出现错误的代码如下:
public class ModServiceFinderImpl<Module> extends BaseFinderImpl<Module> implements ModServiceFinder<Module>{
public PageView<Module> findByModid(String modid, int pageNo, int pageSize ) {
PageView<Module> pv = new PageView<Module>();
if(modid != null && !"".equals(modid)) {
pv = super.findByPage(Module.class,
"from Module m where m.isShow=1 and m.parent.mod_id=" + modid, pageNo, pageSize);
}else {
pv = super.findByPage(Module.class, "from Module m where m.isShow=1",
pageNo, pageSize);
}
return pv;
}
}
错误信息:Illegal class literal for the type parameter Module
解决方法:将类ModServiceFinderImpl<Module>后的泛型参数去掉
修改后的代码:
public class ModServiceFinderImpl extends BaseFinderImpl<Module> implements ModServiceFinder<Module>{
public PageView<Module> findByModid(String modid, int pageNo, int pageSize ) {
PageView<Module> pv = new PageView<Module>();
if(modid != null && !"".equals(modid)) {
pv = super.findByPage(Module.class,
"from Module m where m.isShow=1 and m.parent.mod_id=" + modid, pageNo, pageSize);
}else {
pv = super.findByPage(Module.class, "from Module m where m.isShow=1",
pageNo, pageSize);
}
return pv;
}
}
总结:这个问题与网络上得另一个问题相同:
问题:Hi all,
I'm creating a generic class and in one of the methods I need to know the Class of the generic type currently in use. The reason is that one of the method's I call expects this as an argument.
Example:
public class MyGenericClass<T> {
public void doSomething() {
// Snip...
// Call to a 3rd party lib
T bean = (T)someObject.create(T.class);
// Snip...
}
}
Clearly the example above doesn't work and results in the following error: Illegal class literal for the type parameter T.
My question is: does someone know a good alternative or workaround for this?
解决方法:
Still the same problems : Generic informations are erased at runtime, it cannot be recovered. A workaround is to pass the class T in parameter of a static method :
public class MyGenericClass<T> {
private final Class<T> clazz;
public static <U> MyGenericClass<U> createMyGeneric(Class<U> clazz) {
return new MyGenericClass<U>(clazz);
}
protected MyGenericClass(Class<T> clazz) {
this.clazz = clazz;
}
public void doSomething() {
T instance = clazz.newInstance();
}
}
It's ugly, but it works.
注:对泛型的讲解可产考:
http://www.infoq.com/cn/articles/cf-java-generics