[英]How I can get a instance by a class?
I have a method 我有办法
public static <T> T createObject(Class<T> t){
}
You see, I want to get a instance of T. 你看,我想得到一个T的实例。
I know this can be realized, because: 我知道可以实现,因为:
public <T> T find(Object id, Class<T> type) {
return (T) this.em.find(type, id);
}
Help me........ 帮我........
If the class t
has a no-args constructor, then the Class.newInstance() method will do what is needed: 如果类t
具有无参数构造函数,则Class.newInstance()方法将执行所需的操作:
public static <T> T createObject(Class<T> t)
throws InstantiationException, IllegalAccessException {
return t.newInstance();
}
Note that you have to either propagate or deal with checked exceptions arising from things like: 请注意,您必须传播或处理由以下原因引起的检查异常:
t
object represents an interface or an abstract class, t
对象表示接口或抽象类, t
class doesn't have a no-args constructor, or t
类没有无参数构造函数,或者 t
class or its no-args constructor are not accessible. t
类或其no-args构造函数不可访问。 siunds like you need reflection 像你这样的声音需要反思
import java.reflect.*; ... Class klass = obj.class; Object newObj = klass.newInstance(); return (T)newObj;
note: written from memory, so the api may be slightly different. 注意:是从内存写入的,因此api可能会略有不同。
If you want manage parameters, you can do that : 如果要管理参数,可以执行以下操作:
public static <T> T instantiate(Class<T> clazz, Object ... parameters) throws Exception {
Validate.notNull(clazz, "Argument 'clazz' null!");
if (!ArrayUtils.isEmpty(parameters)) {
Class<?> [] parametersType = new Class<?>[parameters.length];
for(int i=0 ; i<parameters.length ; i++) {
parametersType[i] = parameters[i].getClass();
}
return clazz.getConstructor(parametersType).newInstance(parameters);
}
return clazz.newInstance();
}
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