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Java FIX for java.io.Not Serializable Exception: java.util.Optional
13 points
How to solve java util Optional serializable exception?
Full stack trace:
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Exception in thread "main" java.io.NotSerializableException: java.util.Optional2
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)3
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)4
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)5
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)6
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)7
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)Here is my code which explains what I've tried so far
Below code tries to serialize field Optional age
As the result we get:
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Exception in thread "main" java.io.NotSerializableException: java.util.OptionalMy code to get this exception:
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import java.io.ByteArrayOutputStream;2
import java.io.ObjectOutputStream;3
import java.io.Serializable;4
import java.util.Optional;5
6
public class JavaUtilOptionalNotSerializableException {7
8
private static class Foo implements Serializable {9
private static final long serialVersionUID = 1L;10
11
private final String name;12
private final Optional<Integer> age;13
14
private Foo(String name, Integer age) {15
this.name = name;16
this.age = Optional.ofNullable(age);17
}18
19
public String getName() {20
return name;21
}22
23
public Optional<Integer> getAge() {24
return age;25
}26
}27
28
public static void main(String[] args) throws Exception {29
/*30
Exception in thread "main" java.io.NotSerializableException:31
java.util.Optional32
*/33
tryToSerialize();34
}35
36
private static void tryToSerialize() throws Exception {37
Foo foo = new Foo("123", 456);38
byte[] arr;39
try (ByteArrayOutputStream baos = new ByteArrayOutputStream();40
ObjectOutputStream oos = new ObjectOutputStream(baos)) {41
oos.writeObject(foo);42
arr = baos.toByteArray();43
}44
assert arr != null;45
}46
}Solution no 1 to this problem is just do not use optional as field value
Instead use it as return type from the getter method
eg:
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private final Integer age; // diff1: without Optional2
3
public Optional<Integer> getAge() {4
// diff2: each method invocation return new Optional5
return Optional.ofNullable(age);6
}Entire code which solves your problem:
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import java.io.ByteArrayOutputStream;2
import java.io.ObjectOutputStream;3
import java.io.Serializable;4
import java.util.Optional;5
6
public class JavaUtilOptionalSolution {7
8
private static class Foo implements Serializable {9
private static final long serialVersionUID = 1L;10
11
private final String name;12
private final Integer age; // diff1: without Optional13
14
private Foo(String name, Integer age) {15
this.name = name;16
this.age = age;17
}18
19
public String getName() {20
return name;21
}22
23
public Optional<Integer> getAge() {24
// diff2: each method invocation return new Optional25
return Optional.ofNullable(age);26
}27
}28
29
public static void main(String[] args) throws Exception {30
// serialization works31
tryToSerialize();32
}33
34
private static void tryToSerialize() throws Exception {35
Foo foo = new Foo("123", 456);36
byte[] arr;37
try (ByteArrayOutputStream baos = new ByteArrayOutputStream();38
ObjectOutputStream oos = new ObjectOutputStream(baos)) {39
oos.writeObject(foo);40
arr = baos.toByteArray();41
}42
assert arr != null;43
}44
}Guava internally
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// com.google.common.base.Optional2
3
public abstract class Optional implements Serializable {4
// ..5
}