[英]Using Generics and extending Abstract classes
I've researched this issue a great deal, but have not been very successful in finding a solution close to my situation. 我已经对这个问题进行了大量研究,但是未能成功找到适合我情况的解决方案。 I apologize if I am redundant.
如果有多余,我深表歉意。
Anyway, I am new to generics and so I'm not entirely clear on the syntax. 无论如何,我是泛型新手,因此我对语法尚不完全清楚。 But here is my situation:
但是这是我的情况:
I have an Interface (let's call it IService ) and an implementation ( ServiceImpl ). 我有一个接口(我们称其为IService )和一个实现( ServiceImpl )。 The implementation class has an abstract method that is to be overridden by an extending class ( ServiceExt ).
实现类具有一个抽象方法,该抽象方法将被扩展类( ServiceExt )覆盖。
I have an abstract bean (let's call it AbstractBean ) which has a few fields and is meant to be extended by another bean ( BeanExt ) in order to add some more fields. 我有一个抽象bean(我们称它为AbstractBean ),它具有几个字段,并且打算由另一个bean( BeanExt )进行扩展以添加更多字段。
Ok, now that the situation is laid out, here is my abbreviated code: 好的,现在情况已经摆好了,这是我的缩写代码:
Interface: 接口:
public interface IService <B extends AbstractBean> {
B method(B bean, Object data) throws Exception;
}
Implementation: 执行:
public abstract class ServiceImpl <B extends AbstractBean> implements IService<B> {
public abstract B method(B bean, Object data);
}
Abstract Bean : 抽象豆 :
public abstract class AbstractBean{
private String fname;
private String lname;
[getters and setters]
}
Extended Bean: 扩展Bean:
public class BeanExt extends AbstractBean{
private String phoneNum;
[getter and setter]
}
Extending Class: aka Class giving me issues 扩展班:又名班给我问题
public class ServiceExt <B extends AbstractBean> extends ServiceImpl <B> {
@Override
public <B> BeanExt method(Bbean, Object data) {
if(beaninstanceof AbstractBean){
BeanExt beanExt = (BeanExt) session;
beanExt.setFname("John");
beanExt.setLname("Doe");
beanExt.setPhoneNum("123456789");
return beanExt;
}else{
return null;
}
}
}
Ok, so now eclipse is giving me all kinds of non-descriptive issues and I don't know what to do. 好的,所以现在eclipse给了我各种各样的非描述性问题,我不知道该怎么办。 I've played around with the extending class methods a ton but have not found success.
我已经大量使用了扩展类方法,但没有成功。 Above is how it looks after my last tinkering.
以上是我最后一次修修补补后的样子。
The issues currently presented by my IDE within the class ServiceExt are: 我的IDE当前在ServiceExt类中提出的问题是:
Edit: For further clarification, what I am ultimately trying to do is: 编辑:为了进一步澄清,我最终想做的是:
Update - I've taken all of your input and the changes are reflected below. 更新 -我已接受您的所有输入,所做的更改如下所示。 The issue currently presented by my IDE within the class ServiceExt is:
我的IDE当前在ServiceExt类中提出的问题是:
Interface: 接口:
public interface IService <B extends AbstractBean> {
B method(B bean, Object data) throws Exception;
B otherMethod(HttpServletRequest request) throws Exception;
}
Implementation: 执行:
public abstract class ServiceImpl <B extends AbstractBean> implements IService<B> {
public abstract B method(B bean, Object data);
@Override
public final B otherMethod(HttpServletRequest request) {
return [something];
}
}
Abstract Bean : 抽象豆 :
public abstract class AbstractBean{
private String fname;
private String lname;
[getters and setters]
}
Extended Bean: 扩展Bean:
public class BeanExt extends AbstractBean{
private String phoneNum;
[getter and setter]
}
Extending Class: aka Class giving me issues 扩展班:又名班给我问题
public class ServiceExt extends ServiceImpl <BeanExt> {
@Override
public BeanExt method(BeanExt bean, Object data) {
BeanExt beanExt = (BeanExt) session;
beanExt.setFname("John");
beanExt.setLname("Doe");
beanExt.setPhoneNum("123456789");
return beanExt;
}
}
You are not really overriding the method in super class. 您并没有真正重写超类中的方法。 Here's the overridden method:
这是重写的方法:
@Override
public BeanExt method(BeanExt bean, Object data) {
BeanExt beanExt = (BeanExt) session;
beanExt.setFname("John");
beanExt.setLname("Doe");
beanExt.setPhoneNum("123456789");
return beanExt;
}
Since you're extending from ServiceImpl<BeanExt>
, the type parameter B
is replaced with BeanExt
type, so does the return type and parameter of the method. 由于您是从
ServiceImpl<BeanExt>
扩展而来的,因此类型参数B
被BeanExt
类型替换, BeanExt
的返回类型和参数也被替换。
Also note that I've removed the instanceof
check, as it is really not needed. 还要注意,我已经删除了
instanceof
检查,因为实际上并不需要它。 bean
will always be an instance of AbstractBean
, because that is enforced by the bound you gave to the type parameter declaration of ServiceImpl
class. bean
将始终是AbstractBean
的实例,因为它由您对ServiceImpl
类的类型参数声明赋予的绑定强制执行。
I did not entirely understand what you're trying to do, but is this acceptable/working? 我不完全了解您要做什么,但这可以接受吗?
public class ServiceExt <B extends BeanExt> extends ServiceImpl <B> {
@Override
public B method(B bean, Object data) {
bean.setFname("John");
bean.setLname("Doe");
bean.setPhoneNum("123456789");
return bean;
}
}
I just corrected all the errors: 我只是纠正了所有错误:
interface IService <B extends AbstractBean> {
B method(B bean, Object data) throws Exception;
}
abstract class ServiceImpl <B extends AbstractBean> implements IService<B> {
public abstract B method(B bean, Object data);
}
abstract class AbstractBean{
String fname;
String lname;
}
class BeanExt extends AbstractBean {
String phoneNum;
}
class ServiceExt <B extends AbstractBean> extends ServiceImpl <B> {
@Override public B method(B bean, Object data) {
if (bean instanceof BeanExt) {
BeanExt beanExt = (BeanExt) bean;
beanExt.fname = "John";
beanExt.lname = "Doe";
beanExt.phoneNum = "123456789";
return bean;
}else{
return null;
}
}
}
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