java反射简单示例

java反射入门实例

初次写反射的例子

写一个User类，然后在测试类 Reflection 中用反射的方式获取这个类，并将User对象的值打印到控制台。

1. User实例类，三个属性，和构造器get set方法等。

package org.monkey.reflection;

public class User {
    private String userName;
    private String password;
    private int status;
    
    public User(String userName, String password, int status) {
        this.userName = userName;
        this.password = password;
        this.status = status;
    }
    
    public User() {
    }
    
    public void setUserName(String userName) {
        this.userName = userName;
    }
    
    public void setPassword(String password) {
        this.password = password;
    }
    
    public void setStatus(int status) {
        this.status = status;
    }
    
    public String getUserName() {
        return userName;
    }
    
    public String getPassword() {
        return password;
    }
    
    public int getStatus() {
        return status;
    }
    
    @Override
    public String toString() {
        return "User{" +
                "userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                ", status=" + status +
                '}';
    }
}

2. 测试类Reflection，main方法中用反射创建User对象，并打印到控制台。

// 测试类
package org.monkey.reflection;

import static java.lang.Class.forName;

public class Reflection {
    
    public static void main(String[] args) {
        
        try {
            Class<?> userClass = Class.forName("org.monkey.reflection.User");
            User user = null;
            user = (User) userClass.newInstance();
            System.out.println(user.getUserName());
            System.out.println(user.getUserName());
            System.out.println(user.getPassword());
            System.out.println(user.getStatus());
            System.out.println(user);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        
    }
}

3. 结果如下，因为没有赋值，所有输出的都是创建对象时默认的初始化值。

// 输出结果
null
null
null
0
User{userName='null', password='null', status=0}