The technical principles of the POJO MVCC framework and its application in the Java class library
The technical principles of the POJO MVCC framework and its application in the Java class library
Background introduction:
POJO (PLAIN OELD Java Object) is a simple Java object, which usually does not depend on framework and specific technology.The MVCC (Multi-Vering Concurrency Control) is a concurrent control method for managing the consistency and isolation of managing data in the environment of concurrent operation.The POJO MVCC framework combines these two technologies, providing Java developers with a simple and powerful way to handle the data consistency and isolation of data in the scene.
Technical principle:
The core idea of the POJO MVCC framework is to use the version control to manage concurrent operations.In each data object, the framework will create a version for each operation and use the version information to control the concurrent access.Specifically, the POJO MVCC framework has the following key technical principles:
1. Edition control: Each data object has a version number to identify the version of the object.When performing concurrent operation, the framework will determine whether the operation is allowed according to the version number of the object.
2. Optimistic lock: POJO MVCC framework uses optimistic locks to achieve concurrent control.Each data object contains a version number and data content.When an operation is required to update the object, the frame will first compare whether the version number of the object is consistent with the current version. If it is consistent, the update is allowed; otherwise, it means that the object has been modified by other operations and the current operation will be rejected.
3. Isolation level: The POJO MVCC framework supports multiple isolation levels, such as unsurmitting, reading, repeated reading and serialization.These isolation levels can be configured according to the needs of the application to meet different consistency requirements.
4. Affairs management: The POJO MVCC framework also provides transaction management functions to process the consistency of multiple operations.Developers can use the transaction manager provided by the framework to combine a series of operations into a transaction, and to ensure the consistency of all operations by submitting or rolling.
Application in the Java class library:
The POJO MVCC framework is widely used in the Java library, especially in distributed systems and high concurrent scenes.It provides developers with a simple and flexible data access and concurrent control method.
Below is a Java code example based on the POJO MVCC framework:
public class Account {
// Data object
private String id;
private String name;
private double balance;
// version number
private long version;
// Getters and Setters...
// Update operation
public void updateBalance(double amount) {
// Check the version number
if (version == Database.getCurrentVersion(id)) {
// update data
balance += amount;
// Update version number
version++;
// persistent data
Database.save(this);
} else {
throw new ConcurrentModificationException("Concurrent modification detected!");
}
}
// Query operation
public double getBalance() {
// Get the current version of the data
Account currentData = Database.getData(id, version);
// Return data
return currentData.getBalance();
}
// Affairs example
public void transferMoney(Account destination, double amount) {
try {
// Open transaction
TransactionManager.beginTransaction();
// Operation 1: Transfer amount
updateBalance(-amount);
// Operation 2: Transfer amount
destination.updateBalance(amount);
// Submit a transaction
TransactionManager.commit();
} catch (Exception e) {
// Roll back transactions
TransactionManager.rollback();
e.printStackTrace();
}
}
}
public class Main {
public static void main(String[] args) {
// Create two account objects
Account account1 = new Account("1", "Alice", 1000);
Account account2 = new Account("2", "Bob", 500);
// Transfer operation
account1.transferMoney(account2, 200);
// Query account balance
double balance1 = account1.getBalance();
double balance2 = account2.getBalance();
System.out.println("Balance of account1: " + balance1);
System.out.println("Balance of account2: " + balance2);
}
}
In the above code example, we define an account object account, and add updates and query operations to it.The version control and optimistic lock mechanism provided by the POJO MVCC framework ensure the consistency and isolation of concurrent operation.In addition, we also show how to use the transaction manager to combine multiple operations into one transaction to ensure the consistency of all operations.
Summarize:
The technical principles of the POJO MVCC framework mainly include version control, optimistic lock, isolation level and transaction management.It is widely used in the Java class library, providing developers with a simple and powerful way to handle data consistency and isolation in complicated scenes.By using the POJO MVCC framework reasonably, we can better manage and control data and ensure the reliability and performance of the system in a high concurrent environment.
