IntelliJ IDEA generating serialVersionUID

Question

How do generate this value in IntelliJ IDEA?

I go to Settings -> Errors -> Serialization issues -> Serializable class without ‘serialVersionUID’, but it still doesn't show me the warning. My class PKladrBuilding parent implements interface Serializable.

Part of the code:

public class PKladrBuilding extends PRQObject

public abstract class PRQObject extends PObject

public abstract class PObject implements Serializable

Answer 1

I am not sure if you have an old version of IntelliJ IDEA, but if I go to menu File → Settings... → Inspections → Serialization issues → Serializable class without 'serialVersionUID'` enabled, the class you provide give me warnings.

If I try the first class I see:

BTW: It didn't show me a warning until I added { } to the end of each class to fix the compile error.

Answer 2

After spending some time on Serialization, I find that, we should not generate serialVersionUID with some random value, we should give it a meaningful value.

Here is a details comment on this. I am coping the comment here.

Actually, you should not be "generating" serial version UIDs. It is a dumb "feature" that stems from the general misunderstanding of how that ID is used by Java. You should be giving these IDs meaningful, readable values, e.g. starting with 1L, and incrementing them each time you think the new version of the class should render all previous versions (that might be previously serialized) obsolete. All utilities that generate such IDs basically do what the JVM does when the ID is not defined: they generate the value based on the content of the class file, hence coming up with unreadable meaningless long integers. If you want each and every version of your class to be distinct (in the eyes of the JVM) then you should not even specify the serialVersionUID value isnce the JVM will produce one on the fly, and the value of each version of your class will be unique. The purpose of defining that value explicitly is to tell the serialization mechanism to treat different versions of the class that have the same SVUID as if they are the same, e.g. not to reject the older serialized versions. So, if you define the ID and never change it (and I assume that's what you do since you rely on the auto-generation, and you probably never re-generate your IDs) you are ensuring that all - even absolutely different - versions of your class will be considered the same by the serialization mechanism. Is that what you want? If not, and if you indeed want to have control over how your objects are recognized, you should be using simple values that you yourself can understand and easily update when you decide that the class has changed significantly. Having a 23-digit value does not help at all.

Hope this helps. Good luck.

Answer 3

I am using Android Studio 2.1 and I have better consistency of getting the lightbulb by clicking on the class Name and hover over it for a second.

Answer 4

If you want to add the absent serialVersionUID for a bunch of files, IntelliJ IDEA may not work very well. I come up some simple script to fulfill this goal with ease:

base_dir=$(pwd)
src_dir=$base_dir/src/main/java
ic_api_cp=$base_dir/target/classes

while read f
do
    clazz=${f//\//.}
    clazz=${clazz/%.java/}
    seruidstr=$(serialver -classpath $ic_api_cp $clazz | cut -d ':' -f 2 | sed -e 's/^\s\+//')
    perl -ni.bak -e "print $_; printf qq{%s\n}, q{    private $seruidstr} if /public class/" $src_dir/$f
done

You save this script, say as add_serialVersionUID.sh in your ~/bin folder. Then you run it in the root directory of your Maven or Gradle project like:

add_serialVersionUID.sh < myJavaToAmend.lst

This .lst includes the list of Java files to add the serialVersionUID in the following format:

com/abc/ic/api/model/domain/item/BizOrderTransDO.java
com/abc/ic/api/model/domain/item/CardPassFeature.java
com/abc/ic/api/model/domain/item/CategoryFeature.java
com/abc/ic/api/model/domain/item/GoodsFeature.java
com/abc/ic/api/model/domain/item/ItemFeature.java
com/abc/ic/api/model/domain/item/ItemPicUrls.java
com/abc/ic/api/model/domain/item/ItemSkuDO.java
com/abc/ic/api/model/domain/serve/ServeCategoryFeature.java
com/abc/ic/api/model/domain/serve/ServeFeature.java
com/abc/ic/api/model/param/depot/DepotItemDTO.java
com/abc/ic/api/model/param/depot/DepotItemQueryDTO.java
com/abc/ic/api/model/param/depot/InDepotDTO.java
com/abc/ic/api/model/param/depot/OutDepotDTO.java

This script uses the JDK serialVer tool. It is ideal for a situation when you want to amend a huge number of classes which had no serialVersionUID set in the first place while maintain the compatibility with the old classes.