Java – How to resolve OptimisticLockingFailureException

javamongodbspring-datatestcase

The code that triggers the OptimisticLockingFailureException:

@Test
public void shouldIncrementUserTotalLikesByOne() throws IllegalArgumentException, UserNotFoundException {
    databuilderService.createAll();

    User user = userService.findByEmail("abc@gmail.com");

    long numberOfLikeCount = user.getLikeCount(); 

    userService.incrementUserTotalLikesByOne(user.getId()); 

    userService.save(user);

    long numberOfUpdatedUpdatedCount = user.getLikeCount(); 

    Assert.assertNotNull(numberOfUpdatedUpdatedCount);

    Assert.assertEquals(numberOfUpdatedUpdatedCount, numberOfLikeCount+1);
}

The exception occurs when UserService.save() is called:

org.springframework.dao.OptimisticLockingFailureException: Optimistic lock exception on saving entity:

Best Solution

I had a problem with my model. I added @Version annotation but by mistake there was wrong type of the field and the conversion process occurred during writing to MongoDB throwing OptimisticLockingFailureException exception.

The change @Version annotated field form long type to Long class resolved my problem:

import org.springframework.data.annotation.Version

@Version
private Long version

This blog article gives more details: https://aodcoding.wordpress.com/2015/07/06/preventing-lost-updates-in-mongo-with-spring-optimistic-locking/

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Java – How to test a class that has private methods, fields or inner classes

Update:

Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via @Jailbreak from the Manifold framework.
@Jailbreak Foo foo = new Foo();
// Direct, *type-safe* access to *all* foo's members
foo.privateMethod(x, y, z);
foo.privateField = value;
This way your code remains type-safe and readable. No design compromises, no overexposing methods and fields for the sake of tests.

If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection.

Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. The following patterns will let you do pretty much anything related to the private methods and fields. Of course, you can't change private static final variables through reflection.

Method method = TargetClass.getDeclaredMethod(methodName, argClasses);
method.setAccessible(true);
return method.invoke(targetObject, argObjects);

And for fields:

Field field = TargetClass.getDeclaredField(fieldName);
field.setAccessible(true);
field.set(object, value);

Notes:
1. TargetClass.getDeclaredMethod(methodName, argClasses) lets you look into private methods. The same thing applies for getDeclaredField.
2. The setAccessible(true) is required to play around with privates.

Java – How to efficiently iterate over each entry in a Java Map

Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

On Java 10+:

for (var entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

Best Solution

Related Solutions

Java – How to test a class that has private methods, fields or inner classes

Java – How to efficiently iterate over each entry in a Java Map

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