如何在绑定spring mvc命令对象时将多个参数名称映射到POJO

Question

我的问题实际上是这个问题的衍生…因此，在继续之前检查该线程可能会有所帮助。

在我的Spring Boot项目中，我有两个实体Sender和Recipient，它们代表一个Customer，并且几乎具有相同的字段，因此我使它们扩展了基类Customer;

Customer基类;

@MappedSuperclass
public class Customer extends AuditableEntity {
    @Column(name = "firstname")
    private String firstname;
    @Transient
    private CustomerRole role;
    public Customer(CustomerRole role) {
        this.role = role;
    }
    //other fields & corresponding getters and setters
}

发送者

域对象;

@Entity
@Table(name = "senders")
public class Sender extends Customer {
    public Sender(){
        super.setRole(CustomerRole.SENDER);
    }
}

接受者

域对象;

@Entity
@Table(name = "recipients")
public class Recipient extends Customer {
    public Recipient(){
        super.setRole(CustomerRole.RECIPIENT);
    }
}

说明—Sender和Recipient除了角色不同外，其他内容完全相同。通过使Customer基类本身成为一个实体，这些可以很容易地存储在单个customers表中，但是我有意这样分离实体，因为我有义务在单独的数据库表中持久化每种客户类型。

现在我在一个视图中有一个表单，收集Sender &Recipient，因此，例如要收集名字，我必须对表单字段进行不同的命名，如下所示;

发送方的形式;

<input type="text" id="senderFirstname" name="senderFirstname" value="$!sender.firstname">

的接收部分形式;

<input type="text" id="recipientFirstname" name="recipientFirstname" value="$!recipient.firstname">

但是客户可用的字段太多了，所以我正在寻找一种方法，通过注释将它们映射到pojo，就像这个问题中所问的那样。然而，那里提供的解决方案意味着我必须为两个域对象创建单独的代理，并相应地注释字段，例如

public class SenderProxy {
    @ParamName("senderFirstname")
    private String firstname;
    @ParamName("senderLastname")
    private String lastname;
    //...
}
public class RecipientProxy {
    @ParamName("recipientFirstname")
    private String firstname;
    @ParamName("recipientLastname")
    private String lastname;
    //...
}

所以我很好奇，想知道，有没有一种方法可以将这个代理映射到多个@ParamName，这样基类就可以像下面这样注释?;

@MappedSuperclass
public class Customer extends AuditableEntity {
    @Column(name = "firstname")
    @ParamNames({"senderFirstname", "recipientFirstname"})
    private String firstname;
    @Column(name = "lastname")
    @ParamNames({"senderLastname", "recipientLastname"})
    private String lastname;
    @Transient
    private CustomerRole role;
    public Customer(CustomerRole role) {
        this.role = role;
    }
    //other fields & corresponding getters and setters
}

然后也许找到一种方法来选择基于注释的字段值??

Answer 1

张杰的建议，比如ExtendedBeanInfo

所以我这样做

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Alias {
    String[] value();
}
public class AliasedBeanInfoFactory implements BeanInfoFactory, Ordered {
    @Override
    public BeanInfo getBeanInfo(Class<?> beanClass) throws IntrospectionException {
        return supports(beanClass) ? new AliasedBeanInfo(Introspector.getBeanInfo(beanClass)) : null;
    }
    private boolean supports(Class<?> beanClass) {
        Class<?> targetClass = beanClass;
        do {
            Field[] fields = targetClass.getDeclaredFields();
            for (Field field : fields) {
                if (field.isAnnotationPresent(Alias.class)) {
                    return true;
                }
            }
            targetClass = targetClass.getSuperclass();
        } while (targetClass != null && targetClass != Object.class);
        return false;
    }
    @Override
    public int getOrder() {
        return Ordered.LOWEST_PRECEDENCE - 100;
    }
}
public class AliasedBeanInfo implements BeanInfo {
    private static final Logger LOGGER = LoggerFactory.getLogger(AliasedBeanInfo.class);
    private final BeanInfo delegate;
    private final Set<PropertyDescriptor> propertyDescriptors = new TreeSet<>(new PropertyDescriptorComparator());
    AliasedBeanInfo(BeanInfo delegate) {
        this.delegate = delegate;
        this.propertyDescriptors.addAll(Arrays.asList(delegate.getPropertyDescriptors()));
        Class<?> beanClass = delegate.getBeanDescriptor().getBeanClass();
        for (Field field : findAliasedFields(beanClass)) {
            Optional<PropertyDescriptor> optional = findExistingPropertyDescriptor(field.getName(), field.getType());
            if (!optional.isPresent()) {
                LOGGER.warn("there is no PropertyDescriptor for field[{}]", field);
                continue;
            }
            Alias alias = field.getAnnotation(Alias.class);
            addAliasPropertyDescriptor(alias.value(), optional.get());
        }
    }
    private List<Field> findAliasedFields(Class<?> beanClass) {
        List<Field> fields = new ArrayList<>();
        ReflectionUtils.doWithFields(beanClass,
                fields::add,
                field -> field.isAnnotationPresent(Alias.class));
        return fields;
    }
    private Optional<PropertyDescriptor> findExistingPropertyDescriptor(String propertyName, Class<?> propertyType) {
        return propertyDescriptors
                .stream()
                .filter(pd -> pd.getName().equals(propertyName) && pd.getPropertyType().equals(propertyType))
                .findAny();
    }
    private void addAliasPropertyDescriptor(String[] values, PropertyDescriptor propertyDescriptor) {
        for (String value : values) {
            if (!value.isEmpty()) {
                try {
                    this.propertyDescriptors.add(new PropertyDescriptor(
                            value, propertyDescriptor.getReadMethod(), propertyDescriptor.getWriteMethod()));
                } catch (IntrospectionException e) {
                    LOGGER.error("add field[{}] alias[{}] property descriptor error", propertyDescriptor.getName(),
                            value, e);
                }
            }
        }
    }
    @Override
    public BeanDescriptor getBeanDescriptor() {
        return this.delegate.getBeanDescriptor();
    }
    @Override
    public EventSetDescriptor[] getEventSetDescriptors() {
        return this.delegate.getEventSetDescriptors();
    }
    @Override
    public int getDefaultEventIndex() {
        return this.delegate.getDefaultEventIndex();
    }
    @Override
    public PropertyDescriptor[] getPropertyDescriptors() {
        return this.propertyDescriptors.toArray(new PropertyDescriptor[0]);
    }
    @Override
    public int getDefaultPropertyIndex() {
        return this.delegate.getDefaultPropertyIndex();
    }
    @Override
    public MethodDescriptor[] getMethodDescriptors() {
        return this.delegate.getMethodDescriptors();
    }
    @Override
    public BeanInfo[] getAdditionalBeanInfo() {
        return this.delegate.getAdditionalBeanInfo();
    }
    @Override
    public Image getIcon(int iconKind) {
        return this.delegate.getIcon(iconKind);
    }
    static class PropertyDescriptorComparator implements Comparator<PropertyDescriptor> {
        @Override
        public int compare(PropertyDescriptor desc1, PropertyDescriptor desc2) {
            String left = desc1.getName();
            String right = desc2.getName();
            for (int i = 0; i < left.length(); i++) {
                if (right.length() == i) {
                    return 1;
                }
                int result = left.getBytes()[i] - right.getBytes()[i];
                if (result != 0) {
                    return result;
                }
            }
            return left.length() - right.length();
        }
    }
}