1.UserBean

package reflect;

public class UserBean {
    public String userName;
    
    private int userId;

    public UserBean(){
        this.userName ="nisir";
        this.userId = 1;
    }

    public UserBean(String userName, int userId){
        this.userName = userName;
        this.userId = userId;
    }
    
    public String getName(){
        return userName;
    }
    
    public int getId(){
        return userId;
    }

    private void setName(String userName){
        this.userName = userName;
    }
    
    public static void hello(){
        System.out.println("hello");
    }
        
}

2.Main

package reflect;

import java.lang.reflect.*;

public class Main {

    public static void main(String[] args) {
        Class<?> userBeanClass  = UserBean.class;
        printFields(userBeanClass);
        printMethods(userBeanClass);
        printConstructor(userBeanClass);
        invokeMethods(userBeanClass);
    }
    
    public static <T> void printFields(Class<T> userBeanClass){
        System.out.println("\n==================Field======================");
        Field[] fields = userBeanClass.getDeclaredFields(); 
        for (Field field : fields){
            String fieldString = "";
            fieldString+=Modifier.toString(field.getModifiers()) + " ";  //private、static、protect、public等修饰符
            fieldString+=field.getType().getSimpleName() + " "; // String、int等域类型
            fieldString+=field.getName(); //userName、userId等域名
            fieldString+=";";
            System.out.println(fieldString);
        }
    }
    
    public static <T> void printMethods(Class<T> userBeanClass){
        System.out.println("\n==================Method======================");
        Method[] methods = userBeanClass.getDeclaredMethods();
        for (Method method:methods){
            String methodString = "";
            methodString += Modifier.toString(method.getModifiers()) + " "; //private、static、protect、public等修饰符
            methodString += method.getReturnType().getSimpleName() + " "; //String、int等返回类型
            methodString += method.getName() + "(";
            Class<?>[] parameters = method.getParameterTypes(); //获取方法包含的参数类型
            for (Class<?> parameter : parameters){
                methodString += parameter.getSimpleName() + " "; //参数类型
            }
            methodString += ")";
            System.out.println(methodString);
        }
    }
    
    public static <T> void printConstructor(Class <T> userBeanClass){
        System.out.println("\n==================Constructor======================");
        Constructor<?> [] constructors = userBeanClass.getDeclaredConstructors();
        for (Constructor<?> constructor:constructors){
            String constructorString="";
            constructorString += Modifier.toString(constructor.getModifiers()) + " "; //private、static、protect、public等修饰符
            constructorString +=constructor.getName() + "(";
            Class<?>[] parameters = constructor.getParameterTypes();//获取构造函数包含的参数类型
            for (Class<?> parameter : parameters){
                constructorString+=parameter.getSimpleName()+ ", "; //参数类型
            }
            constructorString =constructorString.substring(0, constructorString.length()-1);
            constructorString+=")";
            System.out.println(constructorString);
        }
    }
    
    public static <T> void invokeMethods(Class <T> userBeanClass){
        System.out.println("\n==================Invoke Method======================");
        try {
            Class<?>[] params = {String.class, int.class};
            Constructor<?> defaultConstructor = userBeanClass.getDeclaredConstructor(); //获取默认构造函数
            Object userBean1 = defaultConstructor.newInstance(); //通过默认构造函数实例化一个对象
            Constructor<?> paramConstructor = userBeanClass.getDeclaredConstructor(params);//获取带参数的构造函数
            Object userBean2 = paramConstructor.newInstance("Nizhifeng", 2);//通过构造函数实例化一个对象
            
            //获取各个方法
            Method getNameMethod = userBeanClass.getDeclaredMethod("getName");
            Method getIdMethod = userBeanClass.getDeclaredMethod("getId");
            Method setNameMethod = userBeanClass.getDeclaredMethod("setName", String.class);
            Method helloMethod = userBeanClass.getDeclaredMethod("hello");
            
            //user1
            Object name = getNameMethod.invoke(userBean1);
            Object id = getIdMethod.invoke(userBean1);
            System.out.println("user1 is "+name);
            System.out.println("user1's id is "+ id);
            setNameMethod.setAccessible(true); //private方法必须setAccessible后才能invoke
            setNameMethod.invoke(userBean1, "cy");
            name = getNameMethod.invoke(userBean1);
            System.out.println("user1 changed to " + name);
            
            //user2
            name = getNameMethod.invoke(userBean2);
            System.out.println("user2 is "+name);
            id = getIdMethod.invoke(userBean2);
            System.out.println("user2's id is " + id);
            
            helloMethod.invoke(null);//静态方法不需要传实例对象
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

3.输出

==================Field======================
public String userName;
private int userId;

==================Method======================
public String getName()
private void setName(String )
public int getId()
public static void hello()

==================Constructor======================
public reflect.UserBean)
public reflect.UserBean(String, int,)

==================Invoke Method======================
user1 is nisir
user1's id is 1
user1 changed to cy
user2 is Nizhifeng
user2's id is 2
hello

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