Java14 反射
反射
Class对象
包路径 getPackage() package对象 获取该类的存放路径类名称 getName() String 对象 获取该类的名称继承类 getSuperclass() Class 对象 获取该类继承的类实现接口 getlnterfaces() Class 型数组 获取该类实现的所有接口泛型擦除 通过反射来类型擦除,添加元素获取class对象的三种方法：
// 1.获取Class对象的三种方法
// 方式1:Class.forName("全类名") 频率最高
Class clazz1 = Class.forName("day29_反射.Person");
System.out.println(clazz1);// 方式2:类名.class 更多的作为参数进行传递
// 内存阶段
Class clazz2 = Person.class;
System.out.println(clazz2);// 方式3:对象名.getClass() 要求要有类的对象,才可以进行使用、
// 运行阶段
Person p1 = new Person("爪爪");
Class clazz3 = p1.getClass();
System.out.println(clazz3);
Class class1 = Person.class;
// 包路径 getPackage() Package 对象 获取该类的存放路径Package package1 = class1.getPackage();System.out.println(package1);// package day30_反射_Class补充// 类名称 getName() String 对象 获取该类的名称String className = class1.getName();System.out.println(className);// day30_反射_Class补充.Person// 继承类 getSuperclass() Class 对象 获取该类继承的类Class superclass = class1.getSuperclass();System.out.println(superclass);// class java.lang.ObjectSystem.out.println("=============");// 实现接口 getlnterfaces() Class 型数组 获取该类实现的所有接口Class[] Interfaces = class1.getInterfaces();for (Class class2 : Interfaces) {System.out.println(class2);
// interface java.io.Serializable
// interface java.lang.Comparable
// interface java.util.Comparator }Person p1 = (Person) class1.newInstance();System.out.println(p1);
ArrayList<String> arrayList = new ArrayList<String>();arrayList.add("爪爪");
// arrayList.add(new Date());
// arrayList.add(123456);// 通过反射来类型擦除,添加元素Class class1 = arrayList.getClass();Method method = class1.getDeclaredMethod("add", Object.class);method.invoke(arrayList, new Date()); method.invoke(arrayList, 123456);System.out.println(arrayList);
package day29_反射_class对象;public class Demo01 {public static void main(String[] args) throws ClassNotFoundException {// 1.获取Class对象的三种方法// 方式1:Class.forName("全类名") 频率最高// 源码阶段Class clazz1 = Class.forName("day29_反射.Person");System.out.println(clazz1);// 方式2:类名.class 更多的作为参数进行传递// 内存阶段Class clazz2 = Person.class;System.out.println(clazz2);// 方式3:对象名.getClass() 要求要有类的对象,才可以进行使用、// 运行阶段Person p1 = new Person("爪爪");Class clazz3 = p1.getClass();System.out.println(clazz3);System.out.println(clazz1 == clazz2);System.out.println(clazz2 == clazz3);}
}
package day29_反射_class对象;public class Person {private String name;public int age;public Person() {super();}public Person(String name) {super();this.name = name;}public Person(String name, int age) {super();this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}
Field成员变量
获取Field类Field[] getFields():获取所有的public的field(包括父类)Field[] getDeclaredFields():获取当前类中所定义的所有field(不包括父类)Field getField(name):根据字段名获取当前类中某个public的field(包括父类)Field getDeclaredField(name):根据字段名获取当前类中某个field(不包括父类)解剖操作:
获取字段的修饰符：
field.getModifiers();获取字段名称：
field.getName();获取字段的数据类型：
field.getType();获取字段的值
field.get(对象);修改字段的值
field.set(对象,新的成员变量的值);package day29_反射_成员变量;import java.lang.reflect.Field;
import java.lang.reflect.Modifier;public class Demo01 {public static void main(String[] args)throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {// 1.获取Class文件对象Class class1 = Person.class;// 2.获取Field类
// Field[] getFields():获取所有的public的field(包括父类)
// Field[] fields1 = class1.getFields();
// for (Field field : fields1) {
// System.out.println(field);
// }// Field[] getDeclaredFields():获取当前类中所定义的所有field(不包括父类)
// Field[] fields2 = class1.getDeclaredFields();
// for (Field field : fields2) {
// System.out.println(field);
// }// Field getField(name):根据字段名获取当前类中某个public的field(包括父类)Field field3 = class1.getField("name");// 就近原则,重名时以当前类为准System.out.println(field3);// Field getDeclaredField(name):根据字段名获取当前类中某个field(不包括父类)Field field = class1.getDeclaredField("age");System.out.println(field);// 3.解剖操作// 获取字段的修饰符int num = field.getModifiers();System.out.println(num);System.out.println(Modifier.isPublic(num));System.out.println(Modifier.isPrivate(num));System.out.println(Modifier.isProtected(num));System.out.println(Modifier.isStatic(num));System.out.println(Modifier.isFinal(num));// 获取字段名称String str = field.getName();System.out.println("字段名称为" + str);// 获取字段的数据类型Class type = field.getType();System.out.println(type);// int// Fu p2 = new Person("爪爪", 21, '男');// 向下转型
// System.out.println(p2.name);// 获取的父类的name为null
// field3.setAccessible(true);
// String name = (String) field3.get(p2);
// System.out.println(name);// 子类的变量name为爪爪// 获取某个对象对应的此字段的值Person p1 = new Person("爪爪", 21, '男');// 反射获取私有的成员变量字段的值--访问field.setAccessible(true);int age = (Integer) field.get(p1);System.out.println(age);// 通过反射修改成员变量的值field.set(p1, 18);System.out.println(p1);}
}
package day29_反射_成员变量;public class Fu {private String card;public String name;//父类的成员变量private String birthday;@Overridepublic String toString() {return "Fu [card=" + card + ", name=" + name + ", birthday=" + birthday + "]";}
}
package day29_反射_成员变量;public class Person extends Fu {public String name;private int age;protected char gender;public Person(String name, int age, char gender) {super();this.name = name;this.age = age;this.gender = gender;}public Person() {super();}@Overridepublic String toString() {return "Person [name=" + name + ", age=" + age + "]";}
}
Method方法
package day29_反射_调用方法;import java.lang.reflect.Method;
import java.lang.reflect.Parameter;public class Demo01 {public static void main(String[] args) throws NoSuchMethodException, SecurityException {// 1.获取文件对象Class class1 = Person.class;// 2.获取方法对象
// Method[] getMethods()：获取所有public的Method（包括父类）
// Method[] methods = class1.getMethods();
// for (Method method : methods) {
// System.out.println(method);
// }// Method[] getDeclaredMethods()：获取当前类的所有Method（不/包括父类）
// Method[] methods = class1.getDeclaredMethods();
// for (Method method : methods) {
// System.out.println(method);
// }
// Method getMethod(name, Class...)：获取某个public的Method（包括父类）
// Method method = class1.getMethod("eat", String.class);
// Method method = class1.getMethod("study", String.class);// 拿到的父类的study方法
// System.out.println(method);// Method getDeclaredMethod(name, Class...)：获取当前类的某个Method（不包括父类）
// Method method = class1.getDeclaredMethod("eat", String.class);
// Method method = class1.getDeclaredMethod("study");//错误,当前类没有study方法
// System.out.println(method);System.out.println("==========");// 3.解剖Method method = class1.getDeclaredMethod("eat", String.class, int.class);// 获取方法的权限修饰符int num = method.getModifiers();System.out.println(num);// 获取方法的名称String name = method.getName();System.out.println(name);// 获取方法的返回值类型Class returnType = method.getReturnType();System.out.println(returnType);// 获取方法的参数System.out.println("获取方法的参数类型,个数");Parameter[] parameters = method.getParameters();for (Parameter parameter : parameters) {System.out.println(parameter);}// 获取方法的异常类型Class[] exceptionType = method.getExceptionTypes();for (Class exception : exceptionType) {System.out.println(exception);}}
}
package day29_反射_调用方法;import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;//通过反射调用方法
public class Demo02 {public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException,IllegalAccessException, IllegalArgumentException, InvocationTargetException {// 1.获取字节码文件对象Class class1 = Class.forName("day29_反射_调用方法.Person");// 2.获取method对应的对象
// Method method = class1.getDeclaredMethod("eat", String.class, int.class);
// // 私有的设置取消校验符
// method.setAccessible(true);
// Person p1 = new Person();
// // 1.对象--实例对象
// // 2.动态参数--调用此方法需要传入的实际的值
// String str = (String) method.invoke(p1, "水煮鱼", 2);
// System.out.println(str);//静态方法调用Method method=class1.getDeclaredMethod("eat", String.class);//1.对象--实例对象//2.动态参数--调用此方法需要传入的实际的值method.invoke(null, "水煮鱼");}
}
package day29_反射_调用方法;import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;public class Demo03 {public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {//获取hello方法Method method=Father.class.getMethod("hello");
// Father father=new Father();
// method.invoke(father);Father father=new Zi();method.invoke(father);}
}class Father {public void hello() {System.out.println("father:hello");}
}class Zi extends Father {public void hello() {System.out.println("Zi:hello");}
}
package day29_反射_调用方法;public class Fu {private void study() {System.out.println("好好学习");}public void study(String sth) {System.out.println("好好学" + sth);}
}
package day29_反射_调用方法;import java.io.IOException;import javax.xml.bind.DataBindingException;public class Person extends Fu {private void eat() {System.out.println("吃饭方法");}public static void eat(String sth) {System.out.println("吃" + sth);}public String eat(String sth, int num) throws IOException {
// protected int eat(String sth, int num)
// throws IOException,
// RuntimeException,
// SecurityException,
// ClassCastException,
// DataBindingException {return "吃" + sth + "已经" + num + "次了";
// return 1;}
}
Constructor构造方法
package day29_反射_构造方法;import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Parameter;public class Demo01 {public static void main(String[] args) throws NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {// 1.获取Class文件对象Class class1 = Person.class;// 2.获取构造方法// getConstructors():获取所有public修饰的Constructor
// Constructor[] cons1 = class1.getConstructors();
// for (Constructor con : cons1) {
// System.out.println(con);
// }// getDeclaredContruectors():获取所有定义的Constructor
// Constructor[] cons2 = class1.getDeclaredConstructors();
// for (Constructor con : cons2) {
// System.out.println(con);
// }// getConstructor(Class...):获取某个public的Constructor:
// Constructor con1 = class1.getConstructor(String.class, int.class);
// System.out.println(con1);// getDeclaredConstructor(Class...):获取某个定义的Constructor:Constructor con2 = class1.getDeclaredConstructor(String.class, int.class);System.out.println(con2);// 3.解剖使用// 获取修饰符int num = con2.getModifiers();System.out.println(num);// 获取参数Parameter[] pars = con2.getParameters();for (Parameter par : pars) {System.out.println(par);}// 反射创建对象con2.setAccessible(true);// 临时取消权限修饰符Person person = (Person) con2.newInstance("爪爪", 18);System.out.println(person);}
}
package day29_反射_构造方法;public class Person {private String name;public int age;protected Person() {super();}private Person(String name) {super();this.name = name;}private Person(String name, int age) {super();this.name = name;this.age = age;}@Overridepublic String toString() {return "Person [name=" + name + ", age=" + age + "]";}
}
练习题1
package day29_反射_构造方法;public class Person {private String name;public int age;protected Person() {super();}private Person(String name) {super();this.name = name;}private Person(String name, int age) {super();this.name = name;this.age = age;}@Overridepublic String toString() {return "Person [name=" + name + ", age=" + age + "]";}}properties文件
classname=homework.Teacher
method=teach
练习题2
package day30_反射_Class补充;import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Field;public class Demo03_result {public static void main(String[] args) throws IllegalArgumentException, IllegalAccessException, IOException {Object object = new Teacher("爪爪", "英语");
// Object object = new Student("爪爪", 30, '男', 163.6, "唱、跳、rap、篮球");saveObject(object);}// 对于任意一个对象,都可以将对象中的字段名和字段值保存到文件private static void saveObject(Object object) throws IllegalArgumentException, IllegalAccessException, IOException {// 1.获取字节码文件对象Class class1 = object.getClass();// 2.获取成员变量Field[] fields = class1.getDeclaredFields();BufferedWriter bw = new BufferedWriter(new FileWriter("a.txt"));for (Field field : fields) {field.setAccessible(true);// 获取字段名String fieldName = field.getName();// 获取字段值
// 获取字段的值,返回值为Object类型的值Object value = field.get(object);bw.write(fieldName + ":" + value);bw.newLine();}bw.close();}
}package day30_反射_Class补充;public class Student {private String name;private int age;private char gender;private double height;private String hobby;public Student(String name, int age, char gender, double height, String hobby) {super();this.name = name;this.age = age;this.gender = gender;this.height = height;this.hobby = hobby;}public Student() {super();}public void study() {System.out.println("good good study");}@Overridepublic String toString() {return "Student [name=" + name + ", age=" + age + ", gender=" + gender + ", height=" + height + ", hobby="+ hobby + "]";}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public char getGender() {return gender;}public void setGender(char gender) {this.gender = gender;}public double getHeight() {return height;}public void setHeight(double height) {this.height = height;}public String getHobby() {return hobby;}public void setHobby(String hobby) {this.hobby = hobby;}}package day30_反射_Class补充;public class Teacher {private String name;private String subject;public void teach() {System.out.println("teach java");}public Teacher() {super();}public Teacher(String name, String subject) {super();this.name = name;this.subject = subject;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSubject() {return subject;}public void setSubject(String subject) {this.subject = subject;}@Overridepublic String toString() {return "Teacher [name=" + name + ", subject=" + subject + "]";}
}