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【反射之Field】获取字段
■getFields()、getDeclaredFields()、getField() 和 getDeclaredField()的用法
1 package reflect.field; 2 3 import java.lang.reflect.Constructor; 4 import java.lang.reflect.Field; 5 import java.lang.reflect.InvocationTargetException; 6 import java.lang.reflect.Method; 7 8 public class FieldMethod { 9 10 public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, SecurityException, NoSuchMethodException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException { 11 Class<?> personClass = Class.forName("reflect.Person"); 12 13 Constructor<?> constructor = personClass.getDeclaredConstructor(String.class, int.class, double.class, String.class); 14 Object p = constructor.newInstance("周娟娟", 23, 80, "14计科1班"); 15 System.out.println(p.toString()); 16 17 18 // 该方法只能获取到公有的字段(属性) 19 Field[] fields = personClass.getFields(); 20 for (Field field : fields) { 21 // System.out.println(field); 22 } 23 24 // 该方法能获取到公有的、私有的、受保护的字段 25 Field[] declaredFields = personClass.getDeclaredFields(); 26 for (Field field : declaredFields) { 27 // System.out.println(field); 28 } 29 30 // 该方法只能获取到公有的字段,若传入的是私有或受保护的则会报错NoSuchFieldException 31 Field nameFieldPublic = personClass.getField("className"); 32 33 nameFieldPublic.set(p, "卓越班"); 34 Method getClassName = personClass.getMethod("getClassName"); 35 Object className = getClassName.invoke(p); 36 System.out.println(className); 37 38 // 该方法可以获取到公有的、私有的、受保护的属性 39 Field nameFieldPrivate = personClass.getDeclaredField("name"); 40 41 nameFieldPrivate.setAccessible(true); 42 // System.out.println(nameFieldPrivate); 43 nameFieldPrivate.set(p, "Jay"); 44 System.out.println(p); 45 46 // 获取到私有属性age 47 Field ageFieldPrivate = personClass.getDeclaredField("age"); 48 // 忽略修饰符访问检查 49 ageFieldPrivate.setAccessible(true); 50 // 设置age的值,必须指明修改的是哪个对象的属性 51 ageFieldPrivate.set(p, 24); 52 System.out.println(p); 53 54 } 55 56 }
1 package reflect; 2 3 public class Person { 4 5 private String name; 6 private int age; 7 protected double weight; 8 public String className; 9 10 public Person() { 11 } 12 13 private Person(int age) { 14 15 } 16 17 public Person(String name, int age, double weight, String className) { 18 super(); 19 this.name = name; 20 this.age = age; 21 this.weight = weight; 22 this.className = className; 23 } 24 25 public double getWeight() { 26 return weight; 27 } 28 29 public void setWeight(double weight) { 30 this.weight = weight; 31 } 32 33 public String getClassName() { 34 return className; 35 } 36 37 public void setClassName(String className) { 38 this.className = className; 39 } 40 41 public String getName() { 42 return name; 43 } 44 45 public void setName(String name) { 46 this.name = name; 47 } 48 49 private int getAge() { 50 return age; 51 } 52 53 public void setAge(int age) { 54 this.age = age; 55 } 56 57 @Override 58 public String toString() { 59 return "Person [name=" + name + ", age=" + age + ", weight=" + weight 60 + ", className=" + className + "]"; 61 } 62 63 64 65 }
【反射之Field】获取字段
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