java.lang.reflect操作对象属性(域)的值

Posted 2022-08-25 byte01

package reflect;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/*2015-10-28*/
public class RefactorDemo 

    /**
     * @param args
     * @throws NoSuchFieldException
     * @throws SecurityException
     * @throws IllegalAccessException
     * @throws IllegalArgumentException
     * @throws NoSuchMethodException
     * @throws InvocationTargetException
     */
    public static void main(String[] args) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException, NoSuchMethodException, InvocationTargetException, InstantiationException 
        String name = "Demo";
        double salary = 20000.0;
        String nameFieldName = "name";
        String salaryFieldName = "salary";

        Constructor<?>[] constructors = Person.class.getConstructors();
        for (Constructor<?> constructor : constructors) 
            Class<?>[] parameterTypes = constructor.getParameterTypes();
            for (Class<?> parameterType : parameterTypes) 
                System.out.println(parameterType.getName());
            
        

        System.out.println("====================================");
        //constructor
        // 这个地方需要关注：如果是基本类型，就是double.class，不是Double.class
        Constructor<Person> constructor = Person.class.getConstructor(String.class, double.class);
        Person tom = constructor.newInstance("Tom", 3000000.0);
        System.out.println(tom);


        // get private Field
        Person person = new Person(name, salary);
        Field field = person.getClass().getDeclaredField(nameFieldName);
        field.setAccessible(true);// 访问控制
        System.out.println(field.get(person));

        person = new Person(name, salary);
        field = person.getClass().getDeclaredField(salaryFieldName);
        field.setAccessible(true);
        System.out.println(field.getDouble(person));

        // set private Field
        person = new Person();
        field = person.getClass().getDeclaredField(nameFieldName);
        field.setAccessible(true);
        field.set(person, name);
        field = person.getClass().getDeclaredField(salaryFieldName);
        field.setAccessible(true);
        field.setDouble(person, salary);
        System.out.println(person);

        // process method
        person = new Person();
        field = person.getClass().getDeclaredField(salaryFieldName);
        field.setAccessible(true);
        field.setDouble(person, 100000.9);
        Method method = person.getClass().getDeclaredMethod("doubleSalary");
        method.invoke(person);
        System.out.println(field.getDouble(person));
    


class Person 
    private String name;
    private double salary;

    public Person() 
        super();
    

    public Person(String name, double salary) 
        super();
        this.name = name;
        this.salary = salary;
    

    public void doubleSalary() 
        this.salary = this.salary * 2;
    

    @Override
    public String toString() 
        return "Person [name=" + name + ", salary=" + salary + "]";
    

Output:

java.lang.String
double
====================================
Person [name=Tom, salary=3000000.0]
Demo
20000.0
Person [name=Demo, salary=20000.0]
200001.8