java-design-patterns | Design patterns implemented in Java | Architecture library
kandi X-RAY | java-design-patterns Summary
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- java-design-patterns has a medium active ecosystem.
- It has 74302 star(s) with 23150 fork(s). There are 3899 watchers for this library.
- It had no major release in the last 12 months.
- There are 219 open issues and 477 have been closed. On average issues are closed in 376 days. There are 54 open pull requests and 0 closed requests.
- It has a neutral sentiment in the developer community.
- The latest version of java-design-patterns is current.
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- java-design-patterns has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.
- java-design-patterns code analysis shows 0 unresolved vulnerabilities.
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- java-design-patterns saves you 24174 person hours of effort in developing the same functionality from scratch.
- It has 51260 lines of code, 4363 functions and 1743 files.
- It has low code complexity. Code complexity directly impacts maintainability of the code.
kandi has reviewed java-design-patterns and discovered the below as its top functions. This is intended to give you an instant insight into java-design-patterns implemented functionality, and help decide if they suit your requirements.
- init data .
- Handle usage processing event
- Create the view .
- Executes a new bake for the given parameters .
- Round round .
- Generates an iterable that returns the last element of the iterable .
- Creates a promotion .
- Handles incoming message .
- Setup the panel .
- Process event loop .
java-design-patterns Key Features
Design patterns implemented in Java
java-design-patterns Examples and Code Snippets
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Community Discussions
Trending Discussions on java-design-patterns
QUESTION
How to properly implement Optimistic Locking at the application layer?
Asked 2021-Mar-03 at 22:15I am a little confused as to why Optimistic Locking is actually safe. If I am checking the version at the time of retrieval with the version at the time of update, it seems like I can still have two requests enter the update block if the OS issues an interrupt and swaps the processes before the commit actually occurs. For example:
latestVersion = vehicle.getVersion();
if (vehicle.getVersion() == latestVersion) {
// update record in database
} else {
// don't update record
}
In this example, I am trying to manually use Optimistic Locking in a Java application without using JPA / Hibernate. However, it seems like two requests can enter the if block at the same time. Can you please help me understand how to do this properly? For context, I am also using Java Design Patterns website as an example.
ANSWER
Answered 2021-Mar-03 at 22:15Well... that's the optimistic part. The optimism is that it is safe. If you have to be certain it's safe, then that's not optimistic.
The example you show definitely is susceptible to a race condition. Not only because of thread scheduling, but also due to transaction isolation level.
A simple read in MySQL, in the default transaction isolation level of REPEATABLE READ, will read the data that was committed at the time your transaction started.
Whereas updating data will act on the data that is committed at the time of the update. If some other concurrent session has updated the row in the database in the meantime, and committed it, then your update will "see" the latest committed row, not the row viewed by your get method.
The way to avoid the race condition is to not be optimistic. Instead, force exclusive access to the record. Doveryai, no proveryai.
If you only have one app instance, you might use a critical section for this.
If you have multiple app instances, critical sections cannot coordinate other instances, so you need to coordinate in the database. You can do this by using pessimistic locking. Either read the record using a locking read query, or else you can use MySQL's user-defined locks.
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