瞬态最终int和瞬态最终整数之间有什么不同.
使用int：
transient final int a = 10;
序列化之前：
a = 10
序列化后：
a = 10
使用整数：
transient final Integer a = 10;
序列化之前：
a = 10
序列化后：
a = null
完整代码：
public class App implements Serializable {
transient final Integer transientFinal = 10;
public static void main(String[] args) {
try {
ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream(
"logInfo.out"));
App a = new App();
System.out.println("Before Serialization ...");
System.out.println("transientFinalString = " + a.transientFinal);
o.writeObject(a);
o.close();
} catch (Exception e) {
// deal with exception
e.printStackTrace();
}
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(
"logInfo.out"));
App x = (App) in.readObject();
System.out.println("After Serialization ...");
System.out.println("transientFinalString = " + x.transientFinal);
} catch (Exception e) {
// deal with exception
e.printStackTrace();
}
}
}
解决方法
如文章中所述
http://www.xyzws.com/Javafaq/can-transient-variables-be-declared-as-final-or-static/0
使字段瞬态将阻止其序列化,但有一个例外：
There is just one exception to this rule,and it is when the transient final field member is initialized to a
constant expressionas those defined in the 07001. Hence,field members declared this way would hold their constant value expression even after deserializing the object.
如果您将访问提到的JSL,您就会知道
A constant expression is an expression denoting a value of
primitive typeor aString
但是Integer不是原始类型,它不是String,因此它不被视为常量表达式的候选者,因此它的值在序列化后不会保留.
演示：
class SomeClass implements Serializable {
public transient final int a = 10;
public transient final Integer b = 10;
public transient final String c = "foo";
public static void main(String[] args) throws Exception {
SomeClass sc = new SomeClass();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(sc);
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(
bos.toByteArray()));
SomeClass sc2 = (SomeClass) ois.readObject();
System.out.println(sc2.a);
System.out.println(sc2.b);
System.out.println(sc2.c);
}
}
输出：
10 null foo
