【Java SE】反射
返回自己和超类的 public 字段、方法、构造器
getFields()
getMethods()
getConstructors() 超类没返回
返回自己的所有 字段、方法、构造器
getDeclaredFields()
getDeclaredMethods()
getDeclaredConstructors()
Person 类
class Person { public Person() {} public Person(String p) {} private String personPrivateField = "personPrivateField"; protected String personProtectedField = "personProtectedField"; public String personPublicField = "personPublicField"; private String personPrivateMethod() { System.out.println("personPrivateMethod"); return "personPrivateMethod"; } protected String personProtectedMethod() { System.out.println("personProtectedMethod"); return "personProtectedMethod"; } public String personPublicMethod() { System.out.println("personPublicMethod"); return "personPublicMethod"; } }
Student 类
class Student extends Person { public Student() {} public Student(String s) {super(s);} private String studentPrivateField = "studentPrivateField"; protected String studentProtectedField = "studentProtectedField"; public String studentPublicField = "studentPublicField"; private String studentPrivateMethod() { System.out.println("print: studentPrivateMethod"); return "studentPrivateMethod"; } private String studentPrivateMethod(String args) { System.out.println("print: studentPrivateMethod, " + args); return "studentPrivateMethod"; } protected String studentProtectedMethod() { System.out.println("print: studentProtectedMethod"); return "studentProtectedMethod"; } protected String studentProtectedMethod(String args) { System.out.println("print: studentProtectedMethod, " + args); return "studentProtectedMethod"; } public String studentPublicMethod() { System.out.println("print: studentPublicMethod"); return "studentPublicMethod"; } public String studentPublicMethod(String args) { System.out.println("print: studentPublicMethod, " + args); return "studentPublicMethod"; } }
反射方法
package cn.ycx.common.reflect; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.lang.reflect.Modifier; /** * 类 * * @author: ycx * @date: 2022-5-21 * @since 0.0.1 */ public class YReflect { public static void main(String[] args) throws Exception { Class c = Class.forName("cn.ycx.common.reflect.Student"); System.out.println("自己和超类的 字段"); // 自己和超类的 public 字段 Field[] fields = c.getFields(); for (Field item : fields) { System.out.println(Modifier.toString(item.getModifiers()) + " " + item.getName()); } System.out.println("自己和超类的 方法"); // 自己和超类的 public 方法 Method[] methods = c.getMethods(); for (Method item : methods) { System.out.println(Modifier.toString(item.getModifiers()) + " " + item.getName()); } System.out.println("自己和超类的 构造器"); // 自己和超类的 Constructor 构造器 Constructor[] constructors = c.getConstructors(); for (Constructor item : constructors) { System.out.println(Modifier.toString(item.getModifiers()) + " " + item.getName()); } System.out.println("自己的 字段"); // 自己的 public 字段 Field[] selfFields = c.getDeclaredFields(); for (Field item : selfFields) { System.out.println(Modifier.toString(item.getModifiers()) + " " + item.getName()); } System.out.println("自己的 方法"); // 自己的 public 方法 Method[] selfMethods = c.getDeclaredMethods(); for (Method item : selfMethods) { System.out.println(Modifier.toString(item.getModifiers()) + " " + item.getName()); } System.out.println("自己的 构造器"); // 自己的 Constructor 构造器 Constructor[] selfConstructors = c.getDeclaredConstructors(); for (Constructor item : selfConstructors) { System.out.println(Modifier.toString(item.getModifiers()) + " " + item.getName()); } } }
获取字段值,循环查找
Student s = new Student(); Class c = s.getClass(); Field studentPrivateField = null; Field studentProtectedField = null; Field studentPublicField = null; Field[] fields = c.getDeclaredFields(); for (Field field : fields) { if ("studentPrivateField".equals(field.getName())) { studentPrivateField = field; } if ("studentProtectedField".equals(field.getName())) { studentProtectedField = field; } if ("studentPublicField".equals(field.getName())) { studentPublicField = field; } } studentPrivateField.setAccessible(true); System.out.println(studentPrivateField.get(s)); System.out.println(studentProtectedField.get(s)); System.out.println(studentPublicField.get(s));
获取字段值,根据名称
Student s = new Student(); Class c = s.getClass(); Field studentPrivateField = c.getDeclaredField("studentPrivateField"); Field studentProtectedField = c.getDeclaredField("studentProtectedField"); Field studentPublicField = c.getDeclaredField("studentPublicField"); studentPrivateField.setAccessible(true); System.out.println(studentPrivateField.get(s));// 参数是字段所属对象 System.out.println(studentProtectedField.get(s)); System.out.println(studentPublicField.get(s));
执行方法,循环查找
Method studentPrivateMethod = null; Method studentProtectedMethod = null; Method studentPublicMethod = null; Student s = new Student(); Method[] selfMethods = s.getClass().getDeclaredMethods();// 自己的方法 for (Method item : selfMethods) { if ( "studentPrivateMethod".equals(item.getName())) { studentPrivateMethod = item; } if ("studentProtectedMethod".equals(item.getName())) { studentProtectedMethod = item; } if ("studentPublicMethod".equals(item.getName())) { studentPublicMethod = item; } } studentPrivateMethod.setAccessible(true);// 私有方法设置可访问 studentPrivateMethod.invoke(s,null); studentProtectedMethod.invoke(s, null); studentPublicMethod.invoke(s, null);
执行方法,根据名称
Student s = new Student(); Class c = s.getClass(); Method studentPrivateMethod = c.getDeclaredMethod("studentPrivateMethod", String.class);// 第一个参数方法名,第二参数类型 Method studentProtectedMethod = c.getDeclaredMethod("studentProtectedMethod", String.class); Method studentPublicMethod = c.getDeclaredMethod("studentPublicMethod", String.class); studentPrivateMethod.setAccessible(true);// 私有方法设置可访问 studentPrivateMethod.invoke(s,"私有"); studentProtectedMethod.invoke(s, "保护"); studentPublicMethod.invoke(s, "公有");
复制任意数组
public static Object arraycopy(Object src, int length) { Class componentType = src.getClass().getComponentType();// 源数组类型 Object dest = Array.newInstance(componentType, length); int minLength = Math.min(Array.getLength(src), length);// 长度最短的 System.arraycopy(src, 0, dest, 0, minLength); return dest; } public static void main(String[] args) throws Exception { Person[] src = { new Person(), new Person() }; Person[] dest = (Person[]) arraycopy(src, 10); System.out.println(dest); }