How does Java database connection handle transactions and concurrency?

Transactions ensure database data integrity, including atomicity, consistency, isolation and durability. JDBC uses the Connection interface to provide transaction control (setAutoCommit, commit, rollback). Concurrency control mechanisms coordinate concurrent operations, using locks or optimistic/pessimistic concurrency control to achieve transaction isolation to prevent data inconsistencies.

Java Database Connection: Transactions and Concurrency Processing

A transaction is a series of operations in the database that either all succeed or all fail . Transactions ensure the integrity of database data and prevent concurrent operations from causing data inconsistencies.

The concept of transaction

• Atomicity: All operations in a transaction either succeed or fail, there is no partial success Case.
• Consistency: After the transaction is executed, the database is in a consistent state and complies with business rules.
• Isolation: Concurrently executed transactions are isolated from each other and will not affect each other.
• Persistence: Once the transaction is submitted successfully, its modifications to the database will take effect permanently.

Transaction Control

Java Database Connection API (JDBC) provides the Connection interface to manage transactions:

• setAutoCommit(false): Disable automatic commit and require manual submission of transactions.
• commit(): Submit the current transaction to make the modification permanent.
• rollback(): Roll back the current transaction and undo all modifications.

Concurrency control

Concurrent operation means that when multiple transactions access the same data at the same time, there is a risk of data inconsistency. The concurrency control mechanism is used to coordinate these concurrent operations and achieve transaction isolation:

• Lock: The database system uses read locks and write locks to control concurrent access to data.
• Optimistic Concurrency Control (OCC): Transactions perform conflict detection when committing. If a conflict is detected, roll back the transaction and try again.
• Pessimistic Concurrency Control (PCC): The transaction acquires an exclusive lock on the data before starting.

Practical Case

Consider the following code example:

Connection conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/database", "user", "password");
conn.setAutoCommit(false); // 禁用自动提交
try {
    // 执行事务中的操作
    ...
    conn.commit(); // 提交事务
} catch (SQLException e) {
    conn.rollback(); // 回滚事务
} finally {
    conn.close(); // 关闭连接
}

This code demonstrates how to use JDBC to manage transactions. It first disables autocommit and then performs the operations within the transaction. Finally, it attempts to commit the transaction and rolls it back if it fails.

Following these principles can ensure the correctness of transactions and concurrency processing in Java database connections and prevent data inconsistencies and concurrency problems.

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