler invocationHandler = Proxy.getInvocationHandler(field.getAnnotation(Value.class));
       // 获取 InvocationHandler 的 memberValues 字段
        Field memberValues = invocationHandler.getClass().getDeclaredField("memberValues");
        memberValues.setAccessible(true);
        Map<String, Object> values = (Map<String, Object>) memberValues.get(invocationHandler);
        System.out.println(values);
    }
}

public @interface Value {
    String value();
}

Field[] fields = User.class.getDeclaredFields();
for (Field field : fields) {
    if ("age".equals(field.getName() )){
        field.setAccessible(true);
          InvocationHandler invocationHandler = Proxy.getInvocationHandler(field.getAnnotation(JSONField.class));
  ......
    }
}

InvocationHandler invocationHandler = Proxy.getInvocationHandler(field.getAnnotation(Value.class));
Field memberValues = invocationHandler.getClass().getDeclaredField("memberValues");
memberValues.setAccessible(true);
Map<String, Object> values = (Map<String, Object>) memberValues.get(invocationHandler);
values.put("value","new_age");
memberValues.setAccessible(false);

 Object o=User.class.newInstance();
//通过反射获取到User的setAge方法，后面的String.class表示这个setAge方法的参数类型，若有多个，则按顺序列出
//同时，若为其他类型，如List,Long,则为List.class,Long.class
 Method m =  (Method) o.getClass().getMethod("setAge",String.class);
 m.invoke(o,"name");
 User user = (User) o;
 System.out.println(user);

   public Object MapToObject(Object object,Map<String, Object> map) throws IllegalAccessException {
        Class cla =  object.getClass();
        Field[] fields = cla.getDeclaredFields();
        for(Field field:fields){
            field.setAccessible(true);
            if("serialVersionUID".equals(field.getName()))continue;
            if(map.get(field.getName())!=null) {
                Object value=map.get(field.getName());
                value=convertValType(value,field.getType());
                field.set(object, value);
            }
        }
        return object;
    }


    private static Object convertValType(Object value, Class<?> fieldTypeClass) {
        Object o = null;
        if (Long.class.getName().equals(fieldTypeClass.getName())
                || long.class.getName().equals(fieldTypeClass.getName())) {
            o = Long.parseLong(value.toString());
        } else if (Integer.class.getName().equals(fieldTypeClass.getName())
                || int.class.getName().equals(fieldTypeClass.getName())) {
            o = Integer.parseInt(value.toString());
        } else if (Float.class.getName().equals(fieldTypeClass.getName())
                || float.class.getName().equals(fieldTypeClass.getName())) {
            o = Float.parseFloat(value.toString());
        } else if (Double.class.getName().equals(fieldTypeClass.getName())
                || double.class.getName().equals(fieldTypeClass.getName())) {
            o = Double.parseDouble(value.toString());
        } else {
            retVal = o;
        }
        return retVal;
    }