Java反射：对象不是声明类的实例

Question

用户类

public class User {
        @Id
        @GeneratedValue(strategy=GenerationType.AUTO)
        private Long id;
        @Column(unique=true)
        private String username;
        @JsonIgnore
        private String password;
        private String firstName;
        private String lastName;
        private Date dob;
        private String motherName;
        private String fatherName;
        private String mobileNumber;
        @Column(unique=true)
        private String email;
        @ManyToOne
        @JoinColumn(name="role_id", nullable=false)
        private Role role;
        private String status;
    
        public void setPassword(String password) {
            this.password = PasswordEncoder.getEncodedPassword(password);
        }
    }

@Data
public class UserRequest {
    private Long id;
    private String username;
    private String password;
    private String firstName;
    private String lastName;
    private Date dob;
    private String motherName;
    private String fatherName;
    private String mobileNumber;
    private String email;
    private Long role;
    private String status;
}

public static void copy(Object dest, Object source) throws IntrospectionException, IllegalArgumentException, IllegalAccessException,
        InvocationTargetException {
    BeanInfo beanInfo = Introspector.getBeanInfo(source.getClass());
    PropertyDescriptor[] pdList = beanInfo.getPropertyDescriptors();
    for (PropertyDescriptor pd : pdList) {
        Method writeMethod = null;
        Method readMethod = null;
        try {
            writeMethod = pd.getWriteMethod();
            readMethod = pd.getReadMethod();
        } catch (Exception e) {
        }

        if (readMethod == null || writeMethod == null) {
            continue;
        }

        Object val = readMethod.invoke(source);
        writeMethod.invoke(dest, val);
    }
}

我把这个复制方法叫做

 Utility.copy(user,userRequest);

并在执行writeMethod.invoke(dest,val）时获得以下异常。有人能帮忙吗？

对象不是在java.base/jdk.internal.reflect.nativeMethodAccessorImpl.Invoke0（原生方法）在java.base/jdk.internal.reflect.nativeMethodAccessorImpl.Invoke(nativeMethodAccessorImpl.java:64)在

Answer 1

您只获得源类的BeanInfo，然后从该BeanInfo...所以WriteMethod是源类的setter，但您是在目标类的实例上调用它的。

您可能需要分别获得源类和目标类的BeanInfo，然后对于源中的每个属性，在目标类中找到同名的属性（如果有的话），并使用该属性的write方法来设置值。