所以我有一个非常大的类,其中有数百个 transient 对象,每次加载父级(在本例中为 Person.class)时都需要重新初始化。 (Peron.class 已加载并保存)
这是我目前的类结构的示例:
public final class Person {
private transient ObjectA a;
private transient ObjectB b;
private transient ObjectC c;
private transient ObjectD d;
//and hundreds more...
public Person() {
initTransientObjects();
}
private void initTransientObjects() {
a = new ObjectA();
b = new ObjectB();
c = new ObjectC();
d = new ObjectD();
//and hundreds more...
}
public void onReloadAfterFirstSave() {
initTransientObjects();
}
}
这使得编写新对象变得非常乏味,我想知道是否有一种方法可以使它更紧凑,如下所示:
public final class Person {
private transient ObjectA a = new ObjectA();
private transient ObjectB b = new ObjectB();
private transient ObjectC c = new ObjectC();
private transient ObjectD d = new ObjectD();
//and hundreds more...
//this way I only have to type the new object once instead of twice
public void onReloadAfterFirstSave() {
//what here? because now transient fields are null
}
}
请注意,我无法使用上述内容的原因是,显然,当再次加载 Person 时, transient 字段将不会被加载,因此会自动设置为 null。
我应该在这里做什么?
编辑:
我还在 Person 类中保存了非 transient 对象以及这些 transient 字段,这就是为什么不选择使用它:
Peron person = new Person(); //every load
最佳答案
你可以尝试这个,但我不赞成这样做,主要是因为你需要非常小心异常(exception)情况。 我假设您的 ObjectA、ObjectB、ObjectC 的构造函数不是空的,如果它们是空的,那么这将更容易实现。
我专门为你制作了一个示例类(class)
import java.lang.reflect.InvocationTargetException;
import java.util.Random;
/**
*
* @author emngaiden
*/
public class Test2 {
ClassContainer[] containers;
Object[] instantieted_objects;
public Test2() {
initObjects();
}
public static void main(String[] args) {
Test2 test=new Test2();
StringBuilder sb=(StringBuilder)test.getObject(2);
sb.append((String)test.getObject(0));
sb.append(((Random)test.getObject(1)).nextDouble());
System.out.println(sb.toString());
}
public Object getObject(int i){
return this.instantieted_objects[i];
}
private void initObjects() {
//total number of objects ObjectA, ObjectB etc...
int number_of_objects = 3;
this.containers = new ClassContainer[number_of_objects];
this.instantieted_objects = new Object[number_of_objects];
//create the containers, you write this only one, and can
//share it between objects of the same class
this.containers[0] = new ClassContainer(String.class,
new Class[]{String.class},
new Object[]{"hello world"}
);
this.containers[1] = new ClassContainer(Random.class,
new Class[]{long.class},
new Object[]{192323l}
);
this.containers[2] = new ClassContainer(StringBuilder.class,
null,
null
);
//poblate the objects in the array
for(int i=0; i<this.containers.length; i++){
try{
this.instantieted_objects[i]=instantiateObject(containers[i]);
}catch(Exception e){
e.printStackTrace();
}
}
}
//returns a new object instance based on the container
private Object instantiateObject(ClassContainer container)
throws NoSuchMethodException, InstantiationException, IllegalAccessException,
IllegalArgumentException, InvocationTargetException {
//no arguments for the constructor means that the constructor is empty
if(container.args!=null){
//get the constructor that matches the Class[] array on its arguments
return
container.obj.getConstructor(container.args)
.newInstance(container.values);
}
else{
return container.obj.newInstance();
}
}
//class to hold the necessary data to instantiate the object
public class ClassContainer {
//the target class, for ObjectA(int,int)this must be ObjectA.class
Class obj;
//the argument classes, it would be {int.class,int.class}
Class[] args;
//the actual values for the constructor, it would be {1,2}
Object[] values;
public ClassContainer(Class obj, Class[] args, Object[] values) {
this.obj = obj;
this.args = args;
this.values = values;
}
}
}
这编写起来很有趣,但我不建议使用它。
关于Java OOP transient 字段在加载 POJO 父级时初始化,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/52549040/