在日常的开发中特别是框架的设计或者实用反射的时候,经常会实用class类去做一些事情,但是由于系统的抽象等问题,经常实用泛型去做一些事情。所以如何在泛型中获取具体的class类呢?
解决方案:父类本身不获取泛型的具体类型,仅提供抽象方法,由子类来提供具体的类型
public abstract class Foo<T> {
public abstract Class getEntityClass();
}
public class Child extends Foo<String> {
public Class getEntityClass() {
return String.class;
}
}
工具类:
mport java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
public class GenericsUtils {
/**
* 通过反射,获得定义Class时声明的父类的范型参数的类型. 如public BookManager extends
* GenricManager<Book>
*
* @param clazz The class to introspect
* @return the first generic declaration, or <code>Object.class</code> if cannot be determined
*/
public static Class getSuperClassGenricType(Class clazz) {
return getSuperClassGenricType(clazz, 0);
}
/**
* 通过反射,获得定义Class时声明的父类的范型参数的类型. 如public BookManager extends GenricManager<Book>
*
* @param clazz clazz The class to introspect
* @param index the Index of the generic ddeclaration,start from 0.
*/
public static Class getSuperClassGenricType(Class clazz, int index)
throws IndexOutOfBoundsException {
Type genType = clazz.getGenericSuperclass();
if (!(genType instanceof ParameterizedType)) {
return Object.class;
}
Type[] params = ((ParameterizedType) genType).getActualTypeArguments();
if (index >= params.length || index < 0) {
return Object.class;
}
if (!(params[index] instanceof Class)) {
return Object.class;
}
return (Class) params[index];
}
}