java反射的使用

1、新建个实体类

// An highlighted block package test.reflect; public class Student { private int id; public String name; private int age; public int getId() { return id; } public void setId(int id) { this.id = id; } 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 Student(){} public Student(String name){ this.name = name; } public void print(){ System.out.println("id:"+this.id+"--name:"+this.name+"--age:"+this.age); } }

2、通过反射获取类的信息

// An highlighted block package test.reflect; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; /** * 反射获取类信息 * */ public class demo01 { public static void main(String[] args) { String path = "test.reflect.Student"; try{ Class clazz = Class.forName(path); System.out.println("包名+类名:"+clazz.getName());//类的包名+类名 System.out.println("类名:"+clazz.getSimpleName());//类名 //获取属性信息 Field[] field = clazz.getFields();//获取public修饰属性 Field[] fields = clazz.getDeclaredFields();//获取所有属性 Field fieldid = clazz.getDeclaredField("id");//获取指定属性 for(Field f : field){ System.out.println("public属性："+f.getName()); } for(Field f : fields){ System.out.println("所有属性："+f.getName()); } System.out.println("指定属性："+fieldid); //获取方法信息 Method[] methods = clazz.getDeclaredMethods(); for(Method mm:methods){ System.out.println("所有方法："+mm); } Method m = clazz.getDeclaredMethod("getId", null); System.out.println("指定方法："+m); //获取构造器 Constructor[] constructors = clazz.getDeclaredConstructors(); for(Constructor c : constructors){ System.out.println("所有构造器："+c); } Constructor c1 = clazz.getDeclaredConstructor(String.class); System.out.println("带参构造器："+c1); Constructor c2 = clazz.getDeclaredConstructor(null); System.out.println("无参构造器："+c2); }catch(Exception e){ } } } 包名+类名:test.reflect.Student 类名:Student public属性：name 所有属性：id 所有属性：name 所有属性：age 指定属性：private int test.reflect.Student.id 所有方法：public void test.reflect.Student.setId(int) 所有方法：public int test.reflect.Student.getAge() 所有方法：public void test.reflect.Student.setAge(int) 所有方法：public java.lang.String test.reflect.Student.getName() 所有方法：public int test.reflect.Student.getId() 所有方法：public void test.reflect.Student.setName(java.lang.String) 所有方法：public void test.reflect.Student.print() 指定方法：public int test.reflect.Student.getId() 所有构造器：public test.reflect.Student() 所有构造器：public test.reflect.Student(java.lang.String) 带参构造器：public test.reflect.Student(java.lang.String) 无参构造器：public test.reflect.Student()

3、通过反射操作类

// An highlighted block package test.reflect; import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; /** * 反射调用方法操作类 * */ public class demo02 { public static void main(String[] args) { String path = "test.reflect.Student"; try { Class clazz = Class.forName(path); Student student = (Student) clazz.newInstance();//调用无参构造器 System.out.println(student.hashCode()); 通过反射调用构造方法 Constructor c1 = clazz.getDeclaredConstructor(String.class); Student s2 = (Student) c1.newInstance("周星星"); System.out.println(s2.getName()); System.out.println("=========================="); //通过反射调用普通方法 Student s3 = (Student) clazz.newInstance(); Method method = clazz.getDeclaredMethod("setId", int.class); method.invoke(s3, 100); System.out.println(s3.getId()); System.out.println("=========================="); //通过反射操作属性 Student s4 = (Student) clazz.newInstance(); Field f1 = clazz.getDeclaredField("age"); Field f2 = clazz.getDeclaredField("id"); Field f3 = clazz.getDeclaredField("name"); f1.setAccessible(true); f2.setAccessible(true); f3.setAccessible(true); f1.set(s4, 20); f2.set(s4, 1); f3.set(s4, "张无忌"); s4.print(); } catch (Exception e) { e.printStackTrace(); } } } 21174459 周星星 ========================== 100 ========================== id:1--name:张无忌--age:20