Java的反射工具很強大，有句著名的話：No reflection ,no frameworks.

工作中直到涉及到UT，才體會到它的重要性，現歸納整理一個小例子：

反射工具類:import?java.lang.reflect.Field;

import?java.lang.reflect.InvocationTargetException;

import?java.lang.reflect.Method;

public?class?ReflectionUtil?{

/***

*?獲取私有成員變量的值

*

*/

public?static?Object?getValue(Object?instance,?String?fieldName)

throws?IllegalAccessException,?NoSuchFieldException?{

Field?field?=?instance.getClass().getDeclaredField(fieldName);

field.setAccessible(true);?//?參數值為true，禁止訪問控制檢查

return?field.get(instance);

}

/***

*?設置私有成員變量的值

*

*/

public?static?void?setValue(Object?instance,?String?fileName,?Object?value)

throws?NoSuchFieldException,?SecurityException,?IllegalArgumentException,?IllegalAccessException?{

Field?field?=?instance.getClass().getDeclaredField(fileName);

field.setAccessible(true);

field.set(instance,?value);

}

/***

*?訪問私有方法

*

*/

public?static?Object?callMethod(Object?instance,?String?methodName,?Class[]?classes,?Object[]?objects)

throws?NoSuchMethodException,?SecurityException,?IllegalAccessException,?IllegalArgumentException,

InvocationTargetException?{

Method?method?=?instance.getClass().getDeclaredMethod(methodName,?classes);

method.setAccessible(true);

return?method.invoke(instance,?objects);

}

}package?com.test;

public?class?Person?{

private?String?name;

private?int?age;

public?Person(String?name,?int?age)?{

this.name?=?name;

this.age?=?age;

}

private?String?getInfo(String?str,?int?num)?{

return?str?+?num?+?"?apples";

}

}import?com.test.Person;

public?class?ReflectTest?{

public?static?void?main(String[]?args)?throws?Exception?{

Person?person?=?new?Person("jack",?25);

//?test?get?private?value

System.out.println("jack's?name:"?+?ReflectionUtil.getValue(person,?"name"));

System.out.println("jack's?age:"?+?ReflectionUtil.getValue(person,?"age"));

//?test?set?private?value

ReflectionUtil.setValue(person,?"name",?"jason");

ReflectionUtil.setValue(person,?"age",?10);

System.out.println("jack's?name:"?+?ReflectionUtil.getValue(person,?"name"));

System.out.println("jack's?age:"?+?ReflectionUtil.getValue(person,?"age"));

//?test?call?private?method

String?result?=?(String)?ReflectionUtil.callMethod(person,?"getInfo",?new?Class[]?{?String.class,?int.class?},

new?Object[]?{?"I?hava?",?4?});

System.out.println("result:?"?+?result);

}

}結果：

jack's?name:jack

jack's?age:25

jack's?name:jason

jack's?age:10

result:?I?hava?4?apples

總結

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