java.lang.ClassCastException: DTOObject cannot be

Question

I am facing a weird issue in my application which runs on Spring Boot 1.4.0M3 which is using Spring cache implementation where provider is Redis where I receive classCastException that same object cannot be casted

I am using Mongodb as database and I have User Object which contains List of Roles object loaded lazily and Roles internally contains Permissions Object like below

@Document
@Data
public class User implements Serializable{
private String passwordResetToken;

private boolean enabled = false;

@DBRef(lazy= true)
private List<Role> roleList;
}

My Role DTO is as below

@Data
@Document
public class Role implements Serializable{
   private String roleName;
    private String description;
    @DBRef(lazy= true)
    private List<Permission> permissions;
}

Now in my spring MVC while loading all roles I am calling all permissions and since this is repetitive operation I thought of caching the result and using redis and while loading the roles value I receive below exception.

raised java.lang.ClassCastException: com.learning.securedapp.domain.Permission cannot be cast to com.learning.securedapp.domain.Permission

Help me to overcome this error.

I am attaching the source code to my project and I receive error at line 91 of RoleController.java

To Replicate in your local environment login to application and click on permissions menu and then roles menu, In Roles menu now click on any edit icon.you will receive above error.

Answer 1

I actually tried the proposed solution (and many variations thereof) with no luck. E.g., this didn't stop the problem from occurring:

restart.include.cache=/spring-data-redis-.*.jar

I updated the above to callout the specific version I was using and it still didn't work.

What I ended up doing which did work was to exclude spring-boot-devtools from my project. I'm using Maven so the annotation was this:

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <version>[1.5.9,)</version>
        <scope>provided</scope>
    </dependency>

This will prevent any version equal to or greater than 1.5.9 from loading up. After I included the above, everything worked as expected. I know this isn't an ideal solution for all, but I made little use of the restart functions of devtools so this was actually a good approach for me.

Answer 2

When you use DevTools with caching, you need to be aware of this limitation.

When the object is serialized into the cache, the application class loader is C1. Then after you change some code/configuration, devtools automatically restart the context and creates a new classloader (C2). When you hit that cache method, the cache abstraction finds an entry in the cache and it deserializes it from the store. If the cache library doesn't take the context classloader into account, that object will have the wrong classloader attached to it (which explains that weird exception A cannot be cast to A).

TL;DR do not serialize classes with devtools if the cache library doesn't use the context classloader. Or put your cache library in the application classloader:

restart.include.yourcache=/my-cache-lib-[\\w-]+\.jar

Answer 3

I am using Spring Boot 2.0.5, and I ended up removing devtools altogether from pom.xml. Thanks to the answer above from @Always Learning.
As much as I hate to do this, but I can't find another way for now!

  <!-- 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
     -->