问题
My question is actually a spin-off of this question as seen here... so it might help to check that thread before proceeding.
In my Spring Boot project, I have two entities Sender and Recipient which represent a Customer and pretty much have the same fields, so I make them extend the base class Customer;
Customer base class;
@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
}
Sender domain object;
@Entity
@Table(name = "senders")
public class Sender extends Customer {
public Sender(){
super.setRole(CustomerRole.SENDER);
}
}
Recipient domain object;
@Entity
@Table(name = "recipients")
public class Recipient extends Customer {
public Recipient(){
super.setRole(CustomerRole.RECIPIENT);
}
}
NOTE - Sender and Recipient are exactly alike except for their roles. These can be easily stored in a single customers Table by making the Customer base class an entity itself, but I intentionally separate the entities this way because I have an obligation to persist each customer type in separate database tables.
Now I have one form in a view that collects details of both Sender & Recipient, so for example to collect the firstname, I had to name the form fields differently as follows;
Sender section of the form;
<input type="text" id="senderFirstname" name="senderFirstname" value="$!sender.firstname">
Recipient section of the form;
<input type="text" id="recipientFirstname" name="recipientFirstname" value="$!recipient.firstname">
But the fields available for a customer are so many that I'm looking for a way to map them to a pojo by means of an annotation as asked in this question here. However, the solutions provided there would mean that I have to create separate proxies for both domain objects and annotate the fields accordingly e.g
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;
//...
}
So I got very curious and was wondering, is there a way to map this Proxies to more than one @ParamName such that the base class for example can just be annotated as follows?;
@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
}
And then perhaps find a way to select value of fields based on annotation??
回答1:
A suggestion from Zhang Jie like ExtendedBeanInfo
so i do it this way
@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();
}
}
}
来源：https://stackoverflow.com/questions/38171022/how-to-map-multiple-parameter-names-to-pojo-when-binding-spring-mvc-command-obje