JPA的乐观锁实现并发执行SQL案例-拓冰建站

JPA乐观锁实现增删改查操作

@Entity
public class Product {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;private String name;@Versionprivate int version;// 构造函数、getter和setter省略
}

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.OptimisticLockException;
import javax.persistence.Persistence;
// dao层
public class ProductDAO {private EntityManagerFactory entityManagerFactory;public ProductDAO() {entityManagerFactory = Persistence.createEntityManagerFactory("your-persistence-unit-name");}public void createProduct(Product product) {EntityManager entityManager = entityManagerFactory.createEntityManager();EntityTransaction transaction = entityManager.getTransaction();try {transaction.begin();entityManager.persist(product);transaction.commit();} catch (Exception e) {if (transaction.isActive()) {transaction.rollback();}e.printStackTrace();} finally {entityManager.close();}}public Product getProductById(Long id) {EntityManager entityManager = entityManagerFactory.createEntityManager();Product product = null;try {product = entityManager.find(Product.class, id);} catch (Exception e) {e.printStackTrace();} finally {entityManager.close();}return product;}public void updateProduct(Product product) {EntityManager entityManager = entityManagerFactory.createEntityManager();EntityTransaction transaction = entityManager.getTransaction();try {transaction.begin();entityManager.merge(product);transaction.commit();} catch (OptimisticLockException e) {if (transaction.isActive()) {transaction.rollback();}e.printStackTrace();} finally {entityManager.close();}}public void deleteProduct(Product product) {EntityManager entityManager = entityManagerFactory.createEntityManager();EntityTransaction transaction = entityManager.getTransaction();try {transaction.begin();entityManager.remove(entityManager.merge(product));transaction.commit();} catch (Exception e) {if (transaction.isActive()) {transaction.rollback();}e.printStackTrace();} finally {entityManager.close();}}
}

在上面的代码中，ProductDAO类用于执行对Product实体的增删改查操作。在创建、更新和删除操作中，使用了乐观锁机制来处理并发冲突。

要使用上述代码，需要按照以下步骤进行：

创建名为"your-persistence-unit-name"的持久化单元，配置与数据库的连接信息。
创建一个Product对象，并设置相应的属性。
创建ProductDAO对象，并调用其相应的方法执行数据库操作。

public class Main {public static void main(String[] args) {ProductDAO dao = new ProductDAO();// 创建Product对象并保存到数据库Product product = new Product();product.setName("Phone");dao.createProduct(product);// 根据ID查询Product对象Product retrievedProduct = dao.getProductById(1L);System.out.println("Retrieved Product: " + retrievedProduct.getName());// 更新Product对象retrievedProduct.setName("New Phone");dao.updateProduct(retrievedProduct);// 删除Product对象dao.deleteProduct(retrievedProduct);}
}

以上代码演示了使用乐观锁实现JPA的增删改查操作的完整案例。你可以根据自己的实际需求进行修改和扩展。记得替换代码中的"your-persistence-unit-name"为你实际的持久化单元名称。

JPA的并发执行SQL增删改查的案例

导入依赖

<dependencies><!-- JPA API --><dependency><groupId>jakarta.persistence</groupId><artifactId>jakarta.persistence-api</artifactId><version>2.2.3</version></dependency><!-- JPA Provider (例如Hibernate) --><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId><version>5.6.1.Final</version></dependency><!-- 数据库驱动 (根据你使用的数据库选择适当的依赖) --><dependency><groupId>数据库驱动的groupId</groupId><artifactId>数据库驱动的artifactId</artifactId><version>数据库驱动的版本号</version></dependency>
</dependencies>

jpa配置省略

假设我们有一个简单的实体类Product，代表产品，包含id、name和stock字段：

@Entity
//设置实体类
public class Product {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;private String name;private int stock;@Versionprivate int version;// 构造函数、getter和setter省略
}

在这个案例中，我们将实现以下功能：

创建新产品并保存到数据库。
根据产品ID查询产品信息。
更新产品的库存数量。
删除产品。

下面是完整的代码demo：

import javax.persistence.*;public class ConcurrentJpaOperations {private EntityManagerFactory entityManagerFactory;public ConcurrentJpaOperations() {entityManagerFactory = Persistence.createEntityManagerFactory("your-persistence-unit-name");}public void createProduct(Product product) {EntityManager entityManager = entityManagerFactory.createEntityManager();EntityTransaction transaction = entityManager.getTransaction();try {transaction.begin();entityManager.persist(product);transaction.commit();} catch (Exception e) {if (transaction.isActive()) {transaction.rollback();}e.printStackTrace();} finally {entityManager.close();}}public Product getProductById(Long id) {EntityManager entityManager = entityManagerFactory.createEntityManager();Product product = null;try {product = entityManager.find(Product.class, id);} catch (Exception e) {e.printStackTrace();} finally {entityManager.close();}return product;}public void updateProductStock(Long id, int newStock) {EntityManager entityManager = entityManagerFactory.createEntityManager();EntityTransaction transaction = entityManager.getTransaction();try {transaction.begin();Product product = entityManager.find(Product.class, id);if (product != null) {product.setStock(newStock);entityManager.merge(product);}transaction.commit();} catch (OptimisticLockException e) {if (transaction.isActive()) {transaction.rollback();}e.printStackTrace();} finally {entityManager.close();}}public void deleteProduct(Long id) {EntityManager entityManager = entityManagerFactory.createEntityManager();EntityTransaction transaction = entityManager.getTransaction();try {transaction.begin();Product product = entityManager.find(Product.class, id);if (product != null) {entityManager.remove(product);}transaction.commit();} catch (Exception e) {if (transaction.isActive()) {transaction.rollback();}e.printStackTrace();} finally {entityManager.close();}}public static void main(String[] args) {ConcurrentJpaOperations jpaOperations = new ConcurrentJpaOperations();// 创建新产品Product product1 = new Product();product1.setName("Product 1");product1.setStock(10);jpaOperations.createProduct(product1);// 并发更新产品库存Thread thread1 = new Thread(() -> {jpaOperations.updateProductStock(1L, 5);});Thread thread2 = new Thread(() -> {jpaOperations.updateProductStock(1L, 3);});thread1.start();thread2.start();try {thread1.join();thread2.join();} catch (InterruptedException e) {e.printStackTrace();}// 查询并输出产品信息Product retrievedProduct = jpaOperations.getProductById(1L);if (retrievedProduct != null) {System.out.println("Retrieved Product: " + retrievedProduct.getName());System.out.println("Stock: " + retrievedProduct.getStock());}// 删除产品jpaOperations.deleteProduct(1L);}
}

在上述代码中，我们创建了一个名为ConcurrentJpaOperations的类，其中包含了创建产品、查询产品、更新产品库存和删除产品的方法。在更新产品库存的方法中，我们使用乐观锁来处理并发冲突。在main方法中，我们创建了两个线程并发地更新产品库存。最后，我们查询并输出产品信息，然后删除产品。